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Sample records for blue organic light-emitting

  1. Highly efficient non-doped blue organic light emitting devices based on anthracene–pyridine derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Haykir, Gulcin; Tekin, Emine; Atalar, Taner; Türksoy, Figen

    2013-12-02

    Four different 2-(10-aryl)anthracen-9-yl)pyridine derivatives 5a–d were synthesized via the Suzuki cross-coupling reaction. Photo-physical characteristics of these materials having strong electron donating or electron withdrawing groups were explored. Multilayer small molecule organic light emitting diodes without any dopant were fabricated in the following sequence: Indium tin oxide/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (50 nm)/5a–d (30 nm)/4,7-diphenyl-1,10-phenanthroline (30 nm)/LiF/Al. The electroluminescent property of the device fabricated with 5d as an emitter exhibited a high external quantum efficiency of 3.80% (at around 1 mA/cm{sup 2}) with Commission Internationale De L'Eclairage coordinates of (0.14, 0.25). - Highlights: • Synthesis and characterization of 2-(10-aryl)anthracen-9-yl)pyridine derivatives • Thermal, photophysical and electrochemical properties of anthracene derivatives • Emitters from blue to greenish blue for organic light emitting device applications • Organic light emitting device fabrication and characterization of 2-(10-aryl)anthracen-9-yl)pyridine derivatives.

  2. Efficient charge balance in blue phosphorescent organic light emitting diodes by two types of mixed layer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hyung Jin; Lee, Ho Won; Lee, Song Eun; Sun, Yong; Hwang, Kyo Min; Yoo, Han Kyu; Lee, Sung Kyu [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Woo Young, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@hongik.ac.kr [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of)

    2015-07-31

    The authors have demonstrated a highly efficient and long-lifetime blue phosphorescent organic light emitting diode (PHOLED) that uses two types of mixed layers. The mixed layers play the role of carrier injection control and exciton generation zone extension. One of the layers is applied for mixing the hole transport layer (HTL) and host material at the HTL side for carrier injection control. The other works as a mixed electron transporting layer (ETL) and host material at the ETL side. The optimized blue PHOLED has been shown to achieve high performance owing to the mixed layer effects. It gave a maximum luminous efficiency of 25.55 cd/A, maximum external quantum efficiency of 13.05%, and lifetime of 7.24 h under 500 cd/m{sup 2}. These results indicate that applying mixed layers is a simple and efficient method that does not require significant structural change. - Highlights: • Highly efficient blue phosphorescent organic light-emitting diode (PHOLEDs) • Hole transporting layer consists with mixed layer for delayed hole injection • The blue PHOLEDs with long lifetime due to suppression of quenching process.

  3. Highly efficient greenish-blue platinum-based phosphorescent organic light-emitting diodes on a high triplet energy platform

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Y. L., E-mail: yilu.chang@mail.utoronto.ca; Gong, S., E-mail: sgong@chem.utoronto.ca; White, R.; Lu, Z. H., E-mail: zhenghong.lu@utoronto.ca [Department of Materials Science and Engineering, University of Toronto, 184 College St., Toronto, Ontario M5S 3E4 (Canada); Wang, X.; Wang, S., E-mail: wangs@chem.queensu.ca [Department of Chemistry, Queen' s University, 90 Bader Lane, Kingston, Ontario K7L 3N6 (Canada); Yang, C. [Department of Chemistry, Wuhan University, Wuhan 430072 (China)

    2014-04-28

    We have demonstrated high-efficiency greenish-blue phosphorescent organic light-emitting diodes (PHOLEDs) based on a dimesitylboryl-functionalized C^N chelate Pt(II) phosphor, Pt(m-Bptrz)(t-Bu-pytrz-Me). Using a high triplet energy platform and optimized double emissive zone device architecture results in greenish-blue PHOLEDs that exhibit an external quantum efficiency of 24.0% and a power efficiency of 55.8 lm/W. This record high performance is comparable with that of the state-of-the-art Ir-based sky-blue organic light-emitting diodes.

  4. High-Efficiency Blue Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence from Phenoxaphosphine and Phenoxathiin Derivatives.

    Science.gov (United States)

    Lee, Sae Youn; Adachi, Chihaya; Yasuda, Takuma

    2016-06-01

    High-efficiency blue thermally activated delayed fluorescence (TADF) molecules, consisting of phenoxaphosphine oxide and phenoxathiin dioxide as acceptor units and 9,9-dimethylacridan as a donor unit, are reported. Maximum external electroluminescence quantum efficiencies of up to 20.5% are achieved in blue organic light-emitting diodes (OLEDs) by employing these materials as TADF emitters.

  5. Blue and green organic light-emitting devices with various film thicknesses for color tuning

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Blue and green organic light-emitting devices with a structure of indium tin oxide (ITO)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1 '-biphenyl-4,4'-diamine (NPB)/aluminum(Ⅲ) bis(2-methyl-8-quinolinato)4 -phenylphenolato (BAlq)/tris(8-hydroxyquinolate)-aluminum (Alq3)/Mg:Ag have been fabricated. Blue to green light emission has been achieved with the change of organic film thickness. Based on energy band diagram and charge carrier tunneling theory, it is concluded that the films of different thicknesses play a role as a color-tuning layer and the color-variable electroluminescence (EL) is ascribed to the modulation function within the charge carrier recombination zone. In the case of heterostructure devices with high performance, the observed EL spectra varies significantly with the thickness of organic films, which is resulted from the shift of recombination region site. It has not been hitherto indicated that the devices compose of identical components could be implemented to realize different color emission by changing the film thickness of functional layers.

  6. Low Power, Red, Green and Blue Carbon Nanotube Enabled Vertical Organic Light Emitting Transistors for Active Matrix OLED Displays

    Energy Technology Data Exchange (ETDEWEB)

    McCarthy, M. A. [University of Florida, Gainesville; Liu, B. [University of Florida, Gainesville; Donoghue, E. P. [University of Florida, Gainesville; Kravchenko, Ivan I [ORNL; Kim, D. Y. [University of Florida, Gainesville; So, Franky [University of Florida, Gainesville; Rinzler, A. G. [University of Florida, Gainesville

    2011-01-01

    Organic semiconductors are potential alternatives to polycrystalline silicon as the semiconductor used in the backplane of active matrix organic light emitting diode displays. Demonstrated here is a light-emitting transistor with an organic channel, operating with low power dissipation at low voltage, and high aperture ratio, in three colors: red, green and blue. The single-wall carbon nanotube network source electrode is responsible for the high level of performance demonstrated. A major benefit enabled by this architecture is the integration of the drive transistor, storage capacitor and light emitter into a single device. Performance comparable to commercialized polycrystalline-silicon TFT driven OLEDs is demonstrated.

  7. Improved efficiency in blue phosphorescent organic light-emitting diodes by the stepwise doping structure

    Science.gov (United States)

    Yang, Liping; Wang, Xiaoping; Kou, Zhiqi; Ji, Changyan

    2017-04-01

    The electro-optical properties of the blue phosphorescent organic light-emitting diodes (PHOLEDs) can be affected by the stepwise doping structure in the emitting layer (EML). A series of multi-EML devices with different doping concentration of blue dopant (FIrpic) are fabricated. The effect of the stepwise doping structure close to the electron transport layer is more obvious than that close to the hole transport layer. When the doping concentration increases gradually from the hole injection side to the electron injection side, the maximum values of the luminance, current and power efficiency can reach to 9745 cd/m2 (at 9 V), 32.0 cd/A and 25.1 lm/W in the device with the asymmetric tri-EML structure, which is improved by about 10% compared with that in the bi-EML device. When the number of the EML is four, the performance of the device becomes worse because of the interface effect resulting from different concentration of dopant.

  8. AZO/Ag/AZO anode for resonant cavity red, blue, and yellow organic light emitting diodes

    Science.gov (United States)

    Gentle, A. R.; Yambem, S. D.; Burn, P. L.; Meredith, P.; Smith, G. B.

    2016-06-01

    Indium tin oxide (ITO) is the transparent electrode of choice for organic light-emitting diodes (OLEDs). Replacing ITO for cost and performance reasons is a major drive across optoelectronics. In this work, we show that changing the transparent electrode on red, blue, and yellow OLEDs from ITO to a multilayer buffered aluminium zinc oxide/silver/aluminium zinc oxide (AZO/Ag/AZO) substantially enhances total output intensity, with better control of colour, its constancy, and intensity over the full exit hemisphere. The thin Ag containing layer induces a resonant cavity optical response of the complete device. This is tuned to the emission spectra of the emissive material while minimizing internally trapped light. A complete set of spectral intensity data is presented across the full exit hemisphere for each electrode type and each OLED colour. Emission zone modelling of output spectra at a wide range of exit angles to the normal was in excellent agreement with the experimental data and hence could, in principle, be used to check and adjust production settings. These multilayer transparent electrodes show significant potential for both eliminating indium from OLEDs and spectrally shaping the emission.

  9. Efficiency of Blue Organic Light-emitting Diodes Enhanced by Employing an Exciton Feedback Layer

    Institute of Scientific and Technical Information of China (English)

    Qian-Qian Yu; Xu Zhang; Jing-Xuan Bi; Guan-Ting Liu; Qi-Wen Zhang; Xiao-Ming Wu; Yu-Lin Hua

    2016-01-01

    We report that a novel exciton feedback effect is observed by introducing the bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (BAlq) inserted between the emitting layer (EML) and the electron transporting layer in blue organic light emitting diodes.As an exciton feedback layer (EFL),the BAlq does not act as a traditional hole blocking effect.The design of this kind of device structure can greatly reduce excitons' quenching due to accumulated space charge at the exciton formation interface.Meanwhile,the non-radiative energy transfer from EFL to the EML can also be utilized to enhance the excitons' formation,which is confirmed by the test of photolumimescent transient lifetime decay and electroluminescence enhancement of these devices.Accordingly,the optimal device presents the improved performances with the maximum current e~ciency of 4.2 cd/A and the luminance of 24600cd/m2,which are about 1.45 times and 1.75 times higher than those of device A (control device) without the EFL,respectively.Simultaneously,the device shows an excellent color stability with a tiny offset of the CIE coordinates (Ax =±0.003,Ay =±0.004) and a relatively lower efficiency roll-off of 26.2% under the driving voltage varying from 3 V to 10 V.

  10. ORGANIC LIGHT EMITTING DIODE (OLED

    Directory of Open Access Journals (Sweden)

    Aririguzo Marvis Ijeaku

    2015-09-01

    Full Text Available An Organic Light Emitting Diode (OLED is a device composed of an organic layer that emits lights in response to an electrical current. Organic light emitting diodes have advanced tremendously over the past decades. The different manufacturing processes of the OLED itself to several advantages over flat panel displays made with LCD technology which includes its light weight and flexible plastic substrates, wider viewing angles, improved brightness, better power efficiency and quicker response time. However, its drawbacks include shorter life span, poor color balance, poor outdoor performance, susceptibility to water damage etc.The application of OLEDs in electronics is on the increase on daily basics from cameras to cell phones to OLED televisions, etc. Although OLEDs provides prospects for thinner, smarter, lighter and ultraflexible electronics displays, however, due to high cost of manufacturing, it is not yet widely used.

  11. Highly efficient multilayer organic pure-blue-light emitting diodes with substituted carbazoles compounds in the emitting layer

    CERN Document Server

    Fischer, A; Chenais, S; Castex, M C; Siove, A; Ades, D; Geffroy, B; Denis, C; Maisse, P; Fischer, Alexis; Forget, Sebastien; Chenais, Sebastien; Castex, Marie-Claude; Siove, Alain; Ades, Dominique; Geffroy, Bernard; Denis, Christine; Maisse, Pascal

    2006-01-01

    Bright blue organic light-emitting diodes (OLEDs) based on 1,4,5,8,N-pentamethylcarbazole (PMC) and on dimer of N-ethylcarbazole (N,N'-diethyl-3,3'-bicarbazyl) (DEC) as emitting layers or as dopants in a 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) matrix are described. Pure blue-light with the C.I.E. coordinates x = 0.153 y = 0.100, electroluminescence efficiency \\eta_{EL} of 0.4 cd/A, external quantum efficiency \\eta_{ext.} of 0.6% and luminance L of 236 cd/m2 (at 60 mA/cm2) were obtained with PMC as an emitter and the 2,9-dimethyl-4,7-diphenyl-1,10-phenantroline (BCP) as a hole-blocking material in five-layer emitting devices. The highest efficiencies \\eta_{EL.} of 4.7 cd/A, and \\eta_{ext} = 3.3% were obtained with a four-layer structure and a DPVBi DEC-doped active layer (CIE coordinates x = 0.158, y=0.169, \\lambda_{peak} = 456 nm). The \\eta_{ext.} value is one the highest reported at this wavelength for blue OLEDs and is related to an internal quantum efficiency up to 20%.

  12. Highly efficient multilayer organic pure blue light emitting diodes with substituted carbazoles compounds in the emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, A [Laboratoire de Physique des Lasers (LPL, CNRS), Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Chenais, S [Laboratoire de Physique des Lasers (LPL, CNRS), Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Forget, S [Laboratoire de Physique des Lasers (LPL, CNRS), Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Castex, M-C [Laboratoire de Physique des Lasers (LPL, CNRS), Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Ades, D [Biomateriaux et Polymeres de Specialite (BPS/B2OA, CNRS), Institut Galilee, Universite Paris 13, Villetaneuse/Faculte de Medecine Lariboisiere-St Louis, Universite Paris 7, 75010 Paris (France); Siove, A [Biomateriaux et Polymeres de Specialite (BPS/B2OA, CNRS), Institut Galilee, Universite Paris 13, Villetaneuse/Faculte de Medecine Lariboisiere-St Louis, Universite Paris 7, 75010 Paris (France); Denis, C [Laboratoire Cellules et Composants, CEA/LITEN/DSEN, CEA Saclay, 91191 Gif-sur-Yvette (France); Maisse, P [Laboratoire Cellules et Composants, CEA/LITEN/DSEN, CEA Saclay, 91191 Gif-sur-Yvette (France); Geffroy, B [Laboratoire Cellules et Composants, CEA/LITEN/DSEN, CEA Saclay, 91191 Gif-sur-Yvette (France)

    2006-03-07

    Bright blue organic light-emitting diodes (OLEDs) based on 1, 4, 5, 8, N-pentamethylcarbazole (PMC) and on dimer of N-ethylcarbazole (N, N'-diethyl-3, 3'-bicarbazyl) (DEC) as emitting layers or as dopants in a 4, 4'-bis(2, 2'-diphenylvinyl)-1, 1'-biphenyl (DPVBi) matrix are described. Pure blue light with the CIE coordinates (x = 0.153, y = 0.100), electroluminescence efficiency {eta}{sub EL} of 0.4 cd A{sup -1}, external quantum efficiency {eta}{sub ext} of 0.6% and luminance L of 236 cd m{sup -2} (at 60 mA cm{sup -2}) were obtained with PMC as an emitter and the 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenantroline (BCP) as a hole-blocking material in five-layer emitting devices. The highest efficiencies {eta}{sub EL} of 4.7 cd A{sup -1} and {eta}{sub ext} = 3.3% were obtained with a four-layer structure and a DPVBi DEC-doped active layer (CIE coordinates x = 0.158, y = 0.169, {lambda}{sub peak} = 456 nm). The {eta}{sub ext} value is one the highest reported at this wavelength for blue OLEDs and is related to an internal quantum efficiency up to 20%.

  13. Highly efficient multilayer organic pure blue light emitting diodes with substituted carbazoles compounds in the emitting layer

    Science.gov (United States)

    Fischer, A.; Chénais, S.; Forget, S.; Castex, M.-C.; Adès, D.; Siove, A.; Denis, C.; Maisse, P.; Geffroy, B.

    2006-03-01

    Bright blue organic light-emitting diodes (OLEDs) based on 1, 4, 5, 8, N-pentamethylcarbazole (PMC) and on dimer of N-ethylcarbazole (N, N'-diethyl-3, 3'-bicarbazyl) (DEC) as emitting layers or as dopants in a 4, 4'-bis(2, 2'-diphenylvinyl)-1, 1'-biphenyl (DPVBi) matrix are described. Pure blue light with the CIE coordinates (x = 0.153, y = 0.100), electroluminescence efficiency ηEL of 0.4 cd A-1, external quantum efficiency ηext of 0.6% and luminance L of 236 cd m-2 (at 60 mA cm-2) were obtained with PMC as an emitter and the 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenantroline (BCP) as a hole-blocking material in five-layer emitting devices. The highest efficiencies ηEL of 4.7 cd A-1 and ηext = 3.3% were obtained with a four-layer structure and a DPVBi DEC-doped active layer (CIE coordinates x = 0.158, y = 0.169, λpeak = 456 nm). The ηext value is one the highest reported at this wavelength for blue OLEDs and is related to an internal quantum efficiency up to 20%.

  14. Deep-blue phosphorescent organic light-emitting diode with external quantum efficiency over 30% using novel Ir complex

    Science.gov (United States)

    Inoue, Hideko; Yamada, Yui; Ohsawa, Nobuharu; Seo, Satoshi; Hosoumi, Shunsuke; Watabe, Takeyoshi; Mitsumori, Satomi; Kido, Hiromitsu

    2016-09-01

    We report a newly developed deep-blue phosphorescent iridium complex exhibiting a narrow emission spectrum. The use of this complex resulted in a deep-blue organic light-emitting diode (OLED) with an external quantum efficiency (EQE) exceeding 30%. Two iridium complexes with a 4H-1,2,4-triazole ligand which has an adamantyl group at the 4-position were synthesized, with the resulting effects of the adamantyl group on photoluminescence (PL) behavior investigated. [Ir(Adm1)3] having a 1-adamantyl group did not exhibit any emissions at room temperature, whereas [Ir(Adm2)3] having a 2-adamantyl group exhibited a blue emission with a peak wavelength of 459 nm and a high PL quantum yield of 0.94. Structural transformations between the ground state and excited state were estimated by molecular orbital calculations, which suggests that [Ir(Adm1)3] undergoes a considerably more extensive change than [Ir(Adm2)3]. It is therefore probable that [Ir(Adm1)3] ultimately experiences thermal deactivation owing to structural relaxation. Furthermore, an OLED was fabricated using [Ir(Adm2)3] as a dopant. The associated electroluminescence spectrum had an emission peak at 457 nm and a relatively small shoulder peak at 485 nm, which are consistent with the PL spectrum. A narrowed emission spectrum with a full width at half maximum of 58 nm was obtained, leading to a deep-blue emission with high color purity (CIE, x = 0.15, y = 0.22). This device ultimately exhibited an extremely high EQE of 32% at 2 mA/cm2, which was likely attributable to an increase in outcoupling efficiency via molecular orientation.

  15. Hybrid white organic light-emitting devices based on phosphorescent iridium-benzotriazole orange-red and fluorescent blue emitters

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Zhen-Yuan, E-mail: xiazhenyuan@hotmail.com [Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237 (China); Su, Jian-Hua [Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237 (China); Chang, Chi-Sheng; Chen, Chin H. [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu, Taiwan 300 (China)

    2013-03-15

    We demonstrate that high color purity or efficiency hybrid white organic light-emitting devices (OLEDs) can be generated by integrating a phosphorescent orange-red emitter, bis[4-(2H-benzotriazol-2-yl)-N,N-diphenyl-aniline-N{sup 1},C{sup 3}] iridium acetylacetonate, Ir(TBT){sub 2}(acac) with fluorescent blue emitters in two different emissive layers. The device based on deep blue fluorescent material diphenyl-[4-(2-[1,1 Prime ;4 Prime ,1 Double-Prime ]terphenyl-4-yl-vinyl)-phenyl]-amine BpSAB and Ir(TBT){sub 2}(acac) shows pure white color with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.33,0.30). When using sky-blue fluorescent dopant N,N Prime -(4,4 Prime -(1E,1 Prime E)-2,2 Prime -(1,4-phenylene)bis(ethene-2,1-diyl) bis(4,1-phenylene))bis(2-ethyl-6-methyl-N-phenylaniline) (BUBD-1) and orange-red phosphor with a color-tuning phosphorescent material fac-tris(2-phenylpyridine) iridium (Ir(ppy){sub 3} ), it exhibits peak luminance yield and power efficiency of 17.4 cd/A and 10.7 lm/W, respectively with yellow-white color and CIE color rendering index (CRI) value of 73. - Highlights: Black-Right-Pointing-Pointer An iridium-based orange-red phosphor Ir(TBT){sub 2}(acac) was applied in hybrid white OLEDs. Black-Right-Pointing-Pointer Duel- and tri-emitter WOLEDs were achieved with either high color purity or efficiency performance. Black-Right-Pointing-Pointer Peak luminance yield of tri-emitter WOLEDs was 17.4 cd/A with yellow-white color and color rendering index (CRI) value of 73.

  16. The Investigation on Color Purity of Blue Organic Light-Emitting Diodes (BOLED by Hole-Blocking Layer

    Directory of Open Access Journals (Sweden)

    Kan-Lin Chen

    2013-01-01

    Full Text Available Organic light-emitting diodes (OLEDs with triple hole-blocking layer (THBL structure, which consist of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, 4,4′-bis(2,2′diphenyl vinil-1,1′-biphenyl (DPVBi, and (4,4′-N,N′-dicarbazolebiphenyl (CBP, have been fabricated. Regardless of applied voltage variation, the luminous efficiency of the OLEDs with THBL structure was increased by 41% as compared with the dual hole-blocking layer (DHBL structure. The CIE coordinates of (0.157, 0.111 of device with THBL structure are close to pure blue emission than that of other devices of DHBL. There is a coordinate with the slight shift of ±Δx,y = (0.001, 0.008 for the device with THBL structure during the applied voltage of 6–9 V. The results indicate that the excitons can be effectively confined in the emitting layer of device, leading to an enhancement of luminance efficiency and more stable coordinate.

  17. Influence of confinement layers in the emitting layer of the blue phosphorescent organic light-emitting diodes

    Science.gov (United States)

    Ji, Chang-Yan; Gu, Zheng-Tian; Kou, Zhi-Qi

    2016-10-01

    The electrical and optical properties of the blue phosphorescent organic light-emitting diodes (PHOLEDs) can be affected by the various structure of confinement layer in the emitting layer (EML). A series of devices with different electron or hole confinement layer (TCTA or Bphen) are fabricated, it is more effective to balance charge carriers injection for the device with the double electron confinement layers structure, the power efficiency and luminance can reach 17.7 lm/W (at 103 cd/m2) and 3536 cd/m2 (at 8 V). In case of the same double electron confinement layers, another series of devices with different profile of EML are fabricated by changing the confinement layers position, the power efficiency and luminance can be improved to 21.7 lm/W (at 103 cd/m2) and 7674 cd/m2 (at 8 V) when the thickness of EML separated by confinement layers increases gradually from the hole injection side to the electron injection side, the driving voltage can also be reduced.

  18. Principles of phosphorescent organic light emitting devices.

    Science.gov (United States)

    Minaev, Boris; Baryshnikov, Gleb; Agren, Hans

    2014-02-07

    Organic light-emitting device (OLED) technology has found numerous applications in the development of solid state lighting, flat panel displays and flexible screens. These applications are already commercialized in mobile phones and TV sets. White OLEDs are of especial importance for lighting; they now use multilayer combinations of organic and elementoorganic dyes which emit various colors in the red, green and blue parts of the visible spectrum. At the same time the stability of phosphorescent blue emitters is still a major challenge for OLED applications. In this review we highlight the basic principles and the main mechanisms behind phosphorescent light emission of various classes of photofunctional OLED materials, like organic polymers and oligomers, electron and hole transport molecules, elementoorganic complexes with heavy metal central ions, and clarify connections between the main features of electronic structure and the photo-physical properties of the phosphorescent OLED materials.

  19. Light Emitting Transistors of Organic Single Crystals

    Science.gov (United States)

    Iwasa, Yoshihiro

    2009-03-01

    Organic light emitting transistors (OLETs) are attracting considerable interest as a novel function of organic field effect transistors (OFETs). Besides a smallest integration of light source and current switching devices, OLETs offer a new opportunity in the fundamental research on organic light emitting devices. The OLET device structure allows us to use organic single crystals, in contrast to the organic light emitting diodes (OLEDs), the research of which have been conducted predominantly on polycrystalline or amorphous thin films. In the case of OFETs, use of single crystals have produced a significant amount of benefits in the studies of pursuit for the highest performance limit of FETs, intrinsic transport mechanism in organic semiconductors, and application of the single crystal transistors. The study on OLETs have been made predominantly on polycrystalline films or multicomponent heterojunctions, and single crystal study is still limited to tetracene [1] and rubrene [2], which are materials with relatively high mobility, but with low photoluminescence efficiency. In this paper, we report fabrication of single crystal OLETs of several kinds of highly luminescent molecules, emitting colorful light, ranging from blue to red. Our strategy is single crystallization of monomeric or oligomeric molecules, which are known to have a very high photoluminescence efficiency. Here we report the result on single crystal LETs of rubrene (red), 4,4'-bis(diphenylvinylenyl)-anthracene (green), 1,4-bis(5-phenylthiophene-2-yl)benzene (AC5) (green), and 1,3,6,8-tetraphenylpyrene (TPPy) (blue), all of which displayed ambipolar transport as well as peculiar movement of voltage controlled movement of recombination zone, not only from the surface of the crystal but also from the edges of the crystals, indicting light confinement inside the crystal. Realization of ambipolar OLET with variety of single crystals indicates that the fabrication method is quite versatile to various light

  20. Carrier recombination spatial transfer by reduced potential barrier causes blue/red switchable luminescence in C8 carbon quantum dots/organic hybrid light-emitting devices

    Directory of Open Access Journals (Sweden)

    Xifang Chen

    2016-04-01

    Full Text Available The underlying mechanism behind the blue/red color-switchable luminescence in the C8 carbon quantum dots (CQDs/organic hybrid light-emitting devices (LEDs is investigated. The study shows that the increasing bias alters the energy-level spatial distribution and reduces the carrier potential barrier at the CQDs/organic layer interface, resulting in transition of the carrier transport mechanism from quantum tunneling to direct injection. This causes spatial shift of carrier recombination from the organic layer to the CQDs layer with resultant transition of electroluminescence from blue to red. By contrast, the pure CQDs-based LED exhibits green–red electroluminescence stemming from recombination of injected carriers in the CQDs.

  1. Highly Efficient Deep Blue Organic Light-Emitting Diodes Based on Imidazole: Significantly Enhanced Performance by Effective Energy Transfer with Negligible Efficiency Roll-off.

    Science.gov (United States)

    Shan, Tong; Liu, Yulong; Tang, Xiangyang; Bai, Qing; Gao, Yu; Gao, Zhao; Li, Jinyu; Deng, Jian; Yang, Bing; Lu, Ping; Ma, Yuguang

    2016-10-10

    Great efforts have been devoted to develop efficient deep blue organic light-emitting diodes (OLEDs) materials meeting the standards of European Broadcasting Union (EBU) standard with Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.06) for flat-panel displays and solid-state lightings. However, high-performanced deep blue OLEDs are still rare for applications. Herein, two efficient deep blue emitters, PIMNA and PyINA, are designed and synthesized by coupling naphthalene with phenanthreneimidazole and pyreneimidazole, respectively. The balanced ambipolar transporting natures of them are demonstrated by single-carrier devices. Their non-doped OLEDs show deep blue emissions with extremely small CIEy of 0.034 for PIMNA and 0.084 for PyINA, with negligible efficiency roll-off. To take advantage of high photoluminescence quantum efficiency of PIMNA and large fraction of singlet exciton formation of PyINA, doped devices are fabricated by dispersing PyINA into PIMNA, a significantly improved maximum external quantum efficiency (EQE) of 5.05% is obtained through very effective energy transfer with CIE coordinates of (0.156, 0.060), and the EQE remains 4.67% at 1000 cd m-2, which is among the best of deep blue OLEDs reported matching stringent EBU standard well.

  2. Organic light-emitting diodes based on 9-(2-naphthyl)anthracene derivatives with a triphenylsilane unit as the deep-blue emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ji Young; Lee, Seul Bee [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Lee, Seok Jae [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@wow.hongik.ac.kr [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Yoon, Seung Soo, E-mail: ssyoon@skku.edu [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2015-02-27

    A series of 9-(2-naphthyl)anthracene derivatives with a triphenylsilane unit, which prevented molecular aggregation and self-quenching effect, was designed and synthesized. By using various bridges between the 9-(2-naphthyl)anthracene group and the triphenylsilane unit, five deep-blue emitters were obtained and applied as non-doped emitting materials in organic light-emitting diodes (OLEDs) with a device structure of indium–tin-oxide (ITO) (180 nm)/4,4-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (NPB) (50 nm)/emitting materials (30 nm)/4,7-diphenyl-1,10-phenanthroline (Bphen) (30 nm)/lithium quinolate (Liq) (2 nm)/Aluminium (100 nm). All devices showed blue emissions and their electroluminescence efficiencies are sensitive to the structural changes of the emitting materials. In particular, a device using 9-(2-naphthalenyl)-10-[6-(triphenylsilyl)-2-naphthalenyl]-anthracene (4) exhibited high luminous, power and quantum efficiencies of 2.28 cd/A, 1.42 lm/W and 2.40% at 20 mA/cm{sup 2}, respectively, and this device showed the deep blue emission with the CIE coordinates of (0.16, 0.10) at 6.0 V. - Highlights: • We synthesized 9-(2-naphthyl)anthracene derivatives with a triphenylsilane unit. • We study the conjugation-length effect on the electroluminescence properties. • The bulky triphenylsilane-anthracene derivatives show resistance to self-aggregation.

  3. Organic bistable light-emitting devices

    Science.gov (United States)

    Ma, Liping; Liu, Jie; Pyo, Seungmoon; Yang, Yang

    2002-01-01

    An organic bistable device, with a unique trilayer structure consisting of organic/metal/organic sandwiched between two outmost metal electrodes, has been invented. [Y. Yang, L. P. Ma, and J. Liu, U.S. Patent Pending, U.S. 01/17206 (2001)]. When the device is biased with voltages beyond a critical value (for example 3 V), the device suddenly switches from a high-impedance state to a low-impedance state, with a difference in injection current of more than 6 orders of magnitude. When the device is switched to the low-impedance state, it remains in that state even when the power is off. (This is called "nonvolatile" phenomenon in memory devices.) The high-impedance state can be recovered by applying a reverse bias; therefore, this bistable device is ideal for memory applications. In order to increase the data read-out rate of this type of memory device, a regular polymer light-emitting diode has been integrated with the organic bistable device, such that it can be read out optically. These features make the organic bistable light-emitting device a promising candidate for several applications, such as digital memories, opto-electronic books, and recordable papers.

  4. Efficient organic light emitting-diodes (OLEDs)

    CERN Document Server

    Chang, Yi-Lu

    2015-01-01

    Following two decades of intense research globally, the organic light-emitting diode (OLED) has steadily emerged as the ultimate display technology of choice for the coming decades. Portable active matrix OLED displays have already become prevalent, and even large-sized ultra-high definition 4K TVs are being mass-produced. More exotic applications such as wearable displays have been commercialized recently. With the burgeoning success in displays, researchers are actively bringing the technology forward into the exciting solid-state lighting market. This book presents the knowledge needed for

  5. New blue-light-emitting ultralong [Cd(L)(TeO3)] (L = polyamine) organic-inorganic hybrid nanofibre bundles: their thermal stability and acidic sensitivity.

    Science.gov (United States)

    Yao, Hong-Bin; Li, Xiao-Bo; Yu, Shu-Hong

    2009-08-03

    A new type of blue-light-emitting ultralong [Cd(L)(TeO(3))] (L = ethylenediamine, diethylenetriamine) nanofibre bundle has been synthesised under reflux in a mixed solvent media. Inorganic Cd(TeO(3)) layers are assumed to exist in the structures and are connected by the organic amine molecules through the coordination between nitrogen atoms and cadmium ions. The composition and formulae of these hybrid materials, based on the proposed structures, have been identified through element analysis (EA), thermal gravity analysis (TGA) and energy dispersive spectra (EDS). The thermal stabilities and optical properties of these nanofibre bundles have been investigated. Thermal decomposition of [Cd(en)(TeO(3))] (en = ethylenediamine) and [Cd(DETA)(TeO(3))] (DETA = diethylenetriamine) at 450 degrees C allowed the formation of a mixture of CdTe and Cd(TeO(3)) phases, and a pure CdTe phase, respectively. In addition, this new kind of hybrid bundle, which demonstrates blue emission, was found to be sensitive to acids, and the emission intensity is strongly dependent on the acidity of the solutions, implying that these hybrid nanofibre bundles could be potentially applied as acid sensors.

  6. Blue Fluorescent Materials Composed of Anthracene-Aryl Amine-Anthracene Derivatives for Organic Light-Emitting Diodes.

    Science.gov (United States)

    Lee, Seul Bee; Song, Ji Young; Yang, Hyung Jin; Kim, Young Kwan; Yoon, Seung Soo

    2015-07-01

    Blue fluorescent emitters based on anthracene-aryl amine-anthracene derivatives were studied for efficient OLEDs. Compound 1 exhibited efficient EL propereties with luminous and power efficien- cies of 4.50 cd/A and 1.75 lm/W at 200 mA/cm2, respectively and CIE coordinates of (0.18, 0.26) at 7.0 V.

  7. Excellent deep-blue emitting materials based on anthracene derivatives for non-doped organic light-emitting diodes

    Science.gov (United States)

    Wang, Zhiqiang; Liu, Wei; Xu, Chen; Ji, Baoming; Zheng, Caijun; Zhang, Xiaohong

    2016-08-01

    Two deep-blue emitting materials 2-tert-butyl-9,10-bis(3,5-diphenylphenyl)anthracene (An-1) and 2-tert-butyl-9,10-bis(3,5-diphenylbiphenyl-4‧-yl)anthracene (An-2) were successfully synthesized by the Pd-catalyzed Suzuki coupling reaction. Both of these compounds have high thermal stabilities and show strong deep-blue emission as solid-state film as well as in n-hexane solution. Two non-doped electroluminescent devices employing An-1 and An-2 as emitting layers were fabricated by vacuum vapor deposition. These devices exhibited highly efficient and stable deep-blue emission with high color purity. The CIE coordinate and maximum EQE of An-1 based device are 4.2% and (0.16, 0.06), respectively. Device based on An-2 achieved a maximum EQE of 4.0% and a CIE coordinate of (0.16, 0.10).

  8. Doped and non-doped organic light-emitting diodes based on a yellow carbazole emitter into a blue-emitting matrix

    CERN Document Server

    Choukri, H; Forget, S; Chenais, S; Castex, M C; Geffroy, B; Ades, D; Siove, A; Choukri, Hakim; Fischer, Alexis; Forget, Sebastien; Chenais, Sebastien; Castex, Marie-Claude; Geffroy, Bernard; Ades, Dominique; Siove, Alain

    2007-01-01

    A new carbazole derivative with a 3,3'-bicarbazyl core 6,6'-substituted by dicyanovinylene groups (6,6'-bis(1-(2,2'-dicyano)vinyl)-N,N'-dioctyl-3,3'-bicarbazyl; named (OcCz2CN)2, was synthesized by carbonyl-methylene Knovenagel condensation, characterized and used as a component of multilayer organic light-emitting diodes (OLEDs). Due to its -donor-acceptor type structure, (OcCz2CN)2 was found to emit a yellow light at max=590 nm (with the CIE coordinates x=0.51; y = 0.47) and was used either as a dopant or as an ultra-thin layer in a blue-emitting matrix of 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi). DPVBi (OcCz2CN)2-doped structure exhibited, at doping ratio of 1.5 weight %, a yellowish-green light with the CIE coordinates (x = 0.31; y = 0.51), an electroluminescence efficiency EL=1.3 cd/A, an external quantum efficiency ext= 0.4 % and a luminance L= 127 cd/m2 (at 10 mA/cm2) whereas for non-doped devices utilizing the carbazolic fluorophore as a thin n...

  9. Blue emitting halogen-phenoxy substituted 1,8-naphthalimides for potential organic light emitting diode applications

    Science.gov (United States)

    Ulla, Hidayath; Raveendra Kiran, M.; Garudachari, B.; Satyanarayan, M. N.; Umesh, G.; Isloor, A. M.

    2014-11-01

    In this paper, we report the synthesis and characterization of six 1,8-naphthalimides [4a-4c and 5a-5c] obtained by the substitution of electron donating halogen-phenoxy groups at the C-4 position. The derivatives were characterized using 1H NMR, 13C NMR, mass spectra, FT-IR, single crystal XRD; photo-physical, thermal, surface morphological and electrochemical properties were also investigated. The derivatives exhibit deep blue photoluminescence in the range 414-423 nm (in CHCl3) and 457-466 nm (in thin film state) on UV excitation with high Stokes' shifts and good chromaticity. The TGA and DSC analysis showed that the derivatives possess good thermal stability (271-284 °C) and melting points (138-201 °C). The HOMO and LUMO energy levels estimated by cyclic voltammetry are in the range 6.21-6.34 eV and 3.31-3.41 eV respectively corresponding to energy band gaps of 2.98-3.15 eV. These energy values are relatively higher than the commonly used electron transporting materials. The optical and electronic properties of the derivatives were tuned by the introduction of different electron donating halogen-phenoxy groups through C-4 position of the naphthalimide moiety. The emissive and electron-transporting properties of the naphthalimide derivative 4a were studied by fabricating a bi-layer and tri-layer devices. Further a phosphorescent device with 4a as electron transport layer (ETL) exhibited superior performance than the device without any ETL and was comparable with the device using standard Alq3 as ETL. These results indicate that the synthesized naphthalimide derivatives could play an important role in the development of OLEDs.

  10. White and Red Organic Light Emitting Materials

    Institute of Scientific and Technical Information of China (English)

    CHOW Tahsin J.; CHIU Ching-Wen; TSAI Mu-Lin

    2004-01-01

    Derivatives of 2,3-(1,4-dialkoxyaceno)norbornadiene underwent ring-opening metathesis polymerization (ROMP) upon the catalysis of a ruthenium complex to afford the corresponding polymers. The polymeric materials containing anthracene chromophores emit white electro-luminescence, which can be fabricated into light-emitting diodes (LED). The broad emission band is composed of a blue emission from anthracene and a red emission from aggregates. A single layer device, ITO/polymer/Ca/Al, can be turned on at 7V and exhibits maximum intensity 427 cd/m2 at 15 V. A double layer device, ITO/polymer/TPBI/Mg:Ag (TPBI = (2,2′,2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)) displayed blue light with turn-on voltage 6 V and maximal intensity 930 cd/m2 at 15 V.Derivatives of bisindolylmaleimide were found to form amorphous solid films which exhibit intensive red luminescence. The property of forming glasses can be ascribed to the nonplanar geometry of these molecules. LED devices were fabricated by a layer of pure dye sandwiched between two charge transporting films. The yellow emission spectrum of the devices utilizing Alq (tris(8-hydoxyquinolinato)aluminum) contains a green component from Alq. Pure red emissions can be achieved by replacing Alq with TPBI. Typical devices can be turned on at ~3 V with maximal intensity 2000 cd/m2. White color devices are under current investigation, in which the green Alq layer is replaced by its blue derivative (bis(2-methyl-8-hydoxyquinolinato)(phenolato)aluminum).

  11. Highly Efficient Sky-Blue Fluorescent Organic Light Emitting Diode Based on Mixed Cohost System for Thermally Activated Delayed Fluorescence Emitter (2CzPN).

    Science.gov (United States)

    Sun, Jin Won; Kim, Kwon-Hyeon; Moon, Chang-Ki; Lee, Jeong-Hwan; Kim, Jang-Joo

    2016-04-20

    The mixed cohosts of 1,3-bis(N-carbazolyl)benzene and 2,8-bis(diphenylphosphoryl)dibenzothiophene have been developed for a highly efficient blue fluorescent oragnic light emitting diode (OLED) doped with a thermally activated delayed fluorescence (TADF) emitter [4,5-di (9H-carbazol-9-yl) phthalonitrile (2CzPN)]. We have demonstrated one of the highest external quantum efficiency of 21.8% in blue fluorescent OLEDs, which is identical to the theoretically achievable maximum electroluminescence efficiency using the emitter. Interestingly, the efficiency roll-off is large even under the excellent charge balance in the device and almost the same as the single host based devices, indicating that the efficiency roll-off in 2CzPN based TADF host is related to the material characteristics, such as low reverse intesystem crossing rate rather than charge imbalance.

  12. Recent Progress toward white organic light emitting diodes

    Institute of Scientific and Technical Information of China (English)

    Tao Yu-Tai

    2004-01-01

    An efficient and stable white organic light emitting diode (WOLED) is highly desirable in potential applications such as lighting, background light source, and full color display.A series of highly fluorescent dyes based on a dipyrazolopyridine skeleton,1,7-diphenyl-l,7-dihydrodipyrazolo[3,4-b,4′,3′-e]pyridine, were synthesized and evaluated as emitting as well as charge-transporting material in the fabrication of electroluminescent devices.Several of the blue derivatives are found to be useful as the source of blue emission in fabricating bright white-emitting devices. The choice of dopants, cathode materials, electron-transporting materials as well as the device configurations greatly affect the emission profile, efficiencies, as well as the device lifetime. The latest progress in achieving a more efficient, color stable, durable white light device will be discussed.

  13. Bipolar Host Materials for Organic Light-Emitting Diodes.

    Science.gov (United States)

    Yook, Kyoung Soo; Lee, Jun Yeob

    2016-02-01

    It is important to balance holes and electrons in the emitting layer of organic light-emitting diodes to maximize recombination efficiency and the accompanying external quantum efficiency. Therefore, the host materials of the emitting layer should transport both holes and electrons for the charge balance. From this perspective, bipolar hosts have been popular as the host materials of thermally activated delayed fluorescent devices and phosphorescent organic light-emitting diodes. In this review, we have summarized recent developments of bipolar hosts and suggested perspectives of host materials for organic light-emitting diodes.

  14. Organic light-emitting diodes: High-throughput virtual screening

    Science.gov (United States)

    Hirata, Shuzo; Shizu, Katsuyuki

    2016-10-01

    Computer networks, trained with data from delayed-fluorescence materials that have been successfully used in organic light-emitting diodes, facilitate the high-speed prediction of good emitters for display and lighting applications.

  15. Enhancement of the Color Rendering Index of White Organic Light-Emitting Devices Based on a Blue and Red Emitting Layer with a Y3Al5O12:Ce3+ Green Phosphor Color-Conversion Layer.

    Science.gov (United States)

    Jang, J S; Lee, K S; Lee, E J; Kwon, M S; Kim, T W

    2015-01-01

    White organic light-emitting devices (WOLEDs) were fabricated utilizing blue and red emitting organic light-emitting devices and a color conversion layer (CCL) made of yttrium aluminum garnet (YAG:Ce3+) phosphors embedded into polymethylmethacrylate. The good color balance for the color conversion of the WOLEDs was achieved utilizing 20-nm blue and 10-nm red OLEDs. The electroluminescence spectrum for the fabricated device showed a white color consisting of the blue color from the 4,4-bis(2,2-diphenylethen-1-yl)bipheny layer, the red color from the tris-(8-hydroxyquinolinato) aluminum: 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran layer, and the green color from the YAG:Ce3+ phosphor. The Commission Internationale de l'Eclairage coordinates of the WOLEDs slightly shifted from (0.25, 0.23) of the blue and red emission OLEDs without phosphors to (0.34, 0.35) of the OLEDs with green phosphors, indicative of the pure white color. WOLEDs with a CCL exhibited three wavelength white emissions with a color rendering index of 86.

  16. Towards fully spray coated organic light emitting devices

    OpenAIRE

    GILISSEN, Koen; STRYCKERS, Jeroen; Manca, Jean; DEFERME, Wim

    2014-01-01

    Pi-conjugated polymer light emitting devices have the potential to be the next generation of solid state lighting. In order to achieve this goal, a low cost, efficient and large area production process is essential. Polymer based light emitting devices are generally deposited using techniques based on solution processing e.g.: spin coating, ink jet printing. These techniques are not well suited for cost-effective, high throughput, large area mass production of these organic devices. Ultrasoni...

  17. Highly Bright White Organic Light-Emitting Diode

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ A highly bright white organic light-emitting diode (OLED) was realized by using a highly bright blue emitting layer, 1,7-diphenyl-4-biphenyl-3,5-dimethyl-l,7-dihydrodipyrazolo[3,4-b;4',3'-e]pyridine (PAP-Ph), together with a 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM)-doped Alq [tris(8-hydroxyquinolinato) aluminum (Ⅲ)] layer to provide the blue, red and green emission for color mixing. With appropriate thickness control, the white-light OLED has a performance that reaches 24700 cd/m2 at 15 V, 1.93 lm/W at 6.5 V, and >300 cd/m2 at 7.7 mA/em2. The Commission Internationale de l'Eclairage (CIE) coordinates of the emitted light vary in a very small range, from (0.35, 0.34) to (0.34, 0.35), when forward voltages change from 6 to 12 V.

  18. Highly Bright White Organic Light-Emitting Diode

    Institute of Scientific and Technical Information of China (English)

    KO; C.; W.

    2001-01-01

    A highly bright white organic light-emitting diode (OLED) was realized by using a highly bright blue emitting layer, 1,7-diphenyl-4-biphenyl-3,5-dimethyl-l,7-dihydrodipyrazolo[3,4-b;4',3'-e]pyridine (PAP-Ph), together with a 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM)-doped Alq [tris(8-hydroxyquinolinato) aluminum (Ⅲ)] layer to provide the blue, red and green emission for color mixing. With appropriate thickness control, the white-light OLED has a performance that reaches 24700 cd/m2 at 15 V, 1.93 lm/W at 6.5 V, and >300 cd/m2 at 7.7 mA/em2. The Commission Internationale de l'Eclairage (CIE) coordinates of the emitted light vary in a very small range, from (0.35, 0.34) to (0.34, 0.35), when forward voltages change from 6 to 12 V.  ……

  19. Laminated active matrix organic light-emitting devices

    Science.gov (United States)

    Liu, Hongyu; Sun, Runguang

    2008-02-01

    Laminated active matrix organic light-emitting device (AMOLED) realizing top emission by using bottom-emitting organic light-emitting diode (OLED) structure was proposed. The multilayer structure of OLED deposited in the conventional sequence is not on the thin film transistor (TFT) backplane but on the OLED plane. The contact between the indium tin oxide (ITO) electrode of TFT backplane and metal cathode of OLED plane is implemented by using transfer electrode. The stringent pixel design for aperture ratio of the bottom-emitting AMOLED, as well as special technology for the top ITO electrode of top-emitting AMOLED, is unnecessary in the laminated AMOLED.

  20. White organic light-emitting devices with mixed interfaces between light emitting layers

    Science.gov (United States)

    Lee, Young Gu; Kee, In Seo; Shim, Hong Shik; Ko, Ick Hwan; Lee, Soonil; Koh, Ken Ha

    2007-06-01

    White organic light-emitting devices with mixed interfaces between emitting layers (MI-EML WOLEDs) showed luminance and efficiency as large as 26213cd/m2 and 9.85cd/A. Efficiencies of MI-EML WOLEDs were about 1.5 times better than those of conventional three-EML WOLEDs for luminance of 1000-5000cd/m2, and their half-decay lifetime showed 3.1 times improvement. Note that if the authors operate typical active-matrix mobile-phone displays based on combination of WOLED and color filters to produce standard white emission for high definition televisions and illumination sources, MI-EML WOLEDs will have advantages of 25% less power consumption and 2.8 times longer lifetime over conventional three-EML WOLEDs.

  1. Sky-Blue Organic Light Emitting Diode with 37% External Quantum Efficiency Using Thermally Activated Delayed Fluorescence from Spiroacridine-Triazine Hybrid.

    Science.gov (United States)

    Lin, Ting-An; Chatterjee, Tanmay; Tsai, Wei-Lung; Lee, Wei-Kai; Wu, Meng-Jung; Jiao, Min; Pan, Kuan-Chung; Yi, Chih-Lung; Chung, Chin-Lung; Wong, Ken-Tsung; Wu, Chung-Chih

    2016-08-01

    Extremely efficient sky-blue organic electroluminescence with external quantum efficiency of ≈37% is achieved in a conventional planar device structure, using a highly efficient thermally activated delayed fluorescence emitter based on the spiroacridine-triazine hybrid and simultaneously possessing nearly unitary (100%) photoluminescence quantum yield, excellent thermal stability, and strongly horizontally oriented emitting dipoles (with a horizontal dipole ratio of 83%).

  2. Synthesis and electroluminescent properties of blue fluorescent materials based on 9,9-diethyl-N,N-diphenyl-9 H-fluoren-2-amine substituted anthracene derivatives for organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seul Bee; Kim, Chanwoo; Park, Soo Na; Kim, Young Seok [Department of Chemistry, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Lee, Ho Won [Department of Information Display, Hongik University, Seoul, 121-791 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@hongik.ac.kr [Department of Information Display, Hongik University, Seoul, 121-791 (Korea, Republic of); Yoon, Seung Soo, E-mail: ssyoon@skku.edu [Department of Chemistry, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of)

    2015-11-30

    Four 9,9-diethyl-N,N-diphenyl-9 H-fluoren-2-amine substituted anthracene derivatives have been designed and synthesized by Suzuki cross coupling reactions. To explore the electroluminescent properties of these blue materials, multilayer blue organic light-emitting diodes were fabricated in the following device structure: indium tin oxide (180 nm)/N,N’-diphenyl-N,N’-(1-napthyl)-(1,1′-phenyl)-4,4′-diamine (50 nm)/blue emitting materials (1–4) (30 nm)/bathophenanthroline (30 nm)/lithium quinolate (2 nm)/Al (100 nm). All devices appeared excellent deep-blue emissions. Among them, a device exhibited a maximum luminance of 5686 cd/m{sup 2}, the luminous, power and external quantum efficiencies of 5.11 cd/A, 3.79 lm/W, and 4.06% with the Commission International de L'Eclairage coordinates of (0.15, 0.15) at 500 cd/m{sup 2}, respectively. - Highlights: • We synthesized blue fluorescent materials based on anthracene derivatives. • The EL efficiencies of these materials depend on the quantum yields in solid states. • These materials have great potential for applications as blue emitter in OLEDs.

  3. Toward inkjet printing of small molecule organic light emitting diodes

    NARCIS (Netherlands)

    Gorter, H.; Coenen, M.J.J.; Slaats, M.W.L.; Ren, M.; Lu, W.; Kuijpers, C.J.; Groen, W.A.

    2013-01-01

    Thermal evaporation is the current standard for the manufacture of small molecule organic light emitting diodes (smOLEDs), but it requires vacuum process, complicated shadow masks and is inefficient in material utilization, resulting in high cost of ownership. As an alternative, wet solution deposit

  4. Organic light emitting diodes with structured electrodes

    Science.gov (United States)

    Mao, Samuel S.; Liu, Gao; Johnson, Stephen G.

    2012-12-04

    A cathode that contain nanostructures that extend into the organic layer of an OLED has been described. The cathode can have an array of nanotubes or a layer of nanoclusters extending out from its surface. In another arrangement, the cathode is patterned and etched to form protruding nanostructures using a standard lithographic process. Various methods for fabricating these structures are provided, all of which are compatible with large-scale manufacturing. OLEDs made with these novel electrodes have greatly enhanced electron injection, have good environmental stability.

  5. Magnetoelectroluminescence in organic light emitting diodes

    CERN Document Server

    Lawrence, Joseph E; Manolopoulos, David E; Hore, P J

    2016-01-01

    The magnetoelectroluminescence of conjugated organic polymer films is widely accepted to arise from a polaron pair mechanism, but their magnetoconductance is less well understood. Here we derive a new relationship between the experimentally measurable magnetoelectroluminescence and magnetoconductance and the theoretically calculable singlet yield of the polaron pair recombination reaction. This relationship is expected to be valid regardless of the mechanism of the magnetoconductance, provided the mobilities of the free polarons are independent of the applied magnetic field (i.e., provided one discounts the possibility of spin-dependent transport). We also discuss the semiclassical calculation of the singlet yield of the polaron pair recombination reaction for materials such as poly(2,5-dioctyloxy-paraphenylene vinylene) (DOO-PPV), the hyperfine fields in the polarons of which can be extracted from light-induced electron spin resonance measurements. The resulting theory is shown to give good agreement with ex...

  6. Blue Light Emitting Diodes based on a partially conjugated Si-containing PPV-copolymer in a multilayer configuration

    NARCIS (Netherlands)

    Garten, F; Hilberer, A; Cacialli, F.; Esselink, F.J; van Dam, Y.; Schlatmann, A.R.; Friend, R.H.; Klapwijk, T.M; Hadziioannou, G

    1997-01-01

    Efficient blue Light Emitting Diodes (LEDs) based on a novel partially conjugated co-polymer (SiPPV) have been realized by a combination of techniques known to enhance the quantum efficiency of organic devices. The copolymer is homogeneously blended in a PVK-matrix to reduce the number of non-radiat

  7. Concave-hemisphere-patterned organic top-light emitting device

    Energy Technology Data Exchange (ETDEWEB)

    Forrest, Stephen R.; Slootsky, Michael; Lunt, Richard

    2015-06-09

    A first device is provided. The first device includes an organic light emitting device, which further comprises a first electrode, a second electrode, and an organic emissive layer disposed between the first and second electrode. Preferably, the second electrode is more transparent than the first electrode. The organic emissive layer has a first portion shaped to form an indentation in the direction of the first electrode, and a second portion shaped to form a protrusion in the direction of the second electrode. The first device may include a plurality of organic light emitting devices. The indentation may have a shape that is formed from a partial sphere, a partial cylinder, a pyramid, or a pyramid with a mesa, among others. The protrusions may be formed between adjoining indentations or between an indentation and a surface parallel to the substrate.

  8. New Optoelectronic Technology Simplified for Organic Light Emitting Diode (OLED)

    OpenAIRE

    Andre F. S. Guedes; Vilmar P. Guedes; Simone Tartari; Mônica L. Souza; Idaulo J. Cunha

    2014-01-01

    The development of Organic Light Emitting Diode (OLED), using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The OLED are the base Poly (3,4-ethylenedioxythiophene), PEDOT, and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by UV-Visible Spectroscopy (UV-Vis), Optical Parameters (OP) and Scanning Electron Microscopy (SEM). In addition,...

  9. Organic Light-Emitting Diodes Driven by Organic Transistors

    Institute of Scientific and Technical Information of China (English)

    胡远川; 董桂芳; 王立铎; 梁琰; 邱勇

    2004-01-01

    Organic thin-film field-effect transistors (OTFTs) with pentacene as the semiconductor have been fabricated for driving an organic light-emitting diode (OLED). The driving circuit includes two OTFTs and one storage capacitor. The field-effect mobility of the transistors in the driving circuit is more than 0.3 cm2/Vs, and the on/off ratio is larger than 104. The light-emission area of the OLED is 0. 04mm2 and the brightness is larger than 400cd/m2 when the selected line voltage, data line voltage and drive voltage all are -40 V. The responding characteristics and holding characteristics are also researched when the selected line voltage and the date line voltage are changed.

  10. Phosphorescent organic light emitting diodes with high efficiency and brightness

    Science.gov (United States)

    Forrest, Stephen R; Zhang, Yifan

    2015-11-12

    An organic light emitting device including a) an anode; b) a cathode; and c) an emissive layer disposed between the anode and the cathode, the emissive layer comprising an organic host compound and a phosphorescent compound exhibiting a Stokes Shift overlap greater than 0.3 eV. The organic light emitting device may further include a hole transport layer disposed between the emissive layer and the anode; and an electron transport layer disposed between the emissive layer and the cathode. In some embodiments, the phosphorescent compound exhibits a phosphorescent lifetime of less than 10 .mu.s. In some embodiments, the concentration of the phosphorescent compound ranges from 0.5 wt. % to 10 wt. %.

  11. Organic light-emitting diodes from homoleptic square planar complexes

    Science.gov (United States)

    Omary, Mohammad A

    2013-11-12

    Homoleptic square planar complexes [M(N.LAMBDA.N).sub.2], wherein two identical N.LAMBDA.N bidentate anionic ligands are coordinated to the M(II) metal center, including bidentate square planar complexes of triazolates, possess optical and electrical properties that make them useful for a wide variety of optical and electrical devices and applications. In particular, the complexes are useful for obtaining white or monochromatic organic light-emitting diodes ("OLEDs"). Improved white organic light emitting diode ("WOLED") designs have improved efficacy and/or color stability at high brightness in single- or two-emitter white or monochrome OLEDs that utilize homoleptic square planar complexes, including bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) ("Pt(ptp).sub.2").

  12. Fabrication of natural DNA-containing organic light emitting diodes

    Science.gov (United States)

    Gomez, Eliot F.; Spaeth, Hans D.; Steckl, Andrew J.; Grote, James G.

    2011-09-01

    The process of creating natural DNA-containing bio-organic light emitting diodes is a fascinating journey from salmon fish to the highly-efficient BiOLED. DNA from salmon sperm is used as a high-performance electron blocking layer, to enhance the efficiency of the BiOLED over its conventional OLED counterpart. An overview of the BiOLED fabrication process and its key steps are presented in this paper.

  13. Highly Efficient, Simplified, Solution-Processed Thermally Activated Delayed-Fluorescence Organic Light-Emitting Diodes.

    Science.gov (United States)

    Kim, Young-Hoon; Wolf, Christoph; Cho, Himchan; Jeong, Su-Hun; Lee, Tae-Woo

    2016-01-27

    Highly efficient, simplified, solution-processed thermally activated delayed-fluorescence organic light-emitting diodes can be realized by using pure-organic thermally activated delayed fluorescence emitters and a multifunctional buffer hole-injection layer, in which high EQE (≈24%) and current efficiency (≈73 cd A(-1) ) are demonstrated. High-efficiency fluorescence red-emitting and blue-emitting devices can also be fabricated in this manner.

  14. Achieving Pure Deep-Blue Electroluminescence with CIE y≤0.06 via a Rational Design Approach for Highly Efficient Non-Doped Solution-Processed Organic Light-Emitting Diodes.

    Science.gov (United States)

    Reddy, Saripally Sudhaker; Sree, Vijaya Gopalan; Cho, Woosum; Jin, Sung-Ho

    2016-11-22

    Deep-blue fluorescent emitters with Commission Internationale de l'Eclairage (CIE) y≤0.06 are urgently needed for high-density storage, full-color displays and solid-state lighting. However, developing such emitters with high color purity and efficiency in solution-processable non-doped organic light-emitting diodes (OLEDs) remains an important challenge. Here, we present the synthesis of two new deep-blue fluorescent emitters (AFpTPI and AFmTPI) based on 10-(9,9-diethyl-9H-fluoren-2-yl)-9,9-dimethyl-9,10-dihydroacridine as a core and 1,3- and/or 1,4-phenylene-linked triphenylimidazole (TPI) analogues for non-doped solution-processable OLEDs. Their thermal, photophysical, electrochemical, and device characteristics are explored, and also strongly supported by density functional theory (DFT) study. AFpTPI and AFmTPI exhibit excellent thermal stability (≈450 °C) with high glass transition temperatures (Tg ; 141-152 °C) and deep-blue emission with high quantum yields. Specifically, the solution-processed non-doped device with AFpTPI as an emitter exhibits a maximum external quantum efficiency (EQE) of 4.56 % with CIE coordinates of (0.15, 0.06), which exactly matches the European Broadcasting Union (EBU) blue standard. In addition, AFmTPI also displays good efficiency and better color purity (EQE: 3.37 %; CIE (0.15, 0.05)). To the best of our knowledge, the present work is the first report on non-doped solution-processable OLEDs with efficiency close to 5 % and CIE y≤0.06.

  15. Organic Light-Emitting Transistors: Materials, Device Configurations, and Operations.

    Science.gov (United States)

    Zhang, Congcong; Chen, Penglei; Hu, Wenping

    2016-03-09

    Organic light-emitting transistors (OLETs) represent an emerging class of organic optoelectronic devices, wherein the electrical switching capability of organic field-effect transistors (OFETs) and the light-generation capability of organic light-emitting diodes (OLEDs) are inherently incorporated in a single device. In contrast to conventional OFETs and OLEDs, the planar device geometry and the versatile multifunctional nature of OLETs not only endow them with numerous technological opportunities in the frontier fields of highly integrated organic electronics, but also render them ideal scientific scaffolds to address the fundamental physical events of organic semiconductors and devices. This review article summarizes the recent advancements on OLETs in light of materials, device configurations, operation conditions, etc. Diverse state-of-the-art protocols, including bulk heterojunction, layered heterojunction and laterally arranged heterojunction structures, as well as asymmetric source-drain electrodes, and innovative dielectric layers, which have been developed for the construction of qualified OLETs and for shedding new and deep light on the working principles of OLETs, are highlighted by addressing representative paradigms. This review intends to provide readers with a deeper understanding of the design of future OLETs.

  16. Blue laser diode (LD) and light emitting diode (LED) applications

    Science.gov (United States)

    Bergh, Arpad A.

    2004-09-01

    The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography.As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc.Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity.Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care.

  17. Capturing triplet emission in white organic light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [Faculty of EHSE, School of Engineering and IT, B-purple-12, Charles Darwin University, Darwin, NT 0909 (Australia)

    2011-08-15

    The state-of-the art in the white organic light emitting devices (WOLEDs) is reviewed for further developments with a view to enhance the capture of triplet emission. In particular, applying the new exciton-spin-orbit-photon interaction operator as a perturbation, rates of spontaneous emission are calculated in a few phosphorescent materials and compared with experimental results. For iridium based phosphorescent materials the rates agree quite well with the experimental results. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Numerical model of multilayer organic light-emitting devices

    Institute of Scientific and Technical Information of China (English)

    Hu Yue; Rao Hai-Bo

    2009-01-01

    A numerical model of multilayer organic light-emitting devices is presented in this article.This model is based on the drift-diffusion equations which include charge injection,transport,space charge effects,trapping,heterojunction interface and recombination process.The device structure in the simulation is ITO/CuPc(20 nm)/NPD(40 nm)/Alq3(60 nm)/LiF/Al.There are two heterojunctions which should be dealt with in the simulation.The Ⅰ-Ⅴ characteristics,carrier distribution and recombination rate of a device are calculated.The simulation results and measured data are in good agreement.

  19. Tungsten oxide buffer layers fabricated in an inert sol-gel process at room-temperature for blue organic light-emitting diodes.

    Science.gov (United States)

    Höfle, Stefan; Bruns, Michael; Strässle, Stefan; Feldmann, Claus; Lemmer, Uli; Colsmann, Alexander

    2013-08-14

    WO3 deposition from tungsten ethoxide precursor solutions at room temperature is demonstrated. The W(OEt)6 precursor can be converted under inert conditions and hence avoids sample contamination with oxygen, opening a pathway to more stable devices. The stoichiometry of all WO3 layers and the optoelectronic performance of the respective SMOLEDs well match thermally evaporated WO3 and its corresponding SMOLEDs. The solution processed WO3 hole injection layers enable the fabrication of blue phosphorescent OLEDs with low onset voltage and current efficiencies of up to 14 cd A(-1) .

  20. New Optoelectronic Technology Simplified for Organic Light Emitting Diode (OLED

    Directory of Open Access Journals (Sweden)

    Andre F. S. Guedes

    2014-06-01

    Full Text Available The development of Organic Light Emitting Diode (OLED, using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The OLED are the base Poly (3,4-ethylenedioxythiophene, PEDOT, and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by UV-Visible Spectroscopy (UV-Vis, Optical Parameters (OP and Scanning Electron Microscopy (SEM. In addition, the thin film obtained by the deposition of PANI, prepared in perchloric acid solution, was identified through PANI-X1. The result obtained by UV-Vis has demonstrated that the Quartz/ITO/PEDOT/PANI-X1 layer does not have displacement of absorption for wavelengths greaters after spin-coating and electrodeposition. Thus, the spectral irradiance of the OLED informed the irradiance of 100 W/m2, and this result, compared with the standard Light Emitting Diode (LED, has indicated that the OLED has higher irradiance. After 1000 hours of electrical OLED tests, the appearance of nanoparticles visible for images by SEM, to the migration process of organic semiconductor materials, was present, then. Still, similar to the phenomenon of electromigration observed in connections and interconnections of microelectronic devices, the results have revealed a new mechanism of migration, which raises the passage of electric current in OLED.

  1. Charge transport and recombination in polyspirobifluorene blue light-emitting diodes

    NARCIS (Netherlands)

    Nicolai, H.T.; Hof, A.; Oosthoek, J.L.M.; Blom, P.W.M.

    2011-01-01

    The charge transport in blue light-emitting polyspirobifluorene is investigated by both steady-state current-voltage measurements and transient electroluminescence. Both measurement techniques yield consistent results and show that the hole transport is space-charge limited. The electron current is

  2. C60/N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine:MoO3 as the interconnection layer for high efficient tandem blue fluorescent organic light-emitting diodes.

    Science.gov (United States)

    Wu, Xiaoming; Bi, Wentao; Hua, Yulin; Sun, Jin'e; Xiao, Zhihui; Wang, Li; Yin, Shougen

    2013-06-17

    The high efficient tandem blue fluorescent organic light emitting diodes (OLEDs) with the transparent interconnection layer (ICL) of fullerence (C60)/Molybdenum oxide (MoO3)-doped N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) were presented. A stack consisting of 0.5 nm of LiF and 1 nm of Ca, which is located from C60 to adjacent electron transporting layer is used as an electron injection layer. The experiment results indicate that the luminance of the tandem device is basically equal to that of the traditional single-unit device, but the current density of the tandem device is much less than that of the single-unit device under a same luminance. The current efficiency and the maximal power efficiency of tandem device with LiF/Ca/C60/NPB:MoO3/MoO3-based interconnection layer have been approximately enhanced by 250% and 126%, respectively. In addition, we also analyze that the mechanism of the efficiency enhancement is ascribed to the effective charge separation and transport of the ICL in tandem OLEDs.

  3. Blue light emitting diodes for optical stimulation of quartz in retrospective dosimetry and dating

    DEFF Research Database (Denmark)

    Bøtter-Jensen, L.; Duller, G.A.T.; Murray, A.S.;

    1999-01-01

    Recently developed blue light emitting diodes (LEDs) for the optical stimulation of quartz for use in routine optically stimulated luminescence (OSL) dating and retrospective dosimetry have been tested. For similar power densities, it was found that the higher energy light provided by the blue LEDs...... (470 nm) gives order of magnitude greater rate of stimulation in quartz than that from conventional blue-green light filtered from a halogen lamp. A practical blue LED OSL configuration is described. From comparisons of OSL decay curves produced by green and blue light sources, and by examination...

  4. Device Optimization and Transient Electroluminescence Studies of Organic light Emitting Devices

    Energy Technology Data Exchange (ETDEWEB)

    Lijuan Zou

    2003-08-05

    Organic light emitting devices (OLEDs) are among the most promising for flat panel display technologies. They are light, bright, flexible, and cost effective. And while they are emerging in commercial product, their low power efficiency and long-term degradation are still challenging. The aim of this work was to investigate their device physics and improve their performance. Violet and blue OLEDs were studied. The devices were prepared by thermal vapor deposition in high vacuum. The combinatorial method was employed in device preparation. Both continuous wave and transient electroluminescence (EL) were studied. A new efficient and intense UV-violet light emitting device was developed. At a current density of 10 mA/cm{sup 2}, the optimal radiance R could reach 0.38 mW/cm{sup 2}, and the quantum efficiency was 1.25%. using the delayed EL technique, electron mobilities in DPVBi and CBP were determined to be {approx} 10{sup -5} cm{sup 2}/Vs and {approx} 10{sup -4} cm{sup 2}/Vs, respectively. Overshoot effects in the transient El of blue light emitting devices were also observed and studied. This effect was attributed to the charge accumulation at the organic/organic and organic/cathode interfaces.

  5. Substituent effect to prevent autoxidation and improve spectral stability in blue light-emitting polyfluorenes.

    Science.gov (United States)

    Li, Jiu Yan; Ziegler, Andreas; Wegner, Gerhard

    2005-07-18

    A group of fluorene-based polymers, PF-1SOR and PF-2SOR, were synthesized and characterized as blue light-emitting materials. PF-1SOR and PF-2SOR displayed nematic liquid crystalline mesophase in films cast from solution. Compared with conventional polyfluorene, PF-1SOR and PF-2SOR display blue-shifted UV absorption and structureless blue fluorescence. The photoluminescence spectra of PF-1SOR and PF-2SOR were found insensitive against thermal treatment in air up to 200 degrees C and the blue electroluminescence in their light-emitting devices was independent of the driving voltage. Compared to the conventional polyfluorenes, the improved spectral stability of these polymers is attributed to the anti-oxidization effect of (3,5-di(tert-butyl)phenoxy)sulfonyl side groups attached to the backbone.

  6. Simulations of charge transport in organic light emitting diodes

    CERN Document Server

    Martin, S J

    2002-01-01

    In this thesis, two approaches to the modelling of charge transport in organic light emitting diodes (OLEDs) are presented. The first is a drift-diffusion model, normally used when considering conventional crystalline inorganic semiconductors (e.g. Si or lll-V's) which have well defined energy bands. In this model, electron and hole transport is described using the current continuity equations and the drift-diffusion current equations, and coupled to Poisson's equation. These equations are solved with the appropriate boundary conditions, which for OLEDs are Schottky contacts; carriers are injected by thermionic emission and tunnelling. The disordered nature of the organic semiconductors is accounted for by the inclusion of field-dependent carrier mobilities and Langevin optical recombination. The second approach treats the transport of carriers in disordered organic semi-conductors as a hopping process between spatially and energetically disordered sites. This method has been used previously to account for th...

  7. Molecular-scale simulation of electroluminescence in a multilayer white organic light-emitting diode

    DEFF Research Database (Denmark)

    Mesta, Murat; Carvelli, Marco; de Vries, Rein J;

    2013-01-01

    we show that it is feasible to carry out Monte Carlo simulations including all of these molecular-scale processes for a hybrid multilayer organic light-emitting diode combining red and green phosphorescent layers with a blue fluorescent layer. The simulated current density and emission profile......In multilayer white organic light-emitting diodes the electronic processes in the various layers--injection and motion of charges as well as generation, diffusion and radiative decay of excitons--should be concerted such that efficient, stable and colour-balanced electroluminescence can occur. Here...... are shown to agree well with experiment. The experimental emission profile was obtained with nanometre resolution from the measured angle- and polarization-dependent emission spectra. The simulations elucidate the crucial role of exciton transfer from green to red and the efficiency loss due to excitons...

  8. Luminescent Enhancement of Heterostructure Organic Light-Emitting Devices Based on Aluminum Quinolines

    Institute of Scientific and Technical Information of China (English)

    Jun-Sheng Yu; Lu Li; Ya-Dong Jiang; Xing-Qiao Ji; Tao Wang

    2007-01-01

    High performance organic light-emitting devices (OLEDs) have been investigated by using fluorescent bis (2-methyl-8-quinolinolato)(para-phenyl-phenolato)aluminum(BAlq) as an emissive layer on the performance of multicolor devices consisting of N, N'-bis-(1-naphthyl)-N,N'diphenyI-l,l'-biphenyI-4,4'-diamine (NPB) as hole transport layer. The results show that the performance of heterostructure blue light-emitting device composed of 8-hydroxyquinoline aluminum (Alq3) as an electron transport layer has been dramatically enhanced. In the case of high performance heterostructure devices, the electroluminescent spectra has been perceived to vary strongly with the thickness of the organic layers due to the different recombination region, which indicates that various color devices composed of identical components could be implemented by changing the film thickness of different functional layers.

  9. Model for Triplet State Engineering in Organic Light Emitting Diodes

    CERN Document Server

    Prodhan, Suryoday; Ramasesha, S

    2014-01-01

    Engineering the position of the lowest triplet state (T1) relative to the first excited singlet state (S1) is of great importance in improving the efficiencies of organic light emitting diodes and organic photovoltaic cells. We have carried out model exact calculations of substituted polyene chains to understand the factors that affect the energy gap between S1 and T1. The factors studied are backbone dimerisation, different donor-acceptor substitutions and twisted geometry. The largest system studied is an eighteen carbon polyene which spans a Hilbert space of about 991 million. We show that for reverse intersystem crossing (RISC) process, the best system involves substituting all carbon sites on one half of the polyene with donors and the other half with acceptors.

  10. Escaped and Trapped Emission of Organic Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    LIANG Shi-Xiong; WU Zhao-Xin; ZHAO Xuan-Ke; HOU Xun

    2012-01-01

    By locating the emitters around the first and second antinode of the metal electrode, the escaped and trapped emission of small molecule based bottom emission organic light-emitting diodes is investigated by using an integrating sphere, a fiber spectrometer and a glass hemisphere. It is found that the external coupling ratio by locating the emitters at the second antinode (at a distance of 220 nm from the cathode) is 70%, which is higher than that of an emitter at the first antinode (60 nm from the cathode) in theory and experiment. Extending the "half-space" dipole model by taking the dipole radiation pattern into account, we also calculate the optical coupling efficiency for the emitter at both the first and second antinode. Our experimental and theoretical results will benefit the optimization of device structures for the higher out-coupling efficiency.%By locating the emitters around the first and second antinode of the metal electrode,the escaped and trapped emission of small molecule based bottom emission organic light-emitting diodes is investigated by using an integrating sphere,a fiber spectrometer and a glass hemisphere.It is found that the external coupling ratio by locating the emitters at the second antinode (at a distance of 220 nm from the cathode) is 70%,which is higher than that of an emitter at the first antinode (60nm from the cathode) in theory and experiment.Extending the "half-space" dipole model by taking the dipole radiation pattern into account,we also calculate the optical coupling efficiency for the emitter at both the first and second antinode.Our experimental and theoretical results will benefit the optimization of device structures for the higher out-coupling efficiency.

  11. An Improved Blue Polymer Light-Emitting Diode by Using Sodium Hydroxide/Ca/Al Cathode

    Institute of Scientific and Technical Information of China (English)

    MA Liang; XIE Zhi-Yuan; LIU Jun; YANG Jun-Wei; CHENG Yan-Xiang; WANG Li-Xiang; WANG Fo-Song

    2005-01-01

    @@ The performance of blue polymer light-emitting diodes (PLEDs) based on poly(9,9-dioctylfluorene) (PFO) is improved by introducing a thin layer of sodium hydroxide (NaOH) between the calcium cathode and the PFO emissive layer. By replacing the commonly used Ca/Al cathode by a NaOH (2.5nm)/Ca (10 nm)/Al cathode,the driving voltage is reduced from 8.3 V to 5.4 V and the light-emitting efficiency is enhanced from 0.46cd/A to 0. 72 cd/A for achieving a luminance of 500 cd/m2, respectively. Moreover, the device with NaOH/Ca/Al cathode shows a pure blue emission of (0.17, 0. 12) at high brightnesses. These improvements are attributed to introduction of a thin layer of NaOH that can lower the interfacial barrier and facilitate electron injection.

  12. Gap state related blue light emitting boron-carbon core shell structures

    Science.gov (United States)

    Singh, Paviter; Kaur, Manpreet; Singh, Bikramjeet; Kaur, Gurpreet; Singh, Kulwinder; Kumar, Manjeet; Bala, Rajni; Thakur, Anup; Kumar, Akshay

    2016-05-01

    Boron- carbon core shell structures have been synthesized by solvo-thermal synthesis route. The synthesized material is highly pure. X-ray diffraction analysis confirms the reduction of reactants in to boron and carbon. Scanning Electron Microscopy (SEM) analysis showed that the shell is uniform with average thickness of 340 nm. Photo luminescence studies showed that the material is blue light emitting with CIE color coordinates: x=0.16085, y=0.07554.

  13. Thin film Encapsulations of Flexible Organic Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Tsai Fa-Ta

    2016-01-01

    Full Text Available Various encapsulated films for flexible organic light emitting diodes (OLEDs were studied in this work, where gas barrier layers including inorganic Al2O3 thin films prepared by atomic layer deposition, organic Parylene C thin films prepared by chemical vapor deposition, and their combination were considered. The transmittance and water vapor transmission rate of the various organic and inorgabic encapsulated films were tested. The effects of the encapsulated films on the luminance and current density of the OLEDs were discussed, and the life time experiments of the OLEDs with these encapsulated films were also conducted. The results showed that the transmittance are acceptable even the PET substrate were coated two Al2O3 and Parylene C layers. The results also indicated the WVTR of the PET substrate improved by coating the barrier layers. In the encapsulation performance, it indicates the OLED with Al2O3 /PET, 1 pair/PET, and 2 pairs/PET presents similarly higher luminance than the other two cases. Although the 1 pair/PET encapsulation behaves a litter better luminance than the 2 pairs/PET encapsulation, the 2 pairs/PET encapsulation has much better life time. The OLED with 2 pairs/PET encapsulation behaves near double life time to the 1 pair encapsulation, and four times to none encapsulation.

  14. Background story of the invention of efficient blue InGaN light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Shuji [University of California, Santa Barbara, CA (United States)

    2015-06-15

    Shuji Nakamura discovered p-type doping in Gallium Nitride (GaN) and developed blue, green, and white InGaN based light emitting diodes (LEDs) and blue laser diodes (LDs). His inventions made possible energy efficient, solid-state lighting systems and enabled the next generation of optical storage. Together with Isamu Akasaki and Hiroshi Amano, he is one of the three recipients of the 2014 Nobel Prize in Physics. In his Nobel lecture, Shuji Nakamura gives an overview of this research and the story of his inventions. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Active Matrix Organic Light Emitting Diode (AMOLED) Environmental Test Report

    Science.gov (United States)

    Salazar, George A.

    2013-01-01

    This report focuses on the limited environmental testing of the AMOLED display performed as an engineering evaluation by The NASA Johnson Space Center (JSC)-specifically. EMI. Thermal Vac, and radiation tests. The AMOLED display is an active-matrix Organic Light Emitting Diode (OLED) technology. The testing provided an initial understanding of the technology and its suitability for space applications. Relative to light emitting diode (LED) displays or liquid crystal displays (LCDs), AMOLED displays provide a superior viewing experience even though they are much lighter and smaller, produce higher contrast ratio and richer colors, and require less power to operate than LCDs. However, AMOLED technology has not been demonstrated in a space environment. Therefore, some risks with the technology must be addressed before they can be seriously considered for human spaceflight. The environmental tests provided preliminary performance data on the ability of the display technology to handle some of the simulated induced space/spacecraft environments that an AMOLED display will see during a spacecraft certification test program. This engineering evaluation is part of a Space Act Agreement (SM) between The NASA/JSC and Honeywell International (HI) as a collaborative effort to evaluate the potential use of AMOLED technology for future human spaceflight missions- both government-led and commercial. Under this SM, HI is responsible for doing optical performance evaluation, as well as temperature and touch screen studies. The NASA/JSC is responsible for performing environmental testing comprised of EMI, Thermal Vac, and radiation tests. Additionally, as part of the testing, limited optical data was acquired to assess performance as the display was subjected to the induced environments. The NASA will benefit from this engineering evaluation by understanding AMOLED suitability for future use in space as well as becoming a smarter buyer (or developer) of the technology. HI benefits

  16. Spectral variation of light-emitting diodes based on organic molecules doped polymer

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Organic light-emitting diodes based on naphthylimine-gallium complexes doped into a PPV derivative have been fabricated by a spin coating method.Color variation from green to blue with increase of the applied voltage has been observed.And the electroluminescent intensity of the blend samples is much stronger than that of the samples containing the complexes only.The results have been attributed to the variation of the recombination zone and the charge transfer between the materials.The process of the charge transport has been analyzed in detail.

  17. White organic light-emitting device with both phosphorescent and fluorescent emissive layers

    Institute of Scientific and Technical Information of China (English)

    Zhang Li-Juan; Hun Yu-Lin; Wu Xiao-Ming; Wang Yu; Yin Shou-Geng

    2008-01-01

    This paper reports the fabrication of novel white organic light-emitting device(WOLED) by using a high efficiency blue fluorescent dye N-(4-((E)-2-(6-((E)-4-(diphenylamino)styryl)naphthalen-2-yl)vinyl)phenyl)-N-phenylbenzenamine (N-BDAVBi) and a red phosphoresecent dye bis (1-(phenyl) isoquinoline) iridium (Ⅲ) acety-lanetonate (Ir(piq)2(acac)). The configuration of the device was ITO/PVK:TPD/CBP: N-BDAVBi /CBP/ BALq:Ir(piq)2(acac)/BCP/Alq3/LiF:AL. By adjusting the proportion of the dopants (N-BDAVBi, Ir(piq)2(acac)) in the light-emitting layer, white light with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35, 0.35) and a maximum luminance of 25350cd/m2 were obtained at an applied voltage of 22V. The WOLED exhibits maximum external quantum and current efficiency of 6.78% and 12ed/A respectively. By placing an undoped spacer CBP layer between the two light-emitting layers and using BCP as hole blocking layer, the colour stabilization slightly changed when the driving voltage increased from 6 to 22 V.

  18. Exciton quenching at PEDOT:PSS anode in polymer blue-light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Abbaszadeh, D.; Wetzelaer, G. A. H. [Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen (Netherlands); Dutch Polymer Institute, P.O. Box 902, 5600 AX, Eindhoven (Netherlands); Nicolai, H. T. [TNO/Holst Centre, High Tech Campus 31, 5605 KN, Eindhoven (Netherlands); Blom, P. W. M., E-mail: blom@mpip-mainz.mpg.de [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany); Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia)

    2014-12-14

    The quenching of excitons at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) anode in blue polyalkoxyspirobifluorene-arylamine polymer light-emitting diodes is investigated. Due to the combination of a higher electron mobility and the presence of electron traps, the recombination zone shifts from the cathode to the anode with increasing voltage. The exciton quenching at the anode at higher voltages leads to an efficiency roll-off. The voltage dependence of the luminous efficiency is reproduced by a drift-diffusion model under the condition that quenching of excitons at the PEDOT:PSS anode and metallic cathode is of equal strength. Experimentally, the efficiency roll-off at high voltages due to anode quenching is eliminated by the use of an electron-blocking layer between the anode and the light-emitting polymer.

  19. Optimized Performances of Thick Film Organic Lighting-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    WANG Xiu-Ru; ZHANG Zhi-Qiang; MA Dong-Ge; SUN Run-Guang

    2008-01-01

    @@ The performance of organic light-emitting diodes (OLEDs) with thick film is optimized.The alternative vana-dium oxide (V2O5) and N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB) layers are used to enhance holes in the emissive region, and 4,7-dipheny-1,10-phenanthroline (Bphen) doped 8-tris-hydroxyquinoline alu-minium (Alq3) is used to enhance electrons is the emissive region, thus ITO/V2O5 (8nm)/NPB (52nm)/V2O5 (8nm)/NPB (52 nm)/Alq3 (30 and 45 nm)/Alq3:Bphen (30wt%, 30 and 45 nm)/LiF (1 nm)/Al (120nm) devices are fabricated.The thick-film devices show the turn-on voltage of about 3 V and the maximal power efficiency of 4.51m/W, which is 1.46 times higher than the conventional thin-film OLEDs.

  20. Emerging Transparent Conducting Electrodes for Organic Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Tze-Bin Song

    2014-03-01

    Full Text Available Organic light emitting diodes (OLEDs have attracted much attention in recent years as next generation lighting and displays, due to their many advantages, including superb performance, mechanical flexibility, ease of fabrication, chemical versatility, etc. In order to fully realize the highly flexible features, reduce the cost and further improve the performance of OLED devices, replacing the conventional indium tin oxide with better alternative transparent conducting electrodes (TCEs is a crucial step. In this review, we focus on the emerging alternative TCE materials for OLED applications, including carbon nanotubes (CNTs, metallic nanowires, conductive polymers and graphene. These materials are selected, because they have been applied as transparent electrodes for OLED devices and achieved reasonably good performance or even higher device performance than that of indium tin oxide (ITO glass. Various electrode modification techniques and their effects on the device performance are presented. The effects of new TCEs on light extraction, device performance and reliability are discussed. Highly flexible, stretchable and efficient OLED devices are achieved based on these alternative TCEs. These results are summarized for each material. The advantages and current challenges of these TCE materials are also identified.

  1. Comparison between blue lasers and light-emitting diodes for future solid-state lighting: Comparison between blue lasers and light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wierer, Jonathan J. [Sandia National Laboratories, Albuquerque NM 87185 USA; Tsao, Jeffrey Y. [Sandia National Laboratories, Albuquerque NM 87185 USA; Sizov, Dmitry S. [Corning Incorporated, One Science Center Dr., Corning NY 14831 USA

    2013-08-01

    Solid-state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light-emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state-of-the-art input-power-density-dependent power-conversion efficiencies; potential improvements both in their peak power-conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL.

  2. Using Organic Light-Emitting Electrochemical Thin-Film Devices to Teach Materials Science

    Science.gov (United States)

    Sevian, Hannah; Muller, Sean; Rudmann, Hartmut; Rubner, Michael F.

    2004-01-01

    Materials science can be taught by applying organic light-emitting electrochemical thin-film devices and in this method students were allowed to make a light-emitting device by spin coating a thin film containing ruthenium (II) complex ions onto a glass slide. Through this laboratory method students are provided with the opportunity to learn about…

  3. Organic Single-Crystal Light-Emitting Transistor Coupling with Optical Feedback Resonators

    NARCIS (Netherlands)

    Bisri, Satria Zulkarnaen; Sawabe, Kosuke; Imakawa, Masaki; Maruyama, Kenichi; Yamao, Takeshi; Hotta, Shu; Iwasa, Yoshihiro; Takenobu, Taishi

    2012-01-01

    Organic light-emitting transistors (OLETs) are of great research interest because they combine the advantage of the active channel of a transistor that can control the luminescence of an in-situ light-emitting diode in the same device. Here we report a novel single-crystal OLET (SCLET) that is coupl

  4. Magnetic field effect in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Niedermeier, Ulrich

    2009-12-14

    The discovery of a magnetic field dependent resistance change of organic light emitting diodes (OLEDs) in the year 2003 has attracted considerable scientific and industrial research interest. However, despite previous progress in the field of organic spin-electronics, the phenomenon of the ''organic magnetoresistance (OMR) effect'' is not yet completely understood. In order to improve the understanding of the microscopic mechanisms which ultimately cause the OMR effect, experimental investigations as well as theoretical considerations concerning the OMR are addressed in this thesis. In polymer-based OLED devices the functional dependencies of the OMR effect on relevant parameters like magnetic field, operating voltage, operating current and temperature are investigated. Based on these results, previously published models for potential OMR mechanisms are critically analyzed and evaluated. Finally, a concept for the OMR effect is favored which suggests magnetic field dependent changes of the spin state of electron-hole pairs as being responsible for changes in current flow and light emission in OLEDs. In the framework of this concept it is possible to explain all results from own measurements as well as results from literature. Another important finding made in this thesis is the fact that the value of the OMR signal in the investigated OLED devices can be enhanced by appropriate electrical and optical conditioning processes. In particular, electrical conditioning causes a significant enhancement of the OMR values, while at the same time it has a negative effect on charge carrier transport and optical device characteristics. These results can be explained by additional results from charge carrier extraction measurements which suggest that electrical conditioning leads to an increase in the number of electronic trap states inside the emission layer of the investigated OLED devices. The positive influence of trap states on the OMR effect is

  5. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Guillermo Bazan; Alexander Mikhailovsky

    2008-08-01

    The objective of the proposed work was to develop the fundamental understanding and practical techniques for enhancement of Phosphorescent Organic Light Emitting Diodes (PhOLEDs) performance by utilizing radiative decay control technology. Briefly, the main technical goal is the acceleration of radiative recombination rate in organometallic triplet emitters by using the interaction with surface plasmon resonances in noble metal nanostructures. Increased photonic output will enable one to eliminate constraints imposed on PhOLED efficiency by triplet-triplet annihilation, triplet-polaron annihilation, and saturation of chromophores with long radiative decay times. Surface plasmon enhanced (SPE) PhOLEDs will operate more efficiently at high injection current densities and will be less prone to degradation mechanisms. Additionally, introduction of metal nanostructures into PhOLEDs may improve their performance due to the improvement of the charge transport through organic layers via multiple possible mechanisms ('electrical bridging' effects, doping-like phenomena, etc.). SPE PhOLED technology is particularly beneficial for solution-fabricated electrophosphorescent devices. Small transition moment of triplet emitters allows achieving a significant enhancement of the emission rate while keeping undesirable quenching processes introduced by the metal nanostructures at a reasonably low level. Plasmonic structures can be introduced easily into solution-fabricated PhOLEDs by blending and spin coating techniques and can be used for enhancement of performance in existing device architectures. This constitutes a significant benefit for a large scale fabrication of PhOLEDs, e.g. by roll-to-roll fabrication techniques. Besides multieexciton annihilation, the power efficacy of PhOLEDs is often limited by high operational bias voltages required for overcoming built-in potential barriers to injection and transport of electrical charges through a device. This problem is

  6. White organic light-emitting diodes with fine chromaticity tuning via ultrathin layer position shifting

    Science.gov (United States)

    Choukri, Hakim; Fischer, Alexis; Forget, Sébastien; Chénais, Sébastien; Castex, Marie-Claude; Adès, Dominique; Siove, Alain; Geffroy, Bernard

    2006-10-01

    Nondoped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting 4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) layer and a blue-emitting 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep blue to pure yellow via bright white with CIE coordinates (x =0.33, y =0.32), an ηext of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9nm, respectively).

  7. White organic light emitting devices with hybrid emissive layers combining phosphorescence and fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Lei Gangtie; Chen Xiaolan; Wang Lei; Zhu Meixiang; Zhu Weiguo [Key Lab of Environmental-friendly Chemistry and Application of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan 411105 (China); Wang Liduo; Qiu Yong [Key Lab of Organic-Optoelectronics and Molecular Sciences of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084 (China)], E-mail: lgt@xtu.edu.cn

    2008-05-21

    We fabricated a white organic light-emitting diode (WOLED) by hybrid emissive layers which combined phosphorescence with fluorescence. In this device, the thin layer of 4-(dicyanomethylene)-2-(t-butyl)-6-(1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran played the role of undoped red emissive layer which was inserted between two blue phosphorescence emissive layers. The blue phosphorescent dye was bis[(4, 6-difluorophenyl)-pyridinato-N, C{sup 2}] (picolinato) Ir(III), which was doped in the host material, N, N'-dicarbazolyl-1, 4-dimethene-benzene. The WOLED showed stable Commission Internationale de L'Eclairage coordinates and a high efficency of 9.6 cd A{sup -1} when the current density was 1.8 A m{sup -2}. The maximum luminance of the device achieved was 17 400 cd m{sup -2} when the current density was 3000 A m{sup -2}.

  8. White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting

    CERN Document Server

    Choukri, H; Forget, S; Chenais, S; Castex, M C; Ades, D; Siove, A; Geffroy, B; Choukri, Hakim; Fischer, Alexis; Forget, Sebastien; Chenais, Sebastien; Castex, Marie-Claude; Ades, Dominique; Siove, Alain; Geffroy, Bernard

    2006-01-01

    Non-doped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting NPB (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi (4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33, y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively).

  9. Synthesis, characterization and properties of novel blue light emitting discrete π-functional polymer consisting of carbazole and anthracene units and their applications in polymer light emitting diodes

    Science.gov (United States)

    Gopal, Ram; Huang, Yi-Chiang; Lee, Hsu-Feng; Chang, Ming-Sien; Huang, Wen-Yao

    2017-03-01

    A new novel blue light emitting polymer containing carbazole and anthracene derivatives has been successfully synthesized via polycondensation chemical reaction of diol and difluoro monomers. An effort has been made to raise the band gap of blue light emitter by lowering the conjugation extent in the backbone. The synthesized blue polymer exhibits decent solubility, good process ability, high thermal stability, high glass transition temperature (272 °C) and the decomposition temperature of 358 °C. The UV-vis absorption spectra and photoluminescence spectra depict that the light emission lies in blue region. The solid state photoluminescence (PL) spectra of the polymer (λPL=456 nm) shows red shift (Δλ = 37 nm) as compared with the corresponding solution PL spectra, presumably due to lower intermolecular distance in solid state. The multi-layered polymer light emitting diode was fabricated, using blue polymer with ITO/PEDOT: PSS/BP/LiF/Al architecture. The luminance-voltage (L-V) and current density-voltage (J-V) curves show a maximum luminance of 7544 cd m-2, a maximum emission efficiency of 4.2 cd A-1, a maximum current density of 453 mA cm-2 at a turn-on voltage of 4.5 V. Moreover, the PLED instigate pure blue EL emission, stable at 436 nm with outstanding CIE coordinates of (x = 0.15, y = 0.08), which is close to the pure NTSC blue coordinates of (0.14, 0.08). [Figure not available: see fulltext.

  10. Colour tuning in white hybrid inorganic/organic light-emitting diodes

    Science.gov (United States)

    Bruckbauer, Jochen; Brasser, Catherine; Findlay, Neil J.; Edwards, Paul R.; Wallis, David J.; Skabara, Peter J.; Martin, Robert W.

    2016-10-01

    White hybrid inorganic/organic light-emitting diodes (LEDs) were fabricated by combining a novel organic colour converter with a blue inorganic LED. An organic small molecule was specifically synthesised to act as down-converter. The characteristics of the white colour were controlled by changing the concentration of the organic molecule based on the BODIPY unit, which was embedded in a transparent matrix, and volume of the molecule and encapsulant mixture. The concentration has a critical effect on the conversion efficiency, i.e. how much of the absorbed blue light is converted into yellow light. With increasing concentration the conversion efficiency decreases. This quenching effect is due to aggregation of the organic molecule at higher concentrations. Increasing the deposited amount of the converter does not increase the yellow emission despite more blue light being absorbed. Degradation of the organic converter was also observed during a period of 15 months from LED fabrication. Angular-dependent measurements revealed slight deviation from a Lambertian profile for the blue and yellow emission peaks leading to a small change in ‘whiteness’ with emission angle. Warm white and cool white light with correlated colour temperatures of 2770 K and 7680 K, respectively, were achieved using different concentrations of the converter molecule. Although further work is needed to improve the lifetime and poor colour rendering, these hybrid LEDs show promising results as an alternative approach for generating white LEDs compared with phosphor-based white LEDs.

  11. Inkjet printing the three organic functional layers of two-colored organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Coenen, Michiel J.J., E-mail: Michiel.Coenen@tmc.nl [Holst Centre, PO BOX 8550, 5605 KN Eindhoven (Netherlands); Slaats, Thijs M.W.L.; Eggenhuisen, Tamara M. [Holst Centre, PO BOX 8550, 5605 KN Eindhoven (Netherlands); Groen, Pim [Holst Centre, PO BOX 8550, 5605 KN Eindhoven (Netherlands); Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629HS Delft (Netherlands)

    2015-05-29

    Inkjet printing allows for the roll-2-roll fabrication of organic electronic devices at an industrial scale. In this paper we demonstrate the fabrication of two-colored organic light emitting diodes (OLEDs) in which three adjacent organic device layers were inkjet printed from halogen free inks. The resulting devices demonstrate the possibilities offered by this technique for the fabrication of OLEDs for signage and personalized electronics. - Highlights: • Two-colored organic light emitting diodes with 3 inkjet printed device layers were fabricated. • All materials were printed from halogen free inks. • Inkjet printing of emissive materials is suitable for signage applications.

  12. White Organic Light-emitting Diodes with A Sr2 SiO4:Eu3+ Color Conversion Layer%White Organic Light-emitting Diodes with A Sr2SiO4:Eu3+ Color Conversion Layer

    Institute of Scientific and Technical Information of China (English)

    Meiso Yokoyama

    2013-01-01

    Hybrid inorganic/organic white organic light emitting diodes (hybrid-WOLEDs) are fabricated by combining the blue phosphorescent organic light emitting diodes (PHOLEDs) with red Sr2 SiO4∶ Eu3+ phosphor spin coated as a color conversion layer (CCL) over the other side of glass substrate on the devices.The basic configuration of the PHOLEDs consists a host material,N,N'-dicarbazolyl-3,5-benzene (mCP) which doped with a blue phosphorescent iridium complexes iridium (Ⅲ)bis [(4,6-di-fluorophenyl)-pyridinato-N-C2'] (FIrpic) to produce high efficient blue organic light emitting diodes.The hybrid-WOLED shows maximum luminous efficiency of 22.1 cd/ A,maximum power efficiency of 11.26 lm/W,external quantum efficiency of 10.2% and CIE coordinates of (0.32,0.34).Moreover,the output spectra and CIE coordinates of the hybrid-WOLED have a small shift in different driving current density,which demonstrate good color stability.

  13. Multicolored Nanofiber Based Organic Light-Emitting Transistor

    DEFF Research Database (Denmark)

    With Jensen, Per Baunegaard; Kjelstrup-Hansen, Jakob; Tavares, Luciana;

    For optoelectronic applications, organic semiconductors have several advantages over their inorganic counterparts such as facile synthesis, tunability via synthetic chemistry, and low temperature processing. Self-assembled, molecular crystalline nanofibers are of particular interest as they could...... form ultra-small light-emitters in future nanophotonic applications. Such organic nanofibers exhibit many interesting optical properties including polarized photo- and electroluminescence, waveguiding, and emission color tunability. We here present a first step towards a multicolored, electrically...... driven device by combining nanofibers made from two different molecules, parahexaphenylene (p6P) and 5,5´-Di-4-biphenyl-2,2´-bithiophene (PPTTPP), which emits blue and green light, respectively. The organic nanofibers are implemented on a bottom gate/bottom contact field-effect transistor platform using...

  14. Focus Issue: Organic light-emitting diodes-status quo and current developments.

    Science.gov (United States)

    List, Emil J W; Koch, Norbert

    2011-11-01

    The guest editors introduce the Optics Express Energy Express supplement Focus Issue, "Organic Light-Emitting Diodes," which includes six invited articles addressing the challenges of light outcoupling and light management in OLEDs.

  15. Device Optimization and Transient Electroluminescence Studies of Organic light Emitting Devices

    CERN Document Server

    Li Juan Zo

    2003-01-01

    Organic light emitting devices (OLEDs) are among the most promising for flat panel display technologies. They are light, bright, flexible, and cost effective. And while they are emerging in commercial product, their low power efficiency and long-term degradation are still challenging. The aim of this work was to investigate their device physics and improve their performance. Violet and blue OLEDs were studied. The devices were prepared by thermal vapor deposition in high vacuum. The combinatorial method was employed in device preparation. Both continuous wave and transient electroluminescence (EL) were studied. A new efficient and intense UV-violet light emitting device was developed. At a current density of 10 mA/cm sup 2 , the optimal radiance R could reach 0.38 mW/cm sup 2 , and the quantum efficiency was 1.25%. using the delayed EL technique, electron mobilities in DPVBi and CBP were determined to be approx 10 sup - sup 5 cm sup 2 /Vs and approx 10 sup - sup 4 cm sup 2 /Vs, respectively. Overshoot effects...

  16. Electroluminescence property of organic light emitting diode (OLED)

    Energy Technology Data Exchange (ETDEWEB)

    Özdemir, Orhan; Kavak, Pelin; Saatci, A. Evrim; Gökdemir, F. Pınar; Menda, U. Deneb; Can, Nursel; Kutlu, Kubilay [Yıldız Technical University, Department of Physics, Esenler, Istanbul (Turkey); Tekin, Emine; Pravadalı, Selin [National Metrology Instıtute of Turkey (TUBİTAK-UME), Kocaeli (Turkey)

    2013-12-16

    Transport properties of electrons and holes were investigated not only in a anthracene-containing poly(p-phenylene-ethynylene)- alt - poly(p-phenylene-vinylene) (PPE-PPV) polymer (AnE-PVstat) light emitting diodes (OLED) but also in an ITO/Ag/polymer/Ag electron and ITO/PEDOT:PSS/polymer/Au hole only devices. Mobility of injected carriers followed the Poole-Frenkel type conduction mechanism and distinguished in the frequency range due to the difference of transit times in admittance measurement. Beginning of light output took place at the turn-on voltage (or flat band voltage), 1.8 V, which was the difference of energy band gap of polymer and two barrier offsets between metals and polymer.

  17. Vertical thinking in blue light emitting diodes: GaN-on-graphene technology

    Science.gov (United States)

    Bayram, C.; Kim, J.; Cheng, C.-W.; Ott, J.; Reuter, K. B.; Bedell, S. W.; Sadana, D. K.; Park, H.; Dimitrakopoulos, C.

    2014-03-01

    In this work, we show that a 2D cleave layer (such as epitaxial graphene on SiC) can be used for precise release of GaNbased light emitting diodes (LEDs) from the LED-substrate interface. We demonstrate the thinnest GaN-based blue LED and report on the initial electrical and optical characteristics. Our LED device employs vertical architecture: promising excellent current spreading, improved heat dissipation, and high light extraction with respect to the lateral one. Compared to conventional LED layer release techniques used for forming vertical LEDs (such as laser-liftoff and chemical lift-off techniques), our process distinguishes itself with being wafer-scalable (large area devices are possible) and substrate reuse opportunity.

  18. Advanced Oxidation of Tartrazine and Brilliant Blue with Pulsed Ultraviolet Light Emitting Diodes.

    Science.gov (United States)

    Scott, Robert; Mudimbi, Patrick; Miller, Michael E; Magnuson, Matthew; Willison, Stuart; Phillips, Rebecca; Harper, Willie F

    2017-01-01

      This study investigated the effect of ultraviolet light-emitting diodes (UVLEDs) coupled with hydrogen peroxide as an advanced oxidation process (AOP) for the degradation of two test chemicals. Brilliant Blue FCF consistently exhibited greater degradation than tartrazine, with 83% degradation after 300 minutes at the 100% duty cycle compared with only 17% degradation of tartrazine under the same conditions. These differences are attributable to the structural properties of the compounds. Duty cycle was positively correlated with the first-order rate constants (k) for both chemicals but, interestingly, negatively correlated with the normalized first-order rate constants (k/duty cycle). Synergistic effects of both hydraulic mixing and LED duty cycle were manifested as novel oscillations in the effluent contaminant concentration. Further, LED output and efficiency were dependent upon duty cycle and less efficient over time perhaps due to heating effects on semiconductor performance.

  19. Triarylboron-Based Fluorescent Organic Light-Emitting Diodes with External Quantum Efficiencies Exceeding 20 .

    Science.gov (United States)

    Suzuki, Katsuaki; Kubo, Shosei; Shizu, Katsuyuki; Fukushima, Tatsuya; Wakamiya, Atsushi; Murata, Yasujiro; Adachi, Chihaya; Kaji, Hironori

    2015-12-01

    Triarylboron compounds have attracted much attention, and found wide use as functional materials because of their electron-accepting properties arising from the vacant p orbitals on the boron atoms. In this study, we design and synthesize new donor-acceptor triarylboron emitters that show thermally activated delayed fluorescence. These emitters display sky-blue to green emission and high photoluminescence quantum yields of 87-100 % in host matrices. Organic light-emitting diodes using these emitting molecules as dopants exhibit high external quantum efficiencies of 14.0-22.8 %, which originate from efficient up-conversion from triplet to singlet states and subsequent efficient radiative decay from singlet to ground states.

  20. Whole device printing for full colour displays with organic light emitting diodes

    Science.gov (United States)

    Choi, Jun-ho; Kim, Kyung-Ho; Choi, Se-Jin; Lee, Hong H.

    2006-05-01

    Whole device printing is presented for realizing full colour displays with red (R), green (G) and blue (B) organic light emitting diodes (OLEDs). In this process, the whole OLED structure is transferred from a patterned mould to a glass substrate. Therefore, a simple step and repeat of the transfer of each of R, G and B OLED for RGB pixels completes the fabrication of the full colour display over a given area. A difference in the work of adhesion at two interfaces enables the transfer. A 'rigiflex' mould is used for the printing. It is rigid enough to allow sub-100 nm resolution and yet flexible enough for intimate contact with the glass substrate, which permits large area application.

  1. High-brightness organic light-emitting diodes for optogenetic control of Drosophila locomotor behaviour

    Science.gov (United States)

    Morton, Andrew; Murawski, Caroline; Pulver, Stefan R.; Gather, Malte C.

    2016-08-01

    Organic light emitting diodes (OLEDs) are in widespread use in today’s mobile phones and are likely to drive the next generation of large area displays and solid-state lighting. Here we show steps towards their utility as a platform technology for biophotonics, by demonstrating devices capable of optically controlling behaviour in live animals. Using devices with a pin OLED architecture, sufficient illumination intensity (0.3 mW.mm‑2) to activate channelrhodopsins (ChRs) in vivo was reliably achieved at low operating voltages (5 V). In Drosophila melanogaster third instar larvae expressing ChR2(H134R) in motor neurons, we found that pulsed illumination from blue and green OLEDs triggered robust and reversible contractions in animals. This response was temporally coupled to the timing of OLED illumination. With blue OLED illumination, the initial rate and overall size of the behavioural response was strongest. Green OLEDs achieved roughly 70% of the response observed with blue OLEDs. Orange OLEDs did not produce contractions in larvae, in agreement with the spectral response of ChR2(H134R). The device configuration presented here could be modified to accommodate other small model organisms, cell cultures or tissue slices and the ability of OLEDs to provide patterned illumination and spectral tuning can further broaden their utility in optogenetics experiments.

  2. Synthesis of Two Blue-light - emitting Complexes with Schiff Base Calixarene as the Ligand

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Two new blue luminescent zinc and beryllium complexes with Schiff base calixarene derivative as the ligand were prepared. Their luminescent properties were determined, which indicated that they had strong blue fluorescent properties. They also had good solubility and film formation. These new complexes can be used as blue organic electroluminescent materials (OELMs) in organic electroluminescent devices.

  3. Synthesis of a Novel Blue- light- emitting Polymer Material Bearing Coumarin Pendants

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel blue luminescent polymer bearing coumarin pendants was prepared. Its luminescent properties were determined indicating that it had strong blue fluorescent properties and good film formation ability. This novel polymer can be used as a blue organic electroluminescent material (OELM) in organic electroluminescent devices.

  4. Spectrum study of top-emitting organic light-emitting devices with micro-cavity structure

    Institute of Scientific and Technical Information of China (English)

    Liu Xiang; Wei Fuxiang; Liu Hui

    2009-01-01

    Blue and white top-emitting organic light-emitting devices OLEDs with cavity effect have been fabricated.TBADN:3%DSAPh and Alq3:DCJTB/TBADN:TBPe/Alq3:C545 were used as emitting materials of microcavity OLEDs.On a patterned glass substrate,silver was deposited as reflective anode,and copper phthalocyanine (CuPc)layer as HIL and 4'-bis[N-(1-Naphthyl)-N-phenyl-amino]biphenyl(NPB)layer as HTL were made.Al/Ag thin films were made as semi-transparent cathode with a transmittance of about 30%.By changing the thickness of indium tin oxide ITO,deep blue with Commission Internationale de L'Eclairage chromaticity coordinates(CIEx,y)of(0.141,0.049)was obtained on TBADN:3%DSAPh devices,and different color(red,blue and green)was obrained on Alq3:DCJTB/TBADN:TBPe/Alq3:C545 devices,full width at half maxima(FWHM)was only 17 nm.The spectral intensity and FWHM of emission in cavity devices have also been studied.

  5. Photodynamic effect of light-emitting diode light on cell growth inhibition induced by methylene blue

    Indian Academy of Sciences (India)

    Lílian S Peloi; Rafael R S Soares; Carlos E G Biondo; Vagner R Souza; Noboru Hioka; Elza Kimura

    2008-06-01

    The aim of this study was to propose the use of red light-emitting diode (LED) as an alternative light source for methylene blue (MB) photosensitizing effect in photodynamic therapy (PDT). Its effectiveness was tested against Staphylococcus aureus (ATCC 26923), Escherichia coli (ATCC 26922), Candida albicans (ATCC 90028) and Artemia salina. The maximum absorption of the LED lamps was at a wavelength of 663 nm, at intensities of 2, 4, 6 and 12 J.cm–2 for 10, 20, 30 and 60 min of exposure, respectively. Assays with and without LED exposure were carried out in plates containing MB at concentrations of 7 to 140.8 M for microorganisms and 13.35 to 668.5 M for microorganisms or microcrustaceans. The LED exposure induced more than 93.05%, 93.7% and 93.33% of growth inhibition for concentrations of 42.2 M for S. aureus (D-value=12.05 min) and 35.2 M for E. coli (D-value=11.51 min) and C. albicans (D-value=12.18 min), respectively after 20 min of exposure. LED exposure for 1 h increased the cytotoxic effect of MB against A. salina from 27% to 75%. Red LED is a promising light device for PDT that can effectively inhibit bacteria, yeast and microcrustacean growth.

  6. Nanostructured High Performance Ultraviolet and Blue Light Emitting Diodes for Solid State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Arto V. Nurmikko; Jung Han

    2007-03-31

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the duration of the contract period include (i) new means of synthesizing AlGaN and InN quantum dots by droplet heteroepitaxy, (ii) synthesis of AlGaInN nanowires as building blocks for GaN-based microcavity devices, (iii) progress towards direct epitaxial alignment of the dense arrays of nanowires, (iv) observation and measurements of stimulated emission in dense InGaN nanopost arrays, (v) design and fabrication of InGaN photonic crystal emitters, and (vi) observation and measurements of enhanced fluorescence from coupled quantum dot and plasmonic nanostructures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  7. Ultraviolet Laser SQUID Microscope for GaN Blue Light Emitting Diode Testing

    Energy Technology Data Exchange (ETDEWEB)

    Daibo, M [Department of Electrical and Electronic Engineering, Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan); Kamiwano, D [Graduate School of Engineering, Iwate University, Morioka 020-8551 (Japan); Kurosawa, T [Graduate School of Engineering, Iwate University, Morioka 020-8551 (Japan); Yoshizawa, M [Graduate School of Engineering, Iwate University, Morioka 020-8551 (Japan); Tayama, N [Department of Electrical and Electronic Engineering, Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan)

    2006-06-01

    We carried out non-contacting measurements of photocurrent distributions in GaN blue light emitting diode (LED) chips using our newly developed ultraviolet (UV) laser SQUID microscope. The UV light generates the photocurrent, and then the photocurrent induces small magnetic fields around the chip. An off-axis arranged HTS-SQUID magnetometer is employed to detect a vector magnetic field whose typical amplitude is several hundred femto-tesla. Generally, it is difficult to obtain Ohmic contacts for p-type GaN because of the low hole concentration in the p-type epitaxial layer and the lack of any available metal with a higher work function compared with the p-type GaN. Therefore, a traditional probecontacted electrical test is difficult to conduct for wide band gap semiconductors without an adequately annealed electrode. Using the UV-laser SQUID microscope, the photocurrent can be measured without any electrical contact. We show the photocurrent vector map which was reconstructed from measured magnetic fields data. We also demonstrate how we found the position of a defect of the electrical short circuits in the LED chip.

  8. Benzophenones as Generic Host Materials for Phosphorescent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Jhulki, Samik; Seth, Saona; Ghosh, Avijit; Chow, Tahsin J; Moorthy, Jarugu Narasimha

    2016-01-20

    Despite the fact that benzophenone has traditionally served as a prototype molecular system for establishing triplet state chemistry, materials based on molecular systems containing the benzophenone moiety as an integral part have not been exploited as generic host materials in phosphorescent organic light-emitting diodes (PhOLEDs). We have designed and synthesized three novel host materials, i.e., BP2-BP4, which contain benzophenone as the active triplet sensitizing molecular component. It is shown that their high band gap (3.91-3.93 eV) as well as triplet energies (2.95-2.97 eV) permit their applicability as universal host materials for blue, green, yellow, and red phosphors. While they serve reasonably well for all types of dopants, excellent performance characteristics observed for yellow and green devices are indeed the hallmark of benzophenone-based host materials. For example, maximum external quantum efficiencies of the order of 19.2% and 17.0% were obtained from the devices fabricated with yellow and green phosphors using BP2 as the host material. White light emission, albeit with rather poor efficiencies, has been demonstrated as a proof-of-concept by fabrication of co-doped and stacked devices with blue and yellow phosphors using BP2 as the host material.

  9. Effect of BCP ultrathin layer on the performance of organic light-emitting devices

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; YU Jun-sheng; LI Lu; TANG Xiao-qing; JIANG Ya-dong

    2008-01-01

    Based on conventional double layer device, triple layer organic light-emitting diodes (OLEDs) with two heterostructures of indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-his(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB)/2,9 -dimethyl-4,7 -diphenyl-1,10-phenanthroline (BCP)/8-Hydroxyquinoline aluminum (Alq3)/Mg:Ag using vacuum deposition method have been fabricated. The influence of different film thickness of BCP layer on the performance of OLEDs has been investigated. The results showed that when the thickness of the BCP layer film gradually varied from 0.1 nm to 4.0 nm, the electrolumines-cence (EL) spectra of the OLEDs shifted from green to greenish-blue to blue, and the BCP layer acted as the recombination region of charge carriers related to EL spectrum, enhancing the brightness and power efficiency. The power efficiency of OLEDs reached as high as 7.3 lm/W.

  10. Efficient Hybrid White Organic Light-Emitting Diodes for Application of Triplet Harvesting with Simple Structure

    CERN Document Server

    Hwang, Kyo Min; Lee, Sungkyu; Yoo, Han Kyu; Baek, Hyun Jung; Kim, Jwajin; Yoon, Seung Soo; Kim, Young Kwan

    2016-01-01

    In this study, we fabricated hybrid white organic light-emitting diodes (WOLEDs) based on triplet harvesting with simple structure. All the hole transporting material and host in emitting layer (EML) of devices were utilized with same material by using N,N'-di-1-naphthalenyl-N,N'-diphenyl-[1,1':4',1":4",1"'-quaterphenyl]-4,4"'-diamine (4P-NPD) which were known to be blue fluorescent material. Simple hybrid WOLEDs were fabricated three color with blue fluorescent and green, red phosphorescent materials. We was investigated the effect of triplet harvesting (TH) by exciton generation zone on simple hybrid WOLEDs. Characteristic of simple hybrid WOLEDs were dominant hole mobility, therefore exciton generation zone was expected in EML. Additionally, we was optimization thickness of hole transporting layer and electron transporting layer was fabricated a simple hybrid WOLEDs. Simple hybrid WOLED exhibits maximum luminous efficiency of 29.3 cd/A and maximum external quantum efficiency of 11.2%. Commission Internatio...

  11. Design rules for charge-transport efficient host materials for phosphorescent organic light-emitting diodes.

    Science.gov (United States)

    May, Falk; Al-Helwi, Mustapha; Baumeier, Björn; Kowalsky, Wolfgang; Fuchs, Evelyn; Lennartz, Christian; Andrienko, Denis

    2012-08-22

    The use of blue phosphorescent emitters in organic light-emitting diodes (OLEDs) imposes demanding requirements on a host material. Among these are large triplet energies, the alignment of levels with respect to the emitter, the ability to form and sustain amorphous order, material processability, and an adequate charge carrier mobility. A possible design strategy is to choose a π-conjugated core with a high triplet level and to fulfill the other requirements by using suitable substituents. Bulky substituents, however, induce large spatial separations between conjugated cores, can substantially reduce intermolecular electronic couplings, and decrease the charge mobility of the host. In this work we analyze charge transport in amorphous 2,8-bis(triphenylsilyl)dibenzofuran, an electron-transporting material synthesized to serve as a host in deep-blue OLEDs. We show that mesomeric effects delocalize the frontier orbitals over the substituents recovering strong electronic couplings and lowering reorganization energies, especially for electrons, while keeping energetic disorder small. Admittance spectroscopy measurements reveal that the material has indeed a high electron mobility and a small Poole-Frenkel slope, supporting our conclusions. By linking electronic structure, molecular packing, and mobility, we provide a pathway to the rational design of hosts with high charge mobilities.

  12. Organic single-crystal light-emitting field-effect transistors

    NARCIS (Netherlands)

    Hotta, Shu; Yamao, Takeshi; Bisri, Satria Zulkarnaen; Takenobu, Taishi; Iwasa, Yoshihiro

    2014-01-01

    Growth and characterisation of single crystals constitute a major field of materials science. In this feature article we overview the characteristics of organic single-crystal light-emitting field-effect transistors (OSCLEFETs). The contents include the single crystal growth of organic semiconductor

  13. Novel Blue Light-emitting PPV-based Copolymer Containing Triazole and Carbazole Units

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A novel alternating conjugated copolymer containing triazole and carbazole units was synthesized by the Wittig reaction. The resulting bipolar conjugated polymer emits a pure light with good thermal stability, which is a promising candidate for polymer light emitting display.

  14. Organic light emitting field effect transistors based on an ambipolar p-i-n layered structure

    Science.gov (United States)

    Maiorano, V.; Bramanti, A.; Carallo, S.; Cingolani, R.; Gigli, G.

    2010-03-01

    A bottom contact/top gate ambipolar "p-i-n" layered light emitting field effect transistor with the active medium inserted between two doped transport layers, is reported. The doping profile results crucial to the capability of emitting light, as well as to the electrical characteristics of the device. In this sense, high output current at relative low applied gate/drain voltage and light emission along the whole large area transistor channel are observed, putting the basis to full integration of organic light emitting field effect transistors in planar complex devices.

  15. Emission properties of an organic light-emitting diode patterned by a photoinduced autostructuration process

    Science.gov (United States)

    Hubert, C.; Fiorini-Debuisschert, C.; Hassiaoui, I.; Rocha, L.; Raimond, P.; Nunzi, J.-M.

    2005-11-01

    The photoluminescence properties of a periodically structured organic light-emitting diode are presented. Patterning is achieved using an original single-step autostructuration technique based on photoinduced effects in azo-polymer films. We show that single beam laser irradiation can lead to the induction of regular two-dimensional surface relief gratings. The waveguide properties of these microstructures as well as their effect on the emission properties of a light-emitting material are studied. We demonstrate a new straightforward technique to improve external light emission efficiency by outcoupling part of the light that was initially guided into the different diode layers.

  16. Red Light-Emitting-Diode Based on an Organic Salt

    Institute of Scientific and Technical Information of China (English)

    孟瑞平; 徐洪光; 徐春祥; 张俊祥; 何国华; 崔一平

    2003-01-01

    A novel organic salt trans-4-[P-(N-ethyl-N-(hydroxylethyl)-amino) styryl]-N-methylpyridiniumtetraphenylborate (abbreviated as ASPT) has been employed as an active layer in an organic electroluminescent device. Bright red emission with high quantum efficiency has been obtained. The brightness of the ASPT device is one order magnitude higher than that of Alqs devices at about 12 V. The device shows high thermal stability because of the ionic interaction within the organic salt molecules. It is assumed that the high performance of such a device is related to the formation of dipole moments in the ASPT layer.

  17. Red Light-Emitting-Diode Based on an Organic Salt

    Science.gov (United States)

    Meng, Rui-Ping; Xu, Hong-Guang; Xu, Chun-Xiang; Zhang, Jun-Xiang; He, Guo-Hua; Cui, Yi-Ping

    2003-06-01

    A novel organic salt trans-4-[P-(N-ethyl-N-(hydroxylethyl)-amino) styryl]-N-methylpyridinium tetraphenylborate (abbreviated as ASPT) has been employed as an active layer in an organic electroluminescent device. Bright red emission with high quantum efficiency has been obtained. The brightness of the ASPT device is one order magnitude higher than that of Alq3 devices at about 12 V. The device shows high thermal stability because of the ionic interaction within the organic salt molecules. It is assumed that the high performance of such a device is related to the formation of dipole moments in the ASPT layer.

  18. Sodium cholate-templated blue light-emitting Ag subnanoclusters: in vivo toxicity and imaging in zebrafish embryos.

    Science.gov (United States)

    Chandirasekar, Shanmugam; Chandrasekaran, Chandramouli; Muthukumarasamyvel, Thangavel; Sudhandiran, Ganapasam; Rajendiran, Nagappan

    2015-01-28

    We report a novel green chemical approach for the synthesis of blue light-emitting and water-soluble Ag subnanoclusters, using sodium cholate (NaC) as a template at a concentration higher than the critical micelle concentration (CMC) at room temperature. However, under photochemical irradiation, small anisotropic and spherically shaped Ag nanoparticles (3-11 nm) were obtained upon changing the concentration of NaC from below to above the CMC. The matrix-assisted laser desorption ionization time-of-flight and electrospray ionization mass spectra showed that the cluster sample was composed of Ag4 and Ag6. The optical properties of the clusters were studied by UV-visible and luminescence spectroscopy. The lifetime of the synthesized fluorescent Ag nanoclusters (AgNCs) was measured using a time-correlated single-photon counting technique. High-resolution transmission electron microscopy was used to assess the size of clusters and nanoparticles. A protocol for transferring nanoclusters to organic solvents is also described. Toxicity and bioimaging studies of NaC templated AgNCs were conducted using developmental stage zebrafish embryos. From the survival and hatching experiment, no significant toxic effect was observed at AgNC concentrations of up to 200 μL/mL, and the NC-stained embryos exhibited blue fluorescence with high intensity for a long period of time, which shows that AgNCs are more stable in living system.

  19. Synthesis of Soluble Host Materials for Highly Efficient Red Phosphorescent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Suh, Min Chul; Park, So-Ra; Cho, Ye Ram; Shin, Dong Heon; Kang, Pil-Gu; Ahn, Dong A; Kim, Hyung Suk; Kim, Chul-Bae

    2016-07-20

    New soluble host materials with benzocarbazole and triphenyltriazine moieties, 11-[3-(4,6-diphenyl-[1,3,5]triazin-2-yl)-phenyl]-11H-benzo[a]carbazole and 11-[3'-(4,6-diphenyl-[1,3,5]triazin-2-yl)-biphenyl-4-yl]-11H-benzo[a]carbazole, were synthesized for highly efficient red phosphorescent organic light-emitting diodes (PHOLED). Hole-transporting benzocarbazole moiety and electron transporting triphenyltriazine moiety, which are severely twisted each other enhance the solubility of those materials in common organic solvent. The improved solubility from this molecular design could be due to a reduced π-π stacking interaction, which gives a very uniform film morphology after spin coating of those materials. As a result, we obtained highly efficient soluble PHOLEDs combined with an evaporated blue common layer structure. The resultant red PHOLED exhibited the maximum current efficiency as well as external quantum efficiency values up to 23.7 cd/A and 19.0%.

  20. Organic/Organic' heterojunctions: organic light emitting diodes and organic photovoltaic devices.

    Science.gov (United States)

    Armstrong, Neal R; Wang, Weining; Alloway, Dana M; Placencia, Diogenes; Ratcliff, Erin; Brumbach, Michael

    2009-05-19

    Heterojunctions created from thin films of two dissimilar organic semiconductor materials [organic/organic' (O/O') heterojunctions] are an essential component of organic light emitting diode displays and lighting systems (OLEDs, PLEDs) and small molecule or polymer-based organic photovoltaic (solar cell) technologies (OPVs). O/O' heterojunctions are the site for exciton formation in OLEDs, and the site for exciton dissociation and photocurrent production in OPVs. Frontier orbital energy offsets in O/O' heterojunctions establish the excess free energy controlling rates of charge recombination and formation of emissive states in OLEDs and PLEDs. These energy offsets also establish the excess free energy which controls charge separation and the short-circuit photocurrent (J(SC) ) in OPVs, and set the upper limit for the open-circuit photopotential (V(OC) ). We review here how these frontier orbital energy offsets are determined using photoemission spectroscopies, how these energies change as a function of molecular environment, and the influence of interface dipoles on these frontier orbital energies. Recent examples of heterojunctions based on small molecule materials are shown, emphasizing those heterojunctions which are of interest for photovoltaic applications. These include heterojunctions of perylenebisimide dyes with trivalent metal phthalocyanines, and heterojunctions of titanyl phthalocyanine with C(60) , and with pentacene. Organic solar cells comprised of donor/acceptor pairs of each of these last three materials confirm that the V(OC) scales with the energy offsets between the HOMO of the donor and LUMO of the acceptor ($E_{{\\rm HOMO}^{\\rm D} } - E_{{\\rm LUMO}^{\\rm A} }$).

  1. High current density in light-emitting transistors of organic single crystals

    NARCIS (Netherlands)

    Takenobu, Taishi; Bisri, Satria Zulkarnaen; Takahashi, Tetsuo; Yahiro, Masayuki; Adachi, Chihaya; Iwasa, Yoshihiro

    2008-01-01

    We measured the external electroluminescence quantum efficiency (eta(ext)) in light-emitting field-effect transistors (LETs) made of organic single crystals and found that, in the ambipolar transport region, eta(ext) is not degraded up to several hundreds A/cm(2) current-density range, which is 2 or

  2. Patterning of Flexible Organic Light Emitting Diode (FOLED) stack using an ultrafast laser

    NARCIS (Netherlands)

    Mandamparambil, R.; Fledderus, H.; Steenberge, G.V.; Dietzel, A.H.

    2010-01-01

    A femtosecond laser has been successfully utilized for patterning thin Flexible Organic Light Emitting Diode (FOLED) structures of individual layer thickness around 100nm. The authors report in this paper a step-like ablation behavior at the layer interfaces which accounts for a local removal of ent

  3. Passivation of organic light emitting diode anode grid lines by pulsed Joule heating

    NARCIS (Netherlands)

    Janka, M.; Gierth, R.; Rubingh, J.E.; Abendroth, M.; Eggert, M.; Moet, D.J.D.; Lupo, D.

    2015-01-01

    We report the self-aligned passivation of a current distribution grid for an organic light emitting diode (OLED) anode using a pulsed Joule heating method to align the passivation layer accurately on the metal grid. This method involves passing an electric current through the grid to cure a polymer

  4. Organic Light-Emitting Device Based on Terbium Complex

    Institute of Scientific and Technical Information of China (English)

    Xu Ying; Deng Zhenbo; Xu Denghui; Xiao Jing; Wang Ruifen

    2005-01-01

    A new rare earth complex Tb(p-MBA)3phen was synthesized, which is first used as an emitting material in organic electroluminescence. By doping it into the conjugated polymer PVK, single-layer and double-layer devices were fabricated with structures: device 1: ITO/PVK∶ Tb(p-MBA)3phen/Al; device 2∶ ITO/PVK: Tb(p-MBA)3phen/AlQ/LiF/Al. The characteristics of these devices have been investigated. The emission of PVK is completely restrained, and only the pure green emission from Tb3+ can be observed in electroluminescence. The optimized device 2 has better monochromatic characteristics with the maximal brightness of 152 cd · m-2 at the voltage of 20 V.

  5. High-efficiency pyrene-based blue light emitting diodes: Aggregation suppression using a calixarene 3D-scaffold

    KAUST Repository

    Chan, Khaileok

    2012-01-01

    An efficient blue light emitting diode based on solution processable pyrene-1,3-alt-calix[4]arene is demonstrated, providing a record current efficiency of 10.5 cd A -1 in a simple non-doped OLED configuration. Complete suppression of pyrene aggregation in the solid state is achieved by controlling chromophore dispersion using the 1,3-alt-calix[4]arene scaffold. © 2012 The Royal Society of Chemistry.

  6. Influence of Energy Level Matching on Device Performances of Organic Light-emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    LIU Chen; ZOU Xue-cheng; YIN Sheng

    2004-01-01

    Through experiments and computer simulation, the influence of the energy levels of organic materials and electrode materials in the organic light-emitting diodes (OLEDs) on the device performances is discussed. Results show that the device performances are influenced by not only the carrier injection barriers at the electrode interface but also the barriers at the organic heterojunction interface. This result is helpful to the selection of the organic materials and their arrangement in the optimal design of OLEDs.

  7. Efficient white organic light-emitting diodes based on iridium complex sensitized copper complex

    Energy Technology Data Exchange (ETDEWEB)

    Su Zisheng; Li Wenlian; Chu Bei; Xu Maoliang; Che Guangbo; Wang Dan; Han Liangliang; Li Xiao; Zhang Dongyu; Bi Defeng; Chen Yiren [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)], E-mail: wllioel@yahoo.com.cn

    2008-04-21

    Efficient double emission-layer white organic light-emitting diodes comprising a yellow emission from bis[(4,6-difluorophenyl)-pyridinato-N,C{sup 2}](picolinato)Ir(III) (FIrpic) sensitized [Cu(bis[2-(diphenylphosphino)phenyl]ether) (6,7-Dicyanodipyrido[2,2-d : 2', 3'-f] quinoxaline)]BF{sub 4}(Cu{sup I} complex) and a blue emission from 4, 4'-bis(2,2'-diphenylvinyl)-1, 1'-biphenyl (DPVBi) were demonstrated. The emission spectrum can be fine tuned by effectively controlling the thicknesses of the two emission layers. The optimized device with 18 nm FIrpic and the Cu{sup I} complex codoped 4, 4'-N,N'-dicarbazole-biphenyl layer and 12 nm DPVBi layer shows a maximum current efficiency of 8.5 cd A{sup -1}, a maximum power efficiency of 5.3 lm W{sup -1} and a maximum luminance of 3290 cd m{sup -2}. Moreover, the device exhibits a CIE coordinate of (0.345, 0.357) at a bias of 8 V and a slight colour variation with increased voltage from 6 to 16 V.

  8. White Organic Light-Emitting Diodes Using Two Phosphorescence Materials in a Starburst Hole-Transporting Layer

    Directory of Open Access Journals (Sweden)

    Tomoya Inden

    2012-01-01

    Full Text Available We fabricated two kinds of white organic light-emitting diodes (WOLEDs; one consisted of two emissive materials of red and blue, and the other of three emissive materials of red, green, and blue. The red and blue emissive materials were phosphorescent. We evaluated the thickness dependence of the CIE coordinate, the external quantum efficiency (EQE, and the luminance by changing the thicknesses of the Ir(btp2acac and FIrpic layers. Samples consisting of three emissive materials revealed the best CIE coordinate and the best EQE in the same sample structure. On the other hand, the samples consisting of two emissive materials revealed the best CIE coordinate and the best EQE in different structures. The best CIE coordinate of (0.33, 0.36 was observed by changing the thicknesses of the stacked active layers. The best EQE was 9.73%, which was observed in the sample consisting of different thickness of stacked active layers.

  9. Phototransferred thermoluminescence from alpha-Al sub 2 O sub 3 :C using blue light emitting diodes

    CERN Document Server

    Bulur, E

    1999-01-01

    Phototransferred thermoluminescence (PTTL) from alpha-Al sub 2 O sub 3 :C single crystals was studied using a blue light emitting diode (LED) for phototransfer of charges from deep traps to the main dosimetry trap. The dose response was found to be linear in the region from approx 5 mGy to approx 5 Gy. It was observed that the corresponding deep traps were located near 500 deg. C and heating to temperatures >600 deg. C removes the PTTL effect induced by the light from the blue LED. The thermal activation energy of the source traps involved in the PTTL production was calculated as 3.23 eV.

  10. Electron-enhanced hole injection in blue polyfluorene-based polymer light-emitting diodes

    NARCIS (Netherlands)

    Woudenbergh, T. van; Wildeman, J.; Blom, P.W.M.; Bastiaansen, J.J.A.M.; Langeveld-Voss, B.M.W.

    2004-01-01

    It has recently been reported that, after electrical conditioning, an ohmic hole contact is formed in poly(9,9-dioctylfluorene) (PFO)-based polymer light-emitting diodes (PLED), despite the large hole-injection barrier obtained with a poly(styrene sulfonic acid)-doped poly(3,4-ethylenedioxythiophene

  11. Optical Experiments Using Mini-Torches with Red, Green and Blue Light Emitting Diodes

    Science.gov (United States)

    Kamata, Masahiro; Matsunaga, Ai

    2007-01-01

    We have developed two kinds of optical experiments: color mixture and fluorescence, using mini-torches with light emitting diodes (LEDs) that emit three primary colors. Since the tools used in the experiments are simple and inexpensive, students can easily retry and develop the experiments by themselves. As well as giving an introduction to basic…

  12. Molecularly controlled interfacial layer strategy toward highly efficient simple-structured organic light-emitting diodes.

    Science.gov (United States)

    Han, Tae-Hee; Choi, Mi-Ri; Woo, Seong-Hoon; Min, Sung-Yong; Lee, Chang-Lyoul; Lee, Tae-Woo

    2012-03-15

    A highly efficient simplified organic light-emitting diode (OLED) with a molecularly controlled strategy to form near-perfect interfacial layer on top of the anode is demonstrated. A self-organized polymeric hole injection layer (HIL) is exploited increasing hole injection, electron blocking, and reducing exciton quenching near the electrode or conducting polymers; this HIL allows simplified OLED comprised a single small-molecule fluorescent layer to exhibits a high current efficiency (∼20 cd/A).

  13. Improved color rendering of phosphor-converted white light-emitting diodes with dual-blue active layers and n-type AlGaN layer.

    Science.gov (United States)

    Yan, Qi-Rong; Zhang, Yong; Li, Shu-Ti; Yan, Qi-Ang; Shi, Pei-Pei; Niu, Qiao-Li; He, Miao; Li, Guo-Ping; Li, Jun-Rui

    2012-05-01

    An InGaN/GaN blue light-emitting diode (LED) structure and an InGaN/GaN blue-violet LED structure were grown sequentially on the same sapphire substrate by metal-organic chemical vapor deposition. It was found that the insertion of an n-type AlGaN layer below the dual blue-emitting active layers showed better spectral stability at the different driving current relative to the traditional p-type AlGaN electron-blocking layer. In addition, color rendering index of a Y3Al5O12:Ce3+ phosphor-converted white LED based on a dual blue-emitting chip with n-type AlGaN reached 91 at 20 mA, and Commission Internationale de L'Eclairage coordinates almost remained at the same point from 5 to 60 mA.

  14. Low-Voltage, Low-Power, Organic Light-Emitting Transistors for Active Matrix Displays

    Science.gov (United States)

    McCarthy, M. A.; Liu, B.; Donoghue, E. P.; Kravchenko, I.; Kim, D. Y.; So, F.; Rinzler, A. G.

    2011-04-01

    Intrinsic nonuniformity in the polycrystalline-silicon backplane transistors of active matrix organic light-emitting diode displays severely limits display size. Organic semiconductors might provide an alternative, but their mobility remains too low to be useful in the conventional thin-film transistor design. Here we demonstrate an organic channel light-emitting transistor operating at low voltage, with low power dissipation, and high aperture ratio, in the three primary colors. The high level of performance is enabled by a single-wall carbon nanotube network source electrode that permits integration of the drive transistor and the light emitter into an efficient single stacked device. The performance demonstrated is comparable to that of polycrystalline-silicon backplane transistor-driven display pixels.

  15. Organic Light-Emitting Diodes on Solution-Processed Graphene Transparent Electrodes

    KAUST Repository

    Wu, Junbo

    2010-01-26

    Theoretical estimates indicate that graphene thin films can be used as transparent electrodes for thin-film devices such as solar cells and organic light-emitting diodes, with an unmatched combination of sheet resistance and transparency. We demonstrate organic light-emitting diodes with solution-processed graphene thin film transparent conductive anodes. The graphene electrodes were deposited on quartz substrates by spincoating of an aqueous dispersion of functionalized graphene, followed by a vacuum anneal step to reduce the sheet resistance. Small molecular weight organic materials and a metal cathode were directly deposited on the graphene anodes, resulting in devices with a performance comparable to control devices on indium-tin-oxide transparent anodes. The outcoupling efficiency of devices on graphene and indium-tin-oxide is nearly identical, in agreement with model predictions. © 2010 American Chemical Society.

  16. High-efficiency white organic light-emitting devices with a non-doped yellow phosphorescent emissive layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Juan; Yu Junsheng, E-mail: jsyu@uestc.edu.cn; Hu Xiao; Hou Menghan; Jiang Yadong

    2012-03-30

    Highly efficient phosphorescent white organic light-emitting devices (PHWOLEDs) with a simple structure of ITO/TAPC (40 nm)/mCP:FIrpic (20 nm, x wt.%)/bis[2-(4-tertbutylphenyl)benzothiazolato-N,C{sup 2} Prime ] iridium (acetylacetonate) (tbt){sub 2}Ir(acac) (y nm)/Bphen (30 nm)/Mg:Ag (200 nm) have been developed, by inserting a thin layer of non-doped yellow phosphorescent (tbt){sub 2}Ir(acac) between doped blue emitting layer (EML) and electron transporting layer. By changing the doping concentration of the blue EML and the thickness of the non-doped yellow EML, a PHWOLED comprised of higher blue doping concentration and thinner yellow EML achieves a high current efficiency of 31.7 cd/A and Commission Internationale de l'Eclairage coordinates of (0.33, 0.41) at a luminance of 3000 cd/m{sup 2} could be observed. - Highlights: Black-Right-Pointing-Pointer We introduce a simplified architecture for phosphorescent white organic light-emitting device. Black-Right-Pointing-Pointer The key concept of device fabrication is combination of doped blue emissive layer (EML) with non-doped ultra-thin yellow EML. Black-Right-Pointing-Pointer Doping concentration of the blue EML and thickness of the yellow EML are sequentially adjusted. Black-Right-Pointing-Pointer High device performance is achieved due to improved charge carrier balance as well as two parallel emission mechanisms in the EMLs.

  17. Microwave assisted transformation of N,N-diphenylamine as precursors of organic light emitting diodes (OLED)

    Energy Technology Data Exchange (ETDEWEB)

    Jefri,; Wahyuningrum, Deana, E-mail: deana@chem.itb.ac.id [Organic Chemistry Research Division, Department of Chemistry, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung 40132 (Indonesia)

    2015-09-30

    In this research, study on the transformation of N,N-diphenylamine (DPA) using iodine (I2) utilizing solid state Microwave Assisted Organic Synthesis (MAOS) method has been carried out. The reaction was performed by variations of three parameters namely the mole of reagents, the amount and type of solid support (alumina/Al2O3), and the reaction conditions. Experimental results showed that neutral-alumina was a better solid support than basic-alumina. The optimum temperature for the reaction was approximately at 125-133 °C with reaction time of 15 minutes and microwave reactor power at 500-600 W. The separation of the yellowish green product solution with preparative Thin Layer Chromatography (TLC) method using n-hexane:ethyl acetate = 4:1 (v/v) as eluent yielded two fractions (I and II) and both fractions can undergo fluorescence under 365 nm UV light. Based on the LC chromatogram with methanol:water = 95:5 (v/v) as eluent and its corresponding mass spectra (ESI+), fraction I contained three compounds, which were tetracarbazole A, triphenylamine, and impurities in the form of plasticizer such as bis(2-ethylhexyl) phthalate. Fraction II also contained three compounds, which were tetracarbazole C, tetraphenylhydrazine, and plasticizer such as bis(2-ethylhexyl) phthalate. Both FT-IR (KBr disks) and NMR (500 MHz, CDCl{sub 3}) spectra of fraction I and II confirmed the aromatic amine groups in those compounds. The observed fluorescence colors of fraction I and II were violet and violet-blue, respectively. Based on their structures and fluorescence characters, the compounds in fraction I and II have the potential to be used as Organic Light Emitting Diode (OLED) compound precursors.

  18. Direct visualization and modeling of carrier distribution in organic light emitting transistor

    Energy Technology Data Exchange (ETDEWEB)

    Mashiko, Yasuhiro; Taguchi, Dai; Manaka, Takaaki [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo, 152-8552 (Japan); Iwamoto, Mitsumasa, E-mail: iwamoto@pe.titech.ac.jp [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo, 152-8552 (Japan); Weis, Martin [Institute of Electronics and Photonics, Slovak University of Technology, Ilkovičova 3, Bratislava 81219 (Slovakia)

    2014-03-03

    By using microscopic electric field induced second harmonic generation (EFISHG) measurement, we studied the carrier distribution in the channel of organic light emitting transistors with an active layer of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole). EFISHG signals were clearly observed in the point where the electroluminescence is generated. Results suggested that the highest enhancement of the electric field is on zero-potential position in the channel, which represents the meeting point of electrons and holes and is an origin of the electroluminescence. The transmission line model analysis of the carrier distribution of the channel supported this conclusion. - Highlights: • Carrier distribution in organic light emitting transistor channel was determined. • Second-harmonic generation images were clearly observed in the emission region. • A transmission line model well accounted for the observed carrier behavior.

  19. Study of natural organic dyes as active material for fabrication of organic light emitting diodes

    Science.gov (United States)

    Sánchez Juárez, A.; Castillo, D.; Guaman, A.; Espinosa, S.; Obregón, D.

    2016-09-01

    The scientific community and some sectors of industry have been working with organic dyes for successful applications in OLED's, OSC's, however, most of the used dyes and pigments are synthetic. In this work is investigated the use of natural dyes for its application in organic light emitting diodes, some of the studied species are chili, blackberry, guayacan flower, cochinilla, tree tomato, capuli, etc. In this study the dyes are deposited by direct deposition and SOL-GEL process doped with the natural organic dye, both methods show good performance and lower fabrication costs for dye extraction, this represents a new alternative for the fabrication of OLED devices with low requirements in technology. Most representative results are presented for Dactylopius Coccus Costa (cochinilla) and raphanus sativus' skin.

  20. Substrate patterning for passive matrix organic light-emitting devices by photolithography processing

    Science.gov (United States)

    Wang, Jun; Yu, Jun-sheng; Lin, Hui; Lou, Shuang-ling; Jiang, Ya-dong

    2007-12-01

    The fabrication technology of high resolution substrate pattern for organic light-emitting devices (OLEDs) was discussed in the paper. Surface morphology and crystallization properties of ITO films and the shape of photolithography pattern were investigated. Experimental results show that three factors including deposition pressure, flow ratio of argon to oxygen and annealing temperature greatly influence the conductance of ITO film.. Some attempts about designing photomask were enumerated and the reverse taper angle separator was successfully fabricated with image reversal process.

  1. Hybrid silicon nanocrystal-organic light-emitting devices for infrared electroluminescence.

    Science.gov (United States)

    Cheng, Kai-Yuan; Anthony, Rebecca; Kortshagen, Uwe R; Holmes, Russell J

    2010-04-14

    We demonstrate hybrid inorganic-organic light-emitting devices with peak electroluminescence (EL) at a wavelength of 868 nm using silicon nanocrystals (SiNCs). An external quantum efficiency of 0.6% is realized in the forward-emitted direction, with emission originating primarily from the SiNCs. Microscopic characterization indicates that complete coverage of the SiNCs on the conjugated polymer hole-transporting layer is required to observe efficient EL.

  2. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Eun Lee, Song; Kwan Kim, Young [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Hwa Yu, Hyeong; Turak, Ayse [Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Young Kim, Woo, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

    2015-06-28

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.

  3. Blue InGaN light-emitting diodes with dip-shaped quantum wells

    Institute of Scientific and Technical Information of China (English)

    Lu Tai-Ping; Wang Hai-Long; Yang Xiao-Dong; LiShu-Ti; Zhang Kang; Liu Chao; Xiao Guo-Wei; Zhou Yu-Gang; ZhengShu-Wen; Yin Yi-An; Wu Le-Juan

    2011-01-01

    InGaN based light-emitting diodes (LEDs) with dip-shaped quantum wells and conventional rectangular quantum wells are numerically investigated by using the APSYS simulation software.It is found that the structure with dipshaped quantum wells shows improved light output power,lower current leakage and less efficiency droop.Based on numerical simulation and analysis,these improvements on the electrical and the optical characteristics are attributed mainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells (MQWs).

  4. Highly efficient exciplex organic light-emitting diodes using thermally activated delayed fluorescent emitters as donor and acceptor materials.

    Science.gov (United States)

    Jeon, Sang Kyu; Yook, Kyoung Soo; Lee, Jun Yeob

    2016-06-01

    Highly efficient exciplex type organic light-emitting diodes were developed using thermally activated delayed fluorescent emitters as donors and acceptors of an exciplex. Blue emitting bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS) was a donor and 9,9'-(5-(4,6-diphenyl-1,3,5-triazin-2-yl)-1,3-phenylene)bis(9H-carbazole) (DDCzTrz) and 9,9',9″-(5-(4,6-diphenyl-1,3,5-triazin-2-yl)benzene-1,2,3-triyl)tris(9H-carbazole) (TCzTrz) were acceptor materials. The exciplexes of DMAC-DPS:TCzTrz and DMAC-DPS:DDCzTrz resulted in high photoluminescence quantum yield and high quantum efficiency in the green exciplex organic light-emitting diodes. High quantum efficiencies of 13.4% and 15.3% were obtained in the DMAC-DPS:DDCzTrz and DMAC-DPS:TCzTrz exciplex devices.

  5. Organic light emitting device architecture for reducing the number of organic materials

    Science.gov (United States)

    D'Andrade, Brian; Esler, James

    2011-10-18

    An organic light emitting device is provided. The device includes an anode and a cathode. A first emissive layer is disposed between the anode and the cathode. The first emissive layer includes a first non-emitting organic material, which is an organometallic material present in the first emissive layer in a concentration of at least 50 wt %. The first emissive layer also includes a first emitting organic material. A second emissive layer is disposed between the first emissive layer and the cathode, preferably, in direct contact with the first emissive layer. The second emissive material includes a second non-emitting organic material and a second emitting organic material. The first and second non-emitting materials, and the first and second emitting materials, are all different materials. A first non-emissive layer is disposed between the first emissive layer and the anode, and in direct contact with the first emissive layer. The first non- emissive layer comprises the first non-emissive organic material.

  6. Patterning of flexible organic light emitting diode (FOLED) stack using an ultrafast laser.

    Science.gov (United States)

    Mandamparambil, Rajesh; Fledderus, Henri; Van Steenberge, Geert; Dietzel, Andreas

    2010-04-12

    A femtosecond laser has been successfully utilized for patterning thin Flexible Organic Light Emitting Diode (FOLED) structures of individual layer thickness around 100nm. The authors report in this paper a step-like ablation behavior at the layer interfaces which accounts for a local removal of entire layers. Various surface analyzing techniques are used to investigate the morphologies and chemical compositions within and in the vicinity of the ablation areas. This study opens a new avenue in selectively ablating different layers from a multilayer stack on flexible substrates using fs lasers allowing post deposition structuring of large area flexible organic electronic devices.

  7. Towards developing a tandem of organic solar cell and light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [School of Engineering and IT, B-purple-12, Faculty of EHS, Charles Darwin University, Darwin, NT 0909 (Australia)

    2011-01-15

    It is proposed here to design a tandem of organic solar cell (OSC) and white organic light emitting diode (WOLED) which can generate power in the day time from the sun and provide lighting at night. With the advancement of chemical technology, such device is expected to be very-cost effective and reasonably efficient. A device thus fabricated has the potential of meeting the world's sustainable domestic and commercial power and lighting needs (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Efficiency droop alleviation in blue light emitting diodes using the InGaN/GaN triangular-shaped quantum well

    Institute of Scientific and Technical Information of China (English)

    Chen Zhao; Hu Chen Wei-Hua; Xiao-Dong; Yang Wei; Liu Lei; Wan Cheng-Hao; Li Lei; He Yong-Fa; Liu Ning-Yang; Wang Lei; Li Din

    2012-01-01

    The InGaN/GaN blue light emitting diode (LED) is numerically investigated using a triangular-shaped quantum well model,which involves analysis on its energy band,carrier concentration,overlap of electron and hole wave functions,radiative recombination rate,and internal quantum efficiency.The simulation results reveal that the InGaN/GaN blue light emitting diode with triangular quantum wells exhibits a higher radiative recombination rate than the conventional light emitting diode with rectangular quantum wells due to the enhanced overlap of electron and hole wave functions (above 90%) under the polarization field.Consequently,the efficiency droop is only 18% in the light emitting diode with triangular-shaped quantum wells,which is three times lower than that in a conventional LED.

  9. Development and Utilization of Host Materials for White Phosphorescent Organic Light-Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Ching; Chen, Shaw

    2013-05-31

    Our project was primarily focused on the MYPP 2015 goal for white phosphorescent organic devices (PhOLEDs or phosphorescent organic light-emitting diodes) for solid-state lighting with long lifetimes and high efficiencies. Our central activity was to synthesize and evaluate a new class of host materials for blue phosphors in the PhOLEDs, known to be a weak link in the device operating lifetime. The work was a collaborative effort between three groups, one primarily responsible for chemical design and characterization (Chen), one primarily responsible for device development (Tang) and one primarily responsible for mechanistic studies and degradation analysis (Rothberg). The host materials were designed with a novel architecture that chemically links groups with good ability to move electrons with those having good ability to move “holes” (positive charges), the main premise being that we could suppress the instability associated with physical separation and crystallization of the electron conducting and hole conducting materials that might cause the devices to fail. We found that these materials do prevent crystallization and that this will increase device lifetimes but that efficiencies were reduced substantially due to interactions between the materials creating new low energy “charge transfer” states that are non-luminescent. Therefore, while our proposed strategy could in principle improve device lifetimes, we were unable to find a materials combination where the efficiency was not substantially compromised. In the course of our project, we made several important contributions that are peripherally related to the main project goal. First, we were able to prepare the proposed new family of materials and develop synthetic routes to make them efficiently. These types of materials that can transport both electrons and holes may yet have important roles to play in organic device technology. Second we developed an important new method for controlling the

  10. Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps

    Science.gov (United States)

    Mickens, Matthew A.

    2012-01-01

    Growing vegetable crops in space will be an essential part of sustaining astronauts during long-term missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop production, there have also been recent interests in analyzing the subtle effects of green light on plant growth, and to determine if it serves as a source of growth enhancement or suppression. A comparative study was performed on two short cycle crops of lettuce (Outredgeous) and radish (Cherry Bomb) grown under two light treatments. The first treatment being red and blue LEDs, and the second treatment consisting of white fluorescent lamps which contain a portion of green light. In addition to comparing biomass production, physiological characterizations were conducted on how the light treatments influence morphology, water use, chlorophyll content, and the production of A TP within plant tissues.

  11. Germafluorene conjugated copolymer——synthesis and applications in blue-light-emitting diodes and host materials

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A germafluorene-fluorene copolymer was successfully obtained via Suzuki polymerization.The ger-manium containing copolymer has an efficient blue light emission under the ultraviolet irradiation and its single layer EL device showed the highest brightness of 2630 cd/m2 at 7.8 V and the highest effi-ciency of 0.301 lm/W at 6.2 V.The copolymer can also serve as the host material for phosphorescent metal complexes with the maximum brightness of 15600 cd/m2 and the quantum efficiency of 8.5%.The results are quite promising and promise that as its analogs of fluorene and silafluorene,germafluorene is an excellent building block for blue light-emitting polymers and host materials.

  12. Germafluorene conjugated copolymer——synthesis and applications in blue-light-emitting diodes and host materials

    Institute of Scientific and Technical Information of China (English)

    CHEN RunFeng; ZHU Rui; ZHENG Chao; LIU ShuJuan; FAN QuLi; HUANG Wei

    2009-01-01

    A germafluorene-fluorene copolymer was successfully obtained via Suzuki polymerization. The ger-manium containing copolymer has an efficient blue light emission under the ultraviolet irradiation and its single layer EL device showed the highest brightness of 2630 cd/m2 at 7.8 V and the highest effi-ciency of 0.301 Im/W at 6.2 V. The copolymer can also serve as the host material for phosphorescent metal complexes with the maximum brightness of 15600 cd/m2 and the quantum efficiency of 8.5%. The results are quite promising and promise that as its analogs of fluorene and silafluorene, germafluorene is an excellent building block for blue light-emitting polymers and host materials.

  13. Study of Nanostructured Polymeric Composites Used for Organic Light Emitting Diodes and Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Nguyen Nang Dinh

    2012-01-01

    Full Text Available Polymeric nanocomposite films from PEDOT and MEH-PPV embedded with surface modified TiO2 nanoparticles for the hole transport layer and emission layer were prepared, respectively, for organic emitting diodes (OLEDs. The composite of MEH-PPV+nc-TiO2 was used for organic solar cells (OSCs. The characterization of these nanocomposites and devices showed that electrical (I-V characteristics and spectroscopic (photoluminescent properties of conjugate polymers were enhanced by the incorporation of nc-TiO2 in the polymers. The organic light emitting diodes made from the nanocomposite films would exhibit a larger photonic efficiency and a longer lasting life. For the organic solar cells made from MEH-PPV+nc-TiO2 composite, a fill factor reached a value of about 0.34. Under illumination by light with a power density of 50 mW/cm2, the photoelectrical conversion efficiency was about 0.15% corresponding to an open circuit voltage Voc = 0.126 V and a shortcut circuit current density Jsc = 1.18 mA/cm2.

  14. Ambient fabrication of flexible and large-area organic light-emitting devices using slot-die coating

    DEFF Research Database (Denmark)

    Sandstrom, Andreas; Dam, Henrik Friis; Krebs, Frederik C;

    2012-01-01

    The grand vision of manufacturing large-area emissive devices with low-cost roll-to-roll coating methods, akin to how newspapers are produced, appeared with the emergence of the organic light-emitting diode about 20 years ago. Today, small organic light-emitting diode displays are commercially...... available in smartphones, but the promise of a continuous ambient fabrication has unfortunately not materialized yet, as organic light-emitting diodes invariably depend on the use of one or more time-and energy-consuming process steps under vacuum. Here we report an all-solution-based fabrication...... of an alternative emissive device, a light-emitting electrochemical cell, using a slot-die roll-coating apparatus. The fabricated flexible sheets exhibit bidirectional and uniform light emission, and feature a fault-tolerant >1-mu m-thick active material that is doped in situ during operation. It is notable...

  15. Efficient inverted organic light-emitting devices by amine-based solvent treatment (Presentation Recording)

    Science.gov (United States)

    Song, Myoung Hoon; Choi, Kyoung-Jin; Jung, Eui Dae

    2015-10-01

    The efficiency of inverted polymer light-emitting diodes (iPLEDs) were remarkably enhanced by introducing spontaneously formed ripple-shaped nanostructure of ZnO (ZnO-R) and amine-based polar solvent treatment using 2-methoxyethanol and ethanolamine (2-ME+EA) co-solvents on ZnO-R. The ripple-shape nanostructure of ZnO layer fabricated by solution process with optimal rate of annealing temperature improves the extraction of wave guide modes inside the device structure, and 2-ME+EA interlayer enhances the electron injection and hole blocking and reduces exciton quenching between polar solvent treated ZnO-R and emissive layer. As a result, our optimized iPLEDs show the luminous efficiency (LE) of 61.6 cd A-1, power efficiency (PE) of 19.4 lm W-1 and external quantum efficiency (EQE) of 17.8 %. This method provides a promising method, and opens new possibilities for not only organic light-emitting diodes (OLEDs) but also other organic optoelectronic devices such as organic photovoltaics, organic thin film transistors, and electrically driven organic diode laser.

  16. STUDY OF DEGRADATION MECHANISM AND PACKAGING OF ORGANIC LIGHT EMITTING DEVICES

    Institute of Scientific and Technical Information of China (English)

    Gu Xu

    2003-01-01

    Organic Light Emitting Devices (OLED) have attracted much attention recently, for their applications in future Flat Panel Displays and lighting products. However, their fast degradation remained a major obstacle to their commercialization. Here we present a brief summary of our studies on both extrinsic and intrinsic causes for the fast degradation of OLEDs. In particular, we focus on the origin of the dark spots by "rebuilding" cathodes, which confirms that the growth of dark spots occurs primarily due to cathode delamination. In the meantime, we recapture the findings from the search for suitable OLED packaging materials, in particular polymer composites, which provide both heat dissipation and moisture resistance, in addition to electrical insulation.

  17. Energy-recycling pixel for active-matrix organic light-emitting diode display

    Science.gov (United States)

    Yang, Che-Yu; Cho, Ting-Yi; Chen, Yen-Yu; Yang, Chih-Jen; Meng, Chao-Yu; Yang, Chieh-Hung; Yang, Po-Chuan; Chang, Hsu-Yu; Hsueh, Chun-Yuan; Wu, Chung-Chih; Lee, Si-Chen

    2007-06-01

    The authors report a pixel structure for active-matrix organic light-emitting diode (OLED) displays that has a hydrogenated amorphous silicon solar cell inserted between the driving polycrystalline Si thin-film transistor and the pixel OLED. Such an active-matrix OLED pixel structure not only exhibits a reduced reflection (and thus improved contrast) compared to conventional OLEDs but also is capable of recycling both incident photon energies and internally generated OLED radiation. Such a feature of energy recycling may be of use for portable/mobile electronics, which are particularly power aware.

  18. Flexible Substrates with Polyimide Buffer Layers for Organic Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    常春; 王立铎; 李扬; 段炼; 邱勇

    2004-01-01

    We report a new method to enhance the properties of the polyethyleneterephthalate (PET) substrates for flexible organic light-emitting diodes (OLEDs). By spin-coating a polyimide (PI) film between the PET and the indiumtin-oxide anode, the flexible substrate with a smooth surface, high transmission over the visible spectrum and good adhesion are achieved. We also compare the flexible OLEDs on different substrates. The diodes on the substrates with polyimide buffer layers exhibit a brightness of 7280cd/m2 at 15 V and the maximum efficiency of 2.64 cd/A.

  19. New hybrid encapsulation for flexible organic light-emitting devices on plastic substrates

    Institute of Scientific and Technical Information of China (English)

    LIU Song; ZHANG DeQiang; LI Yang; DUAN Lian; DONG GuiFang; WANG LiDuo; QIU Yong

    2008-01-01

    The hybrid encapsulation for flexible organic light-emitting devices on plastic substrate was investi-gated. The hybrid encapsulation consisted of four periods of Alq3/LiF layers as the pre-encapsulation layer and a flexible aluminum foil coated with getter as the encapsulation cap. We measured the device lifetime at a continuous constant current of 20 mA/cm2, which corresponded to an initial luminance of 2000 cd/m2, The half-luminance decay time of the encapsulated device was about 458 h. More over, the hybrid encapsulation is ultrathin and flexible, ensuring device bendability.

  20. Interface modification and material synthesis of organic light-emitting diodes using plasma technology

    Science.gov (United States)

    Liang, Rongqing; Ou, Qiongrong; Yang, Cheng; He, Kongduo; Yang, Xilu; Zhong, Shaofeng; plasma application Team

    2015-09-01

    Organic light-emitting diodes (OLEDs), due to their unique properties of solution processability, compatibility with flexible substrates and with large-scale printing technology, attract huge interest in the field of lighting. The integration of plasma technology into OLEDs provides a new route to improve their performance. Here we demonstrate the modification of indium-tin-oxide (ITO) work function by plasma treatment, synthesis of thermally activated delayed fluorescence (TADF) materials using plasma grafting (polymerisation), and multi-layer solution processing achieved by plasma cross-linking.

  1. Efficient organic light-emitting devices with platinum-complex emissive layer

    KAUST Repository

    Yang, Xiaohui

    2011-01-18

    We report efficient organic light-emitting devices having a platinum-complex emissive layer with the peak external quantum efficiency of 17.5% and power efficiency of 45 lm W−1. Variation in the device performance with platinum-complex layer thickness can be attributed to the interplay between carrier recombination and intermolecular interactions in the layer. Efficient white devices using double platinum-complex layers show the external quantum efficiency of 10%, the Commission Internationale d’Énclairage coordinates of (0.42, 0.41), and color rendering index of 84 at 1000 cd m−2.

  2. Optical Characterization of Organic Light-Emitting Thin Films in the Ultraviolet and Visible Spectral Ranges

    CERN Document Server

    Montereali, R M; Nichelatti, E; Di Pompeo, F; Segreto, E; Canci, N; Cavanna, F

    2012-01-01

    The spectrophotometric characterization of high efficiency, optically-active samples such as light-emitting organic bulks and thin films can be problematic because their broad-band luminescence is detected together with the monochromatic transmitted and reflected signals, hence perturbing measurements of optical transmittance and reflectance at wavelengths within the photoexcitation band. As a matter of fact, most commercial spectrophotometers apply spectral filtering before the light beam reaches the sample, not after it. In this Report, we introduce and discuss the method we have developed to correct photometric spectra that are perturbed by photoluminescence.

  3. High efficiency tandem organic light-emitting devices with Al/WO3/Au interconnecting layer

    OpenAIRE

    2007-01-01

    An interconnecting layer of Al (2 nm)/WO3 (3 nm)/Au (16 nm) was studied for application in tandem organic light-emitting devices. It can be seen that the Al/WO3/Au structure plays the role of an excellent interconnecting layer. The introduction of WO3 in the connection unit significantly improves the device efficiency as compared to the case of Al/Au. Thus, the current efficiency of the two-unit tandem devices is enhanced by two factors with respect to the one-unit devices. The green two-u...

  4. Molecular hosts for triplet emitters in organic light-emitting diodes and the corresponding working principle

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper summarizes the mechanism and routes for excitation of triplet emitters in dopant emission based phosphorescent organic light-emitting diodes (PhOLEDs),providing a comprehensive overview of recent progress in molecular hosts for triplet emitters in PhOLEDs.Particularly,based on the nature of different hosts,e.g.,hole transporting,electron transporting or bipolar materials,in which the dopant emitters can be hosted to generate phosphorescence,the respective device performances are summarized and compared.Highlights are given to the relationships among the molecular structure,thermal stability,triplet energy,carrier mobility,molecular orbital energy level and their corresponding device performances.

  5. Organic thin-film transistor arrays for active-matrix organic light emitting diode

    Science.gov (United States)

    Lee, Sangyun; Moon, Hyunsik; Kim, Do H.; Koo, Bon-Won; Jeong, Eun-Jeong; Lee, Bang-Lin; Kim, Joo-Young; Lee, Eunkyung; Hahn, Kook-Min; Han, Jeong-Seok; Park, Jung-Il; Seon, Jong-Baek; Kim, Jung-Woo; Chun, Young-Tea; Kim, Sangyeol; Kang, Sung K.

    2007-09-01

    We developed an active matrix organic light-emitting diodes (AMOLEDs) on a glass using two organic thin-film transistors (OTFTs) and a capacitor in a pixel. OTFTs switching-arrays with 64 scan lines and 64 (RGB) data lines were designed and fabricated to drive OLED arrays. In this study, OTFT devices have bottom contact structures with an ink-jet printed polymer semiconductor and an organic insulator as a gate dielectric. The width and length of the switching OTFT is 500μm and 10μm, respectively and the driving OTFT has 900μm channel width with the same channel length. The characteristics of the OTFTs were examined using test cells around display area. On/off ratio, mobility, on-current of switching OTFT and on-current of driving OTFT were 10 6, 0.1 cm2/V-sec, order of 8μA and over 70 μA respectively. These properties were enough to drive the AMOLEDs over 60 Hz frame rate. AMOLEDs composed of the OTFT switching arrays and OLEDs made by deposition of small molecule materials were fabricated and driven to make moving images, successfully.

  6. Growth and characterization of phosphor-free white light-emitting diodes based on InGaN blue quantum wells and green-yellow quantum dots

    Science.gov (United States)

    Yang, Di; Wang, Lai; Lv, Wen-Bin; Hao, Zhi-Biao; Luo, Yi

    2015-06-01

    Phosphor-free white light-emitting diodes consisting of 4 layers of InGaN/GaN quantum dots and 4 layers of quantum wells have been grown by metal organic chemical vapor deposition. A white emission was demonstrated under electrical injection by mixing the green-yellow light from quantum dots and the blue light from quantum wells. At the injection current of 5 mA, the electroluminescence peak wavelengths of quantum dots and quantum wells were 548 nm and 450 nm, respectively, resulting in the color-rendering index Ra of 62. As the injection current increased, a faster emission enhancement of quantum well and an emission blue shift of the quantum dots were observed, which led to the decrease of Ra.

  7. A multi-zoned white organic light-emitting diode with high CRI and low color temperature

    Science.gov (United States)

    Zhang, Tao; He, Shou-Jie; Wang, Deng-Ke; Jiang, Nan; Lu, Zheng-Hong

    2016-02-01

    White organic light emitting diodes (WOLEDs) is becoming a new platform technology for a range of applications such as flat-panel displays, solid-state lightings etc., and are under intensive research. For general solid-state illumination applications, a WOLED’s color rendering index (CRI) and correlated color temperature (CCT) are two crucial parameters. This paper reports that WOLED device structures can be constructed using four stacked emission layers which independently emit lights at blue, green, yellow and red color respectively. The intensity of each emission layer is then engineered by funneling excitons to the targeted emission layer to achieve an ultrahigh 92 CRI at 5000 cd/m2, and to reduce CCT to below 2500 K.

  8. Advances in phosphors based on organic materials for light emitting devices

    Science.gov (United States)

    Sharma, Kashma; Kumar, Vijay; Kumar, Vinod; Swart, Hendrik C.

    2016-01-01

    A brief overview is presented in the light emitting diodes (LEDs) based on purely organic materials. Organic LEDs are of great interest to the research community because of their outstanding properties and flexibility. Comparison between devices made using different organic materials and their derivatives with respect to synthetic protocols, characterizations, quantum efficiencies, sensitivity, specificity and their applications in various fields have been discussed. This review also discusses the essential requirement and scientific issues that arise in synthesizing cost-effective and environmental friendly organic LEDs diodes based on purely organic materials. This mini review aims to capture and convey some of the key current developments in phosphors formed by purely organic materials and highlights some possible future applications. Hence, this study comes up with a widespread discussion on the various contents in a single platform. Also, it offers avenues for new researchers for futuristic development in the area.

  9. Ultrasonic spray coating polymer and small molecular organic film for organic light-emitting devices

    Science.gov (United States)

    Liu, Shihao; Zhang, Xiang; Zhang, Letian; Xie, Wenfa

    2016-11-01

    Ultrasonic spray coating process (USCP) with high material -utilization, low manufacture costs and compatibility to streamline production has been attractive in researches on photoelectric devices. However, surface tension exists in the solvent is still a huge obstacle to realize smooth organic film for organic light emitting devices (OLEDs) by USCP. Here, high quality polymer anode buffer layer and small molecular emitting layer are successfully realized through USCP by introducing extra-low surface tension diluent and surface tension control method. The introduction of low surface tension methyl alcohol is beneficial to the formation of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films and brings obvious phase separation and improved conductivity to PEDOT:PSS film. Besides, a surface tension control method, in which new stable tension equilibrium is built at the border of wetting layer, is proposed to eliminate the effect of surface tension during the solvent evaporation stage of ultrasonic spray coating the film consists of 9,9-Spirobifluoren-2-yl-diphenyl-phosphine oxide doped with 10 wt% tris [2-(p -tolyl) pyridine] iridium (III). A smooth and homogenous small molecular emitting layer without wrinkles is successfully realized. The effectiveness of the ultrasonic spray coating polymer anode buffer layer and small molecular emitting layer are also proved by introducing them in OLEDs.

  10. The electrodeposition of multilayers on a polymeric substrate in Flexible Organic Light Emitting Diode (OLED)

    Science.gov (United States)

    Guedes, Andre F. S.; Guedes, Vilmar P.; Tartari, Simone; Cunha, Idaulo Jose

    2016-09-01

    The development of Organic Light Emitting Diode (OLED), using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The OLED are the base Poly(3,4-ethylenedioxythiophene), PEDOT, Poly(p-phenylenevinylene), PPV, and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by UV-Visible Spectroscopy (UV-Vis), Optical Parameters (OP) and Scanning Electron Microscopy (SEM). In addition, the thin film obtained by the deposition of PANI, prepared in perchloric acid solution, was identified through PANI-X1. The result obtained by UV-Vis has demonstrated that the PET/ITO/PEDOT/PPV/PANI-X1/Al layer does not have displacement of absorption for wavelengths greaters after spin-coating and electrodeposition. Thus, the spectral irradiance of the OLED informed the irradiance of 100 W/m2, and this result, compared with the standard Light Emitting Diode (LED), has indicated that the OLED has higher irradiance. After 1200 hours of electrical OLED tests, the appearance of nanoparticles visible for images by SEM, to the migration process of organic semiconductor materials, was present, then. Still, similar to the phenomenon of electromigration observed in connections and interconnections of microelectronic devices, the results have revealed a new mechanism of migration, which raises the passage of electric current in OLED.

  11. Stacking multiple connecting functional materials in tandem organic light-emitting diodes

    Science.gov (United States)

    Zhang, Tao; Wang, Deng-Ke; Jiang, Nan; Lu, Zheng-Hong

    2017-01-01

    Tandem device is an important architecture in fabricating high performance organic light-emitting diodes and organic photovoltaic cells. The key element in making a high performance tandem device is the connecting materials stack, which plays an important role in electric field distribution, charge generation and charge injection. For a tandem organic light-emitting diode (OLED) with a simple Liq/Al/MoO3 stack, we discovered that there is a significant current lateral spreading causing light emission over an extremely large area outside the OLED pixel when the Al thickness exceeds 2 nm. This spread light emission, caused by an inductive electric field over one of the device unit, limits one’s ability to fabricate high performance tandem devices. To resolve this issue, a new connecting materials stack with a C60 fullerene buffer layer is reported. This new structure permits optimization of the Al metal layer in the connecting stack and thus enables us to fabricate an efficient tandem OLED having a high 155.6 cd/A current efficiency and a low roll-off (or droop) in current efficiency. PMID:28225028

  12. Effects of spectral parameters on the light properties of red-green-blue white light-emitting diodes.

    Science.gov (United States)

    Xu, Mingsheng; Zhang, Haoxiang; Zhou, Quanbin; Wang, Hong

    2016-06-01

    Red-green-blue white light-emitting diodes (RGB-WLEDs) have great potential as commercial solid-state lighting devices, as well as visible light communication because of their high color-rendering index (CRI) and high response frequency. The quality of light of an RGB-WLED strongly depends on its spectral parameters. In this study, we fabricated RGB-WLEDs with red, blue, and green LEDs and measured the spectral power distribution (SPD). The experimental SPD is consistent with the calculated spectrum. We also measured the SPDs of LEDs with different peak wavelengths and extracted the spectral parameters, which were then used for modeling. We studied the effect of the wavelength and the full width at half-maximum (FWHM) on both the color rendering index and the luminous efficiency (LE) of the RGB-WLED using simulations. We find that the LE improves as the wavelength of the blue LED increases and the wavelength of the red LED decreases. When the wavelength of the green LED increases, the LE increases first, but later decreases. The CRI of the RGB-WLED increases with the wavelengths of the red, blue, and green LEDs first, but then decreases. The optimal wavelengths and FWHMs for maximum color-rendering and LE of the blue, green, and red LEDs are 466, 536, 606 nm; and 26.0, 34.0, and 19.5 nm, respectively.

  13. Organic light-emitting diodes based on a series of new polythienothiophene complexes and highly luminescent quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Vashchenko, A. A. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Goriachiy, D. O., E-mail: goryachii@phystech.edu [Moscow Institute of Physics and Technology (Russian Federation); Vitukhnovsky, A. G. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Tananaev, P. N. [Dukhov Research Institute of Automation (Russian Federation); Vasnev, V. A.; Rodlovskaya, E. N. [Russian Academy of Sciences, Nesmeyanov Institute of Organoelement Compounds (Russian Federation)

    2016-01-15

    Experimental samples of organic light-emitting diodes with transport layers based on polythienothiophenes and using CdSe/CdS/ZnS semiconductor quantum dots with an internal quantum efficiency up to 85% in the emitting layer are investigated. It is shown that solubility and film-forming properties are key for using polythienothiophenes in light-emitting diodes. The most promising polythienothiophenes are identified on the basis of the results obtained.

  14. Novel Na(+) doped Alq3 hybrid materials for organic light-emitting diode (OLED) devices and flat panel displays.

    Science.gov (United States)

    Bhagat, S A; Borghate, S V; Kalyani, N Thejo; Dhoble, S J

    2015-05-01

    Pure and Na(+) -doped Alq3 complexes were synthesized by a simple precipitation method at room temperature, maintaining a stoichiometric ratio. These complexes were characterized by X-ray diffraction, Fourier transform infrared (FTIR), UV/Vis absorption and photoluminescence (PL) spectra. The X-ray diffractogram exhibits well-resolved peaks, revealing the crystalline nature of the synthesized complexes, FTIR confirms the molecular structure and the completion of quinoline ring formation in the metal complex. UV/Vis absorption and PL spectra of sodium-doped Alq3 complexes exhibit high emission intensity in comparison with Alq3 phosphor, proving that when doped in Alq3 , Na(+) enhances PL emission intensity. The excitation spectra of the synthesized complexes lie in the range 242-457 nm when weak shoulders are also considered. Because the sharp excitation peak falls in the blue region of visible radiation, the complexes can be employed for blue chip excitation. The emission wavelength of all the synthesized complexes lies in the bluish green/green region ranging between 485 and 531 nm. The intensity of the emission wavelength was found to be elevated when Na(+) is doped into Alq3 . Because both the excitation and emission wavelengths fall in the visible region of electromagnetic radiation, these phosphors can also be employed to improve the power conversion efficiency of photovoltaic cells by using the solar spectral conversion principle. Thus, the synthesized phosphors can be used as bluish green/green light-emitting phosphors for organic light-emitting diodes, flat panel displays, solid-state lighting technology - a step towards the desire to reduce energy consumption and generate pollution free light.

  15. Sputtering of ZnO buffer layer on Si for GaN blue light emitting materials

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The preparation of high quality ZnO/Si substrates for the growth of GaN blue light emitting materials is considered. ZnO thin films have been deposited on Si(100) and Si(111) substrates by conventional magnetron sputtering. Morphology, crystallinity and c-axis preferred orientation of ZnO thin films have been investigated by transmitting electron microscopy (TEM), X-ray diffraction (XRD) and X-ray rocking curve (XRC). It is proved that the ZnO thin films have perfect structure. The full-width-at-half-maximum (FWHM) of the ZnO(002) XRC of these films is about 1°, while the minimum is 0.353°. This result is better than the minimum FWHM (about 2°) reported by other research groups. Moreover, comparison and discussion are given on film structure of ZnO/Si(100) and ZnO/Si(111)

  16. Sputtering of ZnO buffer layer on Si for GaN blue light emitting materials

    Institute of Scientific and Technical Information of China (English)

    贺洪波; 范正修; 姚振钰; 汤兆胜

    2000-01-01

    The preparation of high quality ZnO/Si substrates for the growth of GaN blue light emitting materials is considered. ZnO thin films have been deposited on Si (100) and Si (111) substrates by conventional magnetron sputtering. Morphology, crystallinity and c-axis preferred orientation of ZnO thin films have been investigated by transmitting electron microscopy (TEM), X-ray diffraction (XRD) and X-ray rocking curve (XRC). It is proved that the ZnO thin films have perfect structure. The full-width-at-half-maximum (FWHM) of the ZnO(002) XRC of these films is about 1°, while the minimum is 0.353°. This result is better than the minimum FWHM (about 2°) reported by other research groups. Moreover, comparison and discussion are given on film structure of ZnO/Si(100) and ZnO/Si(111).

  17. Performance improvement of InGaN blue light-emitting diodes with several kinds of electron-blocking layers

    Institute of Scientific and Technical Information of China (English)

    Chen Jun; Fan Guang-Han; Zhang Yun-Yan; Pang Wei; Zheng Shu-Wen; Yao Guang-Rui

    2012-01-01

    The performance of lnGaN blue light-emitting diodes(LEDs)with different kinds of electron-blocking layers is investigated numerically.We compare the simulated emission spectra,electron and hole concentrations,euergy band diagrams,electrostatic fields,and internal quantum efficiencies of the LEDs.The LED using A1GaN with gradually increasing Al content from 0% to 20% as the electron-blocking layer(EBL)has a strong spectrum intensity,mitigates efficiency droop,and possesses higher output power compared with the LEDs with the other three types of EBLs.These advantages could be because of the lower electron leakage current and more effective hole injection.The optical performance of the specifically designed LED is also improved in the case of large injection current.

  18. Increasing the extraction efficiency of blue light emitting diodes via laser patterned Ga-polar p-GaN surface

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Zhiyuan; Liu, Duo; Zhang, Baitao; He, Jingliang; Liu, Hong; Xu, Xiangang [State Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China)

    2011-09-15

    We report here the laser patterned Ga-polar p-GaN surface to improve the light extraction efficiency of GaN based blue light emitting diodes (LEDs) by using a pulsed UV laser in combination with a mirror scanner. The patterns created on p-GaN are confirmed to be suitable for light extraction and a 34.9% enhancement of the electroluminescent (EL) emission intensity has been obtained. Detailed discussions on the effects of laser on LEDs and the angular dependence of the emission profile are also provided. This method could be extended to other III-V LEDs and LEDs on SiC for fabricating highly efficient LEDs. The schematic of laser fabrication equipment, SEM image of patterned p-GaN surface and guided-modes extraction photograph of patterned GaN epilayer. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Electrical and Optical Properties of InGaN/AIGaN Double Heterostructure Blue Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    SHEN Bo; SHI Hong-Tao; ZHANG Rong; CHEN Zhi-Zhong; ZHENG You-Dou

    2001-01-01

    Electrical and optical properties of InGaN/AlGaN double heterostructure blue light-emitting diodes were inves tigated. Measurement of the forward bias current-voltage behaviour of the device demonstrated a departure from the Shockley model of a p-n diode, and it was observed that the dominant mechanism of carrier transport across the junction is associated with carrier tunnelling. Electroluminescence experiments indicated that there was a main emission band around 2.80eV and a relatively weaker peak at 3.2eV. A significant blueshift of the optical emission band was observed, which was consistent with the tunnelling character of electrical characteris tics. Furthermore, the degradation in I - V characteristics and the low resistance ohmic short of the device were observed.

  20. Comparison of organic light emitting diodes with different mixed layer structures

    Energy Technology Data Exchange (ETDEWEB)

    Kee, Y.Y.; Siew, W.O. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya (Malaysia); Yap, S.S. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya (Malaysia); Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Tou, T.Y., E-mail: tytou@mmu.edu.my [Faculty of Engineering, Multimedia University, 63100 Cyberjaya (Malaysia)

    2014-11-03

    A mixed-source thermal evaporation method was used to fabricate organic light emitting diodes (OLEDs) with uniformly mixed (UM), continuously graded mixed (CGM) and step-wise graded, mixed (SGM) light-emitting layers. N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine and Tris-(8-hydroxyquinoline)aluminum were used, respectively, as the hole- and electron-transport materials. As compared to the conventional, heterojunction OLED, the maximum brightness of UM-, CGM- and SGM-OLEDs without charge injection layers were improved by 2.2, 3.8 and 2.1 times, respectively, while the maximum power efficiencies improved by 1.5, 3.2 and 1.9 times. These improvements were discussed in terms of more distributed recombination zone and removal of interfacial barrier. - Highlights: • Fabrication of OLEDs using a mixed-source evaporation technique • Three different types of mixed-host OLEDs with better brightness • Improved electroluminescence and power efficiencies as compared to conventional OLED.

  1. Study of electrical fatigue by defect engineering in organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Gassmann, Andrea, E-mail: gassmann@e-mat.tu-darmstadt.de [Technische Universität Darmstadt, Materials Science and Geoscience Department, Electronic Materials Division, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Yampolskii, Sergey V. [Technische Universität Darmstadt, Materials Science and Geoscience Department, Materials Modeling Division, Jovanka-Bontschits-Str. 2, 64287 Darmstadt (Germany); Klein, Andreas [Technische Universität Darmstadt, Materials Science and Geoscience Department, Surface Science Division, Jovanka-Bontschits-Str. 2, 64287 Darmstadt (Germany); Albe, Karsten [Technische Universität Darmstadt, Materials Science and Geoscience Department, Materials Modeling Division, Jovanka-Bontschits-Str. 2, 64287 Darmstadt (Germany); Vilbrandt, Nicole [Technische Universität Darmstadt, Chemistry Department, Ernst Berl Institute for Macromolecular Research, Alarich-Weiss-Str. 4, 64287 Darmstadt (Germany); Pekkola, Oili [Technische Universität Darmstadt, Materials Science and Geoscience Department, Electronic Materials Division, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Genenko, Yuri A. [Technische Universität Darmstadt, Materials Science and Geoscience Department, Materials Modeling Division, Jovanka-Bontschits-Str. 2, 64287 Darmstadt (Germany); Rehahn, Matthias [Technische Universität Darmstadt, Chemistry Department, Ernst Berl Institute for Macromolecular Research, Alarich-Weiss-Str. 4, 64287 Darmstadt (Germany); Seggern, Heinz von [Technische Universität Darmstadt, Materials Science and Geoscience Department, Electronic Materials Division, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany)

    2015-02-15

    Graphical abstract: - Highlights: • Electrical fatigue is investigated in PPV-based polymer light-emitting diodes. • Bromide defects remaining from Gilch synthesis limit PLED lifetime. • Electrical stress yields lower hole mobility and transition to dispersive transport. • Triplet excitons reduce lifetime and EL-emission-induced degradation observed. • Self-consistent drift-diffusion model for charge carrier injection and transport. - Abstract: In this work the current knowledge on the electrical degradation of polymer-based light-emitting diodes is reviewed focusing especially on derivatives of poly(p-phenylene-vinylene) (PPV). The electrical degradation will be referred to as electrical fatigue and is understood as mechanisms, phenomena and material properties that change during continuous operation of the device at constant current. The focus of this review lies especially on the effect of chemical synthesis on the transport properties of the organic semiconductor and the device lifetimes. In addition, the prominent transparent conductive oxide indium tin oxide as well as In{sub 2}O{sub 3} will be reviewed and how their properties can be altered by the processing conditions. The experiments are accompanied by theoretical modeling shining light on how the change of injection barriers, charge carrier mobility or trap density influence the current–voltage characteristics of the diodes and on how and which defects form in transparent conductive oxides used as anode.

  2. Light extraction enhancement of organic light-emitting diodes using aluminum zinc oxide embedded anodes.

    Science.gov (United States)

    Hsu, Ching-Ming; Lin, Bo-Ting; Zeng, Yin-Xing; Lin, Wei-Ming; Wu, Wen-Tuan

    2014-12-15

    Aluminum zinc oxide (AZO) has been embedded onto indium tin oxide (ITO) anode to enhance the light extraction from an organic light-emitting diode (OLED). The embedded AZO provides deflection and scattering interfaces on the newly generated AZO/organics and AZO/ITO interfaces rather than the conventional ITO/organic interface. The current efficiency of AZO embedded OLEDs was enhanced by up to 64%, attributed to the improved light extraction by additionally created reflection and scattering of emitted light on the AZO/ITO interfaces which was roughed in AZO embedding process. The current efficiency was found to increase with the increasing AZO embedded area ratio, but limited by the accompanying increases in haze and electrical resistance of the AZO embedded ITO film.

  3. In silico evaluation of highly efficient organic light-emitting materials

    Science.gov (United States)

    Kwak, H. Shaun; Giesen, David J.; Hughes, Thomas F.; Goldberg, Alexander; Cao, Yixiang; Gavartin, Jacob; Dixon, Steve; Halls, Mathew D.

    2016-09-01

    Design and development of highly efficient organic and organometallic dopants is one of the central challenges in the organic light-emitting diodes (OLEDs) technology. Recent advances in the computational materials science have made it possible to apply computer-aided evaluation and screening framework directly to the design space of organic lightemitting diodes (OLEDs). In this work, we will showcase two major components of the latest in silico framework for development of organometallic phosphorescent dopants - (1) rapid screening of dopants by machine-learned quantum mechanical models and (2) phosphorescence lifetime predictions with spin-orbit coupled calculations (SOC-TDDFT). The combined work of virtual screening and evaluation would significantly widen the design space for highly efficient phosphorescent dopants with unbiased measures to evaluate performance of the materials from first principles.

  4. Modeling of organic light emitting diodes: from molecular to device properties (Conference Presentation)

    Science.gov (United States)

    Andrienko, Denis; Kordt, Pascal; May, Falk; Badinski, Alexander; Lennartz, Christian

    2016-09-01

    We will review the progress in modeling of charge transport in disordered organic semiconductors on various length-scales, from atomistic to macroscopic. This includes evaluation of charge transfer rates from first principles, parametrization of coarse-grained lattice and off-lattice models, and solving the master and drift-diffusion equations. Special attention is paid to linking the length-scales and improving the efficiency of the methods. All techniques will be illustrated on an amorphous organic semiconductor, DPBIC, a hole conductor and electron blocker used in state of the art organic light emitting diodes (OLEDs). The outlined multiscale scheme can be used to predict OLED properties without fitting parameters, starting from chemical structures of compounds.

  5. Solution processed organic light-emitting diodes using the plasma cross-linking technology

    Science.gov (United States)

    He, Kongduo; Liu, Yang; Gong, Junyi; Zeng, Pan; Kong, Xun; Yang, Xilu; Yang, Cheng; Yu, Yan; Liang, Rongqing; Ou, Qiongrong

    2016-09-01

    Solution processed multilayer organic light-emitting diodes (OLEDs) present challenges, especially regarding dissolution of the first layer during deposition of a second layer. In this work, we first demonstrated a plasma cross-linking technology to produce a solution processed OLED. The surfaces of organic films can be cross-linked after mixed acetylene and Ar plasma treatment for several tens of seconds and resist corrosion of organic solvent. The film thickness and surface morphology of emissive layers (EMLs) with plasma treatment and subsequently spin-rinsed with chlorobenzene are nearly unchanged. The solution processed triple-layer OLED is successfully fabricated and the current efficiency increases 50% than that of the double-layer OLED. Fluorescent characteristics of EMLs are also observed to investigate factors influencing the efficiency of the triple-layer OLED. Plasma cross-linking technology may open up a new pathway towards fabrication of all-solution processed multilayer OLEDs and other soft electronic devices.

  6. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    CERN Document Server

    Kwang Ohk Cheo

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either alpha-NPD or DPVBi host l...

  7. Application of exciplex in the fabrication of white organic light emitting devices with mixed fluorescent and phosphorescent layers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Dan; Duan, Yahui; Yang, Yongqiang [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science & Engineering, Jilin University, Changchun 130012 (China); Hu, Nan [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science & Engineering, Jilin University, Changchun 130012 (China); Changchun University of Science and Technology, Changchun 130012 (China); Wang, Xiao [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science & Engineering, Jilin University, Changchun 130012 (China); Sun, Fengbo [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science & Engineering, Jilin University, Changchun 130012 (China); Changchun University of Science and Technology, Changchun 130012 (China); Duan, Yu, E-mail: duanyu@jlu.edu.cn [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science & Engineering, Jilin University, Changchun 130012 (China)

    2015-10-15

    In this study, a highly efficient fluorescent/phosphorescent white organic light-emitting device (WOLED) was fabricated using exciplex light emission. The hole-transport material 4,4',4''-tris(N-carbazolyl)triphenylamine (TCTA), and electron-transport material, 4,7-diphenyl-1,10-phenanthroline (Bphen), were mixed to afford a blue-emitting exciplex. The WOLED was fabricated with a yellow phosphorescent dye, Ir(III) bis(4-phenylthieno [3,2-c] pyridinato-N,C{sup 2'}) acetylacetonate (PO-01), combined with the exciplex. In this structure, the energy can be efficiently transferred from the blend layer to the yellow phosphorescent dye, thus improving the efficiency of the utilization of the triplet exciton. The maximum power efficiency of the WOLED reached a value 9.03 lm/W with an external quantum efficiency of 4.3%. The Commission Internationale de I'Eclairage (CIE) color coordinates (x,y) of the device were from (0.39, 0.45) to (0.27, 0.31), with a voltage range of 4–9 V. - Highlights: • An exciplex/phosphorescence hybrid white OLED was fabricated for the first time with blue/orange complementary emitters. • By using exciplex as the blue emitter, non-radiative triplet-states on the exciplex can be harvested for light-emission by transferring them to low triplet-state phosphors.

  8. High performance flexible top-emitting warm-white organic light-emitting devices and chromaticity shift mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Hongying; Deng, Lingling; Chen, Shufen, E-mail: iamsfchen@njupt.edu.cn, E-mail: wei-huang@njupt.edu.cn; Xu, Ying; Zhao, Xiaofei; Cheng, Fan [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 210023 Nanjing (China); Huang, Wei, E-mail: iamsfchen@njupt.edu.cn, E-mail: wei-huang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 210023 Nanjing (China); Jiangsu-Singapore Joint Research Center for Organic/Bio- Electronics and Information Displays and Institute of Advanced Materials, Nanjing University of Technology, Nanjing 211816 (China)

    2014-04-15

    Flexible warm-white top-emitting organic light-emitting devices (TEOLEDs) are fabricated onto PET substrates with a simple semi-transparent cathode Sm/Ag and two-color phosphors respectively doped into a single host material TCTA. By adjusting the relative position of the orange-red EML sandwiched between the blue emitting layers, the optimized device exhibits the highest power/current efficiency of 8.07 lm/W and near 13 cd/A, with a correlated color temperature (CCT) of 4105 K and a color rendering index (CRI) of 70. In addition, a moderate chromaticity variation of (-0.025, +0.008) around warm white illumination coordinates (0.45, 0.44) is obtained over a large luminance range of 1000 to 10000 cd/m{sup 2}. The emission mechanism is discussed via delta-doping method and single-carrier device, which is summarized that the carrier trapping, the exciton quenching, the mobility change and the recombination zone alteration are negative to color stability while the energy transfer process and the blue/red/blue sandwiched structure are contributed to the color stability in our flexible white TEOLEDs.

  9. Evaluation of inorganic and organic light-emitting diode displays for signage application

    Science.gov (United States)

    Sharma, Pratibha; Kwok, Harry

    2006-08-01

    High-brightness, inorganic light-emitting diodes (LEDs) have been successfully utilized for edge-lighting of large displays for signage. Further interest in solid-state lighting technology has been fueled with the emergence of small molecule and polymer-based organic light-emitting diodes (OLEDs). In this paper, edgelit inorganic LED-based displays and state-of-the-art OLED-based displays are evaluated on the basis of electrical and photometric measurements. The reference size for a signage system is assumed to be 600 mm x 600mm based on the industrial usage. With the availability of high power light-emitting diodes, it is possible to develop edgelit signage systems of the standard size. These displays possess an efficacy of 18 lm/W. Although, these displays are environmentally friendly and efficient, they suffer from some inherent limitations. Homogeneity of displays, which is a prime requirement for illuminated signs, is not accomplished. A standard deviation of 3.12 lux is observed between the illuminance values on the surface of the display. In order to distribute light effectively, reflective gratings are employed. Reflective gratings aid in reducing the problem but fail to eliminate it. In addition, the overall cost of signage is increased by 50% with the use of these additional components. This problem can be overcome by the use of a distributed source of light. Hence, the organic-LEDs are considered as a possible contender. In this paper, we experimentally determine the feasibility of using OLEDs for signage applications and compare their performance with inorganic LEDs. Passive matrix, small-molecule based, commercially available OLEDs is used. Design techniques for implementation of displays using organic LEDs are also discussed. It is determined that tiled displays based on organic LEDs possess better uniformity than the inorganic LED-based displays. However, the currently available OLEDs have lower light-conversion efficiency and higher costs than the

  10. Review of organic light-emitting diodes with thermally activated delayed fluorescence emitters for energy-efficient sustainable light sources and displays

    Science.gov (United States)

    Volz, Daniel

    2016-04-01

    Thermally activated delayed fluorescence (TADF) is an emerging hot topic. Even though this photophysical mechanism itself has been described more than 50 years ago and optoelectronic devices with organic matter have been studied, improved, and even commercialized for decades now, the realization of the potential of TADF organic light-emitting diodes (OLEDs) happened only recently. TADF has been proven to be an attractive and very efficient alternative for phosphorescent materials, such as dopants in OLEDs, light-emitting electrochemical cells as well as potent emitters for chemiluminescence. In this review, the TADF concept is introduced in terms that are also understandable for nonchemists. The basic concepts behind this mechanism as well as state-of-the-art examples are discussed. In addition, the future economic impact, especially for the lighting and display market, is addressed here. We conclude that TADF materials are especially helpful to realize efficient, durable deep blue and white displays.

  11. Gravure printed PEDOT:PSS as anode for flexible ITO-free organic light emitting diodes

    Directory of Open Access Journals (Sweden)

    M. Montanino

    2017-06-01

    Full Text Available Roll-to-roll gravure printing is considered as potential leading manufacturing technology for flexible, low cost and large area optoelectronics. However, solution processed multilayer organic electronics are still challenging to be produced, especially in the case of electrodes. In this work, the gravure printing technique was successfully employed to realize the highly conductive poly(3,4ethylenedioxythiophene:poly(styrene sulfonate (PEDOT:PSS polymeric anode and tested for the first time in flexible ITO-free (Indium Thin Oxide organic light emitting diodes (OLEDs. The device performances were found to be similar to those of a reference device containing a spin-coated polymeric anode. A gravure printed dimethyl sulfoxide (DMSO post-treatment was successfully tried to improve the printed anode characteristics. The obtained results show the way for future development for processing flexible ITO-free devices using the most attractive printing technology for roll-to-roll large area manufacturing.

  12. Aligning the Band Structures of Polymorphic Molybdenum Oxides and Organic Emitters in Light-Emitting Diodes

    Science.gov (United States)

    Yun, Jongmin; Jang, Woosun; Lee, Taehun; Lee, Yonghyuk; Soon, Aloysius

    2017-02-01

    Heavy transition-metal oxides are widely studied for key applications in electronics and energy technologies. In cutting-edge organic-light-emitting-diode (OLED) devices, there remain scientific challenges to achieve an efficient transfer of charges between electrodes and the organic layer. Recently, polymorphic MoO3 has been actively investigated to exploit its unique high work-function values, especially for its use in the electrode buffer layer to effectively transfer the charges in OLED devices. However, no systematic fundamental studies of its electronic structure are available. Thus, in this study, we use first-principles density-functional theory to investigate both the crystal structure and the electronic structure of the MoO3 polymorphs, and we conclude with a simple perspective to screen the best candidate for OLED applications via a hole transport-barrier descriptor.

  13. Selective Patterning of Organic Light-Emitting Diodes by Physical Vapor Deposition of Photosensitive Materials

    Science.gov (United States)

    Muroyama, Masakazu; Saito, Ichiro; Yokokura, Seiji; Tanaka, Kuniaki; Usui, Hiroaki

    2009-04-01

    A novel method of patterning polymeric thin films by the vapor deposition of a photosensitive layer followed by photopolymerization and development was proposed. This method was applied to the patterning of the emissive layer (EML) of an organic light-emitting diode (OLED). For the hole transport layer (HTL), N,N,N'-triphenyl-N'-(4-vinylphenyl)-biphenyl-4,4'-diamine (vTPD) and a zinc acrylate (ZnAc) crosslinker were coevaporated. The film was polymerized by postdeposition annealing to yield a polymeric HTL with a high resistance to organic solvents. On this HTL, the photosensitive EML was prepared by coevaporating a 9H-carbazole-9-ethylmethacrylate (CEMA) host material and 4-(dimethylamino)benzophenone (DABP) photoinitiator. UV irradiation on the EML through a photomask initiated radical polymerization, leaving a negative pattern of the irradiated region after immersion in tetrahydrofuran (THF). The photopatterning process was found to cause no damage to the film morphology or the device characteristics.

  14. Carbon Nanotube Driver Circuit for 6 × 6 Organic Light Emitting Diode Display

    KAUST Repository

    Zou, Jianping

    2015-06-29

    Single-walled carbon nanotube (SWNT) is expected to be a very promising material for flexible and transparent driver circuits for active matrix organic light emitting diode (AM OLED) displays due to its high field-effect mobility, excellent current carrying capacity, optical transparency and mechanical flexibility. Although there have been several publications about SWNT driver circuits, none of them have shown static and dynamic images with the AM OLED displays. Here we report on the first successful chemical vapor deposition (CVD)-grown SWNT network thin film transistor (TFT) driver circuits for static and dynamic AM OLED displays with 6 × 6 pixels. The high device mobility of ~45 cm2V−1s−1 and the high channel current on/off ratio of ~105 of the SWNT-TFTs fully guarantee the control capability to the OLED pixels. Our results suggest that SWNT-TFTs are promising backplane building blocks for future OLED displays.

  15. Ultrastrong light-matter coupling in electrically doped microcavity organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Mazzeo, M., E-mail: marco.mazzeo@unisalento.it [Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento, Via Monteroni, 73100 Lecce (Italy); NNL, Istituto Nanoscienze - CNR, Via Arnesano, 73100 Lecce (Italy); Genco, A. [Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento, Via Monteroni, 73100 Lecce (Italy); Gambino, S. [NNL, Istituto Nanoscienze - CNR, Via Arnesano, 73100 Lecce (Italy); CBN, Istituto Italiano Tecnologia, Via Barsanti 1, 73010 Lecce (Italy); Ballarini, D.; Mangione, F.; Sanvitto, D. [NNL, Istituto Nanoscienze - CNR, Via Arnesano, 73100 Lecce (Italy); Di Stefano, O.; Patanè, S.; Savasta, S. [Dipartimento di Fisica e Scienze della Terra, Università di Messina, Viale F. Stagno d' Alcontres 31, 98166 Messina (Italy); Gigli, G. [Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università del Salento, Via Monteroni, 73100 Lecce (Italy); NNL, Istituto Nanoscienze - CNR, Via Arnesano, 73100 Lecce (Italy); CBN, Istituto Italiano Tecnologia, Via Barsanti 1, 73010 Lecce (Italy)

    2014-06-09

    The coupling of the electromagnetic field with an electronic transition gives rise, for strong enough light-matter interactions, to hybrid states called exciton-polaritons. When the energy exchanged between light and matter becomes a significant fraction of the material transition energy an extreme optical regime called ultrastrong coupling (USC) is achieved. We report a microcavity embedded p-i-n monolithic organic light emitting diode working in USC, employing a thin film of squaraine dye as active layer. A normalized coupling ratio of 30% has been achieved at room temperature. These USC devices exhibit a dispersion-less angle-resolved electroluminescence that can be exploited for the realization of innovative optoelectronic devices. Our results may open the way towards electrically pumped polariton lasers.

  16. Charge generation layers for solution processed tandem organic light emitting diodes with regular device architecture.

    Science.gov (United States)

    Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Lemmer, Uli; Colsmann, Alexander

    2015-04-22

    Tandem organic light emitting diodes (OLEDs) utilizing fluorescent polymers in both sub-OLEDs and a regular device architecture were fabricated from solution, and their structure and performance characterized. The charge carrier generation layer comprised a zinc oxide layer, modified by a polyethylenimine interface dipole, for electron injection and either MoO3, WO3, or VOx for hole injection into the adjacent sub-OLEDs. ToF-SIMS investigations and STEM-EDX mapping verified the distinct functional layers throughout the layer stack. At a given device current density, the current efficiencies of both sub-OLEDs add up to a maximum of 25 cd/A, indicating a properly working tandem OLED.

  17. White organic light-emitting diodes with 4 nm metal electrode

    Science.gov (United States)

    Lenk, Simone; Schwab, Tobias; Schubert, Sylvio; Müller-Meskamp, Lars; Leo, Karl; Gather, Malte C.; Reineke, Sebastian

    2015-10-01

    We investigate metal layers with a thickness of only a few nanometers as anode replacement for indium tin oxide (ITO) in white organic light-emitting diodes (OLEDs). The ultrathin metal electrodes prove to be an excellent alternative that can, with regard to the angular dependence and efficiency of the OLED devices, outperform the ITO reference. Furthermore, unlike ITO, the thin composite metal electrodes are readily compatible with demanding architectures (e.g., top-emission or transparent OLEDs, device unit stacking, etc.) and flexible substrates. Here, we compare the sheet resistance of both types of electrodes on polyethylene terephthalate for different bending radii. The electrical performance of ITO breaks down at a radius of 10 mm, while the metal electrode remains intact even at radii smaller than 1 mm.

  18. Reduction of Concentration Quenching in a Nondoped DCM Organic Light-Emitting Diode

    Institute of Scientific and Technical Information of China (English)

    LIU Zhen-Gang; CHEN Zhi-Jian; GONG Qi-Huang

    2005-01-01

    @@ We obtain a nondoped red organic light-emitting diode (OLED) structure ITO/pc-PPV (~30 nm)/DCM (~30 nm)/BCP (~30nm)/Mg:Ag, where DCM refers to 4-(dicyanomethylene)-2-methyl-6-[(4-dimethylaninostyryl)-4-H-pyran]. The OLED shows pure and stable red luminescence depending on the driving voltages. The maximum luminance is 330 Cd/m2 and the turn-on voltage is as low as ~2 V. The reason why the concentration quenching of DCM could be reduced in this structure is investigated. In the preparation process, both the hole-transporting layer and the emitter layer are formed by the spin-coated method. It is believed that this method can lead to a new way to avoid the concentration quenching of red-emitting materials.

  19. Analysis of thermal degradation of organic light-emitting diodes with infrared imaging and impedance spectroscopy.

    Science.gov (United States)

    Kwak, Kiyeol; Cho, Kyoungah; Kim, Sangsig

    2013-12-02

    We propose a route to examine the thermal degradation of organic light-emitting diodes (OLEDs) with infrared (IR) imaging and impedance spectroscopy. Four different OLEDs with tris (8-hydroxyquinolinato) aluminum are prepared in this study for the analysis of thermal degradation. Our comparison of the thermal and electrical characteristics of these OLEDs reveals that the real-time temperatures of these OLEDs obtained from the IR images clearly correlate with the electrical properties and lifetimes. The OLED with poor electrical properties shows a fairly high temperature during the operation and a considerably short lifetime. Based on the correlation of the real-time temperature and the performance of the OLEDs, the impedance results suggest different thermal degradation mechanisms for each of the OLEDs. The analysis method suggested in this study will be helpful in developing OLEDs with higher efficiency and longer lifetime.

  20. High luminance phosphorescent organic light emitting diodes based on Re(I) complex

    Science.gov (United States)

    Su, Bin; Zhao, Jing; Wang, Fujun; Che, Guangbo; Wang, Yang; Wang, Bo; Gao, Lin; Yan, Yongsheng

    2016-10-01

    A novel Re(I) complex with the acenaphtho[1,2-b]pyrazino[2,3-f][1,10]phenanthroline (APPT) ligand Re(APPT)(CO)3Br (abbreviated as Re-APPT) was used to fabricate organic light emitting diodes (OLEDs). From the electroluminescence (EL) spectra of the device at different bias voltages, it could be found that the EL maxima shifted approximately 30 nm. For OLEDs with 5% Re-APPT doped emissive layer, turn-on voltage of 6 V, maximum luminance of 7631 cd/m2 and a current efficiency up to 2.36 cd/A were obtained. We suppose that a direct charge trapping took the dominant position in the EL process. Trapping contributed mostly to this relatively higher luminance.

  1. Efficient Light Extraction from Organic Light-Emitting Diodes Using Plasmonic Scattering Layers

    Energy Technology Data Exchange (ETDEWEB)

    Rothberg, Lewis

    2012-11-30

    Our project addressed the DOE MYPP 2020 goal to improve light extraction from organic light-emitting diodes (OLEDs) to 75% (Core task 6.3). As noted in the 2010 MYPP, “the greatest opportunity for improvement is in the extraction of light from [OLED] panels”. There are many approaches to avoiding waveguiding limitations intrinsic to the planar OLED structure including use of textured substrates, microcavity designs and incorporating scattering layers into the device structure. We have chosen to pursue scattering layers since it addresses the largest source of loss which is waveguiding in the OLED itself. Scattering layers also have the potential to be relatively robust to color, polarization and angular distributions. We note that this can be combined with textured or microlens decorated substrates to achieve additional enhancement.

  2. Novel Digital Driving Method Using Dual Scan for Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Jung, Myoung Hoon; Choi, Inho; Chung, Hoon-Ju; Kim, Ohyun

    2008-11-01

    A new digital driving method has been developed for low-temperature polycrystalline silicon, transistor-driven, active-matrix organic light-emitting diode (AM-OLED) displays by time-ratio gray-scale expression. This driving method effectively increases the emission ratio and the number of subfields by inserting another subfield set into nondisplay periods in the conventional digital driving method. By employing the proposed modified gravity center coding, this method can be used to effectively compensate for dynamic false contour noise. The operation and performance were verified by current measurement and image simulation. The simulation results using eight test images show that the proposed approach improves the average peak signal-to-noise ratio by 2.61 dB, and the emission ratio by 20.5%, compared with the conventional digital driving method.

  3. Thermal analysis of high intensity organic light-emitting diodes based on a transmission matrix approach

    Science.gov (United States)

    Qi, Xiangfei; Forrest, Stephen R.

    2011-12-01

    We use a general transmission matrix formalism to determine the thermal response of organic light-emitting diodes (OLEDs) under high currents normally encountered in ultra-bright illumination conditions. This approach, based on Laplace transforms, facilitates the calculation of transient coupled heat transfer in a multi-layer composite characteristic of OLEDs. Model calculations are compared with experimental data on 5 cm × 5 cm green and red-emitting electrophosphorescent OLEDs under various current drive conditions. This model can be extended to study other complex optoelectronic structures under a wide variety of conditions that include heat removal via conduction, radiation, and convection. We apply the model to understand the effects of using high-thermal- conductivity substrates, and the transient thermal response under pulsed-current operation.

  4. Driving technology for improving motion quality of active-matrix organic light-emitting diode display

    Science.gov (United States)

    Kim, Jongbin; Kim, Minkoo; Kim, Jong-Man; Kim, Seung-Ryeol; Lee, Seung-Woo

    2014-09-01

    This paper reports transient response characteristics of active-matrix organic light emitting diode (AMOLED) displays for mobile applications. This work reports that the rising responses look like saw-tooth waveform and are not always faster than those of liquid crystal displays. Thus, a driving technology is proposed to improve the rising transient responses of AMOLED based on the overdrive (OD) technology. We modified the OD technology by combining it with a dithering method because the conventional OD method cannot successfully enhance all the rising responses. Our method can improve all the transitions of AMOLED without modifying the conventional gamma architecture of drivers. A new artifact is found when OD is applied to certain transitions. We propose an optimum OD selection method to mitigate the artifact. The implementation results show the proposed technology can successfully improve motion quality of scrolling texts as well as moving pictures in AMOLED displays.

  5. Improved Carrier Transfer in Red Organic Light Emitting Diodes Doped with Rubrene

    Institute of Scientific and Technical Information of China (English)

    刘宏宇; 高文宝; 杨开霞; 刘式墉

    2002-01-01

    A red organic light emitting diode doped with rubrene is constructed with the configuration of ITO/NPB/Alq3:rubrene:DCM/Alq3/LiF/Al. In the device, N,N'-bis-(1-naphthl)-N,N:diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) is used as the hole-transporting layer, tris(8-quinolinolato) aluminium (Alq3) as the electron-transporting layer and Alq3 doped with 5,6,11,12-tetraphenylnaphthacene (rubrene) and 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) as the emitting layer. When the doping concentration of rubrene is 6% and that of DCM is 4%, red purity of the device is improved effectively. The experimental phenomena are explained as the result of the improved carrier transfer from rubrene to DCM.

  6. Evaluation of an organic light-emitting diode display for precise visual stimulation.

    Science.gov (United States)

    Ito, Hiroyuki; Ogawa, Masaki; Sunaga, Shoji

    2013-06-11

    A new type of visual display for presentation of a visual stimulus with high quality was assessed. The characteristics of an organic light-emitting diode (OLED) display (Sony PVM-2541, 24.5 in.; Sony Corporation, Tokyo, Japan) were measured in detail from the viewpoint of its applicability to visual psychophysics. We found the new display to be superior to other display types in terms of spatial uniformity, color gamut, and contrast ratio. Changes in the intensity of luminance were sharper on the OLED display than those on a liquid crystal display. Therefore, such OLED displays could replace conventional cathode ray tube displays in vision research for high quality stimulus presentation. Benefits of using OLED displays in vision research were especially apparent in the fields of low-level vision, where precise control and description of the stimulus are needed, e.g., in mesopic or scotopic vision, color vision, and motion perception.

  7. Charge injection and accumulation in organic light-emitting diode with PEDOT:PSS anode

    Energy Technology Data Exchange (ETDEWEB)

    Weis, Martin, E-mail: martin.weis@stuba.sk [Institute of Electronics and Photonics, Slovak University of Technology, Ilkovičova 3, Bratislava 81219 (Slovakia); Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa, E-mail: iwamoto@ome.pe.titech.ac.jp [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2015-04-21

    Organic light-emitting diode (OLED) displays using flexible substrates have many attractive features. Since transparent conductive oxides do not fit the requirements of flexible devices, conductive polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) has been proposed as an alternative. The charge injection and accumulation in OLED devices with PEDOT:PSS anodes are investigated and compared with indium tin oxide anode devices. Higher current density and electroluminescence light intensity are achieved for the OLED device with a PEDOT:PSS anode. The electric field induced second-harmonic generation technique is used for direct observation of temporal evolution of electric fields. It is clearly demonstrated that the improvement in the device performance of the OLED device with a PEDOT:PSS anode is associated with the smooth charge injection and accumulation.

  8. Tuning the Microcavity of Organic Light Emitting Diodes by Solution Processable Polymer-Nanoparticle Composite Layers.

    Science.gov (United States)

    Preinfalk, Jan B; Schackmar, Fabian R; Lampe, Thomas; Egel, Amos; Schmidt, Tobias D; Brütting, Wolfgang; Gomard, Guillaume; Lemmer, Uli

    2016-02-01

    In this study, we present a simple method to tune and take advantage of microcavity effects for an increased fraction of outcoupled light in solution-processed organic light emitting diodes. This is achieved by incorporating nonscattering polymer-nanoparticle composite layers. These tunable layers allow the optimization of the device architecture even for high film thicknesses on a single substrate by gradually altering the film thickness using a horizontal dipping technique. Moreover, it is shown that the optoelectronic device parameters are in good agreement with transfer matrix simulations of the corresponding layer stack, which offers the possibility to numerically design devices based on such composite layers. Lastly, it could be shown that the introduction of nanoparticles leads to an improved charge injection, which combined with an optimized microcavity resulted in a maximum luminous efficacy increase of 85% compared to a nanoparticle-free reference device.

  9. High-Resolution Organic Light-Emitting Diodes Patterned via Contact Printing.

    Science.gov (United States)

    Li, Jinhai; Xu, Lisong; Tang, Ching W; Shestopalov, Alexander A

    2016-07-01

    In this study, we report a contact printing technique that uses polyurethane-acrylate (PUA) polymers as the printing stamps to pattern electroluminescent layers of organic light emitting diodes (OLEDs). We demonstrate that electroluminescent thin films can be printed with high uniformity and resolution. We also show that the performance of the printed devices can be improved via postprinting thermal annealing, and that the external quantum efficiency of the printed devices is comparable with the efficiency of the vacuum-deposited OLEDs. Our results suggest that the PUA-based contact printing can be used as an alternative to the traditional shadow mask deposition, permitting manufacturing of OLED displays with the resolution up to the diffraction limit of visible-light emission.

  10. White organic light-emitting diodes with 4 nm metal electrode

    Energy Technology Data Exchange (ETDEWEB)

    Lenk, Simone; Schwab, Tobias; Schubert, Sylvio; Müller-Meskamp, Lars; Leo, Karl; Reineke, Sebastian [Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01069 Dresden (Germany); Gather, Malte C. [Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01069 Dresden (Germany); Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)

    2015-10-19

    We investigate metal layers with a thickness of only a few nanometers as anode replacement for indium tin oxide (ITO) in white organic light-emitting diodes (OLEDs). The ultrathin metal electrodes prove to be an excellent alternative that can, with regard to the angular dependence and efficiency of the OLED devices, outperform the ITO reference. Furthermore, unlike ITO, the thin composite metal electrodes are readily compatible with demanding architectures (e.g., top-emission or transparent OLEDs, device unit stacking, etc.) and flexible substrates. Here, we compare the sheet resistance of both types of electrodes on polyethylene terephthalate for different bending radii. The electrical performance of ITO breaks down at a radius of 10 mm, while the metal electrode remains intact even at radii smaller than 1 mm.

  11. Study of organic light emitting devices (OLEDs) with optimal emission efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [School of Engineering and IT, B-purple 12, Faculty of EHS, Charles Darwin University, Darwin, NT 0909 (Australia)

    2010-04-15

    The external emission efficiency of organic light emitting devices (OLEDs) is analysed by studying the rate of spontaneous emission of both singlet and triplet excitons and their corresponding radiative lifetimes. Rates of spontaneous emissions are calculated from the first order perturbation theory using the newly discovered time-dependent spin-orbit-exciton-photon interaction operator as the perturbation operator. It is clearly shown how the new interaction operator is responsible for attracting triplet excitons to a phosphor (heavy metal atom) and then it flips the spins to a singlet configuration. Thus, the spin forbidden transition becomes spin allowed. Calculated rates agree with the experimental results qualitatively. Results are of general interests for OLED studies. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. A randomly nano-structured scattering layer for transparent organic light emitting diodes.

    Science.gov (United States)

    Huh, Jin Woo; Shin, Jin-Wook; Cho, Doo-Hee; Moon, Jaehyun; Joo, Chul Woong; Park, Seung Koo; Hwang, Joohyun; Cho, Nam Sung; Lee, Jonghee; Han, Jun-Han; Chu, Hye Yong; Lee, Jeong-Ik

    2014-09-21

    A random scattering layer (RSL) consisting of a random nano-structure (RNS) and a high refractive index planarization layer (HRI PL) is suggested and demonstrated as an efficient internal light-extracting layer for transparent organic light emitting diodes (TOLEDs). By introducing the RSL, a remarkable enhancement of 40% and 46% in external quantum efficiency (EQE) and luminous efficacy (LE) was achieved without causing deterioration in the transmittance. Additionally, with the use of the RSL, the viewing angle dependency of EL spectra was reduced to a marginal degree. The results were interpreted as the stronger influence of the scattering effect over the microcavity. The RSL can be applied widely in TOLEDs as an effective light-extracting layer for extracting the waveguide mode of confined light at the indium tin oxide (ITO)/OLED stack without introducing spectral changes in TOLEDs.

  13. Organic light-emitting diodes using novel embedded al gird transparent electrodes

    Science.gov (United States)

    Peng, Cuiyun; Chen, Changbo; Guo, Kunping; Tian, Zhenghao; Zhu, Wenqing; Xu, Tao; Wei, Bin

    2017-03-01

    This work demonstrates a novel transparent electrode using embedded Al grids fabricated by a simple and cost-effective approach using photolithography and wet etching. The optical and electrical properties of Al grids versus grid geometry have been systematically investigated, it was found that Al grids exhibited a low sheet resistance of 70 Ω □-1 and a light transmission of 69% at 550 nm with advantages in terms of processing conditions and material cost as well as potential to large scale fabrication. Indium Tin Oxide-free green organic light-emitting diodes (OLED) based on Al grids transparent electrodes was demonstrated, yielding a power efficiency >15 lm W-1 and current efficiency >39 cd A-1 at a brightness of 2396 cd m-2. Furthermore, a reduced efficiency roll-off and higher brightness have been achieved compared with ITO-base device.

  14. Light extraction from organic light-emitting diodes for lighting applications by sand-blasting substrates.

    Science.gov (United States)

    Chen, Shuming; Kwok, Hoi Sing

    2010-01-04

    Light extraction from organic light-emitting diodes (OLEDs) by scattering the light is one of the effective methods for large-area lighting applications. In this paper, we present a very simple and cost-effective method to rough the substrates and hence to scatter the light. By simply sand-blasting the edges and back-side surface of the glass substrates, a 20% improvement of forward efficiency has been demonstrated. Moreover, due to scattering effect, a constant color over all viewing angles and uniform light pattern with Lambertian distribution has been obtained. This simple and cost-effective method may be suitable for mass production of large-area OLEDs for lighting applications.

  15. The effects of sodium in ITO by pulsed laser deposition on organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Yong, Thian Khok [Multimedia University, Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Universiti Tunku Abdul Rahman, Faculty of Engineering and Science, Kuala Lumpur (Malaysia); Kee, Yeh Yee; Tan, Sek Sean; Siew, Wee Ong; Tou, Teck Yong [Multimedia University, Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Yap, Seong Shan [Multimedia University, Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Norwegian University of Science and Technology, Department of Physics, Trondheim (Norway)

    2010-12-15

    The depth profile of ITO on glass was measured by the time-of-flight secondary ion mass spectroscopy (TOFSIMS) which revealed high sodium (Na) ion concentration at the ITO surface as well as at the ITO-glass interface as a result of out diffusion with substrate heating. Effects of Na ions on the performance of organic light-emitting diode (OLED) were studied by etching away a few tens of nanometers off the ITO surface with a dilute aquaregia solution of HNO{sub 3}:HCl:H{sub 2}O. A single-layer, molecularly doped ITO/(PVK+TPD+Alq{sub 3})/Al OLEDs were fabricated on bare and etched ITO samples. Although the removal of a 10-nm layer of ITO surface increased the voltage range, brightness, and lifetime, it was insufficient to correlate these improvements with solely to the Na ion reduction without considering the surface roughness. (orig.)

  16. An Electroluminescence Delay Time Model of Bilayer Organic Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    LI Hong-Jian; ZHU Ru-Hui; LI Xue-Yong; YANG Bing-Chu

    2007-01-01

    @@ Based on the mechanism of injection, transport and recombination of the charge carriers, we develop a model to calculate the delay time of electroluminescence (EL) from bilayer organic light emitting diodes. The effect of injection, transport and recombination processes on the EL delay time is discussed, and the relationship between the internal interface barrier and the recombination time is revealed. The results show that the EL delay time is dominated by the recombination process at lower applied voltage and by the transport process at higher applied voltage. When the internal interface barrier varies from 0.15 eV to 0.3 eV, the recombination delay time increases rapidly, while the internal interface barrier exceeds about 0.3eV, the dependence of the recombination delay time on applied voltage is almost undiversified, which may serve as a guideline for designing of a high-speed EL response device.

  17. Lifetime enhanced phosphorescent organic light emitting diode using an electron scavenger layer

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Seokhwan; Kim, Ji Whan; Lee, Sangyeob, E-mail: sy96.lee@samsung.com [Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd., 130 Samsung-ro, Suwon, Gyeonggi 443-803 (Korea, Republic of)

    2015-07-27

    We demonstrate a method to improve lifetime of a phosphorescent organic light emitting diode (OLED) using an electron scavenger layer (ESL) in a hole transporting layer (HTL) of the device. We use a bis(1-(phenyl)isoquinoline)iridium(III)acetylacetonate [Ir(piq){sub 2}(acac)] doped HTL to stimulate radiative decay, preventing thermal degradation in HTL. The ESL effectively prevented non-radiative decay of leakage electron in HTL by converting non-radiative decay to radiative decay via a phosphorescent red emitter, Ir(piq){sub 2}(acac). The lifetime of device (t{sub 95}: time after 5% decrease of luminance) has been increased from 75 h to 120 h by using the ESL in a phosphorescent green-emitting OLED.

  18. Modification of Conductive Polymer for Polymeric Anodes of Flexible Organic Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Wang Guang-Feng

    2009-01-01

    Full Text Available Abstract A conductive polymer, poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate (PEDOT:PSS, was modified with dimethyl sulfoxide (DMSO in solution state, together with sub-sequential thermal treatment of its spin-coated film. The electrical conductivity increased by more than three orders of magnitude improvement was achieved. The mechanism for the conductivity improvement was studied at nanoscale by particle size analysis, field emission scanning electron microscopy (FESEM, and X-ray photoelectron spectroscopy (XPS. Smaller particle size was observed, resulting in larger contact area and better electrical conductive connections. Connection of conductive PEDOT increased on the surface of the PEDOT:PSS particles, which promoted high conductivity. Flexible anodes based on the modified PEDOT:PSS were fabricated. Flexible organic light-emitting diodes (FOLED based the polymeric anodes have a comparable performance to those on indium–tin–oxide (ITO anodes.

  19. Origin of magnetic field effect enhancement by electrical stress in organic light emitting diodes

    Science.gov (United States)

    Bagnich, S. A.; Niedermeier, U.; Melzer, C.; Sarfert, W.; von Seggern, H.

    2009-06-01

    Recently, it has been discovered that the magnetic field effect (MFE) in organic light emitting diodes (OLEDs) based on poly(para-phenylene vinylene) can be enhanced by exposing the diode to moderate electrical stress. Here, we disclose the mechanism behind this way of improving the MFE. We first show that electronic traps in general play an important role for the MFE. Optical depletion of available trap states by infrared illumination leads to a decrease in the MFE. Furthermore, we demonstrate that annealing of the OLED at high temperatures eliminates the MFE improvement of the previously performed electrical conditioning. However, the improvement can be restored by subsequent conditioning at higher current or voltage. Thus it is likely that electrical stress is accompanied by a transformation of the polymer morphology or conformation resulting in a formation of energetic traps for charge carriers.

  20. Colorimetric characterization models based on colorimetric characteristics evaluation for active matrix organic light emitting diode panels.

    Science.gov (United States)

    Gong, Rui; Xu, Haisong; Tong, Qingfen

    2012-10-20

    The colorimetric characterization of active matrix organic light emitting diode (AMOLED) panels suffers from their poor channel independence. Based on the colorimetric characteristics evaluation of channel independence and chromaticity constancy, an accurate colorimetric characterization method, namely, the polynomial compensation model (PC model) considering channel interactions was proposed for AMOLED panels. In this model, polynomial expressions are employed to calculate the relationship between the prediction errors of XYZ tristimulus values and the digital inputs to compensate the XYZ prediction errors of the conventional piecewise linear interpolation assuming the variable chromaticity coordinates (PLVC) model. The experimental results indicated that the proposed PC model outperformed other typical characterization models for the two tested AMOLED smart-phone displays and for the professional liquid crystal display monitor as well.

  1. One-step Double-layer Thermal Evaporation Method for Organic Light Emitting Diodes

    Science.gov (United States)

    Kee, Y. Y.; Yong, T. K.; Ong, D. S.; Tou, T. Y.

    2011-03-01

    A new one-step double-layer thermal evaporation method was used to fabricate organic light emitting diodes (OLEDs) with device structure of: ITO (anode)/N,N_-diphenyl-N,N_-bis(3-methylphenyl)-1,1_-diphenyl-4,4_-diamine (TPD) /tris-(8-hydroxyquinoline)aluminum(3) (Alq3)/Al (cathode). These OLEDs were fabricated in cleanroom on the ITO-coated glass with a sheet resistivity of 20Ω/sq and an optical transmittance of 90%. The I-V and brightness characteristic showed that the new method could produce better performance achieving lower turn-on voltage (-2V), higher peak current efficiency (+29%) and higher brightness (+36%).

  2. Optical Interference Effects by Metal Cathode in Organic Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    WU Zhao-Xin; WANG Li-Duo; QIU Yong

    2004-01-01

    The dependence of light intensities of organic light-emitting diodes (OLEDs) on the distance of emission zone to metal cathode is investigated numerically. The investigation is based on the half-space optical model that accounts for optical interference effects of metal cathode. We find that light intensities of OLEDs are functions of the distance of emission zone from the metal cathode because of the effect of interference of the metal cathode.This interference leads to an optimal location of emission zone in OLEDs for the maximum of light intensities.Optimal locations of emission zone are numerically shown in various emitting colour OLEDs with different metal cathodes and these results are expected to give insight into the preparation of high efficiency full colour or white light OLEDs.

  3. Simulation of mixed-host emitting layer based organic light emitting diodes

    Science.gov (United States)

    Riku, C.; Kee, Y. Y.; Ong, T. S.; Yap, S. S.; Tou, T. Y.

    2015-04-01

    `SimOLED' simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq3) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO / HTM (15 nm) / Mixed host (70 nm) / ETM (10 nm) /Al, are stimulated with ratios TPD:Alq3 of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate.

  4. Discernment of Possible Organic Magnetic Field Effect Mechanisms Using Polymer Light-Emitting Electrochemical Cells

    Science.gov (United States)

    Geng, R.; Subedi, R. C.; Liang, S.; Nguyen, T. D.

    2014-07-01

    We report studies of magnetic field effect (MFE) in polymer light-emitting electrochemical cells (PLEC) using the "super-yellow" poly-(phenylene vynilene) (SY-PPV) polymer in vertical and planar device configurations. The purpose is to discern the existing MFE mechanisms in organic light emitting diodes (OLEDs) where the current and electroluminescence are strongly modulated by a small applied magnetic field. In particular, we investigate the mutual relationship between magneto-conductance (MC) and magneto-electroluminescence (MEL) by studying the role of polaron density dissociated from polaron pairs (PP) on these magnetic responses. In general, the dissociated polaron density is determined by the PP dissociation rate and the PP density. For the planar PLEC, which possesses a small dissociation rate, we observe small and negative MC at all applied voltages regardless of the emission intensity, while MEL becomes positive when electroluminescence quantum efficiency increases. The MC has a much narrower width than the MEL, indicating that the MC and MEL do not share a common origin. However, MC reverses and has the same width as MEL when the device is exposed to a threshold laser power. For the vertical PLEC, characterized by a large dissociation rate, MC and MEL are positive and have the same width. We discuss the results using the existing MFE mechanism in OLEDs. We show that the PP model can explain the positive MEL and MC, while the negative MC can be explained by the bipolaron model. Finally, we present a possibility to complete an all-organic PLEC magnetic sensor by using an inkjet printer.

  5. Organic Light-Emitting Diodes (OLEDs) and Optically-Detected Magnetic Resonance (ODMR) studies on organic materials

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Min [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    Organic semiconductors have evolved rapidly over the last decades and currently are considered as the next-generation technology for many applications, such as organic light-emitting diodes (OLEDs) in flat-panel displays (FPDs) and solid state lighting (SSL), and organic solar cells (OSCs) in clean renewable energy. This dissertation focuses mainly on OLEDs. Although the commercialization of the OLED technology in FPDs is growing and appears to be just around the corner for SSL, there are still several key issues that need to be addressed: (1) the cost of OLEDs is very high, largely due to the costly current manufacturing process; (2) the efficiency of OLEDs needs to be improved. This is vital to the success of OLEDs in the FPD and SSL industries; (3) the lifetime of OLEDs, especially blue OLEDs, is the biggest technical challenge. All these issues raise the demand for new organic materials, new device structures, and continued lower-cost fabrication methods. In an attempt to address these issues, we used solution-processing methods to fabricate highly efficient small molecule OLEDs (SMOLEDs); this approach is costeffective in comparison to the more common thermal vacuum evaporation. We also successfully made efficient indium tin oxide (ITO)-free SMOLEDs to further improve the efficiency of the OLEDs. We employed the spin-dependent optically-detected magnetic resonance (ODMR) technique to study the luminescence quenching processes in OLEDs and organic materials in order to understand the intrinsic degradation mechanisms. We also fabricated polymer LEDs (PLEDs) based on a new electron-accepting blue-emitting polymer and studied the effect of molecular weight on the efficiency of PLEDs. All these studies helped us to better understand the underlying relationship between the organic semiconductor materials and the OLEDs’ performance, and will subsequently assist in further enhancing the efficiency of OLEDs. With strongly improved device performance (in addition to

  6. Growth and photomorphogenesis of pepper plants under red light-emitting diodes with supplemental blue or far-red lighting

    Science.gov (United States)

    Brown, C. S.; Schuerger, A. C.; Sager, J. C.

    1995-01-01

    Light-emitting diodes (LEDs) are a potential irradiation source for intensive plant culture systems and photobiological research. They have small size, low mass, a long functional life, and narrow spectral output. In this study, we measured the growth and dry matter partitioning of 'Hungarian Wax' pepper (Capsicum annuum L.) plants grown under red LEDs compared with similar plants grown under red LEDs with supplemental blue or far-red radiation or under broad spectrum metal halide (MH) lamps. Additionally, we describe the thermal and spectral characteristics of these sources. The LEDs used in this study had a narrow bandwidth at half peak height (25 nm) and a focused maximum spectral output at 660 nm for the red and 735 nm for the far-red. Near infrared radiation (800 to 3000 nm) was below detection and thermal infrared radiation (3000 to 50,000 nm) was lower in the LEDs compared to the MH source. Although the red to far-red ratio varied considerably, the calculated phytochrome photostationary state (phi) was only slightly different between the radiation sources. Plant biomass was reduced when peppers were grown under red LEDs in the absence of blue wavelengths compared to plants grown under supplemental blue fluorescent lamps or MH lamps. The addition of far-red radiation resulted in taller plants with greater stem mass than red LEDs alone. There were fewer leaves under red or red plus far-red radiation than with lamps producing blue wavelengths. These results indicate that red LEDs may be suitable, in proper combination with other wavelengths of light, for the culture of plants in tightly controlled environments such as space-based plant culture systems.

  7. Hyperbranched polymer-cored star polyfluorenes as blue light-emitting materials

    Institute of Scientific and Technical Information of China (English)

    HAN Yang; SUN MingHao; FEI ZhuPing; BO ZhiShan

    2008-01-01

    Hyperbranched polymer-cored star polyfluorenes with high molecular weights and narrow molecular weight distribution were prepared by palladium-catalyzed one-pot Suzuki polycondensation of multi-functional cores and an AB-type monomer. The optical, electrochemical and thermal properties of the hyperbranched polymer-cored star polymers were investigated. These polymers exhibited good ther-mal and color stability in solid state, and there was no significant blue-green emission after the poly-mers had been annealed in air for 2.5 h. Their three-dimensional hyperbranched structures could ef-fectively reduce the aggregation of the peripheral rigid linear conjugated polyfluorene chains.

  8. High-efficiency diphenylsulfon derivatives-based organic light-emitting diode exhibiting thermally activated delayed fluorescence

    CERN Document Server

    Lee, Geon Hyeong

    2016-01-01

    Novel thermally activated delayed fluorescence (TADF) material with diphenyl sulfone (DPS) as an electron acceptor and 3,6-dimethoxycarbazole (DMOC) and 1,3,6,8-Tetramethyl-9H-carbazole (TMC) as electron donors were investigated theoretically for a blue organic light emitting diode (OLED) emitter. We calculate the energies of the first singlet (S1) and first triplet (T1)-excited states of TADF materials by performing density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations on the ground state using a dependence on charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT. The calculated {\\Delta}EST values of TMC-DPS (0.094 eV) was smaller than DMOC-DPS (0.386 eV) because of the large dihedral angles between the donor and accepter moieties. We show that TMC-DPS would have a suitable blue OLED emitter, because it has a large dihedral angle that creates a small spatial overlap between the HOMO and the LUMO and, consequently, the small {\\Delta}EST an...

  9. LOW-POTENTIAL ELECTROSYNTHESIS OF CONDUCTING AND ELECTROACTIVE OLIGOCATECHOLBORANE WITH BLUE LIGHT-EMITTING PROPERTIES

    Institute of Scientific and Technical Information of China (English)

    Bao-yang Lu; Shuai Chen; Lei-qiang Qin; Yao Huang; Jing-kun Xu

    2013-01-01

    Novel conducting oligocatecholborane (OCOB) with electrical conductivity of 3.73 × 10-2 S cm-1 was successfully synthesized by low-potential electropolymerization of catecholborane (COB) in boron trifluoride diethyl etherate at 0.70 V versus Ag/AgC1.FT-IR and 1H-NMR spectra,together with the computational results,proved that COB was polymerized through the coupling at C(4) and C(5) positions and the reactive B-H bond was stable during the electrochemical polymerization.The resulting product was mainly composed of oligomers with short chain lengths by GPC and mass spectral results.The as-formed OCOB film showed good electrochemistry in monomer-free electrolytes with the electrochromic property from opaque blue to sap green.Fluorescence studies indicated that soluble OCOB can emit bright blue light under excitation of 365 nm UV light with the maximum emission at 396 nm and a fluorescence quantum yield of 0.21.The deposited OCOB also exhibited favorable thermal stability and smooth and compact morphology even at high magnifications.

  10. Patterning photo-curable light-emitting organic composites by vertical and horizontal capillarity: a general route to photonic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Mele, Elisa; Camposeo, Andrea; Marco, Carmela De; Persano, Luana; Cingolani, Roberto; Pisignano, Dario [NNL, National Nanotechnology Laboratory of CNR-INFM, Universita del Salento, via Arnesano, I-73100 Lecce (Italy)], E-mail: dario.pisignano@unile.it

    2008-08-20

    We demonstrate the patterning of organic light-emitting composites made by conjugated polymers and photo-curable matrices. Using blends that exhibit both the structural properties of a low-viscosity photo-curable polymer, and the emission features of conjugated light-emitting materials, we study the operational principle of the pattern transfer and the modifications induced by the imprinting and microfluidic procedures on the optical properties of the compounds investigated. The combination of high-resolution silicone and perfluoropolyether elastomeric templates and low-viscosity, light-emitting polymeric blends offers the possibility to easily produce active organic structures with 100 nm scale resolution, thus extending current nanopatterning routes to this important class of composite material.

  11. Manipulating the Local Light Emission in Organic Light-Emitting Diodes by using Patterned Self-Assembled Monolayers

    NARCIS (Netherlands)

    Mathijssen, S.G.J.; Hal, P.A. van; Biggelaar, T.J.M. van den; Smits, E.C.P.; Boer, B. de; Kemerink, M.; Janssen, R.A.J.; Leeuw, D.M. de

    2008-01-01

    In organic light-emitting diodes (OLEDs), interface dipoles play an important role in the process of charge injection from the metallic electrode into the active organic layer.[1,2] An oriented dipole layer changes the effective work function of the electrode because of its internal electric field.

  12. Short-circuit prevention strategies in organic light-emitting diodes and solar cells

    Science.gov (United States)

    Michels, Jasper J.; Jolt Oostra, A.; Blom, Paul W. M.

    2016-08-01

    Short-circuit prevention and repair strategies are essential to allow for upscaled production of organic electronic devices based on thin-film production technology. Occurrence of short circuits is a consequence of manufacturing imperfections and particle contamination. After giving a concise review of short-circuit prevention methods for organic thin-film devices in the open literature of the past decade, this overview article summarizes our recent work on short-circuit prevention in organic light-emitting diodes and organic solar cells by chemical oxidation methods. Our main strategy is based on self-aligned disruption of the conductivity of exposed areas of the typically applied hole transport material poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) by aqueous sodium hypochlorite, prior to cathode deposition. The ten orders of magnitude decrease in local conductivity obtained proves sufficient to let deliberately flawed devices operate at pristine performance levels. We next show that in the case of organic solar cells based on a lithium fluoride/aluminium cathode the shunting junctions can be made sufficiently resistive to allow for near unflawed operation, without applying wet treatment.

  13. Fully solution-processed organic light-emitting electrochemical cells (OLEC) with inkjet-printed micro-lenses for disposable lab-on-chip applications at ambient conditions

    Science.gov (United States)

    Shu, Zhe; Pabst, Oliver; Beckert, Erik; Eberhardt, Ramona; Tünnermann, Andreas

    2016-02-01

    Microfluidic lab-on-chip devices can be used for chemical and biological analyses such as DNA tests or environmental monitoring. Such devices integrate most of the basic functionalities needed for scientific analysis on a microfluidic chip. When using such devices, cost and space-intensive lab equipment is no longer necessary. However, in order to make a monolithic and cost-efficient/disposable microfluidic sensing device, direct integration of the excitation light source for fluorescent sensing is often required. To achieve this, we introduce a fully solution processable deviation of OLEDs, organic light-emitting electrochemical cells (OLECs), as a low-cost excitation light source for a disposable microfluidic sensing platform. By mixing metal ions and a solid electrolyte with light-emitting polymers as active materials, an in-situ doping and in-situ PN-junction can be generated within a three layer sandwich device. Thanks to this doping effect, work function adaptation is not necessary and air-stable electrode can be used. An ambient manufacturing process for fully solution-processed OLECs is presented, which consist of a spin-coated blue light-emitting polymer plus dopants on an ITO cathode and an inkjet-printed PEDOT:PSS transparent top anode. A fully transparent blue OLEC is able to obtain light intensity > 2500 cd/m2 under pulsed driving mode and maintain stable after 1000 cycles, which fulfils requirements for simple fluorescent on-chip sensing applications. However, because of the large refractive index difference between substrates and air, about 80% of emitted light is trapped inside the device. Therefore, inkjet printed micro-lenses on the rear side are introduced here to further increase light-emitting brightness.

  14. Study on temperature characteristics of organic light-emitting diodes based on tris-(8-hydroxylquinoline)-aluminum

    Institute of Scientific and Technical Information of China (English)

    SUO Fan; YU JunSheng; LI WeiZhi; LOU ShuangLing; DENG Jing; JIANG YaDong

    2008-01-01

    Both single-layer and double-layer organic light-emitting devices based on tris-(8-hydroxylquinoline)-aluminum (Alq3) as emitter are fabricated by thermal vacuum deposition. The electroluminescent characteristics of these devices at various temperatures are measured, and the temperature characteristics of device performance are studied. The effect of temperature on device current conduction regime is analyzed in detail. The results show that the current-voltage (Ⅰ-Ⅴ) characteristics of devices are in good agreement with the theoretical prediction of trapped charge limited current (TCLC). In addition, both the charge carrier mobility and charge carrier concentration in the organic layer increase with the rise of temperature, which results in the monotonous increase of Alq3 device current. The current conduction mechanisms of two devices at different temperatures are identical, but the exponent m in current-voltage equation changes randomly with temperature. The device luminance increases slightly and the efficiency decreases monotonously due to the aging of Alq3 luminescent properties caused by high temperature. A tiny blue shift can be observed in the electroluminescent (EL) spectra as the temperature increases, and the reduction of device monochromaticity is caused by the intrinsic characteristics of organic semiconductor energy levels.

  15. Electrical and Optical Properties of a High-Voltage Large Area Blue Light-Emitting Diode

    Science.gov (United States)

    Wang; Wei; Cai; Yong; Huang; Wei; Li; Hai-ou; Zhang; Bao-shun

    2013-08-01

    In this paper, we report a single-chip large area (5×5 mm2) InGaN/GaN blue LED with the optical output power of 4.3 W. This device consists of 24-stages small LED-cells that are connected in series. Driven at 500 mA, the forward voltage is measured to be 87.2 V with a reverse current of 2.63×10-9 A at -120 V. The comparison of two different cooling schemes, i.e., with/without fan cooling, was made; the results suggest that the thermal convection between the heat sink and air is more critical. A simple white LED package was also tried by covering silicone gel mixed with yttrium aluminum garnet (YAG) phosphor. The luminous flux and the correlated color temperature (CCT) were measured to be 1090 lm and 5082 K, when the device was driven at 500 mA. This report also demonstrated the feasibility of the application for camera flash.

  16. Improving color rendering of Y{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} white light-emitting diodes based on dual-blue-emitting active layers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xian-Wen; Zhang, Yong; Li, Shu-Ti; Yan, Qi-Rong; Zheng, Shu-Wen; He, Miao; Fan, Guang-Han [Institute of Optoelectronic Materials and Technology, South China Normal University, Tianhe District, Guangzhou 510631 (China)

    2011-08-15

    An InGaN/GaN blue-violet light-emitting diode (LED) structure and an InGaN/GaN blue LED structure were grown sequentially on the same sapphire substrate by metal-organic chemical vapor deposition (MOCVD). At the low injection current, the intensity ratio of blue-violet light to blue light was almost constant, while the blue light intensity increased gradually with increasing injection current when the latter was more than 40 mA. High color rendering has been realized for a Y{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} phosphor-converted white LED based on dual-blue-emitting active layers relative to a single blue-emitting active layer at the same injection current. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Novel donor-acceptor materials for organic light-emitting diodes based on {alpha}-cinnamoyl cyclic ketene dithioacetals

    Energy Technology Data Exchange (ETDEWEB)

    Peng Ping [Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130023 (China); Sun Shaoguang [Department of Chemistry, Northeast Normal University, Changchun 130024 (China); Zhao Yixin [Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130023 (China); Wu Weicai [Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130023 (China); Xia Haijian [Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130023 (China); Tian Wenjing [Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130023 (China)]. E-mail: wjtian@mail.jlu.edu.cn; Liu Qun [Department of Chemistry, Northeast Normal University, Changchun 130024 (China)

    2007-10-15

    A new family of {alpha}-cinnamoyl cyclic ketene dithioacetals (CCKDA) based on a typical donor-{pi}-acceptor structure were designed and synthesized. These unsymmetrical {pi}-conjugated molecules consisted of different electron-donating moiety and the same ketene dithioacetals acceptor. The introduction of different donor moieties changed energy level parameters of the molecules and allowed a fine tuning of their optical and electrical properties. It is promising to apply these compounds in organic light-emitting diodes (OLED) as light-emitting and electron-transporting materials.

  18. Organic Light-Emitting Devices (OLEDS) and Their Optically Detected Magnetic Resonance (ODMR)

    Energy Technology Data Exchange (ETDEWEB)

    Gang Li

    2003-12-12

    Organic Light-Emitting Devices (OLEDs), both small molecular and polymeric have been studied extensively since the first efficient small molecule OLED was reported by Tang and VanSlyke in 1987. Burroughes' report on conjugated polymer-based OLEDs led to another track in OLED development. These developments have resulted in full color, highly efficient (up to {approx} 20% external efficiency 60 lm/W power efficiency for green emitters), and highly bright (> 140,000 Cd/m{sup 2} DC, {approx}2,000,000 Cd/m{sup 2} AC), stable (>40,000 hr at 5 mA/cm{sup 2}) devices. OLEDs are Lambertian emitters, which intrinsically eliminates the view angle problem of liquid crystal displays (LCDs). Thus OLEDs are beginning to compete with the current dominant LCDs in information display. Numerous companies are now active in this field, including large companies such as Pioneer, Toyota, Estman Kodak, Philipps, DuPont, Samsung, Sony, Toshiba, and Osram, and small companies like Cambridge Display Technology (CDT), Universal Display Corporation (UDC), and eMagin. The first small molecular display for vehicular stereos was introduced in 1998, and polymer OLED displays have begun to appear in commercial products. Although displays are the major application for OLEDs at present, they are also candidates for nest generation solid-state lighting. In this case the light source needs to be white in most cases. Organic transistors, organic solar cells, etc. are also being developed vigorously.

  19. Adjunctive dental therapy via tooth plaque reduction and gingivitis treatment by blue light-emitting diodes tooth brushing

    Science.gov (United States)

    Genina, Elina A.; Titorenko, Vladimir A.; Belikov, Andrey V.; Bashkatov, Alexey N.; Tuchin, Valery V.

    2015-12-01

    The efficacy of blue light-emitting toothbrushes (B-LETBs) (405 to 420 nm, power density 2 mW/cm2) for reduction of dental plaques and gingival inflammation has been evaluated. Microbiological study has shown the multifactor therapeutic action of the B-LETBs on oral pathological microflora: in addition to partial mechanical removal of bacteria, photodynamic action suppresses them up to 97.5%. In the pilot clinical studies, subjects with mild to moderate gingivitis have been randomly divided into two groups: a treatment group that used the B-LETBs and a control group that used standard toothbrushes. Indices of plaque, gingival bleeding, and inflammation have been evaluated. A significant improvement of all dental indices in comparison with the baseline (by 59%, 66%, and 82% for plaque, gingival bleeding, and inflammation, respectively) has been found. The treatment group has demonstrated up to 50% improvement relative to the control group. We have proposed the B-LETBs to serve for prevention of gingivitis or as an alternative to conventional antibiotic treatment of this disease due to their effectiveness and the absence of drug side effects and bacterial resistance.

  20. Influence of Light-emitting Layer Position on White Organic Light-emitting Diodes%发光层位置对白光有机发光二极管的影响

    Institute of Scientific and Technical Information of China (English)

    向东旭; 李海蓉; 谢龙珍; 杨佳明; 王芳; 员朝鑫; 孙永哲

    2015-01-01

    Two types of white organic light-emitting devices ( WOLED) containing a layered light-emitting region composed of a single blue-emitting host and different fluorescent dopants ( blue and orange) were fabricated. The effi-ciency, lifetime, brightness, spectral voltage-dependence and white balance of devices were investigated. The results show that the performance of the devices strongly depends on the stack order of two emitting layers and the thickness of the emitting layer. It is found that the WOLED with an EML sequence of orange/blue ( from anode to cathode) shows better stability than that with an EML sequence of blue/orange. It is due to the rubrene in orange emitting layer that acts as hole-trap sites and captures the passing holes and hence balances the concentration of electrons and holes. The optimized white device exhibits a favorable CIE coordinates (0. 320 1, 0. 345 9) which is close to the standard white light.%同一种主体材料MADN中混掺不同的掺杂剂,分别制备了两种白光有机发光二极管,测试并研究了它们的发光效率、寿命、发光亮度、电致发光光谱以及色平衡度。结果表明,两种白光器件的性能受发光层的顺序和厚度的影响显著。发光层顺序由阳极到阴极方向为橙/蓝的器件的稳定性要优于发光层顺序为蓝/橙的器件,这是由于橙光发光层中的rubrene对空穴的陷进作用可捕获穿越橙光发光层中的空穴,从而有效地调控了器件内部的电子、空穴浓度的平衡。通过对器件的优化,制得了色坐标为(0.3201,0.3459)的接近标准白光的有机电致发光器件。

  1. Methods and apparatus of spatially resolved electroluminescence of operating organic light-emitting diodes using conductive atomic force microscopy

    Science.gov (United States)

    Hersam, Mark C. (Inventor); Pingree, Liam S. C. (Inventor)

    2008-01-01

    A conductive atomic force microscopy (cAFM) technique which can concurrently monitor topography, charge transport, and electroluminescence with nanometer spatial resolution. This cAFM approach is particularly well suited for probing the electroluminescent response characteristics of operating organic light-emitting diodes (OLEDs) over short length scales.

  2. Manipulating the local light emission in organic light-emitting diodes by using patterned self-assembled monolayers

    NARCIS (Netherlands)

    Mathijssen, Simon G. J.; van Hal, Paul A.; van den Biggelaar, Ton J. M.; Smits, Edsger C. P.; de Boer, Bert; Kemerink, Martijn; Janssen, Rene A. J.; de Leeuw, Dago M.

    2008-01-01

    Patterned organic light-emitting diodes are fabricated by using microcontactDrinted self-assembled monolayers on a gold anode (see background figure). Molecules with dipole moments in opposite directions result in an increase or a decrease of the local work function (foreground picture), providing a

  3. Fluorescent Organic Planar pn Heterojunction Light-Emitting Diodes with Simplified Structure, Extremely Low Driving Voltage, and High Efficiency.

    Science.gov (United States)

    Chen, Dongcheng; Xie, Gaozhan; Cai, Xinyi; Liu, Ming; Cao, Yong; Su, Shi-Jian

    2016-01-13

    Fluorescent organic light-emitting diodes capable of radiative utilization of both singlet and triplet excitons are achieved via a simple double-layer planar pn hetero-junction configuration without a conventional emission layer, leading to high external quantum efficiency above 10% and extremely low driving voltages close to the theoretical minima.

  4. Improved Performance of Organic Light-Emitting Diodes with MgF2 as the Anode Buffer Layer

    Institute of Scientific and Technical Information of China (English)

    XIE Jing; ZHANG De-Qiang; WANG Li-Duo; DUAN Lian; QIAO Juan; QIU Yong

    2006-01-01

    @@ Organic light-emitting diodes (OLEDs) based on N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and tris (8-hydroxyquinoline) aluminium (Alq3) are improved by using a thin MgF2 buffer layer sandwiched between the indium tin oxide (ITO) anode and hole transporting layer (HTL) of NPB.

  5. Analytical model for current distribution in large-area organic light emitting diodes with parallel metal grid lines

    NARCIS (Netherlands)

    Barink, M.; Harkema, S.

    2012-01-01

    In this study, an analytical solution for the current distribution of a large-area organic light emitting diodes (OLEDs) with parallel equidistant gridlines is derived. In contrast to numerical methods, this analytical solution allows for a very quick scan of the OLED design space, even for very lar

  6. Enhancing The Efficiency of White Organic Light-emitting Diode Using Energy Recyclable Photovoltaic Cells

    Institute of Scientific and Technical Information of China (English)

    Meiso YOKOYAMA; WU Chung-ming; SU Shui-hsiang

    2012-01-01

    We demonstrate that power recycling is feasible by using a semi-transparent stripped Al electrode as interconnecting layer to merge a white organic light-emitting devices(WOLED)and an organic photovoltaic(OPV)cell.The device is called a PVOLED..It has a glass/ITO/CuPc/m-MTDATA:V2O5/NPB/CBP:FIrpic:DCJTB/ BPhen/LiF/Al/P3HT:PCBM/V2O5/Al structure.The power recycling efficiency of 10.133% is achieved under the WOLED of PVOLED operated at 9 V and at a brightness of 2 110 cd/m2,when the conversion efficiency of OPV is 2.3%.We have found that the power recycling efficiency is decreased under high brightness and high applied voltage due to an increase input power of WOLED.High efficiency(18.3 cd/A)and high contrast ratio(9.3)were obtained at the device operated at 2 500 cd/m2 under an ambient illumination of 24 000 lx.Reasonable white light emission with Commission Internationale De L'Eclairage(CIE)color coordinates of(0.32,0.44)at 20 mA/cm2 and slight color shift occurred in spite of a high current density of 50 mA/cm2.The proposed PVOLED is highly promising for use in outdoors display applications.

  7. Organic Light Emitting Diodes with p-Si Anodes and Semitransparent Ce/Au Cathodes

    Institute of Scientific and Technical Information of China (English)

    SUN Zhiguo; JIANG Guangzhi

    2011-01-01

    The Ce (x nm)/Au (15 nm) stacked layers were used as semitransparent cathodes in the top-emission organic light emitting devices (TOLEDs) fabricated on a p-type silicon anodes and substrate, where x varies from 4 to 16. The consequence of the Ce layer thickness on transmittance and the device performance were studied when the organic layers NPB (60 nm)/ALQ (60 nm) were kept unchanged, where NPB was N, N,n'-bis-(l-naphthl)-diphenyl-l, 1 '-biphenyl-4, 4'-diamine, and AlQ is tris-(8-hydroxyquinoline) aluminum. The cathode of Ce (11 nm)/Au (15 nm) has a transparency of 46%, and the TOLED with it achieves the highest luminescence efficiencies: a current efficiency of 0.91 cd/A at 13.7 V and a peak power efficiency of 0.28 lm/W at 9 V. The tum-on voltage is 3.0 V. The Ce/Au cathode is both chemically and electrically stable.

  8. Use of anodes with tunable work function for improving organic light-emitting diode performance

    Science.gov (United States)

    Li, Meng-Chi; Lo, Yen-Ming; Liao, Shih-Fang; Chen, Hsi-Chao; Chang, Hsin-Hua; Lee, Cheng-Chung; Kuo, Chien-Cheng

    2015-12-01

    The effect of reactive gases-oxygen and hydrogen-on the tunable work function of Al-doped ZnO (AZO) films was studied. An increase in the work function with an increase in the oxygen flow rate was mainly interpreted as reflecting a decrease in the carrier concentration, which was attributed to the filling of oxygen vacancies. However, a decrease in the carrier concentration would result in the resistivity increasing sharply. This article presents a new concept for improving the performance of organic light-emitting diodes (OLEDs) through easy and effective hole injection from a multilayer AZO anode to the organic layer. A bilayer AZO film prepared using a tunable work function technique was used to modify the surface of AZO anodes and to ensure that the anodes had low resistivity. The AZO anode stacked with high-work-function AZO films, similar to hole transport buffer layers, had a low turn-on voltage of 2.89 V, and its luminance efficiency and power efficiency were 5.01% and 6.1% greater than those of tin-doped indium oxide anodes used in OLEDs.

  9. Stretchable active-matrix organic light-emitting diode display using printable elastic conductors

    Science.gov (United States)

    Sekitani, Tsuyoshi; Nakajima, Hiroyoshi; Maeda, Hiroki; Fukushima, Takanori; Aida, Takuzo; Hata, Kenji; Someya, Takao

    2009-06-01

    Stretchability will significantly expand the applications scope of electronics, particularly for large-area electronic displays, sensors and actuators. Unlike for conventional devices, stretchable electronics can cover arbitrary surfaces and movable parts. However, a large hurdle is the manufacture of large-area highly stretchable electrical wirings with high conductivity. Here, we describe the manufacture of printable elastic conductors comprising single-walled carbon nanotubes (SWNTs) uniformly dispersed in a fluorinated rubber. Using an ionic liquid and jet-milling, we produce long and fine SWNT bundles that can form well-developed conducting networks in the rubber. Conductivity of more than 100Scm-1 and stretchability of more than 100% are obtained. Making full use of this extraordinary conductivity, we constructed a rubber-like stretchable active-matrix display comprising integrated printed elastic conductors, organic transistors and organic light-emitting diodes. The display could be stretched by 30-50% and spread over a hemisphere without any mechanical or electrical damage.

  10. Recent advances in the science and engineering of organic light-emitting diodes (Conference Presentation)

    Science.gov (United States)

    Kippelen, Bernard; Gaj, Michael P.; Zhang, Xiaoqing; Choi, Sangmoo; Fuentes-Hernandez, Canek; Zhang, Yadong; Barlow, Stephen; Marder, Seth R.; Voit, Walter E.; Wei, Andrew

    2016-09-01

    In this talk, we will discuss recent advances in the science and engineering of organic light-emitting diodes (OLEDs). First, we will focus on materials in which light emission involves the process of thermally activated delayed fluorescence (TADF). In these materials, triplet excited states can convert into optically emissive singlet excited states by reverse intersystem crossing, allowing for nearly 100% internal quantum efficiency. This process can be used to design a new class of materials that are all organic, offering a lower cost alternative to conventional electrophosphorescent materials that contain heavy and expensive elements such as Pt and Ir. We will discuss molecular design strategies and present examples of materials that can be used as emitters or hosts in the emissive layer. In a second part of this talk, we will review recent progress in fabricating OLEDs on shape memory polymer substrates (SMPs). SMPs are mechanically active, smart materials that can exhibit a significant drop in modulus once an external stimulus such as temperature is applied. In their rubbery state upon heating, the SMP can be easily deformed by external stresses into a temporary geometric configuration that can be retained even after the stress is removed by cooling the SMP to below the glass transition temperature. Reheating the SMP causes strain relaxation within the polymer network and induces recovery of its original shape. We will discuss how these unique mechanical properties can also be extended to a new class of OLEDs.

  11. Spray deposition of organic electroluminescent coatings for application in flexible light emitting devices

    Directory of Open Access Journals (Sweden)

    Mariya Aleksandrova

    2015-12-01

    Full Text Available Organic electroluminescent (EL films of tris(8-hydroxyquinolinatoaluminum (Alq3 mixed with polystyrene (PS binder were produced by spray deposition. The influence of the substrate temperature on the layer’s morphology and uniformity was investigated. The deposition conditions were optimized and simple flexible light-emitting devices consisting of indium-tin oxide/Alq3:PS/aluminum were fabricated on polyethylene terephthalate (PET foil to demonstrate the advantages of the sprayed organic coatings. Same structure was produced by thermal evaporation of Alq3 film as a reference. The influence of the deposition method on the film roughness and contact resistance at the electrode interfaces for both types of structures was estimated. The results were related to the devices’ efficiency. It was found that the samples with sprayed films turn on at 4 V, which is 2 V lower in comparison to the device with thermal evaporated Alq3. The current through the sprayed device is six times higher as well (17 mA vs. 2.8 mA at 6.5 V, which can be ascribed to the lower contact resistance at the EL film/electrode interfaces. This is due to the lower surface roughness of the pulverized layers.

  12. Exploring the Potential of Nucleic Acid Bases in Organic Light Emitting Diodes.

    Science.gov (United States)

    Gomez, Eliot F; Venkatraman, Vishak; Grote, James G; Steckl, Andrew J

    2015-12-01

    Naturally occurring biomolecules have increasingly found applications in organic electronics as a low cost, performance-enhancing, environmentally safe alternative. Previous devices, which incorporated DNA in organic light emitting diodes (OLEDs), resulted in significant improvements in performance. In this work, nucleobases (NBs), constituents of DNA and RNA polymers, are investigated for integration into OLEDs. NB small molecules form excellent thin films by low-temperature evaporation, enabling seamless integration into vacuum deposited OLED fabrication. Thin film properties of adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) are investigated. Next, their incorporation as electron-blocking (EBL) and hole-blocking layers (HBL) in phosphorescent OLEDs is explored. NBs affect OLED performance through charge transport control, following their electron affinity trend: G < A < C < T < U. G and A have lower electron affinity (1.8-2.2 eV), blocking electrons but allowing hole transport. C, T, and U have higher electron affinities (2.6-3.0 eV), transporting electrons and blocking hole transport. A-EBL-based OLEDs achieve current and external quantum efficiencies of 52 cd A(-1) and 14.3%, a ca. 50% performance increase over the baseline device with conventional EBL. The combination of enhanced performance, wide diversity of material properties, simplicity of use, and reduced cost indicate the promise of nucleobases for future OLED development.

  13. A Comparison Between Magnetic Field Effects in Excitonic and Exciplex Organic Light-Emitting Diodes

    Science.gov (United States)

    Sahin Tiras, Kevser; Wang, Yifei; Harmon, Nicholas J.; Wohlgenannt, Markus; Flatte, Michael E.

    In flat-panel displays and lighting applications, organic light emitting diodes (OLEDs) have been widely used because of their efficient light emission, low-cost manufacturing and flexibility. The electrons and holes injected from the anode and cathode, respectively, form a tightly bound exciton as they meet at a molecule in organic layer. Excitons occur as spin singlets or triplets and the ratio between singlet and triplet excitons formed is 1:3 based on spin degeneracy. The internal quantum efficiency (IQE) of fluorescent-based OLEDs is limited 25% because only singlet excitons contribute the light emission. To overcome this limitation, thermally activated delayed fluorescent (TADF) materials have been introduced in the field of OLEDs. The exchange splitting between the singlet and triplet states of two-component exciplex systems is comparable to the thermal energy in TADF materials, whereas it is usually much larger in excitons. Reverse intersystem crossing occurs from triplet to singlet exciplex state, and this improves the IQE. An applied small magnetic field can change the spin dynamics of recombination in TADF blends. In this study, magnetic field effects on both excitonic and exciplex OLEDs will be presented and comparison similarities and differences will be made.

  14. Organic Light Emitting Diodes Using Doped Alq3 as the Hole-transport Layer

    Institute of Scientific and Technical Information of China (English)

    LIANG Chun-Jun; WANG Yang; YI Li-Xin

    2008-01-01

    EFfects of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) doping on the hole conductivity of Alq3 layer are measured.In the hole-only device of Alq3,the current densities increase in 1-3 orders of magnitude upon doping with F4TCNQ,suggesting that the doping can effectively enhance the hole-injection and holetransport ability of Alq3.An organic light-emitting device using an F4TCNQ doped Alq3 layer as the holeinjection and hole-transport layer,and pristine Alq3 as the electron-transport and emitting layer is fabricated and characterized.Bright emission is achieved in the simple OLED with p-doped Alqa as the hole-transport layer and the intrinsic Alq3 as the electron-transport and emitting layer.The emitting efficiency and brightness of the device are further improved by inserting a thin electron block layer to confine the carrier recombination zone in the middle of the organic layers.

  15. Bacterial cellulose membrane as flexible substrate for organic light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Legnani, C.; Vilani, C. [CeDO-Organic Device Center, Dimat-Dimat, Inmetro, Duque de Caxias, RJ (Brazil); Calil, V.L. [CeDO-Organic Device Center, Dimat-Dimat, Inmetro, Duque de Caxias, RJ (Brazil); LOEM-Molecular Optoelectronic Laboratory-Physics Department-PUC-Rio, Rio de Janeiro, RJ (Brazil); Barud, H.S. [Institute of Chemistry, Sao Paulo State University-UNESP, CP 355 Araraquara, SP (Brazil); Quirino, W.G. [CeDO-Organic Device Center, Dimat-Dimat, Inmetro, Duque de Caxias, RJ (Brazil); Achete, C.A. [CeDO-Organic Device Center, Dimat-Dimat, Inmetro, Duque de Caxias, RJ (Brazil); COPPE-Programa de Engenharia Metalurgica e de Materiais, UFRJ, Rio de Janeiro, RJ (Brazil); Ribeiro, S.J.L. [Institute of Chemistry, Sao Paulo State University-UNESP, CP 355 Araraquara, SP (Brazil); Cremona, M. [CeDO-Organic Device Center, Dimat-Dimat, Inmetro, Duque de Caxias, RJ (Brazil); LOEM-Molecular Optoelectronic Laboratory-Physics Department-PUC-Rio, Rio de Janeiro, RJ (Brazil)], E-mail: cremona@fis.puc-rio.br

    2008-12-01

    Bacterial cellulose (BC) membranes produced by gram-negative, acetic acid bacteria (Gluconacetobacter xylinus), were used as flexible substrates for the fabrication of Organic Light Emitting Diodes (OLED). In order to achieve the necessary conductive properties indium tin oxide (ITO) thin films were deposited onto the membrane at room temperature using radio frequency (r.f.) magnetron sputtering with an r.f. power of 30 W, at pressure of 8 mPa in Ar atmosphere without any subsequent thermal treatment. Visible light transmittance of about 40% was observed. Resistivity, mobility and carrier concentration of deposited ITO films were 4.90 x 10{sup -4} Ohm cm, 8.08 cm{sup 2}/V-s and - 1.5 x 10{sup 21} cm{sup -3}, respectively, comparable with commercial ITO substrates. In order to demonstrate the feasibility of devices based on BC membranes three OLEDs with different substrates were produced: a reference one with commercial ITO on glass, a second one with a SiO{sub 2} thin film interlayer between the BC membrane and the ITO layer and a third one just with ITO deposited directly on the BC membrane. The observed OLED luminance ratio was: 1; 0.5; 0.25 respectively, with 2400 cd/m{sup 2} as the value for the reference OLED. These preliminary results show clearly that the functionalized biopolymer, biodegradable, biocompatible bacterial cellulose membranes can be successfully used as substrate in flexible organic optoelectronic devices.

  16. Anomalous hole injection deterioration of organic light-emitting diodes with a manganese phthalocyanine layer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyunbok [Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Lee, Jeihyun; Yi, Yeonjin, E-mail: yeonjin@yonsei.ac.kr [Institute of Physics and Applied Physics, Yonsei University, 50 Yonsei-ro, Seodaemun-Gu, Seoul 120-749 (Korea, Republic of); Cho, Sang Wan [Department of Physics, Yonsei University, 1 Yonseidae-gil, Wonju-si, Gangwon-do 220-710 (Korea, Republic of); Kim, Jeong Won [Korea Research Institute of Standards and Science, 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of)

    2015-01-21

    Metal phthalocyanines (MPcs) are well known as an efficient hole injection layer (HIL) in organic devices. They possess a low ionization energy, and so the low-lying highest occupied molecular orbital (HOMO) gives a small hole injection barrier from an anode in organic light-emitting diodes. However, in this study, we show that the hole injection characteristics of MPc are not only determined by the HOMO position but also significantly affected by the wave function distribution of the HOMO. We show that even with the HOMO level of a manganese phthalocyanine (MnPc) HIL located between the Fermi level of an indium tin oxide anode and the HOMO level of a N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine hole transport layer the device performance with the MnPc HIL is rather deteriorated. This anomalous hole injection deterioration is due to the contracted HOMO wave function, which leads to small intermolecular electronic coupling. The origin of this contraction is the significant contribution of the Mn d-orbital to the MnPc HOMO.

  17. Solution-Processed Organic Thin-Film Transistor Array for Active-Matrix Organic Light-Emitting Diode

    Science.gov (United States)

    Harada, Chihiro; Hata, Takuya; Chuman, Takashi; Ishizuka, Shinichi; Yoshizawa, Atsushi

    2013-05-01

    We developed a 3-in. organic thin-film transistor (OTFT) array with an ink-jetted organic semiconductor. All layers except electrodes were fabricated by solution processes. The OTFT performed well without hysteresis, and the field-effect mobility in the saturation region was 0.45 cm2 V-1 s-1, the threshold voltage was 3.3 V, and the on/off current ratio was more than 106. We demonstrated a 3-in. active-matrix organic light-emitting diode (AMOLED) display driven by the OTFT array. The display could provide clear moving images. The peak luminance of the display was 170 cd/m2.

  18. Excited states structure and processes: Understanding organic light-emitting diodes at the molecular level

    Energy Technology Data Exchange (ETDEWEB)

    Shuai, Zhigang, E-mail: zgshuai@tsinghua.edu.cn [MOE Key Laboratory of Organic OptoElectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, 100084 Beijing (China); Peng, Qian, E-mail: qpeng@iccas.ac.cn [Beijing National Laboratory for Molecular Science (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, 100190 Beijing (China)

    2014-04-01

    Photo- or electro-excited states in polyatomic molecules, aggregates, and conjugated polymers are at the center of organic light-emitting diodes (OLEDs). These can decay radiatively or non-radiatively, determining the luminescence quantum efficiency of molecular materials. According to Kasha’s rule, light-emission is dictated by the lowest-lying excited state. For conjugated polymers, the electron correlation effect can lead the lowest-lying excited state to the even-parity 2A{sub g} state which is non-emissive. To understand the nature of the low-lying excited state structure, we developed the density matrix renormalization group (DMRG) theory and its symmetrization scheme for quantum chemistry applied to calculate the excited states structure. We found there are three types of 1B{sub u}/2A{sub g} crossover behaviors: with electron correlation strength U, with bond length alternation, and with conjugation length. These directly influence the light-emitting property. For the electro-excitation, carriers (electron and hole) are injected independently, forming both singlet and triplet excited bound states with statistically 25% and 75% portions, respectively. We found that the exciton formation rate can depend on spin manifold, and for conjugated polymers, the singlet exciton can have larger formation rate leading to the internal electroluminescence quantum efficiency larger than the 25% spin statistical limit. It is originated from the interchain electron correlation as well as intrachain lattice relaxation. For the dipole allowed emissive state, the radiative decay process via either spontaneous emission or stimulated emission can be computed from electronic structure plus vibronic couplings. The challenging issue lies in the non-radiative decay via non-adiabatic coupling and/or spin–orbit coupling. We developed a unified correlation function formalism for the excited state radiative and non-radiative decay rates. We emphasized the low-frequency mode mixing

  19. Organic light-emitting diodes incorporating nanometer thick films of europium-cored complexes

    Science.gov (United States)

    Phelan, Gregory D.; Carlson, Brenden; Jiang, Xuezhong; Jen, Alex K. Y.; Dalton, Larry R.

    2002-11-01

    Europium cored complexes may be used as a source of red emission in light emitting diodes. Novel europium cored complexes have been synthesized and incorporated into organic light emitting diodes (OLED's). These complexes emit red light at 615 nm with a full width half maximum (FWHM) of less than 5 nm. The europium complexes consist of one equivalent of europium chelated to three equivalents of a nonsymmetrical β-diketone ligand. The Claissen condensation of a polycyclic aromatic sensitizer and an ester of a fluorinated carboxylic acid create the ligands. The use of a sensitizer such as phenanthrene results in a ligand that has an emission band that directly overlaps with the absorption band of europium. The use of fluorinated chains improves the overall processibility as well as the charge transfer capability of the resulting metal cored complex. The europium core is further encapsulated by the inclusion of an additional polycyclic aromatic compound such as 4, 7 diphenyl - 1, 10 phenanthroline. Emission of 615 nm light is accomplished through excitation of the ligand and efficient Forrester energy transfer to the europium complex. A multiple layer device consisting of a substrate of indium tin oxide, followed by thin layers of BTPD-PFCB (with a thickness of 20nm), a polymer blend containing the europium complex (30 nm), followed by a layer of calcium (50nm) and finally a protective layer of silver (120 nm). The polymer blends were either poly(n-vinyl carbazole)(PVK) or poly vinyl naphthalene (PVN). The device performance was further improved by the incorporation of another lanthanide metal complex. These complexes were based upon similar ligands surrounding gadolinium. In these devices, there is a Dexter energy transfer as well as the Forster energy transfer. For the devices that are based on a PVN:PBD as a polymer host, the lowest turn on voltage was 12.0 volts. The devices that use PVK:TPD devices was 178 cd/m2 with an external quantum efficiency of 0.61%.For

  20. White organic light-emitting devices based on fac tris(2-phenylpyridine) iridium sensitized 5,6,11,12-tetraphenylnap-hthacene

    Institute of Scientific and Technical Information of China (English)

    DING Gui-ying; WANG Jin; JIANG Wen-long; WANG Jing; WANG Li-zhong; CHANG XI

    2008-01-01

    We have fabricated the white organic light-emitting devices (WOLEDs) based on 4,4'-bis(2,2-diphenyl vinyl)-1,1'-biphenyl (DPVBi) and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene (rubrene).The device structure is ITO/2T-NATA (20 nm)/NPBX (20 nm)/CBP:x%Ir(ppy)3:0.5% rubrene (8 nm)/NPBX (5 nm)/DPVBi (30 nm)/Alq(30nm)/LiF(0.5 nm)/Al.In the devices,DPVBi acts as a blue light-emitting layer,the rubrene is sensitized by a phosphorescent material,fac tris (2-phenylpyridine) iridium [Ir(ppy)3],acts as a yellow light-emitting layer,and N,N'-bis-(1-naphthyl)-N,N'-dipheny1-1,1'-biphenyl-4,4'-diamine (NPBX) acts as a hole transporting and exciton blocker layer,respectively.When the concentration of Ir(PPY)3 is 6wt%,the maximum luminance is 24960 cd/m2 at an applied voltage of 15 V,and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.

  1. Device Architecture and Materials for Organic Light-Emitting Devices Targeting High Current Densities and Control of the Triplet Concentration

    CERN Document Server

    Schols, Sarah

    2011-01-01

    Device Architecture and Materials for Organic Light-Emitting Devices focuses on the design of new device and material concepts for organic light-emitting devices, thereby targeting high current densities and an improved control of the triplet concentration. A new light-emitting device architecture, the OLED with field-effect electron transport, is demonstrated. This device is a hybrid between a diode and a field-effect transistor. Compared to conventional OLEDs, the metallic cathode is displaced by one to several micrometers from the light-emitting zone, reducing optical absorption losses. The electrons injected by the cathode accumulate at an organic heterojunction and are transported to the light-emission zone by field-effect. High mobilities for charge carriers are achieved in this way, enabling a high current density and a reduced number of charge carriers in the device. Pulsed excitation experiments show that pulses down to 1 µs can be applied to this structure without affecting the light intensity, sug...

  2. Recent advances in light outcoupling from white organic light-emitting diodes

    Science.gov (United States)

    Gather, Malte C.; Reineke, Sebastian

    2015-01-01

    Organic light-emitting diodes (OLEDs) have been successfully introduced to the smartphone display market and have geared up to become contenders for applications in general illumination where they promise to combine efficient generation of white light with excellent color quality, glare-free illumination, and highly attractive designs. Device efficiency is the key requirement for such white OLEDs, not only from a sustainability perspective, but also because at the high brightness required for general illumination, losses lead to heating and may, thus, cause rapid device degradation. The efficiency of white OLEDs increased tremendously over the past two decades, and internal charge-to-photon conversion can now be achieved at ˜100% yield. However, the extraction of photons remains rather inefficient (typically <30%). Here, we provide an introduction to the underlying physics of outcoupling in white OLEDs and review recent progress toward making light extraction more efficient. We describe how structures that scatter, refract, or diffract light can be attached to the outside of white OLEDs (external outcoupling) or can be integrated close to the active layers of the device (internal outcoupling). Moreover, the prospects of using top-emitting metal-metal microcavity designs for white OLEDs and of tuning the average orientation of the emissive molecules within the OLED are discussed.

  3. Fabrication of an Organic Light-Emitting Diode from New Host π Electron Rich Zinc Complex

    Science.gov (United States)

    Jafari, Mohammad Reza; Janghouri, Mohammad; Shahedi, Zahra

    2016-09-01

    A new π electron rich zinc complex was used as a fluorescent material in organic light-emitting diodes (OLEDs). Devices with a structure of indium tin oxide/poly (3,4-ethylenedi-oxythiophene):poly(styrenesulfonate) (PEDOT: PSS) (50 nm)/polyvinylcarbazole (60 nm)/Zn: %2 porphyrin derivatives (45 nm)/Al (150 nm) were fabricated. Porphyrin derivatives accounting for 2 wt.% in the π electron rich zinc complex were used as a host. The electroluminescence (EL) spectra of porphyrin derivatives indicated a red shift, as π electron rich zinc complex EL spectra. The device (4) has also a luminance of 3420 cd/m2 and maximum efficiency of 1.58 cd/A at 15 V, which are the highest values among four devices. The result of Commission International del'Eclairage (CIE) (X, Y) coordinate and EL spectrum of device (3) indicated that it is more red shifted compared to other devices. Results of this work indicate that π electron rich zinc complex is a promising host material for high efficiency red OLEDs and has a simple structure compared to Alq3-based devices.

  4. Patternless light outcoupling enhancement method for top-emission organic light-emitting diodes

    Science.gov (United States)

    Kim, Doo-Hoon; Lee, Ho-Nyeon

    2016-11-01

    An increase of 65% in the luminous flux of a top-emission organic light-emitting diode (TE-OLED) was obtained by fabricating a stacked N,N‧-bis(naphthalen-1-yl)-N,N‧-bis(phenyl)benzidine (NPB) (0.2 µm)/CaF2 (2.5 µm) light outcoupling layer on the TE-OLED. The high-refractive-index NPB layer extracted the trapped light energy in the TE-OLED for input into the light outcoupling layer and protected the top cathode of the TE-OLED from damage due to the CaF2 layer. The surface morphology of the CaF2 layer had an irregular shape consisting of randomly dispersed pyramids; the irregular structure scattered the waveguide mode energy into air. By combining the effects of the NPB and CaF2 layers, the external quantum efficiency of the TE-OLED was increased significantly. The light outcoupling layer can be fabricated using a thermal evaporation process without patterning and, hence, provides a practical solution for the enhancement of TE-OLED light outcoupling using a patternless fabrication process.

  5. Lifetime improvement mechanism in organic light-emitting diodes with mixed materials at a heterojunction interface

    Science.gov (United States)

    Minagawa, Masahiro; Takahashi, Noriko

    2016-02-01

    To investigate the lifetime improvement mechanism caused by mixing at the heterojunction interface, organic light-emitting diodes (OLEDs) with stacked and mixed 4,4‧-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (α-NPD)/tris(8-hydroxyquinoline)aluminum (Alq3) interfaces were fabricated, and changes in their displacement current due to continuous operation were measured. A decrease in accumulated holes at the α-NPD/Alq3 interface was observed in the stacked configuration devices over longer operations. These results indicate that the injected hole density was reduced during continuous operation, implying that the carrier balance became uneven in the emission region. However, few accumulated holes and changes in the displacement current due to continuous operation were observed in the devices having the mixed layer. Therefore, it was deduced that the number of holes concentrated between the α-NPD and Alq3 layers was decreased by mixing at the heterojunction interface, and that the change in the number of holes was smaller during continuous operation, resulting in less degradation.

  6. Highly flexible peeled-off silver nanowire transparent anode using in organic light-emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Ya-Hui; Duan, Yu, E-mail: duanyu@jlu.edu.cn; Wang, Xiao; Yang, Dan; Yang, Yong-Qiang; Chen, Ping; Sun, Feng-Bo; Xue, Kai-Wen; Zhao, Yi

    2015-10-01

    Graphical abstract: - Highlights: • An ultra-smooth AgNW film on a flexible photopolymer substrate has been fabricated. • The AgNW film has a low sheet resistance with high transparency and flexibility. • OLEDs based on AgNW:NOA63 substrate can be bent at a radius of curvature of 2 mm. - Abstract: Materials to replace indium tin oxide (ITO) for high transmittance and electrical conductivity are urgently needed. In this paper, we adopted a silver nanowire (AgNW)-photopolymer (NOA63) film as a new platform for flexible optoelectronic devices. This design combined a transparent electrode and a flexible substrate. We utilized this application to obtain flexible organic light-emitting devices (FOLEDs). A peel-off process combined with a spin-coating process created an ultra-smooth silver nanowire anode on a photopolymer substrate. The performance of the device was achieved via the perfect morphology of the AgNW anode, the optimal 5 mg/ml concentration of AgNW solution, and the 45.7 Ω/□ sheet resistance of the AgNW film. The maximum current efficiency of the FOLED is 13 cd/A with stable mechanical flexibility even when bent to a radius of curvature of 2 mm. The outstanding performance of the FOLED with peeled off AgNW anode shows that this approach is a promising alternative to ITO for FOLEDs.

  7. Synthesis and design of organic light-emitting devices containing lanthanide-cored complexes

    Science.gov (United States)

    Phelan, Gregory D.; Carlson, Brenden; Lawson, Rhys; Rowe, Daniel; Allen, Kolby; Dalton, Larry; Jiang, Xuezhong; Kim, Joo H.; Jen, Alex K.

    2004-02-01

    There is a considerable interest in the use of metal centered materials as a light source in the growing field of organic light emitting devices (OLED's). In these devices, a polymeric host matrix containing either a carbazole type polymer or polyfluorene derivatives is used to help facilitate energy transfer to the luminophore. We have shown that by using a gadolinium complex that consist of three equivalents of a chelated dibenzoylmethane b-diketone ligand and one equivalent of a phenanthroline type ligand as a component in the host matrix, the performance of a double layer type OLED is improved. We have studied OLED systems that contain tris chelated europium compounds that contain three equivalents of partially fluorinated β-diketone type ligands and an equivalent of a phenanthroline type ligand. In these devices, the external efficiency has shown a 30-fold increase. We have also shown there is an increase for Osmium based OLED's that use the gadolinium complex as part of the polymer matrix. In these devices, the maximum quantum efficiency increased from 2.1% to a value of 3.8%.

  8. Active matrix organic light emitting diode (OLED)-XL life test results

    Science.gov (United States)

    Fellowes, David A.; Wood, Michael V.; Hastings, Arthur R., Jr.; Ghosh, Amalkumar P.; Prache, Olivier

    2008-04-01

    OLED displays have been known to exhibit high levels of performance with regards to contrast, response time, uniformity, and viewing angle, but a lifetime improvement has been perceived to be essential for broadening the applications of OLED's in the military and in the commercial market. As a result of this need, the US Army and eMagin Corporation established a Cooperative Research and Development Agreement (CRADA) to improve the lifetime of OLED displays. In 2006, eMagin Corporation developed long-life OLED-XL devices for use in their AMOLED microdisplays for head-worn applications, and RDECOM CERDEC NVESD ran life tests on these displays, finding over 200% lifetime improvement for the XL devices over the standard displays. Early results were published at the 2007 SPIE Defense and Security Symposium. Further life testing of XL and standard devices at ambient conditions and at high temperatures will be presented this year along with a recap of previous data. This should result in a better understanding of the applicability of AMOLEDs in military and commercial head mounted systems: where good fits are made, and where further development might be needed. This is a continuation of the paper "Life test results of OLED-XL long-life devices for use in active matrix organic light emitting diode (AMOLED) displays for head mounted applications" presented at SPIE DSS in 2007.

  9. Separated Carbon Nanotube Macroelectronics for Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Fu, Yue; Zhang, Jialu; Wang, Chuan; Chen, Pochiang; Zhou, Chongwu

    2012-02-01

    Active matrix organic light-emitting diode (AMOLED) display holds great potential for the next generation visual technologies due to its high light efficiency, flexibility, lightweight, and low-temperature processing. However, suitable thin-film transistors (TFTs) are required to realize the advantages of AMOLED. Pre-separated, semiconducting enriched carbon nanotubes are excellent candidates for this purpose because of their excellent mobility, high percentage of semiconducting nanotubes, and room-temperature processing compatibility. Here we report, for the first time, the demonstration of AMOLED displays driven by separated nanotube thin-film transistors (SN-TFTs) including key technology components such as large-scale high-yield fabrication of devices with superior performance, carbon nanotube film density optimization, bilayer gate dielectric for improved substrate adhesion to the deposited nanotube film, and the demonstration of monolithically integrated AMOLED display elements with 500 pixels driven by 1000 SN-TFTs. Our approach can serve as the critical foundation for future nanotube-based thin-film display electronics.

  10. Thermally cross-linkable hole transport polymers for solution-based organic light-emitting diodes.

    Science.gov (United States)

    Cha, Seung Ji; Cho, Se-Na; Lee, Woo-Hyung; Chung, Ha-Seul; Kang, In-Nam; Suh, Min Chul

    2014-04-01

    Two thermally cross-linkable hole transport polymers that contain phenoxazine and triphenylamine moieties, X-P1 and X-P2, are developed for use in solution-processed multi-stack organic light-emitting diodes (OLEDs). Both X-P1 and X-P2 exhibit satisfactory cross-linking and optoelectronic properties. The highest occupied molecular orbital (HOMO) levels of X-P1 and X-P2 are -5.24 and -5.16 eV, respectively. Solution-processed super yellow polymer devices (ITO/X-P1 or X-P2/PDY-132/LiF/Al) with X-P1 or X-P2 hole transport layers of various thicknesses are fabricated with the aim of optimizing the device characteristics. The fabricated multi-stack yellow devices containing the newly synthesized hole transport polymers exhibit satisfactory currents and power efficiencies. The optimized X-P2 device exhibits a device efficiency that is dramatically improved by more than 66% over that of a reference device without an HTL.

  11. Hybrid Perovskite Light-Emitting Diodes Based on Perovskite Nanocrystals with Organic-Inorganic Mixed Cations.

    Science.gov (United States)

    Zhang, Xiaoli; Liu, He; Wang, Weigao; Zhang, Jinbao; Xu, Bing; Karen, Ke Lin; Zheng, Yuanjin; Liu, Sheng; Chen, Shuming; Wang, Kai; Sun, Xiao Wei

    2017-03-07

    Organic-inorganic hybrid perovskite materials with mixed cations have demonstrated tremendous advances in photovoltaics recently, by showing a significant enhancement of power conversion efficiency and improved perovskite stability. Inspired by this development, this study presents the facile synthesis of mixed-cation perovskite nanocrystals based on FA(1-x) Csx PbBr3 (FA = CH(NH2 )2 ). By detailed characterization of their morphological, optical, and physicochemical properties, it is found that the emission property of the perovskite, FA(1-x) Csx PbBr3 , is significantly dependent on the substitution content of the Cs cations in the perovskite composition. These mixed-cation perovskites are employed as light emitters in light-emitting diodes (LEDs). With an optimized composition of FA0.8 Cs0.2 PbBr3 , the LEDs exhibit encouraging performance with a highest reported luminance of 55 005 cd m(-2) and a current efficiency of 10.09 cd A(-1) . This work provides important instructions on the future compositional optimization of mixed-cation perovskite for obtaining high-performance LEDs. The authors believe this work is a new milestone in the development of bright and efficient perovskite LEDs.

  12. Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

    Science.gov (United States)

    Wang, Nana; Cheng, Lu; Ge, Rui; Zhang, Shuting; Miao, Yanfeng; Zou, Wei; Yi, Chang; Sun, Yan; Cao, Yu; Yang, Rong; Wei, Yingqiang; Guo, Qiang; Ke, You; Yu, Maotao; Jin, Yizheng; Liu, Yang; Ding, Qingqing; di, Dawei; Yang, Le; Xing, Guichuan; Tian, He; Jin, Chuanhong; Gao, Feng; Friend, Richard H.; Wang, Jianpu; Huang, Wei

    2016-11-01

    Organometal halide perovskites can be processed from solutions at low temperatures to form crystalline direct-bandgap semiconductors with promising optoelectronic properties. However, the efficiency of their electroluminescence is limited by non-radiative recombination, which is associated with defects and leakage current due to incomplete surface coverage. Here we demonstrate a solution-processed perovskite light-emitting diode (LED) based on self-organized multiple quantum wells (MQWs) with excellent film morphologies. The MQW-based LED exhibits a very high external quantum efficiency of up to 11.7%, good stability and exceptional high-power performance with an energy conversion efficiency of 5.5% at a current density of 100 mA cm-2. This outstanding performance arises because the lower bandgap regions that generate electroluminescence are effectively confined by perovskite MQWs with higher energy gaps, resulting in very efficient radiative decay. Surprisingly, there is no evidence that the large interfacial areas between different bandgap regions cause luminescence quenching.

  13. Optoelectronic properties of a novel fluorene derivative for organic light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Junsheng; Lou, Shuangling; Qian, Jincheng; Jiang, Yadong [University of Electronic Science and Technology of China (UESTC), State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, Chengdu (China); Zhang, Qing [Shanghai Jiaotong University, Department of Polymer Science, School of Chemistry and Chemical Technology, Shanghai (China)

    2009-03-15

    We report the optoelectronic properties of a novel fluorene derivative of 6,6'-(9H-fluoren-9,9-diyl)bis(2,3-bis (9,9-dihexyl-9H-fluoren-2-yl)quinoxaline) (BFLBBFLYQ) used for organic light-emitting diode. UV-Vis absorption, photoluminescence (PL) and electroluminescence (EL) spectra of BFLBBFLYQ and the blend doped with N,N'-biphenyl-N,N'-bis-(3-methylphenyl)-1,1'-biphenyl-4,4'-di- amine (TPD) in solid state and in solution were investigated. The results showed that BFLBBFLYQ had a PL peak at 451 nm in solid and solution states and an EL peak at 483 nm with a broad emission band, resulting from fluorenone defects. Exciplex emission was observed in BFLBBFLYQ-TPD blend solid state with a green emission peaking at 530 nm. Also the blend in solution showed solvatochromism in polarity solvent upon UV irradiation. A new absorption band appeared at around 470 nm of BFLBBFLYQ-TPD blend in chloroform solution, and disappeared when diluted in absorption spectrum. Meanwhile, a low energy emission band from 530 to 580 nm appeared and increased with material concentration and UV irradiation time. (orig.)

  14. Efficient green phosphorescent tandem organic light emitting diodes with solution processable mixed hosts charge generating layer

    Energy Technology Data Exchange (ETDEWEB)

    Talik, N.A.; Yeoh, K.H.; Ng, C.Y.B [Low Dimensional Research Center, Department of Physics, University Malaya, 50603 Kuala Lumpur (Malaysia); ItraMAS Corporation. Sdn. Bhd., 542A-B Mukim 1, Lorong Perusahaan Baru 2, Kawasan Perindustrian, Perai 13600, Penang (Malaysia); Yap, B.K. [Center of Microelectronic and Nanotechnology Engineering (CeMNE), College of Engineering, Universiti Tenaga Nasional, Jln. Uniten-Ikram, 4300 Kajang, Selangor (Malaysia); Woon, K.L., E-mail: ph7klw76@um.edu.my [Low Dimensional Research Center, Department of Physics, University Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-10-15

    A novel solution processable charge generating layer (CGL) that consists of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HATCN{sub 6})/Poly(N-vinylcarbazole) (PVK): 1,1-bis-(4-bis(4-tolyl)-aminophenyl) cyclohexene (TAPC) for a tandem green phosphorescent organic light emitting diode (PHOLED) is demonstrated. The use of orthogonal solvent to dissolve HATCN{sub 6} and PVK:TAPC is the key to overcome the interface erosion problem for the solution processed CGL. The current efficiency of the 2 wt% TAPC mixed with PVK is the highest at 24.2 cd/A, which is more than three-folds higher than that of the single device at 1000 cd/m{sup 2}. - Highlights: • A solution processable tandem OLED is built using a novel charge generating layer. • HATCN{sub 6} and PVK:TAPC are shown to be effective charge generating layers. • The turn on voltages for tandem devices are almost similar to single unit. • 2 wt% TAPC blended with PVK exhibits three-folds increase in efficiency.

  15. Flexible organic light emitting diodes fabricated on biocompatible silk fibroin substrate

    Science.gov (United States)

    Liu, Yuqiang; Xie, Yuemin; Liu, Yuan; Song, Tao; Zhang, Ke-Qin; Liao, Liangsheng; Sun, Baoquan

    2015-10-01

    Flexible and biodegradable electronics are currently under extensive investigation for biocompatible and environmentally-friendly applications. Synthetic plastic foils are widely used as substrates for flexible electronics. But typical plastic substrates such as polyethylene naphthalate (PEN) could not be degraded in a natural bio-environment. A great demand still exists for a next-generation biocompatible and biodegradable substrate for future application. For example, electronic devices can be potentially integrated into the human body. In this work, we demonstrate that the biocompatible and biodegradable natural silk fibroin (SF) films embedded with silver nanowires (AgNWs) mesh could be employed as conductive transparent substrates to fabricate flexible organic light emitting diodes (OLEDs). Compared with commercial PEN substrates coated with indium tin oxide, the AgNWs/SF composite substrates exhibit a similar sheet resistance of 12 Ω sq-1, a lower surface roughness, as well as a broader light transmission range. Flexible OLEDs based on AgNWs/SF substrates achieve a current efficiency of 19 cd A-1, demonstrating the potential of the flexible AgNWs/SF films as conductive and transparent substrates for next-generation biodegradable devices.

  16. Tunable color parallel tandem organic light emitting devices with carbon nanotube and metallic sheet interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, Jorge; Desirena, Haggeo; De la Rosa, Elder [Centro de Investigaciones en Optica, A.P. 1-948, León, Guanajuato 37160 (Mexico); Papadimitratos, Alexios [Solarno Inc., Coppell, Texas 75019 (United States); University of Texas at Dallas, Richardson, Texas 75080 (United States); Zakhidov, Anvar A., E-mail: Zakhidov@utdallas.edu [Solarno Inc., Coppell, Texas 75019 (United States); University of Texas at Dallas, Richardson, Texas 75080 (United States); Energy Efficiency Center, National University of Science and Technology, MISiS, Moscow 119049 (Russian Federation)

    2015-11-21

    Parallel tandem organic light emitting devices (OLEDs) were fabricated with transparent multiwall carbon nanotube sheets (MWCNT) and thin metal films (Al, Ag) as interlayers. In parallel monolithic tandem architecture, the MWCNT (or metallic films) interlayers are an active electrode which injects similar charges into subunits. In the case of parallel tandems with common anode (C.A.) of this study, holes are injected into top and bottom subunits from the common interlayer electrode; whereas in the configuration of common cathode (C.C.), electrons are injected into the top and bottom subunits. Both subunits of the tandem can thus be monolithically connected functionally in an active structure in which each subunit can be electrically addressed separately. Our tandem OLEDs have a polymer as emitter in the bottom subunit and a small molecule emitter in the top subunit. We also compared the performance of the parallel tandem with that of in series and the additional advantages of the parallel architecture over the in-series were: tunable chromaticity, lower voltage operation, and higher brightness. Finally, we demonstrate that processing of the MWCNT sheets as a common anode in parallel tandems is an easy and low cost process, since their integration as electrodes in OLEDs is achieved by simple dry lamination process.

  17. Frustrated total internal reflection in organic light-emitting diodes employing sphere cavity embedded in polystyrene

    Science.gov (United States)

    Zhu, Peifen

    2016-02-01

    The light extraction efficiency of top-emitting organic light-emitting diodes (OLEDs) is numerically investigated employing the finite-difference time-domain method. The periodic nanostructures formed by embedding the sphere arrays in polystyrene (PS) are placed on top of OLED to frustrate the total internal reflection at the interface between OLED and free space. These nanostructures serve as an intermediate medium to extract the light out of OLED devices. Efficiently coupling both evanescent waves and propagation waves into spheres and subsequently extracting these light waves out of the sphere is key to achieving high extraction efficiency. By tuning the thickness of PS layer, both of the in-coupling efficiency and out-coupling efficiency are optimized for achieving high light extraction efficiency. Thicker PS layer results in higher in-coupling efficiency in sphere while the thinner PS layer leads to higher out-coupling efficiency. Thus the maximum light extraction is a trade-off between the in-coupling efficiency and out-coupling efficiency. The study shows that light extraction efficiency of 89% can be achieved by embedding 0.90 μm TiO2 sphere in 0.30 μm PS layer with optimized in-coupling efficiency, out-coupling efficiency and cavity effect.

  18. Platinum (II) azatetrabenzoporphyrins for near-infrared organic light emitting diodes

    Science.gov (United States)

    Huang, L.; Park, C. D.; Fleetham, T.; Li, J.

    2016-12-01

    This article describes a series of platinum (II) azatetrabenzoporphyrin emitters for near-infrared (NIR) organic light emitting diode (OLED) applications. Platinum (II) aza-triphenyltetrabenzoporphyrin (PtNTBP) results in a 72 nm shift in the photoluminescent (PL) emission spectrum to 842 nm compared to 770 nm of the platinum (II) tetraphenyltetrabenzoporphyrin (PtTPTBP). Also, the full width at half maximum of the emission spectrum of PtNTBP was significantly narrowed to 27 nm compared to 40 nm for PtTPTBP. The multilayer devices fabricated by thermal vacuum evaporation process employing PtTPTBP, PtNTBP, and cis-PtN2TBP exhibit electroluminescent (EL) emission peak at 770 nm, 848 nm, and 846 nm with the peak external quantum efficiency (EQE) of 8.0%, 2.8%, and 1.5%, respectively. Even with the decrease in EQE of devices employing PtNTBP and cis-PtN2TBP compared with those employing PtTPTBP, the combination of the spectral narrowing and the bathochromic shift to lower energy EL emission demonstrates the promise of PtNTBP for NIR applications. In the meanwhile, the solution-processed single-layer device using PtNTBP demonstrates the EQE of 0.33% and the peak EL emission at 844 nm.

  19. White organic light-emitting diodes based on C545T doped emitting system

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Hua-Ping; Zhou, Fan; Zhang, Liang [Department of Materials Science, Shanghai University, Jiading, Shanghai (China); Li, Jun; Jiang, Xue-Yin; Zhang, Zhi-Lin; Zhang, Jian-Hua [Department of Materials Science, Shanghai University, Jiading, Shanghai (China); Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai (China); Zhang, Xiao-Wen [Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin (China)

    2012-02-15

    Fluorescent white organic light-emitting diodes (WOLEDs) with single-emitting layer (EML) and double-EML structures were demonstrated using a 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10(2-benzothiazolyl)quinolizine-[9,9a,1gh]coumarin (C545T) doped emitting system. With the incorporation of double-EML structure, white emission with Commission Internationale de L'Eclairage (CIE) color coordinates of (0.331, 0.335) and luminous efficiency of 8.04 cd/A was obtained. Moreover, WOLED with a single-EML structure shows superior electroluminescence performances such as lower voltage, higher luminance, and enhanced power efficiency. These improvements are attributed to its high energy transfer ability via the intermediation of C545T. The Forster's radius was given to clarify the actual energy transfer process. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Effects of diamond-like carbon thin film in organic light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Seong-Shan; Yong, Thian-Khok [Faculty of Engineering, Multimedia University, Cyberjaya, 63100 Selangor (Malaysia); Tou, Teck-Yong, E-mail: tytou@mmu.edu.m [Faculty of Engineering, Multimedia University, Cyberjaya, 63100 Selangor (Malaysia)

    2009-07-01

    Ultrathin diamond-like carbon (DLC) was deposited by pulsed Nd:YAG laserablation of graphite target on the indium tin oxide (ITO) surface that functioned as the buffered anode for single-layer organic light emitting devices (OLEDs). Deposited by 355 nm Nd:YAG laser, DLC films were characterized by the Raman spectroscopy and the bulk resistivity measurement. Insertion of DLC in the hole-transport ITO/DLC/TPD/Al device slightly increased the injection current density and reduced the turn-on voltage. But DLC insertion in the electron-transport ITO/DLC/Alq{sub 3}/Al device greatly decreased the injection current density and increased the turn-on voltage. For the ITO/DLC/(TPD + Alq{sub 3} + PVK)/Al device, that was doped with Alq{sub 3} and TPD, improved performance with a higher current density and brightness were consistently obtained. Possible mechanisms for the DLC effect in these single-layer devices were discussed.

  1. Hole injection enhancement in organic light emitting devices using plasma treated graphene oxide

    Science.gov (United States)

    Jesuraj, P. Justin; Parameshwari, R.; Kanthasamy, K.; Koch, J.; Pfnür, H.; Jeganathan, K.

    2017-03-01

    The hole injection layer (HIL) with high work function (WF) is desirable to reduce the injection barrier between anode and hole transport layer in organic light emitting devices (OLED). Here, we report a novel approach to tune the WF of graphene oxide (GO) using oxygen and hydrogen plasma treatment and its hole injection properties in OLEDs. The mild exposure of oxygen plasma on GO (O2-GO) significantly reduces the injection barrier by increasing the WF of anode (4.98 eV) through expansion of Csbnd O bonds. In contrast, the hole injection barrier was drastically increased for hydrogen plasma treated GO (H2-GO) layers as the WF is lowered by the contraction of Csbnd O bond. By employing active O2-GO as HIL in OLEDs found to exhibit superior current efficiency of 4.2 cd/A as compared to 3.3 cd/A for pristine GO. Further, the high injection efficiency of O2-GO infused hole only device can be attributed to the improved energy level matching. Ultraviolet and X-ray photoelectron spectroscopy were used to correlate the WF of HIL infused anode towards the enhanced performance of OLEDs with their capricious content of Csbnd O in GO matrix.

  2. Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes

    Science.gov (United States)

    Lee, Jaeho; Han, Tae-Hee; Park, Min-Ho; Jung, Dae Yool; Seo, Jeongmin; Seo, Hong-Kyu; Cho, Hyunsu; Kim, Eunhye; Chung, Jin; Choi, Sung-Yool; Kim, Taek-Soo; Lee, Tae-Woo; Yoo, Seunghyup

    2016-06-01

    Graphene-based organic light-emitting diodes (OLEDs) have recently emerged as a key element essential in next-generation displays and lighting, mainly due to their promise for highly flexible light sources. However, their efficiency has been, at best, similar to that of conventional, indium tin oxide-based counterparts. We here propose an ideal electrode structure based on a synergetic interplay of high-index TiO2 layers and low-index hole-injection layers sandwiching graphene electrodes, which results in an ideal situation where enhancement by cavity resonance is maximized yet loss to surface plasmon polariton is mitigated. The proposed approach leads to OLEDs exhibiting ultrahigh external quantum efficiency of 40.8 and 62.1% (64.7 and 103% with a half-ball lens) for single- and multi-junction devices, respectively. The OLEDs made on plastics with those electrodes are repeatedly bendable at a radius of 2.3 mm, partly due to the TiO2 layers withstanding flexural strain up to 4% via crack-deflection toughening.

  3. Analyzing degradation effects of organic light-emitting diodes via transient optical and electrical measurements

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Tobias D., E-mail: Tobias.Schmidt@physik.uni-augsburg.de; Jäger, Lars; Brütting, Wolfgang, E-mail: Wolfgang.Bruetting@physik.uni-augsburg.de [Institute of Physics, University of Augsburg, Augsburg (Germany); Noguchi, Yutaka [Department of Electronics and Bioinformatics, School of Science and Technology, Meiji University, Kawasaki (Japan); Center of Frontier Science, Chiba University, Chiba (Japan); Ishii, Hisao [Center of Frontier Science, Chiba University, Chiba (Japan)

    2015-06-07

    Although the long-term stability of organic light-emitting diodes (OLEDs) under electrical operation made significant progress in recent years, the fundamental underlying mechanisms of the efficiency decrease during operation are not well understood. Hence, we present a comprehensive degradation study of an OLED structure comprising the well-known green phosphorescent emitter Ir(ppy){sub 3}. We use transient methods to analyze both electrical and optical changes during an accelerated aging protocol. Combining the results of displacement current measurements with time-resolved investigation of the excited states lifetimes of the emitter allows for a correlation of electrical (e.g., increase of the driving voltage due to trap formation) and optical (e.g., decrease of light-output) changes induced by degradation. Therewith, it is possible to identify two mechanisms resulting in the drop of the luminance: a decrease of the radiative quantum efficiency of the emitting system due to triplet-polaron-quenching at trapped charge carriers and a modified charge carrier injection and transport, as well as trap-assisted non-radiative recombination resulting in a deterioration of the charge carrier balance of the device.

  4. Performance Enhancement of Organic Light-Emitting Diodes Using Electron-Injection Materials of Metal Carbonates

    Science.gov (United States)

    Shin, Jong-Yeol; Kim, Tae Wan; Kim, Gwi-Yeol; Lee, Su-Min; Shrestha, Bhanu; Hong, Jin-Woong

    2016-05-01

    Performance of organic light-emitting diodes was investigated depending on the electron-injection materials of metal carbonates (Li2CO3 and Cs2CO3 ); and number of layers. In order to improve the device efficiency, two types of devices were manufactured by using the hole-injection material (Teflon-amorphous fluoropolymer -AF) and electron-injection materials; one is a two-layer reference device ( ITO/Teflon-AF/Alq3/Al ) and the other is a three-layer device (ITO/Teflon-AF/Alq3/metal carbonate/Al). From the results of the efficiency for the devices with hole-injection layer and electron-injection layer, it was found that the electron-injection layer affects the electrical properties of the device more than the hole-injection layer. The external-quantum efficiency for the three-layer device with Li2CO3 and Cs2CO3 layer is improved by approximately six and eight times, respectively, compared with that of the two-layer reference device. It is thought that a use of electron-injection layer increases recombination rate of charge carriers by the active injection of electrons and the blocking of holes.

  5. Spectral-distortion-free light extraction from organic light-emitting diodes using nanoscale photonic crystal

    Science.gov (United States)

    Shim, Yong Sub; Nyun Kim, Kyu; Hwang, Ju Hyun; Hwee Park, Cheol; Jung, Sun-Gyu; Park, Young Wook; Ju, Byeong-Kwon

    2017-01-01

    Despite their generally good performance, photonic crystal (PC)-based organic light-emitting diodes (OLEDs) encounter a serious spectral distortion problem. In this study, we obtained spectral-distortion-free PC-based OLEDs by lowering the pitch (period of the PC) to less than a half the emission wavelength, using a simple and scalable nanoscale process of laser interference lithography. The demonstrated OLEDs with 200 nm pitch-size nanoscale periodic hole arrays exhibited negligible changes in the Internal Commission on Illumination 1931 color coordinate of Δ (0.0104, 0.0078) and a peak wavelength of Δ0 nm (relative to the reference), while maintaining the function of the internal light extraction layer, manifested as a 23% enhancement of the external quantum efficiency (EQE). The enhancement of the EQE reached 85% after incorporating a micro-lens array. The improved light extraction, spectral-distortion-free characteristic, and excellent color stability over a broad range of viewing angles were successfully derived by performing finite difference time domain simulations.

  6. Device based on the coupling of an organic light-emitting diode with a photoconductive material

    Energy Technology Data Exchange (ETDEWEB)

    El Amrani, A. [Universite de Limoges, Faculte des Sciences et Techniques, CNRS, UMR 6172, Institut de Recherche XLIM, Departement MINACOM, 123 Av Albert Thomas, 87060 Limoges (France); Lucas, B. [Universite de Limoges, Faculte des Sciences et Techniques, CNRS, UMR 6172, Institut de Recherche XLIM, Departement MINACOM, 123 Av Albert Thomas, 87060 Limoges (France)], E-mail: bruno.lucas@unilim.fr; Moliton, A. [Universite de Limoges, Faculte des Sciences et Techniques, CNRS, UMR 6172, Institut de Recherche XLIM, Departement MINACOM, 123 Av Albert Thomas, 87060 Limoges (France)

    2008-02-15

    We have realized a device based on the coupling of an organic light-emitting diode (with tri(8-hydroxyquinoline)aluminium for light emission) as an input unit with a photoconductive material as an output unit. Various photoconductive materials like pentacene, Cu-phtalocyanine and fullerene were investigated under green light illumination with an emission peak at 550 nm. Photocurrent measurements versus light intensity and bias voltage (applied between two 50 {mu}m distant indium-tin oxide bottom electrodes for the current to flow through the materials) were realized at room temperature a photocurrent gain around 4 is obtained when the materials are subjected to a luminance of about 5000 cd/m{sup 2} and for bias voltage of - 50 V. Besides, it was shown that to obtain a device with a fast photocurrent response by switching the light off and on, it is necessary to apply a bias voltage higher than - 200 V in these conditions, the gain is multiplied by a factor of 3.

  7. Organic Light Emitting Diodes with Lithium Contained Alq3 as Electron Injection Layer

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Novel lithium doped tris-8-hydroxylquinoline aluminium (Alq3:Li) layer is deposited between emission layer and electron injection aluminium electrode as an electron injection assistant layer in different organic light emitting diodes(OLED) to lower the electron injection barrier. In these devices, Alq3 is used as emission layer, and a bilayer film of N, N' -bis- ( 1-naphhyl)-N, N' -diphenyl- 1,1' -biphenyle-4,4" -diamine (NPB) and 4,4' , 4" -tris (3-methyl-phenylphenylamino) triphenylamine(m-MTDATA) used as hole transport layer(HTL). The electroluminescent performance of devices with different thicknesses of Alq3: Li shows that the insertion of the lithium doped Alq3 layer can reduce the turn on voltage by at least 2 volts, and the stability of devices with this lithium doped Alq3 layer is improved too. It can also change the efficiency of devices. Compared with an ultra-thin lithium fluoride(IiF) layer, Alq3 : Li sheet gives similar effects but higher efficiency and can be much thicker and hence it is easier to control the deposition.

  8. Manipulation and control of the interfacial polarization in organic light-emitting diodes by dipolar doping

    Science.gov (United States)

    Jäger, Lars; Schmidt, Tobias D.; Brütting, Wolfgang

    2016-09-01

    Most of the commonly used electron transporting materials in organic light-emitting diodes exhibit interfacial polarization resulting from partially aligned permanent dipole moments of the molecules. This property modifies the internal electric field distribution of the device and therefore enables an earlier flat band condition for the hole transporting side, leading to improved charge carrier injection. Recently, this phenomenon was studied with regard to different materials and degradation effects, however, so far the influence of dilution has not been investigated. In this paper we focus on dipolar doping of the hole transporting material 4,4-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (NPB) with the polar electron transporting material tris-(8-hydroxyquinolate) aluminum (Alq3). Impedance spectroscopy reveals that changes of the hole injection voltage do not scale in a simple linear fashion with the effective thickness of the doped layer. In fact, the measured interfacial polarization reaches a maximum value for a 1:1 blend. Taking the permanent dipole moment of Alq3 into account, an increasing degree of dipole alignment is found for decreasing Alq3 concentration. This observation can be explained by the competition between dipole-dipole interactions leading to dimerization and the driving force for vertical orientation of Alq3 dipoles at the surface of the NPB layer.

  9. High-contrast top-emitting organic light-emitting devices

    Institute of Scientific and Technical Information of China (English)

    Chen Shu-Fen; Chen Chun-Yan; Yang Yang; Xie Jun; Huang Wei; Shi Hong-Ying; Cheng Fan

    2012-01-01

    In this paper we report on a high-contrast top-emitting organic light-emitting device utilizing a moderate-reflection contrast-enhancement stack and a high refractive index anti-reflection layer.The contrast-enhancement stack consists of a thin metal anode layer,a dielectric bilayer,and a thick metal underlayer.The resulting device,with the optimized contrast-enhancement stack thicknesses of Ni (30 nm)/MgF2 (62 nm)/ZnS (16 nm)/Ni (20 nm) and the 25-nm-thick ZnS anti-reflection layer,achieves a luminous reflectance of 4.01% in the visible region and a maximum current efficiency of 0.99 cd/A (at 62.3 mA/cm2) together with a very stable chromaticity.The contrast ratio reaches 561∶1 at an on-state brightness of 1000 cd/m2 under an ambient illumination of 140 lx.In addition,the anti-reflection layer can als0 enhance the transmissivity of the cathode and improve light out-coupling by the effective restraint of microcavity effects.

  10. Passivation of organic light emitting diode anode grid lines by pulsed Joule heating

    Science.gov (United States)

    Janka, M.; Gierth, R.; Rubingh, J.-E.; Abendroth, M.; Eggert, M.; Moet, D. J. D.; Lupo, D.

    2015-09-01

    We report the self-aligned passivation of a current distribution grid for an organic light emitting diode (OLED) anode using a pulsed Joule heating method to align the passivation layer accurately on the metal grid. This method involves passing an electric current through the grid to cure a polymer dielectric. Uncured polymer is then rinsed away, leaving a patterned dielectric layer that conforms to the shape of the grid lines. To enhance the accuracy of the alignment, heat conduction into the substrate and the transparent electrode is limited by using short current pulses instead of a constant current. Excellent alignment accuracy of the dielectric layer on printed metal grid lines has been achieved, with a typical 4-μm dielectric overhang. In addition to good accuracy, pulsed Joule heating significantly cuts down process time and energy consumption compared to heating with a constant current. The feasibility of using a printed current distribution grid and Joule heating was demonstrated in an OLED device.

  11. Concentration-insensitive phosphorescent organic light emitting devices (PhOLEDs) for easy manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Dumur, Frédéric, E-mail: frederic.dumur@univ-amu.fr [Aix-Marseille Université, CNRS, ICR, UMR 7273, F-13397 Marseille (France); Lepeltier, Marc [Institut Lavoisier de Versailles, UMR 8180 CNRS, Université de Versailles Saint-Quentin en Yvelines, 45 avenue des Etats-Unis, 78035 Versailles Cedex (France); Zamani Siboni, Hossein, E-mail: hzamanis@uwaterloo.ca [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West Waterloo, ON, Canada N2L 3G1 (Canada); Xiao, Pu; Graff, Bernadette; Lalevée, Jacques [Institut de Science des Matériaux de Mulhouse IS2M, UMR 7361 CNRS, Université de Haute Alsace, 15 rue Jean Starcky, 68057 Mulhouse Cedex (France); Gigmes, Didier [Aix-Marseille Université, CNRS, ICR, UMR 7273, F-13397 Marseille (France); Aziz, Hany [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West Waterloo, ON, Canada N2L 3G1 (Canada)

    2014-07-01

    Two heteroleptic iridium(III) complexes Ir(piq){sub 2}(dbm) and Ir(btp){sub 2}(acac) have been tested as emitters for phosphorescent OLEDs (PhOLEDs). Interestingly, device performance exhibited a marked insensitivity to the dopant concentration. In this study, a dibenzoylmethane (dbm)-based complex has also been tested for the first time as dopant for OLEDs. To evaluate the emissive properties of this new emitter belonging to a family of complexes that has not been investigated yet, identical devices were prepared with the well-known red dopant Ir(btp){sub 2}(acac) for comparison. The new complex Ir(piq){sub 2}(dbm) exhibited comparable performance to that obtained with Ir(btp){sub 2}(acac). - Highlights: • A new neutral iridium complex has been tested as emitter. • TD-DFT calculations and electrochemical measurements were carried out to support the experimental results. • UV–visible absorption and photoluminescence spectroscopy of complexes were investigated. • Concentration-insensitive phosphorescent organic light emitting devices were obtained.

  12. Carbon nanotube sheets as transparent charge injectors in organic light-emitting diodes

    Science.gov (United States)

    Williams, Christopher; Zhang, Mei; Ovalle, Raquel; Trivedi, Krutarth; Kuznetsov, Alexander; Lee, Sergey; Baughman, Ray; Zakhidov, Anvar

    2006-03-01

    Carbon nanotubes (CNTs) have been recognized for their potential in many applications ranging from high strength materials and fibers to true nanoscale electronics. Recently a method for making strong and transparent CNT sheets has been developed, producing free-standing multiwall nanotube sheets which are easy to process [1]. Their mechanical and electrical properties allow them to meet the needs of a wide range of applications, particularly in optoelectronics. We show here the potential for using these thin, flexible CNT sheets in the development of flexible organic light-emitting diode (OLED) displays. The high transparency of the sheets, the high degree of orientation of tubes and the high work function of the material make them suitable hole injectors for typical hole transport materials used in OLEDs and polymeric LEDs (PLEDs). We show that CNT sheets can be used as anodes for both PLEDs and molecular OLEDs. We also introduce a method for producing inverted OLEDs on existing drive electronics for active matrix displays and a design for a transparent display using CNT sheets as both the electron and hole injector. [1] M. Zhang, S. Fang, A. Zakhidov, S. Lee, A. Aliev, C. Williams, K. Atkinson, R. Baughman, Science 309, 1215 (2005)

  13. Light extraction enhancement from organic light-emitting diodes with randomly scattered surface fixture

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Dong-Ying; Shi, Xiao-Bo; Gao, Chun-Hong; Cai, Shi-Duan; Jin, Yue; Liao, Liang-Sheng, E-mail: lsliao@suda.edu.cn

    2014-09-30

    Graphical abstract: - Highlights: • A combination of scattering layer and roughened substrate is used for light extraction from OLEDs. • The scattering layer is readily achieved by spin-coating the TiO{sub 2} sol. • The enhancement relying scattering depends on the size of TiO{sub 2} nano particles. • With the light extraction techniques the uniform emission is achieved. - Abstract: A combination of a scattering medium layer and a roughened substrate was proposed to enhance the light extraction efficiency of organic light-emitting diodes (OLEDs). Comparing with a reference OLED without any scattering layer, 65% improvement in the forward emission has been achieved with a scattering layer formed on an intentionally roughened external substrate surface of the OLED by spin-coating a sol–gel fabricated matrix containing well dispersed titania (TiO{sub 2}) particles. Such a combination method not only demonstrated efficient extraction of the light trapped in the glass substrate but also achieved homogenous emission from the OLED panel. The proposed technique, convenient and inexpensive, is believed to be suitable for the large area OLED production in lighting applications.

  14. White organic light-emitting diodes with an ultra-thin premixed emitting layer

    CERN Document Server

    Jeon, T; Tondelier, Denis; Bonnassieux, Yvan; Forget, Sebastien; Chenais, Sebastien; Ishow, Elena

    2014-01-01

    We described an approach to achieve fine color control of fluorescent White Organic Light-Emitting Diodes (OLED), based on an Ultra-thin Premixed emitting Layer (UPL). The UPL consists of a mixture of two dyes (red-emitting 4-di(4'-tert-butylbiphenyl-4-yl)amino-4'-dicyanovinylbenzene or fvin and green-emitting 4-di(4'-tert-butylbiphenyl-4-yl)aminobenzaldehyde or fcho) premixed in a single evaporation cell: since these two molecules have comparable structures and similar melting temperatures, a blend can be evaporated, giving rise to thin films of identical and reproducible composition compared to those of the pre-mixture. The principle of fine color tuning is demonstrated by evaporating a 1-nm-thick layer of this blend within the hole-transport layer (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (\\alpha-NPB)) of a standard fluorescent OLED structure. Upon playing on the position of the UPL inside the hole-transport layer, as well as on the premix composition, two independent parameters are available to finel...

  15. Improvement in Device Performance and Reliability of Organic Light-Emitting Diodes through Deposition Rate Control

    Directory of Open Access Journals (Sweden)

    Shun-Wei Liu

    2014-01-01

    Full Text Available We demonstrated a fabrication technique to reduce the driving voltage, increase the current efficiency, and extend the operating lifetime of an organic light-emitting diode (OLED by simply controlling the deposition rate of bis(10-hydroxybenzo[h]qinolinato beryllium (Bebq2 used as the emitting layer and the electron-transport layer. In our optimized device, 55 nm of Bebq2 was first deposited at a faster deposition rate of 1.3 nm/s, followed by the deposition of a thin Bebq2 (5 nm layer at a slower rate of 0.03 nm/s. The Bebq2 layer with the faster deposition rate exhibited higher photoluminescence efficiency and was suitable for use in light emission. The thin Bebq2 layer with the slower deposition rate was used to modify the interface between the Bebq2 and cathode and hence improve the injection efficiency and lower the driving voltage. The operating lifetime of such a two-step deposition OLED was 1.92 and 4.6 times longer than that of devices with a single deposition rate, that is, 1.3 and 0.03 nm/s cases, respectively.

  16. Enhanced electronic injection in organic light-emitting diodes by incorporating silver nanoclusters and cesium carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ying-Chung; Gao, Chia-Yuan [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Chen, Kan-Lin [Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung, Taiwan (China); Sze, Po-Wen [Department of Electro-Optical Science and Engineering, Kao Yuan University, Kaohsiung, Taiwan (China); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2015-10-01

    Highlights: • The localized electric field around SNCs is enhanced. • When the cesium carbonate/silver nanoclusters/cesium carbonate electron-injection structure replaces the cesium carbonate electron-injection structure, higher electron-injection ability is obtained. • The structure for efficient electron injection is critical to characteristics of the device. - Abstract: The influence of the cesium carbonate/silver nanoclusters/cesium carbonate electron-injection structure (CSC-EIS) on the performance of organic light-emitting diodes is investigated in this study. The silver nanoclusters (SNCs) are introduced between the electron-injection layers by means of thermal evaporation. When the CSC-EIS replaces the cesium carbonate electron-injection structure, higher electron-injection ability is obtained because the electron-injection barrier between the cathode and the electron-transport layer is remarkably reduced from 1.2 to 0 eV. In addition, surface plasmon resonance effect will cause the enhanced localized electric field around the SNCs, resulting that electron-injection ability is further enhanced from the cathode to the emitting layer.

  17. Simulation of mixed-host emitting layer based organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Riku, C.; Kee, Y. Y.; Ong, T. S.; Tou, T. Y. [Faculty of Engineering, Multimedia University, 631000 Cyberjaya (Malaysia); Yap, S. S. [Faculty of Engineering, University of Malaya, 50603 Kuala Lampur (Malaysia)

    2015-04-24

    ‘SimOLED’ simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq{sub 3}) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO / HTM (15 nm) / Mixed host (70 nm) / ETM (10 nm) /Al, are stimulated with ratios TPD:Alq{sub 3} of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate.

  18. Influences of wide-angle and multi-beam interference on the chromaticity and efficiency of top-emitting white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Lingling; Zhou, Hongwei; Chen, Shufen, E-mail: iamsfchen@njupt.edu.cn; Liu, Bin; Wang, Lianhui [Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Shi, Hongying [Jiangsu-Singapore Joint Research Center for Organic/Bio- Electronics and Information Displays and Institute of Advanced Materials, Nanjing Tech University, Nanjing 211816 (China); Huang, Wei, E-mail: iamdirector@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Jiangsu-Singapore Joint Research Center for Organic/Bio- Electronics and Information Displays and Institute of Advanced Materials, Nanjing Tech University, Nanjing 211816 (China)

    2015-02-28

    Wide-angle interference (WI) and multi-beam interference (MI) in microcavity are analyzed separately to improve chromaticity and efficiency of the top-emitting white organic light-emitting diodes (TWOLEDs). A classic electromagnetic theory is used to calculate the resonance intensities of WI and MI in top-emitting organic light-emitting diodes (TOLEDs) with influence factors (e.g., electrodes and exciton locations) being considered. The role of WI on the performances of TOLEDs is revealed through using δ-doping technology and comparing blue and red EML positions in top-emitting and bottom-emitting devices. The blue light intensity significantly increases and the chromaticity of TWOLEDs is further improved with the use of enhanced WI (the blue emitting layer moving towards the reflective electrode) in the case of a weak MI. In addition, the effect of the thicknesses of light output layer and carrier transport layers on WI and MI are also investigated. Apart from the microcavity effect, other factors, e.g., carrier balance and carrier recombination regions are considered to obtain TWOLEDs with high efficiency and improved chromaticity near white light equal-energy point.

  19. Control of a White Organic Light Emitting Diode emission parameters using a single doped RGB active layer

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, D. [Departamento de Ciência dos Materiais e i3N – Instituto de Nanoestruturas, Nanomodelação e Nanofabricação, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica (Portugal); Pinto, A.; Califórnia, A.; Gomes, J. [CeNTI – Centro de Nanotecnologia, Materiais Técnicos, Funcionais e Inteligentes, Rua Fernando Mesquita 2785, 4760-034 Vila Nova de Famalicão (Portugal); Pereira, L., E-mail: luiz@ua.pt [Departmento de Física e i3N – Instituto de Nanoestruturas, Nanomodelação e Nanofabricação, Universidade de Aveiro, 3810-193 Aveiro (Portugal)

    2016-09-15

    Highlights: • A simple WOLED for Solid State Lighting is proposed with high color stability. • Energy transfer and electroluminescence dynamics of a single RGB layer for WOLEDs. • White shade modulation and stability over large emitting areas and applied voltages. - Abstract: Solid State Lighting technologies based on Organic Light Emitting Diodes, became an interesting focus due to their unique properties. The use of a unique RGB active layer for white emission, although simple in theory, shows difficulty to stabilize both CIE coordinates and color modulation. In this work, a WOLED using a simple RGB layer, was developed achieving a high color stability and shade modulation. The RGB matrix comprises a blue host material NPB, doped with two guests, a green (Coumarin 153) and a red (DCM1) in low concentrations. The RGB layer carrier dynamics allows for the white emission in low device complexity and high stability. This was also shown independent of the white shade, obtained through small changes in the red dopant resulting in devices ranging from warm to cool white i.e. an easy color tuning. A detailed analysis of the opto-electrical behavior is made.

  20. White Organic Light-Emitting Devices Based on 2-(2-Hydroxyphenyl) Benzothiazole and Its Chelate Metal Complex

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-Ming; HUA Yu-Lin; WANG Zhao-Qi; ZHENG Jia-Jin; FENG Xiu-Lan; SUN Yuan-Yuan

    2005-01-01

    @@ We present three kinds of organic light-emitting devices (OLED) fabricated to achieve the emission of bright and pure white light. Device A, with a double-layered structure using 2-(2-hydroxyphenyl) benzothiazole (HBT) and poly (N-vinylcarbazole) (PVK) as the emitting layer (EML) and the hole transport layer (HTL) respectively,could realize the blue-green light emission. Bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)2), synthesized with zinc acetate dihydrate and HBT to form a complex, is used as main EMLs in a similar structure to fabricate devices B and C. Bright and pure white light emissions can be obtained from device C which was fabricated with a green-white emitting host Zn(BTZ)2 and red dopant 5,6,11,12-tetraphenylnaphthacene (rubrene). The maximum quantum efficiency of device C could reach 0.63%, and the corresponding brightness and CIE coordinates were 4000cd/m2 and (x = 0.341, y = 0.334) at the driving voltage of 20 V.

  1. Two stacked tandem white organic light-emitting diodes employing WO3 as a charge generation layer

    Science.gov (United States)

    Bin, Jong-Kwan; Lee, Na Yeon; Lee, SeungJae; Seo, Bomin; Yang, JoongHwan; Kim, Jinook; Yoon, Soo Young; Kang, InByeong

    2016-09-01

    Recently, many studies have been conducted to improve the electroluminescence (EL) performance of organic lightemitting diodes (OLEDs) by using appropriate organic or inorganic materials as charge generation layer (CGL) for their application such as full color displays, backlight units, and general lighting source. In a stacked tandem white organic light-emitting diodes (WOLEDs), a few emitting units are electrically interconnected by a CGL, which plays the role of generating charge carriers, and then facilitate the injection of it into adjacent emitting units. In the present study, twostacked WOLEDs were fabricated by using tungsten oxide (WO3) as inorganic charge generation layer and 1,4,5,8,9,11- hexaazatriphenylene hexacarbonitrile (HAT-CN) as organic charge generation layer (P-CGL). Organic P-CGL materials were used due to their ease of use in OLED fabrication as compared to their inorganic counterparts. To obtain high efficiency, we demonstrate two-stacked tandem WOLEDs as follows: ITO/HIL/HTL/HTL'/B-EML/ETL/N-CGL/P-CGL (WO3 or HAT-CN)/HTL″/YG-EML/ETL/LiF/Al. The tandem devices with blue- and yellow-green emitting layers were sensitive to the thickness of an adjacent layer, hole transporting layer for the YG emitting layer. The WOLEDs containing the WO3 as charge generation layer reach a higher power efficiency of 19.1 lm/W and the current efficiency of 51.2 cd/A with the white color coordinate of (0.316, 0.318) than the power efficiency of 13.9 lm/W, and the current efficiency of 43.7 cd/A for organic CGL, HAT-CN at 10 mA/cm2, respectively. This performance with inserting WO3 as CGL exhibited the highest performance with excellent CIE color coordinates in the two-stacked tandem OLEDs.

  2. Molecular hole transporting materials for organic light-emitting diodes (OLEDs)

    Science.gov (United States)

    Loy, Douglas E.

    Organic light-emitting devices are rapidly becoming viable contenders in the display market. One of the major obstacles to the commercial viability of OLEDs is device stability and lifetime. Device stability has been partially, if not mostly, attributed to thermal instability of the organic charge transport layers. Some characteristics of good hole transporters for OLEDs are reversible oxidation, high thermal stability, and the ability to form amorphous films upon vacuum deposition. The main objective of this research was to design novel hole transporting materials with improved thermal stability, while retaining favorable electronic properties. Molecular structure can have drastic effects on the properties of the thin organic films of the hole transporting layers. Hole transporters with increased molecular asymmetry and rigidity have been demonstrated to give amorphous materials with higher glass transition temperatures. While asymmetry provides materials that are more thermally stable, the asymmetry must not be to an extent that would cause electronic asymmetry. Electronic asymmetry resulting from dipoles can act as local charge traps thus hindering hole transport. Increasing molecular rigidity provides materials with increased thermal stability, as well as improved hole mobility. The increased mobility is due in part to the better conjugation with materials held in a planar orientation. A direct correlation has been found between the thermal stability of a OLED and the glass transition of the hole transporting material used. Structural design, synthesis and characterization of novel hole transporting materials will be reported, as well as their performance in electroluminescent devices. Device operation and architecture will also be discussed, including the use of hole transporters as host for emitting materials.

  3. Soluble Flavanthrone Derivatives: Synthesis, Characterization, and Application to Organic Light-Emitting Diodes.

    Science.gov (United States)

    Kotwica, Kamil; Bujak, Piotr; Data, Przemyslaw; Krzywiec, Wojciech; Wamil, Damian; Gunka, Piotr A; Skorka, Lukasz; Jaroch, Tomasz; Nowakowski, Robert; Pron, Adam; Monkman, Andrew

    2016-06-01

    Simple modification of benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine-8,16-dione, an old and almost-forgotten vat dye, by reduction of its carbonyl groups and subsequent O-alkylation, yields solution-processable, electroactive, conjugated compounds of the periazaacene type, suitable for the use in organic electronics. Their electrochemically determined ionization potential and electron affinity of about 5.2 and -3.2 eV, respectively, are essentially independent of the length of the alkoxyl substituent and in good agreement with DFT calculations. The crystal structure of 8,16-dioctyloxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine (FC-8), the most promising compound, was solved. It crystallizes in space group P1‾ and forms π-stacked columns held together in the 3D structure by dispersion forces, mainly between interdigitated alkyl chains. Molecules of FC-8 have a strong tendency to self-organize in monolayers deposited on a highly oriented pyrolytic graphite surface, as observed by STM. 8,16-Dialkoxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines are highly luminescent, and all have photoluminescence quantum yields of about 80 %. They show efficient electroluminescence, and can be used as guest molecules with a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl host in guest/host-type organic light-emitting diodes. The best fabricated diodes showed a luminance of about 1900 cd m(-12) , a luminance efficiency of about 3 cd A(-1) , and external quantum efficiencies exceeding 0.9 %.

  4. Synthesis and light-emitting properties of organic electroluminescent compounds and their metal complexes

    Institute of Scientific and Technical Information of China (English)

    CUI Jianzhong; Kim Sung-Hoon

    2004-01-01

    Several organic electroluminescent (EL) compounds, 2,2′-(1,4-phenylenedivinylene)bis-3,3-dimethyl-in- dolenine (1), 2,2′-(1,4-phenylenedivinylene)bis-benzoxazole (2), 2,2′-(1,4-phenylenedivinylene)bis-benzothiazole (3), 4,4′- (1,4-phenylenedivinylene)bis-quinoline (4), 2,2′-(1,4-phenyle- nedivinylene)bis-quinoline (5), 2,2′-(1,4-phenylenedivinyle- ne)bis-1,3,3-trimethyl-indolenine dichlo ride (6), 2,2′-(1,4- phenylene-divinylene)bis-1-hydro-3,3-dimethyl-indolenine dichloride (7), 2,2′-(1,4-phenylenedivinylene)bis-8-acetoxy- quinoline (8), 2,2′-(1,4-phenylenedivinylene)bis-8-hydroxyq- uinoline (9) and metal complexes of 9, Al(PHQ) (10) and Zn(PHQ) (11), have been synthesized and characterized. The crystal structure of 6 was determined. Light emitting properties of the prepared compounds have been investigated. 1 produces an orange-yellow emission (λmax = 575 nm). The cation, 6, gives a red emission (λmax = 607 nm), which is shifted 32 nm to the red compared to 1. 8 produces a yellow emission (λmax = 567 nm). The metal complex 10 gives a red emission (λmax = 610 nm), which is a red shift of 43 nm compared to 8. The change in structure in the prepared compound caused a change in the electron distribution in the compounds, which induces a large wavelength shift of the emitted-light. Thermal analysis showed that the decomposition temperatures of the metal complexes (10, 11) were higher than those for the smaller organic molecular compounds (1-9). Therefore, metal complexes (10, 11) can be used as EL materials over a larger temperature range.

  5. Electroluminescence emission patterns of organic light-emitting transistors based on crystallized fluorene-type polymers

    Science.gov (United States)

    Kajii, Hirotake; Ohtomo, Takahiro; Ohmori, Yutaka

    2017-03-01

    The electroluminescence (EL) emission patterns of organic light-emitting transistors (OLETs) based on crystallized poly(9,9-dioctylfluorene) (F8), poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly(9,9-dioctylfluorene-co-dithienyl-benzothiadiazole) (F8TBT) films are investigated. For the single-layer devices and the mixed-layer device without an F8/F8BT interface, only line-shaped EL emission patterns are observed between source/drain (S/D) electrodes. For an F8BT (F8TBT)/F8 heterostructure device, a localized electric field is generated by the positive (negative) charges of the accumulated holes (electrons) in the F8 upper layer, which allow the injection of electrons (holes) in the F8BT (F8TBT) lower layer at a lower (higher) gate voltage. The F8/F8BT device exhibits unique light emission properties with a surface like EL emission pattern between S/D electrodes at a lower gate voltage. The interfacial structure is important for forming field-effect transistor channels along different organic layers to obtain a surface like emission between S/D electrodes. For the F8TBT/F8 OLET, the hole carrier transport mainly occurs at the F8TBT lower layer, and line-shaped EL emission patterns are observed in the vicinity of the source electrode upon varying the gate voltages owing to the worse carrier balance between the F8TBT lower layer and the F8 upper layer.

  6. Optical, electrical, and magnetic field studies of organic materials for light emitting diodes and photovoltaic applications

    Science.gov (United States)

    Basel, Tek Prasad

    We studied optical, electrical, and magnetic field responses of films and devices based on organic semiconductors that are used for organic light emitting diodes (OLEDs) and photovoltaic (OPV) solar cell applications. Our studies show that the hyperfine interaction (HFI)-mediated spin mixing is the key process underlying various magnetic field effects (MFE) and spin transport in aluminum tris(8-hydroxyquinoline)[Alq3]-based OLEDs and organic spin-valve (OSV). Conductivity-detected magnetic resonance in OLEDs and magneto-resistance (MR) in OSVs show substantial isotope dependence. In contrast, isotope-insensitive behavior in the magneto-conductance (MC) of same devices is explained by the collision of spin ½ carriers with triplet polaron pairs. We used steady state optical spectroscopy for studying the energy transfer dynamics in films and OLEDs based on host-guest blends of the fluorescent polymer and phosphorescent molecule. We have also studied the magnetic-field controlled color manipulation in these devices, which provide a strong proof for the `polaron-pair' mechanism underlying the MFE in organic devices. The critical issue that hampers organic spintronics device applications is significant magneto-electroluminescence (MEL) at room temperature (RT). Whereas inorganic spin valves (ISVs) show RT magneto-resistance, MR>80%, however, the devices do not exhibit electroluminescence (EL). In contrast, OLEDs show substantive EL emission, and are particularly attractive because of their flexibility, low cost, and potential for multicolor display. We report a conceptual novel hybrid organic/inorganic spintronics device (h-OLED), where we employ both ISV with large MR at RT, and OLED that has efficient EL emission. We investigated the charge transfer process in an OPV solar cell through optical, electrical, and magnetic field measurements of thin films and devices based on a low bandgap polymer, PTB7 (fluorinated poly-thienothiophene-benzodithiophene). We found that

  7. Near-infrared light-emitting ambipolar organic field-effect transistors

    NARCIS (Netherlands)

    Smits, Edsger C. P.; Setayesh, Sepas; Anthopoulos, Thomas D.; Buechel, Michael; Nijssen, Wim; Coehoorn, Reinder; Blom, Paul W. M.; de Boer, Bert; de Leeuw, Dago M.

    2007-01-01

    Near-IR light-emitting ambipolar OFETs are demonstrated, employing a squaraine derivative as the electroactive layer. Efficient control of the emission-region position in the channel is achieved by varying the drain/gate potentials. By using a transport model, combined with experimental results, str

  8. Graphene oxide/graphene vertical heterostructure electrodes for highly efficient and flexible organic light emitting diodes

    Science.gov (United States)

    Jia, S.; Sun, H. D.; Du, J. H.; Zhang, Z. K.; Zhang, D. D.; Ma, L. P.; Chen, J. S.; Ma, D. G.; Cheng, H. M.; Ren, W. C.

    2016-05-01

    The relatively high sheet resistance, low work function and poor compatibility with hole injection layers (HILs) seriously limit the applications of graphene as transparent conductive electrodes (TCEs) for organic light emitting diodes (OLEDs). Here, a graphene oxide/graphene (GO/G) vertical heterostructure is developed as TCEs for high-performance OLEDs, by directly oxidizing the top layer of three-layer graphene films with ozone treatment. Such GO/G heterostructure electrodes show greatly improved optical transmittance, a large work function, high stability, and good compatibility with HIL materials (MoO3 in this work). Moreover, the conductivity of the heterostructure is not sacrificed compared to the pristine three-layer graphene electrodes, but is significantly higher than that of pristine two-layer graphene films. In addition to high flexibility, OLEDs with different emission colors based on the GO/G heterostructure TCEs show much better performance than those based on indium tin oxide (ITO) anodes. Green OLEDs with GO/G heterostructure electrodes have the maximum current efficiency and power efficiency, as high as 82.0 cd A-1 and 98.2 lm W-1, respectively, which are 36.7% (14.8%) and 59.2% (15.0%) higher than those with pristine graphene (ITO) anodes. These findings open up the possibility of using graphene for next generation high-performance flexible and wearable optoelectronics with high stability.The relatively high sheet resistance, low work function and poor compatibility with hole injection layers (HILs) seriously limit the applications of graphene as transparent conductive electrodes (TCEs) for organic light emitting diodes (OLEDs). Here, a graphene oxide/graphene (GO/G) vertical heterostructure is developed as TCEs for high-performance OLEDs, by directly oxidizing the top layer of three-layer graphene films with ozone treatment. Such GO/G heterostructure electrodes show greatly improved optical transmittance, a large work function, high stability

  9. Understanding and predicting the orientation of heteroleptic phosphors in organic light-emitting materials (Conference Presentation)

    Science.gov (United States)

    Schmidt, Tobias D.; Jurow, Matthew; Mayr, Christian; Lampe, Thomas; Djurovic, Peter I.; Thompson, Mark E.; Brütting, Wolfgang

    2016-09-01

    Organic light-emitting diodes (OLEDs) have made tremendous progress in recent years. The internal quantum efficiency was continuously improved and is nowadays close to the ideal value of unity in state-of-the-art OLEDs. However, still only a small fraction of the internally generated power can be used for lighting aspects as most of the light is captured inside the device due to low outcoupling factors of typically 25%. One promising approach to increase this limiting factor is using an anisotropic orientation of the dye molecules. In particular, horizontal orientation of transition dipole vectors (TDV) of the emitting species is a powerful tool to improve the efficiency of OLEDs. In order to understand the underlying mechanisms for emitter orientation of heteroleptic phosphors, we compared the anisotropy factor of emissive guest/host systems prepared by thermal evaporation using different Ir-complexes incorporating coumarin and phenylpyridin based ligands. These molecules exhibit similar high permanent dipole moments and electrostatic surface potentials but differ in their molecular structure. Interestingly, only molecules with both aromatic and aliphatic ligands show non-isotropic distributions of their TDVs when co-deposited with a matrix material. From these findings we conclude that molecular orientation of heteroleptic Ir-complexes occurs instantaneously at the surface of the growing film and is driven by chemical interactions with the surrounding media, i.e. the vacuum and the aromatic matrix side. Furthermore, it is possible to predict the anisotropy factor for arbitrary molecular orientation with a mathematical model taking into account the geometrical distribution of the TDV on the molecules.

  10. Organic light emitting diode improves diabetic cutaneous wound healing in rats.

    Science.gov (United States)

    Wu, Xingjia; Alberico, Stephanie; Saidu, Edward; Rahman Khan, Sazzadur; Zheng, Shijun; Romero, Rebecca; Sik Chae, Hyun; Li, Sheng; Mochizuki, Amane; Anders, Juanita

    2015-01-01

    A major complication for diabetic patients is chronic wounds due to impaired wound healing. It is well documented that visible red wavelengths can accelerate wound healing in diabetic animal models and patients. In vitro and in vivo diabetic models were used to investigate the effects of organic light emitting diode (OLED) irradiation on cellular function and cutaneous wound healing. Human dermal fibroblasts were cultured in hyperglycemic medium (glucose concentration 180 mM) and irradiated with an OLED (623 nm wavelength peak, range from 560 to 770 nm, power density 7 or 10 mW/cm2 at 0.2, 1, or 5 J/cm2). The OLED significantly increased total adenosine triphosphate concentration, metabolic activity, and cell proliferation compared with untreated controls in most parameters tested. For the in vivo experiment, OLED and laser (635 ± 5 nm wavelength) treatments (10 mW/cm2 , 5 J/cm2 daily for a total of seven consecutive days) for cutaneous wound healing were compared using a genetic, diabetic rat model. Both treatments had significantly higher percentage of wound closure on day 6 postinjury and higher total histological scores on day 13 postinjury compared with control. No statistical difference was found between the two treatments. OLED irradiation significantly increased fibroblast growth factor-2 expression at 36-hour postinjury and enhanced macrophage activation during initial stages of wound healing. In conclusion, the OLED and laser had comparative effects on enhancing diabetic wound healing.

  11. Multi-solution processes of small molecule for flexible white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Yu-Sheng, E-mail: ystsai@nfu.edu.tw [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Chittawanij, Apisit; Hong, Lin-Ann; Guo, Siou-Wei [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Wang, Ching-Chiun [Department of Solid State Lighting Technology, Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan, ROC (China); Juang, Fuh-Shyang [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Lai, Shih-Hsiang [Department of Solid State Lighting Technology, Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan, ROC (China); Lin, Yang-Ching [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China)

    2016-04-01

    Most small molecule organic light emitting diode (SM-OLED) device structures are made in one layer using solution-based processing because the solution is usually a high dissolvent material that easily attacks the layer below it. We demonstrate a simple and reliable stamping technique for fabricating multi-solution process flexible white SM-OLEDs. The structure is anode/spin-hole injection layer/spin-emitting layer/stamping-electron transport layer/cathode. Poly(di-methyl silane) (PDMS) stamp is used for transferring electron transport layer. An intermediate ultraviolet-ozone surface treatment is introduced to temporarily modify the PDMS stamp surface. Then, the solution-based electron transport layer film can therefore be uniformly formed on top of the PDMS surface. After that the electron transport layer film on the PDMS stamp is transfer-printed onto the emitting layer with suitable heating and pressing. A solution-based processing is successfully established to efficiently fabricate flexible white SM-OLEDs. The SM-OLEDs were obtained at the current density of 20 mA/cm{sup 2}, luminance of 1062 cd/m{sup 2}, current efficiency of 5.57 cd/A, and Commission internationale de l'éclairage coordinate of (0.32, 0.35). - Highlights: • All solution-processed small molecule materials (emitting layer, electron transport layer). • Poly(di-methylsilane) (PDMS) stamp is subsequently used for stamping transfer. • The flexible white SM-OLEDs are based on solution-processes with a low-cost method.

  12. Transparent conductive PVP/AgNWs films for flexible organic light emitting diodes by spraying method

    Science.gov (United States)

    Hu, Jun-tao; Mei, Wen-juan; Ye, Kang-li; Wei, Qing-qing; Hu, Sheng

    2016-05-01

    In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%—67.9% at 380—780 nm, and the sheet resistance is 30 Ω/□ which is equivalent to that of commercial indium tin oxide (ITO). During cyclic bending tests to 500 cycles with bending radius of 5 mm, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transparent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs).

  13. Organic Light-Emitting Diode with Color Tunable between Bluish-White Daylight and Orange-White Dusk Hue

    Directory of Open Access Journals (Sweden)

    Shih-Yun Liao

    2014-01-01

    Full Text Available The varying color of sunlight diurnally exhibits an important effect on circadian rhythm of living organisms. The bluish-white daylight that is suitable for work shows a color temperature as high as 9,000 K, while the homey orange-white dusk hue is as low as 2,000 K. We demonstrate in this report the feasibility of using organic light-emitting diode (OLED technology to fabricate sunlight-style illumination with a very wide color temperature range. The color temperature can be tuned from 2,300 K to 9,300 K, for example, by changing the applied voltage from 3 to 11 V for the device composing red and yellow emitters in the first emissive layer and blue emitter in the second. Unlike the prior arts, the color-temperature span can be made much wider without any additional carrier modulation layer, which should enable a more cost effective fabrication. For example, the color-temperature span is 7,000 K for the above case, while it is 1,700 K upon the incorporation of a nanoscale hole modulation layer in between the two emissive layers. The reason why the present device can effectively regulate the shifting of recombination zone is because the first emissive layer itself possesses an effective hole modulation barrier of 0.2 eV. This also explains why the incorporation of an extra hole modulation layer with a 0.7 eV barrier did not help extend the desirable color-temperature span since excessive holes may be blocked.

  14. Tunable and white light emitting AlPO4 mesoporous glass by design of inorganic/organic luminescent species

    Directory of Open Access Journals (Sweden)

    Jin He

    2015-04-01

    Full Text Available The realization of tunable and white light emitting sources employed by UV-LED with single-host phosphors has been an exciting development in the search for high luminous efficiency and excellent color rendering index white-light source. A tunable and white light emitting mesoporous glass was prepared by utilizing both inorganic/organic (Europium/coumarin luminescent species in the meso-structure. The tunable and white light emission was deliberately designed by CIE calculation based on the individual emission spectra, which was realized by tailoring the emission of Eu2+/Eu3+ ions and coumarin 535 in sol-gel AlPO4 mesoporous glass. This simple and versatile procedure is not limited in the combination of rare earth and organic dye and is therefore extendable to other luminescent species in meso-structure for color-tunable efficient solid-state lighting sources.

  15. Tunable and white light emitting AlPO{sub 4} mesoporous glass by design of inorganic/organic luminescent species

    Energy Technology Data Exchange (ETDEWEB)

    He, Jin; Li, Rihong, E-mail: lirihong@siom.ac.cn; Yuan, Xinqiang; Zhang, Long, E-mail: lzhang@siom.ac.cn [Key Laboratory of Materials for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang, Yan [Key Laboratory of Materials for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Shiqing [College of Materials Science and Engineering, China Jiliang University, Hangzhou, Zhejiang 310018 (China)

    2015-04-01

    The realization of tunable and white light emitting sources employed by UV-LED with single-host phosphors has been an exciting development in the search for high luminous efficiency and excellent color rendering index white-light source. A tunable and white light emitting mesoporous glass was prepared by utilizing both inorganic/organic (Europium/coumarin) luminescent species in the meso-structure. The tunable and white light emission was deliberately designed by CIE calculation based on the individual emission spectra, which was realized by tailoring the emission of Eu{sup 2+}/Eu{sup 3+} ions and coumarin 535 in sol-gel AlPO{sub 4} mesoporous glass. This simple and versatile procedure is not limited in the combination of rare earth and organic dye and is therefore extendable to other luminescent species in meso-structure for color-tunable efficient solid-state lighting sources.

  16. Ordered and ultrathin reduced graphene oxide LB films as hole injection layers for organic light-emitting diode.

    Science.gov (United States)

    Yang, Yajie; Yang, Xiaojie; Yang, Wenyao; Li, Shibin; Xu, Jianhua; Jiang, Yadong

    2014-01-01

    In this paper, we demonstrated the utilization of reduced graphene oxide (RGO) Langmuir-Blodgett (LB) films as high performance hole injection layer in organic light-emitting diode (OLED). By using LB technique, the well-ordered and thickness-controlled RGO sheets are incorporated between the organic active layer and the transparent conducting indium tin oxide (ITO), leading to an increase of recombination between electrons and holes. Due to the dramatic increase of hole carrier injection efficiency in RGO LB layer, the device luminance performance is greatly enhanced comparable to devices fabricated with spin-coating RGO and a commercial conducting polymer PEDOT:PSS as the hole transport layer. Furthermore, our results indicate that RGO LB films could be an excellent alternative to commercial PEDOT:PSS as the effective hole transport and electron blocking layer in light-emitting diode devices.

  17. Development of fullerene-containing composites for organic light-emitting devices

    Science.gov (United States)

    Yuan, Yanyan

    2007-12-01

    In order to widen the practical applications of Organic Light Emitting Devices (OLEDs), the device efficiency and device stability must be improved. The anode structure of an OLED device, including the anode and the adjacent contacting organic layer, plays important roles in both device efficiency and stability issues. In this study, C60 is used to engineer the anode structure by incorporating C60 into common hole transport materials, forming organic-C60 composites. N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB):C 60 composites have been studied for use with indium tin oxide (ITO) anodes. Compared with a conventional device without C60, the composite device at a C60 composition of 10 wt.% has improved efficiency by 25% due to more balanced electron-hole currents. Copper phthalocyanine (CuPc):C60 composites have been studied for use with Au anodes. When the Au/CuPc:C60 composite anode structure at an optimum C60 composition of 30 wt.% is used to replace the conventional ITO/CuPc anode structure, a significant increase in current efficiency (˜2 times) is achieved. This result suggests a new possibility to replace the problematic ITO anode with an Au anode. Moreover, the CuPc:C60 composites also form efficient hole injection structures with other metals, namely, Ag, Mg, and Al. The versatility of the composite anode structure is attributed to the complementary role of the two constituents: C60 facilitates hole injection from the metals to the composite; CuPc plays the primary role of transferring holes from the composite to the hole transport NPB layer. The composites enable more thermally stable anode structures as concluded by annealing experiments. It is found that the main reason for the improved thermal stability of the composite anode structure is not interface modification, but the higher thermal stability of the composite materials. No chemical interaction between the components of the composites is detected.

  18. Soft lithography microlens fabrication and array for enhanced light extraction from organic light emitting diodes (OLEDs)

    Science.gov (United States)

    Leung, Wai Y.; Park, Joong-Mok; Gan, Zhengqing; Constant, Kristen P.; Shinar, Joseph; Shinar, Ruth; ho, Kai-Ming

    2014-06-03

    Provided are microlens arrays for use on the substrate of OLEDs to extract more light that is trapped in waveguided modes inside the devices and methods of manufacturing same. Light extraction with microlens arrays is not limited to the light emitting area, but is also efficient in extracting light from the whole microlens patterned area where waveguiding occurs. Large microlens array, compared to the size of the light emitting area, extract more light and result in over 100% enhancement. Such a microlens array is not limited to (O)LEDs of specific emission, configuration, pixel size, or pixel shape. It is suitable for all colors, including white, for microcavity OLEDs, and OLEDs fabricated directly on the (modified) microlens array.

  19. Long-Range Energy Transfer and Singlet-Exciton Migration in Working Organic Light-Emitting Diodes

    Science.gov (United States)

    Ingram, Grayson L.; Nguyen, Carmen; Lu, Zheng-Hong

    2016-06-01

    Rapid industrialization of organic light-emitting devices for flat-panel displays and solid-state lighting makes a deep understanding of device physics more desirable than ever. Developing reliable experimental techniques to measure fundamental physical properties such as exciton diffusion lengths is a vital part of developing device physics. In this paper, we present a study of exciton diffusion and long-range energy transfer in working organic light-emitting devices, and a study of the interplay between these two tangled processes through both experimental probes and simulations. With the inclusion of multiple factors including long-range energy transfer, exciton boundary conditions, and the finite width of the exciton generation zone, we quantify exciton migration based on emission characteristics from rubrene sensing layers placed in working organic light-emitting devices. This comprehensive analysis is found to be essential to accurately measuring exciton diffusion length, and in the present case the measured singlet-exciton diffusion length in the archetype material 4' -bis(carbazol-9-yl)biphenyl is 4.3 ±0.3 nm with a corresponding diffusivity of (2.6 ±0.3 )×10-4 cm2/s .

  20. Efficient and mechanically robust stretchable organic light-emitting devices by a laser-programmable buckling process

    Science.gov (United States)

    Yin, Da; Feng, Jing; Ma, Rui; Liu, Yue-Feng; Zhang, Yong-Lai; Zhang, Xu-Lin; Bi, Yan-Gang; Chen, Qi-Dai; Sun, Hong-Bo

    2016-05-01

    Stretchable organic light-emitting devices are becoming increasingly important in the fast-growing fields of wearable displays, biomedical devices and health-monitoring technology. Although highly stretchable devices have been demonstrated, their luminous efficiency and mechanical stability remain impractical for the purposes of real-life applications. This is due to significant challenges arising from the high strain-induced limitations on the structure design of the device, the materials used and the difficulty of controlling the stretch-release process. Here we have developed a laser-programmable buckling process to overcome these obstacles and realize a highly stretchable organic light-emitting diode with unprecedented efficiency and mechanical robustness. The strained device luminous efficiency -70 cd A-1 under 70% strain - is the largest to date and the device can accommodate 100% strain while exhibiting only small fluctuations in performance over 15,000 stretch-release cycles. This work paves the way towards fully stretchable organic light-emitting diodes that can be used in wearable electronic devices.

  1. Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5 kA cm-2

    Science.gov (United States)

    Tian, Pengfei; Althumali, Ahmad; Gu, Erdan; Watson, Ian M.; Dawson, Martin D.; Liu, Ran

    2016-04-01

    The aging characteristics of blue InGaN micro-light emitting diodes (micro-LEDs) with different sizes have been studied at an extremely high current density 3.5 kA cm-2 for emerging micro-LED applications including visible light communication (VLC), micro-LED pumped organic lasers and optogenetics. The light output power of micro-LEDs first increases and then decreases due to the competition of Mg activation in p-GaN layer and defect generation in the active region. The smaller micro-LEDs show less light output power degradation compared with larger micro-LEDs, which is attributed to the lower junction temperature of smaller micro-LEDs. It is found that the high current density without additional junction temperature cannot induce significant micro-LED degradation at room temperature but the combination of the high current density and high junction temperature leads to strong degradation. Furthermore, the cluster LEDs, composed of a micro-LED array, have been developed with both high light output power and less light output degradation for micro-LED applications in solid state lighting and VLC.

  2. A flexible organic active matrix circuit fabricated using novel organic thin film transistors and organic light-emitting diodes

    KAUST Repository

    Gutiérrez-Heredia, Gerardo

    2010-10-04

    We present an active matrix circuit fabricated on plastic (polyethylene naphthalene, PEN) and glass substrates using organic thin film transistors and organic capacitors to control organic light-emitting diodes (OLEDs). The basic circuit is fabricated using two pentacene-based transistors and a capacitor using a novel aluminum oxide/parylene stack (Al2O3/ parylene) as the dielectric for both the transistor and the capacitor. We report that our circuit can deliver up to 15 μA to each OLED pixel. To achieve 200 cd m-2 of brightness a 10 μA current is needed; therefore, our approach can initially deliver 1.5× the required current to drive a single pixel. In contrast to parylene-only devices, the Al2O 3/parylene stack does not fail after stressing at a field of 1.7 MV cm-1 for >10 000 s, whereas \\'parylene only\\' devices show breakdown at approximately 1000 s. Details of the integration scheme are presented. © 2010 IOP Publishing Ltd.

  3. A flexible organic active matrix circuit fabricated using novel organic thin film transistors and organic light-emitting diodes

    Science.gov (United States)

    Gutiérrez-Heredia, G.; González, L. A.; Alshareef, H. N.; Gnade, B. E.; Quevedo-López, M.

    2010-11-01

    We present an active matrix circuit fabricated on plastic (polyethylene naphthalene, PEN) and glass substrates using organic thin film transistors and organic capacitors to control organic light-emitting diodes (OLEDs). The basic circuit is fabricated using two pentacene-based transistors and a capacitor using a novel aluminum oxide/parylene stack (Al2O3/parylene) as the dielectric for both the transistor and the capacitor. We report that our circuit can deliver up to 15 µA to each OLED pixel. To achieve 200 cd m-2 of brightness a 10 µA current is needed; therefore, our approach can initially deliver 1.5× the required current to drive a single pixel. In contrast to parylene-only devices, the Al2O3/parylene stack does not fail after stressing at a field of 1.7 MV cm-1 for >10 000 s, whereas 'parylene only' devices show breakdown at approximately 1000 s. Details of the integration scheme are presented.

  4. Dependence of Performance of Organic Light-emitting Devices on Sheet Resistance of Indium-tin-oxide Anodes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The dependence of the performance of organic light-emitting devices(OLEDs) on the sheet resistance of indium-tin-oxide(ITO) anodes was investigated by measuring the steady state current density brightness voltage characteristics and the electroluminescent spectra. The device with a higher sheet resistance anode shows a lower current density, a lower brightness level, and a higher operation voltage. The electroluminescence(EL) efficiencies of the devices with the same structure but different ITO anodes show more complicated differences. Furthermore, the shift of the light-emitting zone toward the anode was found when an anode with a higher sheet resistance was used. These performance differences are discussed and attributed to the reduction of hole injection and the increase in voltage drop over ITO anode with the increase in sheet resistance.

  5. An organic light-emitting devices of highly efficient white phosphor using an electron/exciton blocker

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Highly efficient white phosphorescent organic light-emitting devices (WOLEDs) was fabricated using an electron/exciton blocker. The device structure is ITO/2T-NATA(25 nm)/NPBX(25-dnm)/CBP:5%Ir(ppy)3:0.5%Rubrene(8 nm)/NPBX(dnm)/DPVBi(30 nm)/TPBi(20 nm)/Alq(10nm)/LiF(1nm)/Al, in which N,N' -bis- (1-naphthyl)- N,N' -dipheny1-1, 1' - bi-phenyl-4,4 ' -diamine (NPBX) functions as a hole transport layer and electron/exciton blocker, 4,4,N,N 'dicarbazolebiphenyl (CB P) is host, 4,4' -bis(2,2 -diphenyl vinyl)-1,1' -biphenyl (DPVB. i) is blue fluorescent dye, 5,6,11,12,-tetraphenylnaphthacene (rubrene) is fluorescent dye, factris (2-phenylpyridine) iridium (Ir(ppy)3) is phosphorescent sensitizer and tris(8-hydroxyquinoline) aluminum (Alq3) is an electron transport layer. The WOLEDs have obtained white light emission by adjusting the thickness of NPBX, when the concentration of Ir(ppy)3 is 5-wt% and rubrene is 0.5-wt%,respectively, the thickness of the doped emissive layer is 8 nm, the WOLEDs show a maximum luminous efficiency is 11.2 cd/A with d of 10 nm at 7 V and a maximum luminance of 28170 cd/m2 at 17 V, the CIE coordinates is (0.37.0.42), which is in white region.

  6. A new blue-emitting phosphor of Ce 3+-activated CaLaGa 3S 6O for white-light-emitting diodes

    Science.gov (United States)

    Yu, Ruijin; Wang, Jing; Zhang, Mei; Zhang, Jianhui; Yuan, Haibin; Su, Qiang

    2008-03-01

    A new blue-emitting chalcogenide phosphor, Ce3+-activated CaLaGa3S6O, with a high purity crystalline was synthesized by a two-step solid-state reaction. Photoluminescence properties of CaLaGa3S6O:Ce3+ were investigated comparatively with the commercial blue-emitting phosphor BaMgAl10O17:Eu2+. It shows a more perfect and efficient broad absorption band around the 398 nm emission of the commercial near ultraviolet light-emitting diodes (LEDs), and presents a comparable blue-emitting performance. The blue light-emitting LED with the CIE chromaticity coordinates of (0.147, 0.089) was successfully fabricated by precoating CaLaGa3S6O:Ce3+ phosphor onto a 398 nm-emitting InGaN chip. All these results indicate that CaLaGa3S6O:Ce3+ is a promising blue phosphor candidate for white LEDs.

  7. OLED Fundamentals: Materials, Devices, and Processing of Organic Light-Emitting Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Blochwitz-Nimoth, Jan; Bhandari, Abhinav; Boesch, Damien; Fincher, Curtis R.; Gaspar, Daniel J.; Gotthold, David W.; Greiner, Mark T.; Kido, Junji; Kondakov, Denis; Korotkov, Roman; Krylova, Valentina A.; Loeser, Falk; Lu, Min-Hao; Lu, Zheng-Hong; Lussem, Bjorn; Moro, Lorenza; Padmaperuma, Asanga B.; Polikarpov, Evgueni; Rostovtsev, Vsevolod V.; Sasabe, Hisahiro; Silverman, Gary; Thompson, Mark E.; Tietze, Max; Tyan, Yuan-Sheng; Weaver, Michael; Xin , Xu; Zeng, Xianghui

    2015-05-26

    What is an organic light emitting diode (OLED)? Why should we care? What are they made of? How are they made? What are the challenges in seeing these devices enter the marketplace in various applications? These are the questions we hope to answer in this book, at a level suitable for knowledgeable non-experts, graduate students and scientists and engineers working in the field who want to understand the broader context of their work. At the most basic level, an OLED is a promising new technology composed of some organic material sandwiched between two electrodes. When current is passed through the device, light is emitted. The stack of layers can be very thin and has many variations, including flexible and/or transparent. The organic material can be polymeric or composed small molecules, and may include inorganic components. The electrodes may consist of metals, metal oxides, carbon nanomaterials, or other species, though of course for light to be emitted, one electrode must be transparent. OLEDs may be fabricated on glass, metal foils, or polymer sheets (though polymeric substrates must be modified to protect the organic material from moisture or oxygen). In any event, the organic material must be protected from moisture during storage and operation. A control circuit, the exact nature of which depends on the application, drives the OLED. Nevertheless, the control circuit should have very stable current control to generate uniform light emission. OLEDs can be designed to emit a single color of light, white light, or even tunable colors. The devices can be switched on and off very rapidly, which makes them suitable for displays or for general lighting. Given the amazing complexity of the technical and design challenges for practical OLED applications, it is not surprising that applications are still somewhat limited. Although organic electroluminescence is more than 50 years old, the modern OLED field is really only about half that age – with the first high

  8. Rosin-enabled ultraclean and damage-free transfer of graphene for large-area flexible organic light-emitting diodes

    Science.gov (United States)

    Zhang, Zhikun; Du, Jinhong; Zhang, Dingdong; Sun, Hengda; Yin, Lichang; Ma, Laipeng; Chen, Jiangshan; Ma, Dongge; Cheng, Hui-Ming; Ren, Wencai

    2017-02-01

    The large polymer particle residue generated during the transfer process of graphene grown by chemical vapour deposition is a critical issue that limits its use in large-area thin-film devices such as organic light-emitting diodes. The available lighting areas of the graphene-based organic light-emitting diodes reported so far are usually square with about 1% deviation over a large area. Such clean, damage-free graphene has produced the four-inch monolithic flexible graphene-based organic light-emitting diode with a high brightness of about 10,000 cd m-2 that can already satisfy the requirements for lighting sources and displays.

  9. White organic light-emitting devices using Zn(BTZ)2 doped with Rubrene as emitting layer

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jiajin; HUA Yulin; YIN Shougen; FENG Xiulan; WU Xiaoming; SUN Yuanyuan; LI Yongfang; YANG Chunhe; SHUAI Zhigang

    2005-01-01

    Zn(BTZ)2 was synthesized from the complex reaction between zinc acetate dihydrate and 2-(2- hydroxyphenyl) benzothiazolate. Then Zn(BTZ)2 was used as main light-emitting material doped with different amounts of fluorescent dye Rubrene and fabricated a series of white organic light emitting devices. The configurations were as follows: ITO/PVK:TPD/Zn(BTZ)2:Rubrene/Al. The doping concentration of Rubrene in Zn(BTZ)2 was 1.2%, 0.12%, 0.08% and 0.05%, respectively. According to the EL spectra and CIE coordinates of the above devices, the optimum doping concentration (0.05%, weight percent) had been determined. The steady and bright white light emitting of the device with 0.05% doping concentration had been obtained, and the white emission covered a wide range of driving voltage (10-22.5 V). The CIE coordinates were (x=0.341, y=0.334) at the driving voltage of 20 V, which was very close to the equi-energy point (x=0.333, y=0.333), and the corresponding luminance and external quantum efficiency were 4048 Cd/m2 and 0.63% (4.05 Cd/A), respectively. Lastly, we also discussed the emitting mechanisms of the material and the devices.

  10. Simulation study of blue InGaN multiple quantum well light-emitting diodes with different hole injection layers

    Institute of Scientific and Technical Information of China (English)

    Wu Le-Juan; Yin Yi-An; Yang Xiao-Dong; Li Shu-Ti; Liu Chao; Wang Hai-Long; Lu Tai-Ping; Zhang Kang; Xiao Guo-Wei; Zhou Yu-Gang; Zheng Shu-Wen

    2012-01-01

    InGaN-based light-emitting diodes with p-GaN and p-AlGaN hole injection layers are numerically studied using the APSYS simulation software.The simulation results indicate that light-emitting diodes with p-AlGaN hole injection layers show superior optical and electrical performance,such as an increase in light output power,a reduction in current leakage and alleviation of efficiency droop.These improvements can be attributed to the p-AlGaN serving as hole injection layers,which can alleviate the band bending induced by the polarization field,thereby improving both the hole injection efficiency and the electron blocking efficiency.

  11. Flexible organic light-emitting diodes with poly-3,4-ethylenedioxythiophene as transparent anode

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The flexible oragnic light-emitting diodes (OLEDs) fabricated on poly-3,4-ethylenedioxythiophene/poly- styrenesulfonate (PEDOT/PSS) coated substrates were demonstrated. How the fabricating processes and the device structure will affect the device performance was studied and the atomic force microscopy was employed to analyze the mophorlogy of the conducting polymer anode. Under optimized conditions, flexible OLEDs with PEDOT anode showed the brightness up to 2760 cd/m2 and maximum external quantum efficiency of 1.4%. These data are comparable to those of conventional flexible OLEDs with ITO anode.

  12. Thin film encapsulation for organic light-emitting diodes using inorganic/organic hybrid layers by atomic layer deposition.

    Science.gov (United States)

    Zhang, Hao; Ding, He; Wei, Mengjie; Li, Chunya; Wei, Bin; Zhang, Jianhua

    2015-01-01

    A hybrid nanolaminates consisting of Al2O3/ZrO2/alucone (aluminum alkoxides with carbon-containing backbones) grown by atomic layer deposition (ALD) were reported for an encapsulation of organic light-emitting diodes (OLEDs). The electrical Ca test in this study was designed to measure the water vapor transmission rate (WVTR) of nanolaminates. We found that moisture barrier performance was improved with the increasing of the number of dyads (Al2O3/ZrO2/alucone) and the WVTR reached 8.5 × 10(-5) g/m(2)/day at 25°C, relative humidity (RH) 85%. The half lifetime of a green OLED with the initial luminance of 1,500 cd/m(2) reached 350 h using three pairs of the Al2O3 (15 nm)/ZrO2 (15 nm)/alucone (80 nm) as encapsulation layers.

  13. Physical phenomena in efficiency and stability of organic light-emitting devices

    Science.gov (United States)

    Luo, Yichun

    2007-12-01

    Operational stability and luminescence efficiency of organic light-emitting devices (OLEDs) continue to be the most important issues for a wide commercialization of this technology. Thus, the main theme of this sandwich-style thesis is to investigate physical phenomena related to the operational stability and luminescence efficiency of OLEDs, and to eventually improve device performances by using various device structures and power driving schemes. Operational stability of OLEDs is generally governed by intrinsic degradation. Aimed at a comprehensive description of intrinsic degradation mechanism, a number of degradation models have been reported in literature. In these models, the intrinsic degradation is generally attributed to the role of positive charges (holes) in decreasing the luminescence efficiency during device operation. In this thesis, we report a further investigation that leads to the discovery that excessive injection of negative charges (electrons) can also induce significant degradation of devices. The rate of degradation is found to be determined primarily by the density of excessive charges (whether they are holes or electrons) in the vicinity of the emitting layer, where the higher the density, the faster the device degradation. In view of the above understanding of degradation mechanism, we developed a hole-injection-tunable-anode-buffer-layer (HITABL) at the anode contact of the devices to improve device stability. By using the HITABL, one can make the necessary diminutive adjustments to the hole injection of a device and achieve a proper charge balance, and thus significantly improve the operational stability of the devices. In terms of luminescence efficiency, the effects of electric field and electric current (hole current or electron current) on luminescence efficiency of a fluorescent dye doped emitting layer are studied, respectively. Results show that a doped emitting layer demonstrates a smaller decrease in luminescence efficiency than

  14. Enhanced forward efficiency of Y3Al5O12:Ce3+ phosphor from white light-emitting diodes using blue-pass yellow-reflection filter.

    Science.gov (United States)

    Oh, Jeong Rok; Cho, Sang-Hwan; Lee, Yong-Hee; Do, Young Rag

    2009-04-27

    This paper reports a simple approach for the design of blue-excitation-light passing and phosphor-yellow-emission-light reflecting dielectric multilayers to recycle the backward emission of Y(3)Al(5)O(12):Ce(3+) (YAG:Ce) yellow phosphors on top of a blue InGaN light-emitting diode (LED) cup. The insertion of modified quarter-wave films of alternate high- and low-refractive index dielectric films (TiO(2)/SiO(2)) into the interface between a YAG:Ce phosphor layer and glass substrate resulted in 1.64 and 1.95 fold increase in efficiency and luminous efficacy of the forward white emission compared with that of a conventional phosphor on top of a blue LED cup with a lower correlated color temperature (< 4000 K).

  15. Effects of white, blue, and red light-emitting diodes on carotenoid biosynthetic gene expression levels and carotenoid accumulation in sprouts of tartary buckwheat (Fagopyrum tataricum Gaertn.).

    Science.gov (United States)

    Tuan, Pham Anh; Thwe, Aye Aye; Kim, Yeon Bok; Kim, Jae Kwang; Kim, Sun-Ju; Lee, Sanghyun; Chung, Sun-Ok; Park, Sang Un

    2013-12-18

    In this study, the optimum wavelengths of light required for carotenoid biosynthesis were determined by investigating the expression levels of carotenoid biosynthetic genes and carotenoid accumulation in sprouts of tartary buckwheat (Fagopyrum tataricum Gaertn.) exposed to white, blue, and red light-emitting diodes (LEDs). Most carotenoid biosynthetic genes showed higher expression in sprouts irradiated with white light at 8 days after sowing than in those irradiated with blue and red lights. The dominant carotenoids in tartary buckwheat sprouts were lutein and β-carotene. The richest accumulation of total carotenoids was observed in sprouts grown under white light (1282.63 μg g(-1) dry weight), which was relatively higher than that in sprouts grown under blue and red lights (940.86 and 985.54 μg g(-1), respectively). This study might establish an effective strategy for maximizing the production of carotenoids and other important secondary metabolites in tartary buckwheat sprouts by using LED technology.

  16. Novel fluorene-carzazole-based conjugated copolymers containing pyrazoline and benzothiazole segments for blue light-emitting materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of novel fluorene-carbazole-based copolymers with pyrazoline and benzothiazole units were synthesized successfully through Suzuki coupling reactions. The molecular structures and thermal properties of these polymers were characterized by FT-IR,1H NMR, DSC and TGA. GPC results indicated that the weight-average molecular weight (Mw) and polydispersity of these polymers were in range (12,000-14,000) and (1.8-2.0), respectively. The two resulting polymers have high photoluminescence quantum efficiency implying that they may be promising candidates for polymer light-emitting diodes (PLEDs).

  17. Voltage Drop Compensation Method for Active Matrix Organic Light Emitting Diode Displays

    Science.gov (United States)

    Choi, Sang-moo; Ryu, Do-hyung; Kim, Keum-nam; Choi, Jae-beom; Kim, Byung-hee; Berkeley, Brian

    2011-03-01

    In this paper, the conventional voltage drop compensation methods are reviewed and the novel design and driving scheme, the advanced power de-coupled (aPDC) driving method, is proposed to effectively compensate the voltage IR drop of active matrix light emitting diode (AMOLED) displays. The advanced PDC driving scheme can be applied to general AMOLED pixel circuits that have been developed with only minor modification or without requiring modification in pixel circuit. A 14-in. AMOLED panel with the aPDC driving scheme was fabricated. Long range uniformity (LRU) of the 14-in. AMOLED panel was improved from 43% without the aPDC driving scheme, to over 87% at the same brightness by using the scheme and the layout complexity of the panel with new design scheme is less than that of the panel with the conventional design scheme.

  18. Fabrication of organic light-emitting diode pixels by laser-assisted forward transfer

    Science.gov (United States)

    Fardel, Romain; Nagel, Matthias; Nüesch, Frank; Lippert, Thomas; Wokaun, Alexander

    2007-08-01

    Fabrication of a polymer light-emitting device was achieved by a laser forward transfer technique using the decomposition of a thin triazene polymer film by a XeCl excimer laser. The dry deposition process allows transfer of a bilayer consisting of the electroluminescent polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] covered with an aluminum electrode onto a receiver substrate. The soft transfer results in laterally well resolved pixels (≈500μm), whose fluorescence as well as electroluminescence spectra remain unaltered. The rectifying and smooth current-voltage characteristics add to the merits of this laser-based transfer method that opens up the possibility of direct-writing heat- and UV-sensitive materials.

  19. Integration of Organic Light Emitting Diodes and Organic Photodetectors for Lab-on-a-Chip Bio-Detection Systems

    Directory of Open Access Journals (Sweden)

    Graeme Williams

    2014-02-01

    Full Text Available The rapid development of microfluidics and lab-on-a-chip (LoC technologies have allowed for the efficient separation and manipulation of various biomaterials, including many diagnostically relevant species. Organic electronics have similarly enjoyed a great deal of research, resulting in tiny, highly efficient, wavelength-selective organic light-emitting diodes (OLEDs and organic photodetectors (OPDs. We consider the blend of these technologies for rapid detection and diagnosis of biological species. In the ideal system, optically active or fluorescently labelled biological species can be probed via light emission from OLEDs, and their subsequent light emission can be detected with OPDs. The relatively low cost and simple fabrication of the organic electronic devices suggests the possibility of disposable test arrays. Further, with full integration, the finalized system can be miniaturized and made simple to use. In this review, we consider the design constraints of OLEDs and OPDs required to achieve fully organic electronic optical bio-detection systems. Current approaches to integrated LoC optical sensing are first discussed. Fully realized OLED- and OPD-specific photoluminescence detection systems from literature are then examined, with a specific focus on their ultimate limits of detection. The review highlights the enormous potential in OLEDs and OPDs for integrated optical sensing, and notes the key avenues of research for cheap and powerful LoC bio-detection systems.

  20. Very-High Color Rendering Index Hybrid White Organic Light-Emitting Diodes with Double Emitting Nanolayers

    Institute of Scientific and Technical Information of China (English)

    Baiquan Liu; Miao Xu; Lei Wang; Hong Tao; Yueju Su; Dongyu Gao; Linfeng Lan; Jianhua Zou; Junbiao Peng

    2014-01-01

    A very-high color rendering index white organic light-emitting diode (WOLED) based on a simple structure was successfully fabricated. The optimized device exhibits a maximum total efficiency of 13.1 and 5.4 lm/W at 1,000 cd/m2. A peak color rendering index of 90 and a relatively stable color during a wide range of luminance were obtained. In addition, it was demonstrated that the 4,40,40-tri(9-carbazoyl) triphenylamine host influenced strongly the performance of this WOLED. These results may be beneficial to the design of both material and device architecture for high-performance WOLED.

  1. Enhanced Pixel-Driving Circuits for Active-Matrix Organic-Light-Emitting Diode Displays with Large Sizes

    Science.gov (United States)

    Yu, Sang Ho; Choi, Sung Wook; Shin, Hong Jae; Kwack, Kae Dal; Kim, Tae Whan

    2005-03-01

    Enhanced pixel-driving circuits for active-matrix organic-light-emitting diode (AM-OLED) displays with large sizes and highly uniform brightnesses were designed for system on panel. The driving method used the pre-charge functions of the data for a highly uniform brightness during a short time to program the current. The currents of the designed pixel-driving circuits were not significantly affected by variations in the threshold voltages, or by the mobilities of the driving thin-film transistors. These results indicate that the proposed pixel-driving circuits hold promise for potential applications in AM-OLED displays with large sizes and highly uniform brightnesses.

  2. High-efficiency fluorescent organic light-emitting diodes enabled by triplet-triplet annihilation and horizontal emitter orientation

    Energy Technology Data Exchange (ETDEWEB)

    Mayr, Christian, E-mail: Christian.Mayr@physik.uni-augsburg.de; Schmidt, Tobias D.; Brütting, Wolfgang, E-mail: Wolfgang.Bruetting@physik.uni-augsburg.de [Institute of Physics, University of Augsburg, 86135 Augsburg (Germany)

    2014-11-03

    A green organic light-emitting diode with the fluorescent emitter Coumarin 545T shows an external quantum efficiency (η{sub EQE}) of 6.9%, clearly exceeding the classical limit of 5% for fluorescent emitters. The analysis of the angular dependent photoluminescence spectrum of the emission layer reveals that 86% of the transition dipole moments are horizontally oriented. Furthermore, transient electroluminescence measurements demonstrate the presence of a delayed emission originating from triplet-triplet annihilation. A simulation based efficiency analysis reveals quantitatively the origin for the high η{sub EQE}: a radiative exciton fraction higher than 25% and a light-outcoupling efficiency of nearly 30%.

  3. Unique Room Temperature Light Emitting Diode Based on 2D Hybrid Organic-Inorganic Low Dimensional Perovskite Semiconductor

    CERN Document Server

    Vassilakopoulou, Anastasia; Koutselas, Ioannis

    2016-01-01

    Room temperature single layer light emitting diode(LED), based on a two dimensional hybrid organic-inorganic semiconductor(HOIS), is demonstrated. This simple, low cost excitonic LED operates at low voltages. Such an excitonic device is presented for the first time as functioning at room temperature. The newly introduced class of perovskite LEDs, until now based on 3D perovksite HOIS, is now broadened with the implementation of the 2D HOIS. Novel functionalities can be realized since it is now possible to access the hybrid's 2D semiconductor advantageous properties, such as the increased excitonic peak wavelength tunability, excitonic binding energy and oscillator strength.

  4. Mechanisms of Loss in Internal Quantum Efficiency in III-Nitride-based Blue-and Green-Light Emitting Diodes

    Science.gov (United States)

    Huang, Li

    The overarching goals of the research conducted for this dissertation have been to understand the scientific reasons for the losses in the internal quantum efficiency (IQE) in Group III-nitride-based blue and especially green light-emitting diodes (LEDs) containing a multi-quantum well (MQW) active region and to simultaneously develop LED epitaxial structures to ameliorate these losses. The p-type AlGaN EBL was determined to be both mandatory and effective in the prevention of electron overflow from the MQW region into the p-type cladding layer and the resultant lowering of the IQE. The overflow phenomenon was partially due to the low concentration (˜ 5 x 1017 cm-3) and mobility (˜ 10 cm2/(V•s)) of the holes injected into the active region. Electroluminescence (EL) studies of LEDs without an EBL revealed a dominant emission from donor-acceptor pair recombination in the p-type GaN layer. The incorporation of a 90 nm compositionally graded In0-0.1 Ga1-0.9N buffer layer between each MQW and n-GaN cladding layer grown on an Al/SiC substrate resulted in an increase in the luminescence intensity and a blue-shift in the emission wavelength, as observed in photoluminescence (PL) spectra. The graded InGaN buffer layer reduced the stress and thus the piezoelectric field across the MQW; this improved the electron/hole overlap that, in turn, resulted in an enhanced radiative recombination rate and an increase in efficiency. A direct correlation was observed between an increase in the IQE measured in temperature-dependent PL (TDPL) and an increase in the roughness of all the upper InGaN QW/GaN barrier interfaces, as determined using cross-sectional transmission electron microscopy of the MQW. These results agreed in general with the average surface roughness values of the pit-free region on the top GaN barrier determined via atomic force microscopy and the average roughness values of all the interfaces in the MQW calculated from the FWHM of the emission peak in the PL

  5. Source Driver Channel Reduction Schemes Employing Corresponding Pixel Alignments for Current Programming Active-Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Hong, Soon-Kwang; Oh, Du-Hwan; Jeong, Seok-Hee; Park, Young-Ju; Kim, Byeong-Koo; Ha, Yong-Min; Jang, Jin

    2008-03-01

    We propose two types of novel scheme for reducing the number of output channels of driver-integrated circuit (D-IC) for the current programming compensation pixel structures of active-matrix organic light-emitting diodes (AMOLEDs). One is a 2:1 data demultiplexing technique that can reduce the number of output channels of D-IC by half. The proposed second scheme is a vertically aligned red (R), green (G), and blue (B) subpixel scheme instead of a horizontally aligned R-G-B subpixel one, which is regarded as the conventional pixel alignment scheme. We have also successfully implemented these schemes in a 2.4-in.-sized QCIF + (176 × RGB × 220) AMOLED using p-type excimer laser annealing (ELA) low-temperature polycrystalline silicon (LTPS) technology and evaluated key performance characteristics.

  6. Flexion bonding transfer of multilayered graphene as a top electrode in transparent organic light-emitting diodes

    Science.gov (United States)

    Tae Lim, Jong; Lee, Hyunkoo; Cho, Hyunsu; Kwon, Byoung-Hwa; Sung Cho, Nam; Kuk Lee, Bong; Park, Jonghyurk; Kim, Jaesu; Han, Jun-Han; Yang, Jong-Heon; Yu, Byoung-Gon; Hwang, Chi-Sun; Chu Lim, Seong; Lee, Jeong-Ik

    2015-12-01

    Graphene has attracted considerable attention as a next-generation transparent conducting electrode, because of its high electrical conductivity and optical transparency. Various optoelectronic devices comprising graphene as a bottom electrode, such as organic light-emitting diodes (OLEDs), organic photovoltaics, quantum-dot LEDs, and light-emitting electrochemical cells, have recently been reported. However, performance of optoelectronic devices using graphene as top electrodes is limited, because the lamination process through which graphene is positioned as the top layer of these conventional OLEDs is a lack of control in the surface roughness, the gapless contact, and the flexion bonding between graphene and organic layer of the device. Here, a multilayered graphene (MLG) as a top electrode is successfully implanted, via dry bonding, onto the top organic layer of transparent OLED (TOLED) with flexion patterns. The performance of the TOLED with MLG electrode is comparable to that of a conventional TOLED with a semi-transparent thin-Ag top electrode, because the MLG electrode makes a contact with the TOLED with no residue. In addition, we successfully fabricate a large-size transparent segment panel using the developed MLG electrode. Therefore, we believe that the flexion bonding technology presented in this work is applicable to various optoelectronic devices.

  7. 3.4-Inch Quarter High Definition Flexible Active Matrix Organic Light Emitting Display with Oxide Thin Film Transistor

    Science.gov (United States)

    Hatano, Kaoru; Chida, Akihiro; Okano, Tatsuya; Sugisawa, Nozomu; Inoue, Tatsunori; Seo, Satoshi; Suzuki, Kunihiko; Oikawa, Yoshiaki; Miyake, Hiroyuki; Koyama, Jun; Yamazaki, Shunpei; Eguchi, Shingo; Katayama, Masahiro; Sakakura, Masayuki

    2011-03-01

    In this paper, we report a 3.4-in. flexible active matrix organic light emitting display (AMOLED) display with remarkably high definition (quarter high definition: QHD) in which oxide thin film transistors (TFTs) are used. We have developed a transfer technology in which a TFT array formed on a glass substrate is separated from the substrate by physical force and then attached to a flexible plastic substrate. Unlike a normal process in which a TFT array is directly fabricated on a thin plastic substrate, our transfer technology permits a high integration of high performance TFTs, such as low-temperature polycrystalline silicon TFTs (LTPS TFTs) and oxide TFTs, on a plastic substrate, because a flat, rigid, and thermally-stable glass substrate can be used in the TFT fabrication process in our transfer technology. As a result, this technology realized an oxide TFT array for an AMOLED on a plastic substrate. Furthermore, in order to achieve a high-definition AMOLED, color filters were incorporated in the TFT array and a white organic light-emitting diode (OLED) was combined. One of the features of this device is that the whole body of the device can be bent freely because a source driver and a gate driver can be integrated on the substrate due to the high mobility of an oxide TFT. This feature means “true” flexibility.

  8. Light-Emitting-Diodes based on ordered InGaN nanocolumns emitting in the blue, green and yellow spectral range

    Science.gov (United States)

    Bengoechea-Encabo, A.; Albert, S.; Lopez-Romero, D.; Lefebvre, P.; Barbagini, F.; Torres-Pardo, A.; Gonzalez-Calbet, J. M.; Sanchez-Garcia, M. A.; Calleja, E.

    2014-10-01

    The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN (planar) layers of similar composition and thickness. Electroluminescence spectra show a very small blue shift with increasing current (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.

  9. Optical Properties of Hybrid Inorganic/Organic Thin Film Encapsulation Layers for Flexible Top-Emission Organic Light-Emitting Diodes.

    Science.gov (United States)

    An, Jae Seok; Jang, Ha Jun; Park, Cheol Young; Youn, Hongseok; Lee, Jong Ho; Heo, Gi-Seok; Choi, Bum Ho; Lee, Choong Hun

    2015-10-01

    Inorganic/organic hybrid thin film encapsulation layers consist of a thin Al2O3 layer together with polymer material. We have investigated optical properties of thin film encapsulation layers for top-emission flexible organic light-emitting diodes. The transmittance of hybrid thin film encapsulation layers and the electroluminescent spectrum of organic light-emitting diodes that were passivated by hybrid organic/inorganic thin film encapsulation layers were also examined as a function of the thickness of inorganic Al203 and monomer layers. The number of interference peaks, their intensity, and their positions in the visible range can be controlled by varying the thickness of inorganic Al2O3 layer. On the other hand, changing the thickness of monomer layer had a negligible effect on the optical properties. We also verified that there is a trade-off between transparency in the visible range and the permeation of water vapor in hybrid thin film encapsulation layers. As the number of dyads decreased, optical transparency improved while the water vapor permeation barrier was degraded. Our study suggests that, in top-emission organic light-emitting diodes, the thickness of each thin film encapsulation layer, in particular that of the inorganic layer, and the number of dyads should be controlled for highly efficient top-emission flexible organic light-emitting diodes.

  10. Optimal Color Stability for White Organic Light-Emitting Diode (WOLED by Using Multiple-Ultra-Thin Layers (MUTL

    Directory of Open Access Journals (Sweden)

    Kan-Lin Chen

    2013-01-01

    Full Text Available The work demonstrates the improvement of color stability for white organic light-emitting diode (WOLED. The devices were prepared by vacuum deposition on ITO-glass substrates. These guest materials of 5,6,11,12-tetraphenylnaphthacene (Rubrene were deposited in 4,4′-bis(2,2-diphenyl vinyl-1,1′-biphenyl (DPVBi, resulting in an emitting layer. Experimental results reveal that the properties in the multiple-ultra-thin layer (MUTL are better than those of the emitting layer with a single guest material, reaching the commercial white-light wavelength requirement of 400–700 nm. The function of the MUTL is as the light-emitting and trapping layer. The results show that the MUTL has excellent carrier capture effect, leading to high color stability of the device at various applied voltages. The Commissions Internationale De L’Eclairage (CIE coordinate of this device at 3~7 V is few displacement and shows a very slight variation of (0.016, 0.009. The CIE coordinates at a maximal luminance of 9980 cd/m2 are (0.34, 0.33.

  11. Improved performance of organic light-emitting diodes using a Zn complex

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Yoon-Ki; Kim, Dong-Eun; Kwon, Oh-Kwan; Kwon, Young-Soo [Dong-A University, Busan (Korea, Republic of); Kim, Won-Sam; Lee, Burm-Jong [Inje University, Gimhae (Korea, Republic of)

    2006-09-15

    We have synthesized new electroluminescence materials, including [2-(2-hydroxyphenyl) benzoxazole] (Zn(HPB){sub 2}) and [(1,10-phenanthroline)(8-hydroxyquinoline)] Zn(phen)q. The photoluminescence (PL) spectra of Zn(HPB){sub 2} and Zn(phen)q were observed to be blue and yellowish green, respectively. The ionization potential (IP) and the electron affinity (EA) of each Zn complex were measured using cyclic voltammetry (CV). Zn(HPB){sub 2} was used as an emitting material while Zn(phen)q and Alq{sub 3} were used as electron transport materials. We investigated the electron transport properties of Zn(phen)q compared with Alq{sub 3}. The fundamental structures of the organic lightemitting diodes (OLEDs) were ITO/NPB/Zn(HPB){sub 2}/Zn(phen)q and Alq{sub 3}/LiF/Al. As a result, the electron transport properties of Zn(phen)q were better than those of Alq{sub 3}. Therefore, Zn(phen)q should be useful as an electron transport material to enhance the performance of OLEDs.

  12. Design of efficient molecular organic light-emitting diodes by a high-throughput virtual screening and experimental approach

    Science.gov (United States)

    Gómez-Bombarelli, Rafael; Aguilera-Iparraguirre, Jorge; Hirzel, Timothy D.; Duvenaud, David; MacLaurin, Dougal; Blood-Forsythe, Martin A.; Chae, Hyun Sik; Einzinger, Markus; Ha, Dong-Gwang; Wu, Tony; Markopoulos, Georgios; Jeon, Soonok; Kang, Hosuk; Miyazaki, Hiroshi; Numata, Masaki; Kim, Sunghan; Huang, Wenliang; Hong, Seong Ik; Baldo, Marc; Adams, Ryan P.; Aspuru-Guzik, Alán

    2016-10-01

    Virtual screening is becoming a ground-breaking tool for molecular discovery due to the exponential growth of available computer time and constant improvement of simulation and machine learning techniques. We report an integrated organic functional material design process that incorporates theoretical insight, quantum chemistry, cheminformatics, machine learning, industrial expertise, organic synthesis, molecular characterization, device fabrication and optoelectronic testing. After exploring a search space of 1.6 million molecules and screening over 400,000 of them using time-dependent density functional theory, we identified thousands of promising novel organic light-emitting diode molecules across the visible spectrum. Our team collaboratively selected the best candidates from this set. The experimentally determined external quantum efficiencies for these synthesized candidates were as large as 22%.

  13. Preparation of organic light-emitting diode using coal tar pitch, a low-cost material, for printable devices.

    Directory of Open Access Journals (Sweden)

    Miki Yamaoka

    Full Text Available We have identified coal tar pitch, a very cheap organic material made from coal during the iron-making process, as a source from which could be obtained emissive molecules for organic light-emitting diodes. Coal tar pitch was separated by simple dissolution in organic solvent, and subsequent separation by preparative thin-layer chromatography was used to obtain emissive organic molecules. The retardation factor of preparative thin-layer chromatography played a major role in deciding the emission characteristics of the solution as photoluminescence spectra and emission-excitation matrix spectra could be controlled by modifying the solution preparation method. In addition, the device characteristics could be improved by modifying the solution preparation method. Two rounds of preparative thin-layer chromatography separation could improve the luminance of organic light-emitting diodes with coal tar pitch, indicating that less polar components are favorable for enhancing the luminance and device performance. By appropriate choice of the solvent, the photoluminescence peak wavelength of separated coal tar pitch could be shifted from 429 nm (cyclohexane to 550 nm (chloroform, and consequently, the optical properties of the coal tar pitch solution could be easily tuned. Hence, the use of such multicomponent materials is advantageous for fine-tuning the net properties at a low cost. Furthermore, an indium tin oxide/poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate/coal tar pitch/LiF/Al system, in which the emissive layer was formed by spin-coating a tetrahydrofuran solution of coal tar pitch on the substrate, showed a luminance of 176 cd/m(2. In addition, the emission spectrum of coal tar pitch was narrowed after the preparative thin-layer chromatography process by removing the excess emissive molecules.

  14. Preparation of organic light-emitting diode using coal tar pitch, a low-cost material, for printable devices.

    Science.gov (United States)

    Yamaoka, Miki; Asami, Shun-Suke; Funaki, Nayuta; Kimura, Sho; Yingjie, Liao; Fukuda, Takeshi; Yamashita, Makoto

    2013-01-01

    We have identified coal tar pitch, a very cheap organic material made from coal during the iron-making process, as a source from which could be obtained emissive molecules for organic light-emitting diodes. Coal tar pitch was separated by simple dissolution in organic solvent, and subsequent separation by preparative thin-layer chromatography was used to obtain emissive organic molecules. The retardation factor of preparative thin-layer chromatography played a major role in deciding the emission characteristics of the solution as photoluminescence spectra and emission-excitation matrix spectra could be controlled by modifying the solution preparation method. In addition, the device characteristics could be improved by modifying the solution preparation method. Two rounds of preparative thin-layer chromatography separation could improve the luminance of organic light-emitting diodes with coal tar pitch, indicating that less polar components are favorable for enhancing the luminance and device performance. By appropriate choice of the solvent, the photoluminescence peak wavelength of separated coal tar pitch could be shifted from 429 nm (cyclohexane) to 550 nm (chloroform), and consequently, the optical properties of the coal tar pitch solution could be easily tuned. Hence, the use of such multicomponent materials is advantageous for fine-tuning the net properties at a low cost. Furthermore, an indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/coal tar pitch/LiF/Al system, in which the emissive layer was formed by spin-coating a tetrahydrofuran solution of coal tar pitch on the substrate, showed a luminance of 176 cd/m(2). In addition, the emission spectrum of coal tar pitch was narrowed after the preparative thin-layer chromatography process by removing the excess emissive molecules.

  15. Improvement in Brightness Uniformity by Compensating for the Threshold Voltages of Both the Driving Thin-Film Transistor and the Organic Light-Emitting Diode for Active-Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Fan, Ching-Lin; Lai, Hui-Lung; Chang, Jyu-Yu

    2010-05-01

    In this paper, we propose a novel pixel design and driving method for active-matrix organic light-emitting diode (AM-OLED) displays using low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs). The proposed threshold voltage compensation circuit, which comprised five transistors and two capacitors, has been verified to supply uniform output current by simulation work using the automatic integrated circuit modeling simulation program with integrated circuit emphasis (AIM-SPICE) simulator. The driving scheme of this voltage programming method includes four periods: precharging, compensation, data input, and emission. The simulated results demonstrate excellent properties such as low error rate of OLED anode voltage variation (<1%) and high output current. The proposed pixel circuit shows high immunity to the threshold voltage deviation characteristics of both the driving poly-Si TFT and the OLED.

  16. Synthesis and Characterization of New Thienopyrazine-cored Dendrimer for Non-Doped Organic Red Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    李青; 李久艳; 段永恒; 高占先; 刘迪

    2011-01-01

    A new thieno-[3,4-b]-pyrazine-cored dendrimer with polyphenyls dendrons (D2TP) was designed and synthesized for application as red emitter in non-doped organic light-emitting diodes (OLEDs). The bulky dendritic arms enable this molecule to possess significant molecular weight and good solubility in common organic solvents. As a result, D2TP is suitable for solution processing methods such as spin coating to make thin films and devices. In addition, these large dendrons provide site-isolation effect on the planar emissive core to prevent fluorescence quenching or intermolecular interaction. The photophysical and electrochemical properties of D2TP were investigated in its dilute solutions. D2TP was used as non-doped emitter to fabricate OLEDs by spin coating method and saturated red electroluminescence was obtained.

  17. Highly Efficient Nondoped Organic Light Emitting Diodes Based on Thermally Activated Delayed Fluorescence Emitter with Quantum-Well Structure.

    Science.gov (United States)

    Meng, Lingqiang; Wang, Hui; Wei, Xiaofang; Liu, Jianjun; Chen, Yongzhen; Kong, Xiangbin; Lv, Xiaopeng; Wang, Pengfei; Wang, Ying

    2016-08-17

    Highly efficiency nondoped thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs) with multiquantum wells structure were demonstrated. By using an emitting layer with seven quantum wells, the nondoped TADF OLEDs exhibit high efficiency with EQE of 22.6%, a current efficiency of 69 cd/A, and a power efficiency of 50 lm/W, which are higher than those of the conventional doped OLED and among the best of the TADF OLEDs. The high performance of the devices can be ascribed to effective confinement of the charges and excitons in the emission layer by the quantum well structure. The emission layer with multiquantum well structure is demonstrated to be cost effective for highly efficient nondoped TADF OLEDs and holds great potential for organic electronics.

  18. Enhanced efficiency of organic light-emitting devices with corrugated nanostructures based on soft nano-imprinting lithography

    Science.gov (United States)

    Liu, Yue-Feng; An, Ming-Hui; Zhang, Xu-Lin; Bi, Yan-Gang; Yin, Da; Zhang, Yi-Fan; Feng, Jing; Sun, Hong-Bo

    2016-11-01

    An enhanced efficiency organic light-emitting device (OLED) with corrugated nanostructures on a small-molecule organic film has been demonstrated. By patterning the hole transport layer via soft nano-imprinting lithography and coating with Ag, a nanostructured cathode is introduced to enhance the light extraction of the OLED without affecting the flatness and conductivity of the indium-tin-oxide film. Both luminance and current efficiency are improved compared with those of conventional planar devices. The observable improvement in luminance and current efficiency can be ascribed to the surface plasmonic and scattering effects caused by the Ag nanostructures. Moreover, theoretical simulations also demonstrate that the power loss to surface plasmon-polariton modes has been recovered.

  19. Organic Light Emitting Device as a fluorescence spectroscopy's light source : one step towards the lab-on-a-chip device

    Science.gov (United States)

    Camou, S.; Kitamura, M.; Gouy, Jean-Philippe; Fujita, Hiroyuki; Arakawa, Yasuhiko; Fujii, Teruo

    2003-02-01

    Many papers were recently dedicated to the lab-on-a-chip applications, where all the basic elements should be integrated directly onto the microchip. The fluorescence spectroscopy is mostly used as a detection method due to its high reliability and sensitivity, but requires light source and photo-detector. For the first time, we then propose to use Organic material Light Emitting Diode (OLED) to supply a light source for the optical detection based on fluorescence spectroscopy. By combining this OLED with micro-fluidic channels patterned in PDMS layer, the integration of light source on the chip is then achieved. First, the ability of Organic Material to excite fluorescent response from dye is demonstrated. Then, some configurations are described in order to decrease the major drawbacks that have to be solved before applying such kind of devices.

  20. Studies of solution-processed organic light-emitting diodes and their materials

    Energy Technology Data Exchange (ETDEWEB)

    Hellerich, Emily [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    A hitherto unexplored approach is presented in which a small molecule is used as a host to polymer guests in solution-processed OLEDs. We find that the small molecule host results in much more efficient devices than the often-used alternative polymer host when used for the guests presented. It is likely that nano- and microstructural differences between the hosts contribute to the improvements, which highlights some interesting characteristics that can help to better understand the nature of these mixtures. A number of the guests used in this study were newly synthesized benzobisoxazole-based copolymers. New organic copolymers are presented that are based on the chemical structure of benzobisoxazoles, which have been shown in the past to have good electron transporting properties. The novel concept in this publication pertains to a change in the direction of polymerization, also known as the conjugation pathway, which we show increases the emission efficiency. This work highlights a unique and useful property of organic semiconducting materials in that they can be synthesized to create the desired characteristics. Earlier work is described that kick-started in our research group the use of small molecules in solution-processed OLEDs. Originally these devices were to be used in magnetoresistance studies, but the project took a different path when the devices were more efficient than expected. The efficient use of small molecules in solution-processed OLEDs is highlighted, which at the time was not often the case. Also, the important observation of the effect of solvent choice on the resultant film is emphasized, with discussion of the likely cause of these effects. Microcavity OLEDs are introduced in which the transparent anode ITO is replaced with semi-transparent thin silver, which creates an optical cavity within the devices. The goal was to expand a previous work that created an on-chip spectrometer covering wavelengths 493 to 639 nm. In this case, a spin

  1. Novel concepts for high-efficiency white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Gregor

    2007-07-01

    This work deals with novel concepts to realize high efficiency white OLEDs by combining fluorescent blue and phosphorescent green and orange emitters. A key point determining the maximum efficiency possible, as well as the device structure to be chosen to reach high efficiency, is the triplet exciton energy of the fluorescent blue emitter. If its triplet state is lower than that of the phosphorescent emitters, mutual exciton quenching can occur. This problem is solved by the first concept with spatial separation of the fluorescent blue from the phosphorescent emitters by a large-gap exciton blocking layer. To still realize exciton generation on both sides, the interlayer has to be ambipolar. On the other hand, if the triplet exciton energy of the fluorescent blue is higher than that of at least one of the phosphorescent emitters, appropriate arrangement of the emission layers makes a separation layer obsolete, since phosphorescence quenching does not occur anymore. Moreover, the intrinsically non-radiative triplet excitons of the fluorescent blue emitter may be harvested by the phosphor for light emission, which means that even 100% internal quantum efficiency is possible. The last chapter 6 deals with this second concept, where the main issue is to simultaneously achieve exciton harvesting as complete as possible and a balanced white emission spectrum by appropriately distributing singlet and triplet excitons to the used emitters. All emitters used in this work are commercially available and their molecular structure is disclosed in order to make the results transparent. (orig.)

  2. Use of silane-functionalized graphene oxide in organic photovoltaic cells and organic light-emitting diodes.

    Science.gov (United States)

    Lee, Chang Yeong; Le, Quyet Van; Kim, Cheolmin; Kim, Soo Young

    2015-04-14

    Graphene oxide (GO) and silane-functionalized GO (sGO) sheets obtained through a simple sonication exfoliation method are employed as hole transport layers to improve the efficiency of organic photovoltaic (OPV) cells and organic light-emitting diodes (OLED). GO was functionalized using (3-glycidyl oxypropyl)trimethoxysilane (GPTMS) and triethoxymethylsilane (MTES). The appearance of new peaks in the Fourier-transform infrared spectra of the sGOs indicates the formation of Si-O-C, Si-O-Si, Si-H, and Si-O-C moieties, which provide evidence of the addition of silane to the GO surface. Furthermore, the appearance of Si-O-Si bonds in the synchrotron radiation photoelectron spectra (SRPES) of the MTES-sGO and GPTMS-sGO samples suggests that silane groups were effectively functionalized onto the GO sheets. An OPV cell with GO layers showed a lower performance with a power conversion efficiency (PCE) of 2.06%; in contrast, OPV cells based on GPTMS-sGO and MTES-sGO have PCE values of 3.00 and 3.08%, respectively. The OLED devices based on GPTMS-sGO and MTES-sGO showed a higher maximum luminance efficiency of 13.91 and 12.77 cd A(-1), respectively, than PEDOT:PSS-based devices (12.34 cd A(-1)). The SRPES results revealed that the work functions of GO, GPTMS-sGO, and MTES-sGO were 4.8, 4.9, and 5.0 eV, respectively. Therefore, the increase in the PCE value is attributed to improved band-gap alignment. It is thought that sGO could be used as an interfacial layer in OPV and OLED devices.

  3. A dual-blue light-emitting diode based on strain-compensated InGaN-AlGaN/GaN quantum wells

    Institute of Scientific and Technical Information of China (English)

    Yan Qi-Rong; Yan Qi-Ang; Shi Pei-Pei; Niu Qiao-Li; Li Shu-Ti; Zhang Yong

    2013-01-01

    A strain-compensated InGaN quantum well (QW) active region employing a tensile A1GaN barrier is analyzed.Its spectral stability and efficiency droop for a dual-blue light-emitting diode (LED) are improved compared with those of the conventional InGaN/GaN QW dual-blue LEDs based on a stacking structure of two In0.18Ga0.82N/GaN QWs and two In0.12Ga0.88N/GaN QWs on the same sapphire substrate.It is found that the optimal performance is achieved when the AI composition of the strain-compensated A1GaN layer is 0.12 in blue QW and 0.21 in blue-violet QW.The improvement performance can be attributed to the strain-compensated InGaN-AlGaN/GaN QW,which can provide a better carrier confinement and effectively reduce leakage current.

  4. In vitro and in vivo efficacy of new blue light emitting diode phototherapy compared to conventional halogen quartz phototherapy for neonatal jaundice.

    Science.gov (United States)

    Chang, Yun Sil; Hwang, Jong Hee; Kwon, Hyuk Nam; Choi, Chang Won; Ko, Sun Young; Park, Won Soon; Shin, Son Moon; Lee, Munhyang

    2005-02-01

    High intensity light emitting diodes (LEDs) are being studied as possible light sources for the phototherapy of neonatal jaundice, as they can emit high intensity light of narrow wavelength band in the blue region of the visible light spectrum corresponding to the spectrum of maximal bilirubin absorption. We developed a prototype blue gallium nitride LED phototherapy unit with high intensity, and compared its efficacy to commercially used halogen quartz phototherapy device by measuring both in vitro and in vivo bilirubin photodegradation. The prototype device with two focused arrays, each with 500 blue LEDs, generated greater irradiance than the conventional device tested. The LED device showed a significantly higher efficacy of bilirubin photodegradation than the conventional phototherapy in both in vitro experiment using microhematocrit tubes (44+/-7% vs. 35+/-2%) and in vivo experiment using Gunn rats (30+/-9% vs. 16+/-8%). We conclude that high intensity blue LED device was much more effective than conventional phototherapy of both in vitro and in vivo bilirubin photodegradation. Further studies will be necessary to prove its clinical efficacy.

  5. Understanding different efficiency droop behaviors in InGaN-based near-UV, blue and green light-emitting diodes through differential carrier lifetime measurements

    CERN Document Server

    Wang, Lai; Wang, Jiaxing; Hao, Zhibiao; Luo, Yi; Sun, Changzheng; Han, Yanjun; Xiong, Bing; Wang, Jian; Li, Hongtao

    2016-01-01

    Efficiency droop effect under high injection in GaN-based light emitting diodes (LEDs) strongly depends on wavelength, which is still not well understood. In this paper, through differential carrier lifetime measurements on commercialized near-UV, blue, and green LEDs, their different efficiency droop behaviors are attributed to different carrier lifetimes, which are prolonged as wavelength increases. This relationship between carrier lifetime and indium composition of InGaN quantum well is believed owing to the polarization-induced quantum confinement Stark effect. Long carrier lifetime not only increases the probability of carrier leakage, but also results in high carrier concentration in quantum well. In other words, under the same current density, the carrier concentration in active region in near-UV LED is the lowest while that in green one is the highest. If considering the efficiency droop depending on carrier concentration, the behaviors of LEDs with different wavelengths do not show any abnormality. ...

  6. Performance improvement of blue light-emitting diodes with an AlInN/GaN superlattice electron-blocking layer

    Institute of Scientific and Technical Information of China (English)

    Zhao Fang; Yao Guang-Rui; Song Jing-Jing; Ding Bin-Bin; Xiong Jian-Yong; Su Chen; Zheng Shu-Wen

    2013-01-01

    The characteristics of a blue light-emitting diode (LED) with an AlInN/GaN superlattice (SL) electron-blocking layer (EBL) are analyzed numerically.The cartier concentrations in the quantum wells,energy band diagrams,electrostatic fields,and internal quantum efficiency are investigated.The results suggest that the LED with an AlInN/GaN SL EBL has better hole injection efficiency,lower electron leakage,and smaller electrostatic fields in the active region than the LED with a conventional rectangular AlGaN EBL or a A1GaN/GaN SL EBL.The results also indicate that the efficiency droop is markedly improved when an AlInN/GaN SL EBL is used.

  7. Efficient polymer light-emit ting diodes with violet blue emission based on blends of PSiF6-PPP and PSiFC6C6

    Institute of Scientific and Technical Information of China (English)

    TIAN Renyu; MO Yueqi; PENG Junbiao

    2006-01-01

    Efficient polymer light-emitting diodes (PLEDs) with violet blue emission were fabricated using blends of copolymers of paraphenylene-cosilafluorene (PSiF6-PPP) and polymer of poly (9,9'alkyl-3,6-silafluorene) (PSiFC6C6). The performances of the devices are sensitive to the blend ratio.When the mass ratio of PSiF6-PPP to PSiFC6C6 is 1.96% at luminance of 105 cd.m-2, its electroluminescent (EL) spectrum peaks at 398 nm and full width at half maximum is 67 nm. The improvements of the device performances were due to the energy transfer from PSiFC6C6 to PSiF6-PPP and the balanced injection of electrons and holes.

  8. Flexible bottom-emitting white organic light-emitting diodes with semitransparent Ni/Ag/Ni anode.

    Science.gov (United States)

    Koo, Ja-Ryong; Lee, Seok Jae; Lee, Ho Won; Lee, Dong Hyung; Yang, Hyung Jin; Kim, Woo Young; Kim, Young Kwan

    2013-05-01

    We fabricated a flexible bottom-emitting white organic light-emitting diode (BEWOLED) with a structure of PET/Ni/Ag/Ni (3/6/3 nm)/ NPB (50 nm)/mCP (10 nm)/7% FIrpic:mCP (10 nm)/3% Ir(pq)(2) acac:TPBi (5 nm)/7% FIrpic:TPBi (5 nm)/TPBi (10 nm)/Liq (2 nm)/ Al (100 nm). To improve the performance of the BEWOLED, a multilayered metal stack anode of Ni/Ag/Ni treated with oxygen plasma for 60 sec was introduced into the OLED devices. The Ni/Ag/Ni anode effectively enhanced the probability of hole-electron recombination due to an efficient hole injection into and charge balance in an emitting layer. By comparing with a reference WOLED using ITO on glass, it is verified that the flexible BEWOLED showed a similar or better electroluminescence (EL) performance.

  9. Localized surface plasmon enhanced emission of organic light emitting diode coupled to DBR-cathode microcavity by using silver nanoclusters.

    Science.gov (United States)

    Khadir, Samira; Chakaroun, Mahmoud; Belkhir, Abderrahmane; Fischer, Alexis; Lamrous, Omar; Boudrioua, Azzedine

    2015-09-01

    In this work, we aim to increase the emission of the standard guest-host organic light emitting diode (OLED) thanks to localized surface plasmon and to investigate this effect in a microcavity. As a first step, we consider thermal deposition of silver clusters within an OLED guest-host stack. We investigate both the influence of the size of silver nanoparticles (Ag-NPs) and their position within the OLED heterostructure. Secondly, we study the optimized OLED within a microcavity formed by Al-cathode top mirror and a Distributed Bragg Reflector (DBR) bottom mirror. The experimental results show a substantial enhancement of the electroluminescence (EL) intensity as well as a reduction of the spectral width at a half maximum.

  10. Embedded Touch Sensing Circuit Using Mutual Capacitance for Active-Matrix Organic Light-Emitting Diode Display

    Science.gov (United States)

    Park, Young-Ju; Seok, Su-Jeong; Park, Sang-Ho; Kim, Ohyun

    2011-03-01

    We propose and simulate an embedded touch sensing circuit for active-matrix organic light-emitting diode (AMOLED) displays. The circuit consists of three thin-film transistors (TFTs), one fixed capacitor, and one variable capacitor. AMOLED displays do not have a variable capacitance characteristic, so we realized a variable capacitor to detect touches in the sensing pixel by exploiting the change in the mutual capacitance between two electrodes that is caused by touch. When a dielectric substance approaches two electrodes, the electric field is shunted so that the mutual capacitance decreases. We use the existing TFT process to form the variable capacitor, so no additional process is needed. We use advanced solid-phase-crystallization TFTs because of their stability and uniformity. The proposed circuit detects multi-touch points by a scanning process.

  11. Time-Domain Quaternary-Weighted Pulse Width Modulation Driving Method for Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Park, Hyun-Sang; Kuk, Seung-Hee; Han, Min-Koo

    2008-03-01

    We proposed a new digital driving method and its pixel structure for active matrix organic light-emitting diode (AMOLED) displays employing time-domain quaternary-weighted pulse width modulation. In the new digital driving method, the luminance of AMOLED displays is accurately determined by averaging photon flux to the desired level over a frame period. The proposed pixel was verified by spice simulation and the output linearity between the grayscale and the OLED current was successfully achieved. In the proposed digital driving pixel, the timing margin was increased and the effect on luminance of AMOLED displays by the troublesome variation of the thin-film transistors (TFTs) was suppressed without additional compensation schemes.

  12. A New Low Temperature Polycrystalline Silicon Thin Film Transistor Pixel Circuit for Active Matrix Organic Light Emitting Diode

    Science.gov (United States)

    Fan, Ching-Lin; Lin, Yi-Yan; Chang, Jyu-Yu; Sun, Bo-Jhang; Liu, Yan-Wei

    2010-06-01

    This study presents one novel compensation pixel design and driving method for active matrix organic light-emitting diode (AMOLED) displays that use low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs) with a voltage feed-back method and the simulation results are proposed and verified by SPICE simulator. The measurement and simulation of LTPS TFT characteristics demonstrate the good fitting result. The proposed circuit consists of four TFTs and two capacitors with an additional signal line. The error rates of OLED anode voltage variation are below 0.3% under the threshold voltage deviation of driving TFT (ΔVTH = ±0.33 V). The simulation results show that the pixel design can improve the display image non-uniformity by compensating the threshold voltage deviation of driving TFT and the degradation of OLED threshold voltage at the same time.

  13. Efficient hybrid organic-inorganic light emitting diodes with self-assembled dipole molecule deposited metal oxides

    Science.gov (United States)

    Park, Ji Sun; Lee, Bo Ram; Lee, Ju Min; Kim, Ji-Seon; Kim, Sang Ouk; Song, Myoung Hoon

    2010-06-01

    We investigate the effect of self-assembled dipole molecules (SADMs) on ZnO surface in hybrid organic-inorganic polymeric light-emitting diodes (HyPLEDs). Despite the SADM being extremely thin, the magnitude and orientation of SADM dipole moment effectively influenced the work function of the ZnO. As a consequence, the charge injection barrier between the conduction band of the ZnO and the lowest unoccupied molecular orbital of poly(9,9'-dioctylfluorene)-co-benzothiadiazole could be efficiently controlled resulting that electron injection efficiency is remarkably enhanced. The HyPLEDs modified with a negative dipolar SADM exhibited enhanced device performances, which correspond to approximately a fourfold compared to those of unmodified HyPLEDs.

  14. Effect of gold nanorods and nanocubes on electroluminescent performances in organic light-emitting diodes and its working mechanism

    Directory of Open Access Journals (Sweden)

    Ying Xu

    2015-06-01

    Full Text Available In this manuscript we investigated the influence of Au nanoparticles on electrical and electroluminescent (EL performances in organic light-emitting diodes (OLEDs via doping as-synthesized Au nanorods (NRs or nanocubes (NCs into hole transport layer (HTL. Through accurately controlling the distance between the Au NRs and the emitting layer, altering the guest emitter’s lifetime, and replacing Au NRs with Au NCs to satisfy a better spectrum overlap with the emission guest, we got a conclusion that doping Au NRs or NCs into HTL has no significant influence on the device’s electrical and EL performances, although we observed an increase in the spontaneous emission rate in a fluorescent material by the exciton-surface plasmon-coupling. Our results suggest that a further research on emission mechanism in surface plasmon-enhanced OLEDs is still in process.

  15. Photon management in solution-processed organic light-emitting diodes: a review of light outcoupling micro- and nanostructures

    Science.gov (United States)

    Gomard, Guillaume; Preinfalk, Jan B.; Egel, Amos; Lemmer, Uli

    2016-07-01

    To allow a greater acceptance in the display and lighting markets, organic light-emitting diode (OLED) technology is currently the subject of intensive research efforts aimed at manufacturing cost-effective devices with higher efficiencies. In this regard, strategies matured in the field of photonics and nanophotonics can be applied for photon management purposes to improve the outcoupling of the generated light and to control the emission pattern. In this review, we report on the recent experimental and numerical advances to pursue those goals by highlighting the example of bottom-emitting devices. The cases of periodical micro- and nanostructures, as well as of stochastic ensembles that can be easily implemented using printing techniques, are covered herein. It is shown that beyond the sole optical properties, such additional elements can simultaneously improve the electrical characteristics of solution-processed OLEDs, and thus enable an optimization of the devices at different levels.

  16. Large magneto-conductance and magneto-electroluminescence in exciplex-based organic light-emitting diodes at room temperature

    Science.gov (United States)

    Ling, Yongzhou; Lei, Yanlian; Zhang, Qiaoming; Chen, Lixiang; Song, Qunliang; Xiong, Zuhong

    2015-11-01

    In this work, we report on large magneto-conductance (MC) over 60% and magneto-electroluminescence (MEL) as high as 112% at room temperature in an exciplex-based organic light-emitting diode (OLED) with efficient reverse intersystem crossing (ISC). The large MC and MEL are individually confirmed by the current density-voltage characteristics and the electroluminescence spectra under various magnetic fields. We proposed that this type of magnetic field effect (MFE) is governed by the field-modulated reverse ISC between the singlet and triplet exciplex. The temperature-dependent MFEs reveal that the small activation energy of reverse ISC accounts for the large MFEs in the present exciplex-based OLEDs.

  17. n-type ZnS used as electron transport material in organic light-emitting diodes

    Institute of Scientific and Technical Information of China (English)

    Du Peng; Zhang Xi-Qing; Sun Xue-Bai; Yao Zhi-Gang; Wang Yong-Sheng

    2006-01-01

    This paper reports on the n-type ZnS used as electron transport layer for the organic light-emitting diodes(OLEDs). The naphthyl-substituted benzidine derivative (NPB) and tris (8-hydroxyquinoline) aluminium (Alq3)are used as the hole transport layer and the emitting layer respectively. The insertion of the n-type ZnS layer enhances the electron injection in the OLEDs. The study was carried out on OLEDs of structures: indium-tin-oxide (ITO)/NPB/Alq3/ZnS/LiF/AL, ITO/NPB/Alqa/LiF/AL and ITO/NPB/Alq3/AL. The luminance and efficiency of the device containing this electron transport layer are increased significantly over those obtained from conventional devices due to better carrier balance.

  18. Enhanced light emission from top-emitting organic light-emitting diodes by optimizing surface plasmon polariton losses

    CERN Document Server

    Fuchs, Cornelius; Wieczorek, Martin; Gather, Malte C; Hofmann, Simone; Reineke, Sebastian; Leo, Karl; Scholz, Reinhard

    2015-01-01

    We demonstrate enhanced light extraction for monochrome top-emitting organic light-emitting diodes (OLEDs). The enhancement by a factor of 1.2 compared to a reference sample is caused by the use of a hole transport layer (HTL) material possessing a low refractive index (1.52). The low refractive index reduces the in-plane wave vector of the surface plasmon polariton (SPP) excited at the interface between the bottom opaque metallic electrode (anode) and the HTL. The shift of the SPP dispersion relation decreases the power dissipated into lost evanescent excitations and thus increases the outcoupling efficiency, although the SPP remains constant in intensity. The proposed method is suitable for emitter materials owning isotropic orientation of the transition dipole moments as well as anisotropic, preferentially horizontal orientation, resulting in comparable enhancement factors. Furthermore, for sufficiently low refractive indices of the HTL material, the SPP can be modeled as a propagating plane wave within ot...

  19. Lifetime Improvement of Organic Light Emitting Diodes using LiF Thin Film and UV Glue Encapsulation

    Science.gov (United States)

    Huang, Jian-Ji; Su, Yan-Kuin; Chang, Ming-Hua; Hsieh, Tsung-Eong; Huang, Bohr-Ran; Wang, Shun-Hsi; Chen, Wen-Ray; Tsai, Yu-Sheng; Hsieh, Huai-En; Liu, Mark O.; Juang, Fuh-Shyang

    2008-07-01

    This work demonstrates the use of lithium fluoride (LiF) as a passivation layer and a newly developed UV glue for encapsulation on the LiF passivation layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with double protective layers showed a 25-fold increase in operational lifetime compared to those without any packaging layers. LiF has a low melting point and insulating characteristics and it can be adapted as both a protective layer and pre-encapsulation film. The newly developed UV glue has a fast curing time of only 6 s and can be directly spin-coated onto the surface of the LiF passivation layer. The LiF thin film plus spin-coated UV glue is a simple packaging method that reduces the fabrication costs of OLEDs.

  20. Tetra-methyl substituted copper (II phthalocyanine as a hole injection enhancer in organic light-emitting diodes

    Directory of Open Access Journals (Sweden)

    Yu-Long Wang

    2015-10-01

    Full Text Available We have enhanced hole injection and lifetime in organic light-emitting diodes (OLEDs by incorporating the isomeric metal phthalocyanine, CuMePc, as a hole injection enhancer. The OLED devices containing CuMePc as a hole injection layer (HIL exhibited higher luminous efficiency and operational lifetime than those using a CuPc layer and without a HIL. The effect of CuMePc thickness on device performance was investigated. Atomic force microscope (AFM studies revealed that the thin films were smooth and uniform because the mixture of CuMePc isomers depressed crystallization within the layer. This may have caused the observed enhanced hole injection, indicating that CuMePc is a promising HIL material for highly efficient OLEDs.

  1. Enabling Lambertian-Like Warm White Organic Light-Emitting Diodes with a Yellow Phosphor Embedded Flexible Film

    Directory of Open Access Journals (Sweden)

    Cheng-Chang Chen

    2014-01-01

    Full Text Available We demonstrate in this report a new constructive method of fabricating white organic light-emitting devices (OLEDs with a flexible plastic film embedded with yellow phosphor. The flexible film is composed of polydimethylsiloxane (PDMS and fabricated by using spin coating followed by peeling technology. From the results, the resultant electroluminescent spectrum shows the white OLED to have chromatic coordinates of 0.38 and 0.54 and correlated color temperature of 4200 K. The warm white OLED exhibits the yield of 10.3 cd/A and the luminous power efficiency of 5.4 lm/W at a luminance of 1000 cd/m2. A desirable Lambertian-like far-field pattern is detected from the white OLEDs with the yellow phosphor containing PDMS film. This method is simple, reproducible, and cost-effective, proving to be a highly feasible approach to realize white OLED.

  2. Electroluminescence and negative differential resistance studies of TPD:PBD:Alq3 blend organic-light-emitting diodes

    Indian Academy of Sciences (India)

    M A Mohd Sarjidan; S H Basri; N K Za’aba; M S Zaini; W H Abd Majid

    2015-02-01

    Ternary system of single-layer organic-light-emitting diodes (OLEDs) were fabricated containing tris(8-hydroxyquinoline) aluminium (Alq3) blended with N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole small molecules. Electroluminescence properties were investigated with respect to blend systems. Significant improvement in turn-on voltage and luminance intensity was observed by employing the blends technique. Negative differential resistance (NDR) characteristics observed at a low voltage region in blended OLED is related to the generation of guest hopping site and phonon scattering phenomenon. However, luminescence of the devices is not altered by the NDR effect.

  3. Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes

    Directory of Open Access Journals (Sweden)

    M. H. Doan

    2012-06-01

    Full Text Available The influences of the laser lift-off (LLO process on the InGaN/GaN blue light emitting diode (LED structures, grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition, have been comprehensively investigated. The vertical LED structures on Cu carriers are fabricated using electroplating, LLO, and inductively coupled plasma etching processes sequentially. A detailed study is performed on the variation of defect concentration and optical properties, before and after the LLO process, employing high-resolution transmission electron microscopy (HRTEM, scanning electron microscopy (SEM observations, cathodoluminescence (CL, photoluminescence (PL, and high-resolution X-ray diffraction (HRXRD measurements. The SEM observations on the distribution of dislocations after the LLO show well that even the GaN layer near to the multiple quantum wells (MQWs is damaged. The CL measurements reveal that the peak energy of the InGaN/GaN MQW emission exhibits a blue-shift after the LLO process in addition to a reduced intensity. These behaviors are attributed to a diffusion of indium through the defects created by the LLO and creation of non-radiative recombination centers. The observed phenomena thus suggest that the MQWs, the active region of the InGaN/GaN light emitting diodes, may be damaged by the LLO process when thickness of the GaN layer below the MQW is made to be 5 μm, a conventional thickness. The CL images on the boundary between the KrF irradiated and non-irradiated regions suggest that the propagation of the KrF laser beam and an accompanied recombination enhanced defect reaction, rather than the propagation of a thermal shock wave, are the main origin of the damage effects of the LLO process on the InGaN/GaN MQWs and the n-GaN layer as well.

  4. A facile method to enhance out-coupling efficiency in organic light-emitting diodes via a random-pyramids textured layer

    Science.gov (United States)

    Zhu, Wenqing; Xiao, Teng; Zhai, Guangsheng; Yu, Jingting; Shi, Guanjie; Chen, Guo; Wei, Bin

    2016-09-01

    We demonstrate a facile method to enhance light extraction in organic light-emitting diodes using a polymer layer with a texture consisting of random upright pyramids. The simple fabrication technique of the textured layer is based on silicon alkali-etching and imprint lithography. With the textured layer applied to the external face of the glass substrate, the organic light-emitting diode achieved a 26% enhancement of current efficiency and a 30% enhancement of power efficiency without spectral distortion over wide viewing angles. A ray-tracing optical simulation reveals that the textured layer can alter the traveling path of light and assist in out-coupling a large portion of light delivered into the substrate. The proposed method is a promising approach for achieving enhanced efficiency organic light-emitting diodes for the simple fabrication process and the effective light extraction.

  5. Rosin-enabled ultraclean and damage-free transfer of graphene for large-area flexible organic light-emitting diodes

    Science.gov (United States)

    Zhang, Zhikun; Du, Jinhong; Zhang, Dingdong; Sun, Hengda; Yin, Lichang; Ma, Laipeng; Chen, Jiangshan; Ma, Dongge; Cheng, Hui-Ming; Ren, Wencai

    2017-01-01

    The large polymer particle residue generated during the transfer process of graphene grown by chemical vapour deposition is a critical issue that limits its use in large-area thin-film devices such as organic light-emitting diodes. The available lighting areas of the graphene-based organic light-emitting diodes reported so far are usually graphene, good solubility and sufficient strength enable ultraclean and damage-free transfer. The transferred graphene has a low surface roughness with an occasional maximum residue height of about 15 nm and a uniform sheet resistance of 560 Ω per square with about 1% deviation over a large area. Such clean, damage-free graphene has produced the four-inch monolithic flexible graphene-based organic light-emitting diode with a high brightness of about 10,000 cd m−2 that can already satisfy the requirements for lighting sources and displays. PMID:28233778

  6. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chiao-Wen Yeh

    2010-03-01

    Full Text Available White light-emitting diodes (WLEDs have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV LEDs and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED or polymer light-emitting diode (PLED, have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm and nUV (380-400 nm LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+ is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

  7. High Stability White Organic Light-Emitting Diode (WOLED Using Nano-Double-Ultra Thin Carrier Trapping Materials

    Directory of Open Access Journals (Sweden)

    Kan-Lin Chen

    2014-01-01

    Full Text Available The structure of indium tin oxide (ITO (100 nm/molybdenum trioxide (MoO3 (15 nm/N,N0-bis-(1-naphthyl-N,N0-biphenyl-1,10-biphenyl-4,40-diamine (NPB (40 nm/4,4′-Bis(2,2-diphenylvinyl-1,1′-biphenyl (DPVBi (10 nm/5,6,11,12-tetraphenylnaphthacene (Rubrene (0.2 nm/DPVBi (24 nm/Rubrene (0.2 nm/DPVBi (6 nm/4,7-diphenyl-1,10-phenanthroline (BPhen: cesium carbonate (Cs2Co3 (10 nm/Al (120 nm with high color purity and stability white organic light-emitting diode (WOLED was fabricated. The function of the multiple-ultra-thin material (MUTM, such as Rubrene, is as the yellow light-emitting layer and trapping layer. The results show that the MUTM has an excellent carrier capture effect, resulting in high color stability of the device at different applied voltages. The Commissions Internationale De L’Eclairage (CIE coordinate of this device at 3~7 V is few displacement and shows a very slight variation of (±0.01, ±0.01. The maximum brightness of 9986 cd/m2 and CIE coordinates of (0.346, 0.339 are obtained at 7 V. The enhanced performance of the device may result from the direct charge trapping in MUTM and it can be found in the electroluminescence (EL process.

  8. SYNTHESIS AND CHARACTERIZATION OF BLUE LIGHT-EMITTING POLY(ARYL ETHER)S CONTAINING PYRIMIDINE-INCORPORATED OLIGOFLUORENE PENDANTS WITH BIPOLAR FEATURE

    Institute of Scientific and Technical Information of China (English)

    Guo-xin Jiang; Chun-lei Bian; Jun-qiao Ding; Li-xiang Wang

    2013-01-01

    Novel blue light-emitting poly(aryl ether)s comprising of bipolar oligofluorene pendants as chromophores have been designed and synthesized,in which pyrimidine and arylamine moieties are utilized as the electron acceptor and electron donor,respectively.Through varying π bridge length from monofluorene to bifluorene and end-cappers from hydrogen to carbazole and diphenylamine,the emission color of the resulting polymers covers from deep blue to greenish blue,and their HOMO and LUMO levels can be modulated to facilitate charge injection to improve the device performance.Polymer lightemitting diodes (PLEDs) are fabricated with the device structure of ITO/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) (50 nm)/polymer (80 nm)/Ca (10 nm)/A1 (200 nm).Among these polymers,P2Cz5F-Py with bifluorene bridge and carbazole end-capper shows excellent trade-off between the efficiency and emission wavelength,having a peak luminous efficiency as high as 1.26 cd/A and Commission Internationale de L'Eclairage (CIE) coordinates of (0.17,0.17).

  9. New Driving Scheme to Improve Hysteresis Characteristics of Organic Thin Film Transistor-Driven Active-Matrix Organic Light Emitting Diode Display

    Science.gov (United States)

    Yamamoto, Toshihiro; Nakajima, Yoshiki; Takei, Tatsuya; Fujisaki, Yoshihide; Fukagawa, Hirohiko; Suzuki, Mitsunori; Motomura, Genichi; Sato, Hiroto; Tokito, Shizuo; Fujikake, Hideo

    2011-02-01

    A new driving scheme for an active-matrix organic light emitting diode (AMOLED) display was developed to prevent the picture quality degradation caused by the hysteresis characteristics of organic thin film transistors (OTFTs). In this driving scheme, the gate electrode voltage of a driving-OTFT is directly controlled through the storage capacitor so that the operating point for the driving-OTFT is on the same hysteresis curve for every pixel after signal data are stored in the storage capacitor. Although the number of OTFTs in each pixel for the AMOLED display is restricted because OTFT size should be large enough to drive organic light emitting diodes (OLEDs) due to their small carrier mobility, it can improve the picture quality for an OTFT-driven flexible OLED display with the basic two transistor-one capacitor circuitry.

  10. Emitting materials based on phenylanthracene-substituted naphthalene derivatives for organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun Woo; Kim, Hye Jeong; Kim, Young Seok; Kim, Jwajin [Department of Chemistry, Sungkyunkwan University, Suwon 440‐746 (Korea, Republic of); Lee, Song Eun; Lee, Ho Won [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@wow.hongik.ac.kr [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Yoon, Seung Soo, E-mail: ssyoon@skku.edu [Department of Chemistry, Sungkyunkwan University, Suwon 440‐746 (Korea, Republic of)

    2015-09-15

    This study reports the emitting materials based on phenylanthracene-substituted naphthalene derivatives to achieve efficient electroluminescent properties for OLED applications. An OLED device using 4,4′-bis(10-phenylanthracen-9-yl)-1,1′-binaphthalene exhibited the blue emission with the CIE coordinates of (0.19, 0.16) and efficient electroluminescent properties with the luminance, power and external quantum efficiency of 1.70 cd/A, 0.79 lm/W and 1.26% at 20 mA/cm{sup 2}, respectively. Also, the other device using 1,4-bis(10-phenylanthracene-9-yl)naphthalene exhibited white emission with the CIE coordinates of (0.34, 0.43) at 7V, respectively. This device exhibits the luminance, power and external quantum efficiency of 2.22 cd/A, 1.13 lm/W and 0.86% at 20 mA/cm{sup 2}, respectively. - Highlights: • We synthesized fluorescent materials based on phenylanthracene derivatives. • Electroluminescence properties of these materials depend on the molecular structures. • These blue and white materials have great potential for application in OLEDs.

  11. Characterization and luminescent properties of zinc–Schiff base complexes for organic white light emitting devices

    Directory of Open Access Journals (Sweden)

    Vandna Nishal

    2015-12-01

    Full Text Available Zinc complexes with Schiff base ligands bis(salicylideneethylene-1,2-diamine (salen, bis(salicylidenepropylene-1,3-diamine (salpen, bis(salicylidenebutylene-1,4-diamine (salbutene, bis(salicylidenehexylene-1,6-diamine (salhexene, bis(salicylideneheptylene-1,7-diamine (salheptene were synthesized and characterized. All these metal complexes exhibited high thermal stability. The photo-physical properties of zinc complexes were investigated by taking their UV–vis absorption and photoluminescent spectra. The complexes of Schiff bases with zinc gave blue luminescence (430–450 nm under excitation of ultraviolet energy source which can be efficiently used for the generation of white light for display applications.

  12. Near-Infrared Light-Emitting Ambipolar Organic Field-Effect Transistors

    NARCIS (Netherlands)

    Smits, E.C.P.; Setayesh, S.; Anthopoulos, T.D.; Buechel, M.; Nijssen, W.; Coehoorn, R.; Blom, P.W.M.; Leeuw, D.M. de

    2006-01-01

    Recent years have seen tremendous advances in the area of organic-based optoelectronic devices and several applications previously envisioned are now reaching the stage of commercial exploitation.[1] Organic field-effect transistors (OFETs) are among these devices and can be arguably viewed as a pos

  13. Hybrid resonant organic-inorganic nanostructures for novel light emitting devices and solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Agranovich, Vladimir M. [Institute of Spectroscopy, Russian Academy of Science, Troitsk, Moscow (Russian Federation); Chemistry Department, University of Texas at Dallas, Texas (United States); Rupasov, Valery I. [ANTEOS, Inc., Shrewsbury, Massachusetts 01545 (United States); Silvestri, Leonardo [Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Milano (Italy)

    2010-06-15

    The energy transfer from an inorganic layer to an organic component of resonant hybrid organic/inorganic nanos-tructures can be used for creation of new type of LED. We mentioned the problem of electrical pumping which has to be solved. As was first suggested in 1979 by Dexter the transfer energy in opposite direction from organic part of nanostructure to semiconductor layer can be used for the creation of new type of solar cells. In this note we stress the importance of the idea by Dexter for photovoltaics and solar cells. We argue that the organic part in such hybrid structures can play a role of an effective organic collector of the light energy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Nanoimprinted organic semiconductor laser pumped by a light-emitting diode.

    Science.gov (United States)

    Tsiminis, Georgios; Wang, Yue; Kanibolotsky, Alexander L; Inigo, Anto R; Skabara, Peter J; Samuel, Ifor D W; Turnbull, Graham A

    2013-05-28

    An organic semiconductor laser, simply fabricated by UV-nanoimprint lithography (UV-NIL), that is pumped with a pulsed InGaN LED is demonstrated. Molecular weight optimization of the polymer gain medium on a nanoimprinted polymer distributed feedback resonator enables the lowest reported UV-NIL laser threshold density of 770 W cm(-2) , establishing the potential for scalable organic laser fabrication compatible with mass-produced LEDs.

  15. Variation of the external quantum efficiency with temperature and current density in red, blue, and deep ultraviolet light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jun Hyuk; Lee, Jong Won; Kim, Dong Yeong; Kim, Jong Kyu, E-mail: kimjk@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Cho, Jaehee, E-mail: jcho@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 54896 (Korea, Republic of); Schubert, E. Fred [Department for Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo [LED Business, Samsung Electronics, Yongin 446-920 (Korea, Republic of)

    2016-01-14

    The temperature-dependent external quantum efficiencies (EQEs) were investigated for a 620 nm AlGaInP red light-emitting diodes (LEDs), a 450 nm GaInN blue LED, and a 285 nm AlGaN deep-ultraviolet (DUV) LED. We observed distinct differences in the variation of the EQE with temperature and current density for the three types of LEDs. Whereas the EQE of the AlGaInP red LED increases as temperature decreases below room temperature, the EQEs of GaInN blue and AlGaN DUV LEDs decrease for the same change in temperature in a low-current density regime. The free carrier concentration, as determined from the dopant ionization energy, shows a strong material-system-specific dependence, leading to different degrees of asymmetry in carrier concentration for the three types of LEDs. We attribute the EQE variation of the red, blue, and DUV LEDs to the different degrees of asymmetry in carrier concentration, which can be exacerbated at cryogenic temperatures. As for the EQE variation with temperature in a high-current density regime, the efficiency droop for the AlGaInP red and GaInN blue LEDs becomes more apparent as temperature decreases, due to the deterioration of the asymmetry in carrier concentration. However, the EQE of the AlGaN DUV LED initially decreases, then reaches an EQE minimum point, and then increases again due to the field-ionization of acceptors by the Poole-Frenkel effect. The results elucidate that carrier transport phenomena allow for the understanding of the droop phenomenon across different material systems, temperatures, and current densities.

  16. Anatomical features of pepper plants (Capsicum annuum L.) grown under red light-emitting diodes supplemented with blue or far-red light

    Science.gov (United States)

    Schuerger, A. C.; Brown, C. S.; Stryjewski, E. C.

    1997-01-01

    Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves and stems. One LED (660) array supplied 90% red light at 660 nm (25nm band-width at half-peak height) and 1% far-red light between 700-800nm. A second LED (660/735) array supplied 83% red light at 660nm and 17% far-red light at 735nm (25nm band-width at half-peak height). A third LED (660/blue) array supplied 98% red light at 660nm, 1% blue light between 350-550nm, and 1% far-red light between 700-800nm. Control plants were grown under broad spectrum metal halide lamps. Plants were gron at a mean photon flux (300-800nm) of 330 micromol m-2 s-1 under a 12 h day-night photoperiod. Significant anatomical changes in stem and leaf morphologies were observed in plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of choloplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660/blue LED array, and lowest in peppers grown under the 660 or 660/735 LED arrays. Most anatomical features of pepper stems and leaves were similar among plants grown under 660 or 660/735 LED arrays. The effects of spectral quality on anatomical changes in stem and leaf tissues of peppers generally correlate to the amount of blue light present in the primary light source.

  17. Variation of the external quantum efficiency with temperature and current density in red, blue, and deep ultraviolet light-emitting diodes

    Science.gov (United States)

    Park, Jun Hyuk; Lee, Jong Won; Kim, Dong Yeong; Cho, Jaehee; Schubert, E. Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

    2016-01-01

    The temperature-dependent external quantum efficiencies (EQEs) were investigated for a 620 nm AlGaInP red light-emitting diodes (LEDs), a 450 nm GaInN blue LED, and a 285 nm AlGaN deep-ultraviolet (DUV) LED. We observed distinct differences in the variation of the EQE with temperature and current density for the three types of LEDs. Whereas the EQE of the AlGaInP red LED increases as temperature decreases below room temperature, the EQEs of GaInN blue and AlGaN DUV LEDs decrease for the same change in temperature in a low-current density regime. The free carrier concentration, as determined from the dopant ionization energy, shows a strong material-system-specific dependence, leading to different degrees of asymmetry in carrier concentration for the three types of LEDs. We attribute the EQE variation of the red, blue, and DUV LEDs to the different degrees of asymmetry in carrier concentration, which can be exacerbated at cryogenic temperatures. As for the EQE variation with temperature in a high-current density regime, the efficiency droop for the AlGaInP red and GaInN blue LEDs becomes more apparent as temperature decreases, due to the deterioration of the asymmetry in carrier concentration. However, the EQE of the AlGaN DUV LED initially decreases, then reaches an EQE minimum point, and then increases again due to the field-ionization of acceptors by the Poole-Frenkel effect. The results elucidate that carrier transport phenomena allow for the understanding of the droop phenomenon across different material systems, temperatures, and current densities.

  18. Electrosynthesis of Chirality Conducting Poly[N-(9-fluorenylmethoxycarbonyl)-L-phenylalanine] with Good Blue Light-Emitting Properties

    Institute of Scientific and Technical Information of China (English)

    来存远; 郭文娟; 唐新德; 裴梅山

    2012-01-01

    Poly[N-(9-fluorenylmethoxycarbonyl)-L-phenylalanine] (PN9FPA) films with good fluorescence properties and chirality were prepared electrochemically by direct anodic oxidation of N-(9-fluorenylmethoxycarbonyl)- L-phenylalanine (N9FPA) in boron trifluoride diethyletherate (BFEE). Fourier transform infrared spectroscopy measurement showed that the polymerization of N9FPA occurred mainly at the C(2) and C(7) positions. The fluo- rescence spectra indicated that PN9FPA films were blue-light emitters. In addition, the structures and properties of the monomer and the polymers were characterized and evaluated with CV, UV, TGA and SEM.

  19. Improvement in Brightness Uniformity by Compensating for the Threshold Voltages of Both the Driving Thin-Film Transistor and the Organic Light-Emitting Diode for Active-Matrix Organic Light-Emitting Diode Displays

    Directory of Open Access Journals (Sweden)

    Ching-Lin Fan

    2014-01-01

    Full Text Available This paper proposes a novel pixel circuit design and driving method for active-matrix organic light-emitting diode (AM-OLED displays that use low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs as driving element. The automatic integrated circuit modeling simulation program with integrated circuit emphasis (AIM-SPICE simulator was used to verify that the proposed pixel circuit, which comprises five transistors and one capacitor, can supply uniform output current. The voltage programming method of the proposed pixel circuit comprises three periods: reset, compensation with data input, and emission periods. The simulated results reflected excellent performance. For instance, when ΔVTH=±0.33 V, the average error rate of the OLED current variation was low (<0.8%, and when ΔVTH_OLED=+0.33 V, the error rate of the OLED current variation was 4.7%. Moreover, when the I×R (current × resistance drop voltage of a power line was 0.3 V, the error rate of the OLED current variation was 5.8%. The simulated results indicated that the proposed pixel circuit exhibits high immunity to the threshold voltage deviation of both the driving poly-Si TFTs and OLEDs, and simultaneously compensates for the I×R drop voltage of a power line.

  20. Multi-color light-emitting transistors composed of organic single crystals

    NARCIS (Netherlands)

    Yomogida, Yohei; Sakai, Hayato; Sawabe, Kosuke; Gocho, Shota; Bisri, Satria Zulkarnaen; Nakanotani, Hajime; Adachi, Chihaya; Hasobe, Taku; Iwasa, Yoshihiro; Takenobu, Taishi

    2013-01-01

    We report a novel concept for multi-color light emission from an ambipolar organic single-crystal transistor using natural optical waveguides, the self-absorption effect, Davydov splitting and the unique alignment of the transition dipole moments. We used 9,10-bis(2,2-diphenylvinyl)-anthracene singl

  1. Highly Efficient Simplified Organic Light-Emitting Diodes Utilizing F4-TCNQ as an Anode Buffer Layer

    Institute of Scientific and Technical Information of China (English)

    DONG Mu-Sen; WU Xiao-Ming; HUA Yu-Lin; QI Qing-Jin; YIN Shou-Gen

    2010-01-01

    @@ We demonstrate that the electroluminescent performances of organic light-emitting diodes(OLEDs)are significantly improved by evaporating a thin F4-TCNQ film as an anode buffer layer on the ITO anode.The optimum Alq3-based OLEDs with F4-TCNQ buffer layer exhibit a lower turn-on voltage of 2.6 V,a higher brightness of39820cd/m2 at 13 V,and a higher current efficiency of 5.96cd/A at 6 V,which are obviously superior to those of the conventional device(turn-on voltage of 4.1 V,brightness of 18230cd/m2 at 13 V,and maximum current efficiency of 2.74 cd/A at 10 V).Furthermore,the buffered devices with F4-TCNQ as the buffer layer could not only increase the efficiency but also simplify the fabrication process compared with the p-doped devices in which F4-TCNQ is doped into/3-NPB as p-HTL(3.11 cd/A at 7 V).The reason why the current efficiency of the p-doped devices is lower than that of the buffered devices is analyzed based on the concept of doping,the measurement of absorption and photoluminescence spectra of the organic materials,and the current density-voltage characteristics of the corresponding hole-only devices.

  2. Electroluminescence in organic single-layer light-emitting diodes at high fields

    Institute of Scientific and Technical Information of China (English)

    杨盛谊; 徐征; 王振家; 侯延冰; 徐叙; 张希清

    2001-01-01

    By considering the interaction between Fowler-Nordheim tunneling injection theory and charge carriers transporting through the bulk, an electroluminescence model for organic single-layer diodes is presented. The expressions of the recombination current density, recombination efficiency and conductivity of the diodes are provided, which elucidate the controlling role of the electric field on mobility and recombination zone. The equilibrium of two opposite charge carriers injection and the central position of recombination zone are two important preconditions for reducing the leakage current. Space-charge-limited current occurs only over a certain high bias, meanwhile, the quantity of injection carriers increases over the transport capacity of the bulk.

  3. Organic Light-Emitting Devices with a LiF Hole Blocking Layer

    Institute of Scientific and Technical Information of China (English)

    LIAN Jia-Rong; YUAN Yong-Bo; ZHOU Xiang

    2007-01-01

    We introduce a thin LiF layer into tris-8-hydroxyquinoline aluminium (Alq3) based bilayer organic light-emittingdevices to block hole transport. By varying the thickness and position of this LiF layer in Alq3, we obtain an electroluminescent efficiency increase by a factor of two with respect to the control devices without a LiF blocking layer. By using a 10nm dye doped Alq3 sensor layer, we prove that LiF can block holes and excitons effectively.Experimental results suggest that the thin LiF layer may be a good hole and exciton blocking layer.

  4. Organic light emitting diodes (OLEDS) and OLED-based structurally integrated optical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yuankun [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    rate due to microheterogeneity. Effect of TiO2 doping was also discussed. Stretched exponential analysis also generates calibration curves with higher sensitivity, which is preferred from the operational point of view. The work of enhanced integration was shown in chapter 7 with a polymer photodetector, which enables the preferred operation mode, decay time measurement, due to fast reponse (<20 μs). Device thickness was enlarged for maximum absorption of the PL, which was realized by slow spincoating rate and shorter spincoating time. Film prepared this way shows more crystalline order by Raman spectra, probably due to slow evaporation. This also ensures charge transport is not affected even with a thick film as indicated in the response time. Combination of OLEDs and polymer photodetectors present opportunities for solution processed all-organic sensors, which enables cheap processing at large scale. Future development can focus on monolithically integration of OLEDs and organic photodetectors (OPD) on the same substrate at a small scale, which could be enabled by inkjet printing. As OLED and OPD technologies continue to advance, small-sized, flexible and all-organic structurally integrated sensor platforms will become true in the near future.

  5. White organic light emitting diodes based on DCM dye sandwiched in 2-methyl-8-hydroxyquinolinolatolithium

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Amit [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Department of Chemistry, M.D. University, Rohtak, Haryana 124001 (India); Srivastava, Ritu, E-mail: ritu@mail.nplindia.ernet.i [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Bawa, Sukhwant S. [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Singh, Devender; Singh, Kapoor [Department of Chemistry, M.D. University, Rohtak, Haryana 124001 (India); Chauhan, Gayatri [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Singh, Ishwar [Department of Chemistry, M.D. University, Rohtak, Haryana 124001 (India); Kamalasanan, Modeeparampil N. [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India)

    2010-08-15

    Stable white electroluminescence (EL) has been achieved from organic LED, in which an ultrathin 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM) dye layer has been inserted in between two 2-methyl-8-hydroxyquinolinolatolithium [LiMeq] emitter layer and by optimizing the position of the DCM dye layer from the {alpha}-NPD/LiMeq interface. Electroluminescence spectra, current-voltage-luminescence (I-V-L) characteristics of the devices have been studied by changing the position of the dye layer. As the distance of DCM layer from {alpha}-NPD/LiMeq interface is increased, the intensity of host emission enhances rapidly. Introduction of thin layer of DCM in emissive layer increases the turn on voltage. The best Commission International de L' Eclairage (CIE) coordinates i.e. (0.32, 0.33) were obtained with device structure ITO/{alpha}-NPD(30 nm) /LiMeq(10 nm)/DCM(1 nm)/LiMeq(25 nm)/BCP(6 nm)/Alq{sub 3}(28 nm)/LiF(1 nm)/Al(100 nm). The EL spectrum covers the whole visible spectra range 400-700 nm. The color rendering index (CRI) for our best white light (Device 4) is 47.4. The device shows very good color stability in terms of CIE coordinates with voltages. The maximum luminescence 1240 cd/m{sup -2} has been achieved at 19 V.

  6. Tandem organic light-emitting diode with a molybdenum tri-oxide thin film interconnector layer

    Institute of Scientific and Technical Information of China (English)

    Lu Fei-Ping; Wang Qian; Zhou Xiang

    2013-01-01

    A 10-nm-thick molybdenum tri-oxide (MoO3) thin film was used as the interconnector layer in tandem organic lightemitting devices (OLEDs).The tandem OLEDs with two identical emissive units consisting of N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB) / tris(8-hydroxyquinoline) aluminum (Alq3) exhibited current efficiency-current density characteristics superior to the conventional single-unit devices.At 20 mA/cm2,the current efficiency of the tandem OLEDs using the interconnector layers of MoO3 thin film was about 4.0 cd/A,which is about twice that of the corresponding conventional single-unit device (1.8 cd/A).The tandem OLED showed a higher power efficiency than the conventional single-unit device for luminance over 1200 cd/m2.The experimental results demonstrated that a MoO3 thin film with a proper thickness can be used as an effective interconnector layer in tandem OLEDs.Such an interconnector layer can be easily fabricated by simple thermal evaporation,greatly simplifying the device processing and fabrication processes required by previously reported interconnector layers.A possible explanation was proposed for the carrier generation of the MoO3 interconnector layer.

  7. The Comparison of the Efficacy of Blue Light-Emitting Diode Light and 980-nm Low-Level Laser Light on Bone Regeneration.

    Science.gov (United States)

    Dereci, Ömür; Sindel, Alper; Serap Toru, Havva; Yüce, Esra; Ay, Sinan; Tozoğlu, Sinan

    2016-11-01

    The aim of this study is to histologically compare effects of blue light-emitting diode (LED) light (400-490 nm) and Ga-Al-As low-level diode laser light (980 nm) on bone regeneration of calvarial critical-sized defects in rats. Thirty Wistar Albino rats were included in the study. The experimental groups were as follows: blue LED light (400-490 nm) group (LED); 980-nm low-level laser light group (LL); and no-treatment, control group (CL). A critical-sized defect of 8 mm was formed on calvaria of rats. Each animal was sacrificed 21 days after defect formation. Calvarias of all rats were dissected and fixated for histological examination. Histomorphometric measurements of total horizontal length of the newly produced bone tissue, total vertical length of the newly produced bone tissue, and diameter of the newly produced longest bone trabecula were performed with a computer program in micrometers. There was a statistically significant increase in the total horizontal length and total vertical length in LL and LED groups compared to that in the CL group (P  0.05). A statistically significant difference was observed in the longest bone trabecula and LL groups compared to that in CL (P  0.05). In conclusion, blue LED light significantly enhances bone regeneration in critical-sized defects when compared with CL group, but does not have a statistically significant effect on bone regeneration when compared with 980-nm low-level laser light.

  8. A solvent/non-solvent system for achieving solution-processed multilayer organic light-emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yue; Wu, Zhaoxin, E-mail: zhaoxinwu@mail.xjtu.edu.cn; He, Lin; Jiao, Bo; Hou, Xun

    2015-08-31

    We developed a solvent/non-solvent system to fabricate the multilayer organic light-emitting devices (OLEDs) based on poly(N-vinylcarbazole) (PVK) by solution-process. This solvent system consists of both the solvent and non-solvent of PVK, in which fluorescent small molecules could be fully dissolved and directly spin-coated on top of the PVK layer; it could effectively avoid the redissolution of PVK during the spin-coating process of small molecules emitting layer. In the further investigation of this system, we also demonstrated the three-component solvent system, and found out that the third component, a less volatile solvent of PVK, was crucial for preparing a smoother interface between PVK and emitting layer. Compared with OLEDs through the vacuum deposition, the devices fabricated by solution-process from the solvent/non-solvent system showed comparable efficiency, which indicate that the solvent/non-solvent system can be used as an alternative process to prepare the polymer and small molecule multilayer devices through all-solution-process. - Highlights: • We fabricate the multilayer OLEDs by solution-process using a novel system. • We develop a solvent/non-solvent system of polymer (PVK) to avoid redissolution. • Small molecules could be fully dissolved and directly spin-coated on PVK layer. • The devices fabricated by the system and vacuum deposition show comparable efficiency.

  9. Low-temperature synthesis of indium tin oxide nanowires as the transparent electrodes for organic light emitting devices.

    Science.gov (United States)

    Kee, Yeh Yee; Tan, Sek Sean; Yong, Thian Khok; Nee, Chen Hon; Yap, Seong Shan; Tou, Teck Yong; Sáfrán, György; Horváth, Zsolt Endre; Moscatello, Jason P; Yap, Yoke Khin

    2012-01-20

    Low-temperature growth of indium tin oxide (ITO) nanowires (NWs) was obtained on catalyst-free amorphous glass substrates at 250 °C by Nd:YAG pulsed-laser deposition. These ITO NWs have branching morphology as grown in Ar ambient. As suggested by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), our ITO NWs have the tendency to grow vertically outward from the substrate surface, with the (400) plane parallel to the longitudinal axis of the nanowires. These NWs are low in electrical resistivity (1.6×10⁻⁴ Ω cm) and high in visible transmittance (~90–96%), and were tested as the electrode for organic light emitting devices (OLEDs). An enhanced current density of ~30 mA cm⁻² was detected at bias voltages of ~19–21 V with uniform and bright emission. We found that the Hall mobility of these NWs is 2.2–2.7 times higher than that of ITO film, which can be explained by the reduction of Coulomb scattering loss. These results suggested that ITO nanowires are promising for applications in optoelectronic devices including OLED, touch screen displays, and photovoltaic solar cells.

  10. Accurate optical simulation of nano-particle based internal scattering layers for light outcoupling from organic light emitting diodes

    Science.gov (United States)

    Egel, Amos; Gomard, Guillaume; Kettlitz, Siegfried W.; Lemmer, Uli

    2017-02-01

    We present a numerical strategy for the accurate simulation of light extraction from organic light emitting diodes (OLEDs) comprising an internal nano-particle based scattering layer. On the one hand, the light emission and propagation through the OLED thin film system (including the scattering layer) is treated by means of rigorous wave optics calculations using the T-matrix formalism. On the other hand, the propagation through the substrate is modeled in a ray optics approach. The results from the wave optics calculations enter in terms of the initial substrate radiation pattern and the bidirectional reflectivity distribution of the OLED stack with scattering layer. In order to correct for the truncation error due to a finite number of particles in the simulations, we extrapolate the results to infinitely extended scattering layers. As an application example, we estimate the optimal particle filling fraction for an internal scattering layer in a realistic OLED geometry. The presented treatment is designed to emerge from electromagnetic theory with as few additional assumptions as possible. It could thus serve as a baseline to validate faster but approximate simulation approaches.

  11. Near infrared organic light-emitting diodes based on acceptor-donor-acceptor (ADA) using novel conjugated isatin Schiff bases

    Energy Technology Data Exchange (ETDEWEB)

    Taghi Sharbati, Mohammad, E-mail: m.t.sharbati@sutech.ac.i [Department of Electrical and Electronics Engineering, Shiraz University of Technology, Shiraz (Iran, Islamic Republic of); Soltani Rad, Mohammad Navid, E-mail: soltani@sutech.ac.i [Department of Chemistry, Shiraz University of Technology, Shiraz 71555-313 (Iran, Islamic Republic of); Behrouz, Somayeh [Department of Chemistry, Shiraz University of Technology, Shiraz 71555-313 (Iran, Islamic Republic of); Gharavi, Alireza [Photonics Lab, Department of Electrical and Computer Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Emami, Farzin [Department of Electrical and Electronics Engineering, Shiraz University of Technology, Shiraz (Iran, Islamic Republic of)

    2011-04-15

    Fabrications of a single layer organic light emitting diodes (OLEDs) based on two conjugated acceptor-donor-acceptor (ADA) isatin Schiff bases are described. The electroluminescent spectra of these materials range from 630 to 700 nm and their band gaps were measured between 1.97 and 1.77 eV. The measured maximum external quantum efficiencies (EQE) for fabricated OLEDs are 0.0515% and 0.054% for two acceptor-donor-acceptor chromophores. The Commission International De L'Eclairage (CIE) (1931) coordinates of these two compounds were attained and found to be (0.4077, 0.4128) and (0.4411, 0.4126) for two used acceptor-donor-acceptor chromophores. The measured I-V curves demonstrated the apparent diode behavior of two ADA chromophores. The turn-on voltages in these OLEDs are directly dependent on the thickness. These results have demonstrated that ADA isatin Schiff bases could be considered as promising electroluminescence-emitting materials for fabrication of OLEDs.

  12. A High-Performance Current-Mode Source Driver IC for Mobile Active Matrix Organic Light Emitting Diode Displays

    Science.gov (United States)

    Jeong, Il-Hun; Kwon, Oh-Kyong

    2008-03-01

    In this paper, we describe two types of 8-bit current-mode driver ICs with a small area and good performance for applications high accuracy current-mode digital-to-analog converters (DACs), and improved channel-to-channel uniformity for active matrix organic light-emitting diode (AMOLED) displays. One uses the proposed current steering DAC (type A), which is an improved architecture of a binary-weighted DAC, and the other uses a DAC that is a combination of a thermometer-decoded of the DAC and a binary-weighted type. The measured results show that the peak integral nonlinearity (INL) is within ±0.5 the least significant bit (LSB), the peak differential nonlinearity (DNL) is within ±0.5 LSB, and the nonuniformity of output current among channels and chips is within ±0.5 LSB. The size of the driver IC is 15,820 ×1,500 µm2 and the total power consumption of the current-mode driver IC is less than 9 mW when the display has full-white pattern with a luminance of 150 cd/m2. The chip area and power consumption with the proposed current DAC are reduced by 26 and 10%, respectively, compared with those of conventional driver ICs with a fully binary-weighted DAC.

  13. Investigation of Pattern-Induced Brightness Non-uniformity in Active-Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Kim, Kyoung-Bo; Park, Hye-Hyang; Kwon, Ohseob; Kim, Moojin; Lee, Ki-Yong; Park, Yongwoo; Choi, JongHyun; Yu, CheolHo; Kim, Hye-Dong; Kim, Sung Chul; Chung, Ho-Kyoon

    2008-01-01

    We recently improved the brightness non-uniformity in active-matrix organic light-emitting diode (AMOLED) regarding non-uniform laser energy distribution by applying a “shot mixing” technique in sequential lateral solidification (SLS) method. Although the new SLS technique was employed, another brightness non-uniformity that appeared as oblique lines on AMOLED panels became a crucial issue. In this work, we attempted to investigate the origins of the non-uniformity. Our systematic analysis on the oblique lines revealed that the line type non-uniformity was attributed to both the SLS process and the thin-film transistor (TFT) fabrication processes. In particular, we found that such oblique patterns might be related to moiré patterns that appear when primary grain boundaries aligned in a repetitive pattern is placed over other repetitive TFT patterns such as metal lines. We adopted a method to diminish the moiré pattern type non-uniformity by applying top emission TFT structure.

  14. Structural Characterization of Sputtered Silicon Thin Films after Rapid Thermal Annealing for Active-Matrix Organic Light Emitting Diode

    Science.gov (United States)

    Mugiraneza, Jean de Dieu; Miyahira, Tomoyuki; Sakamoto, Akinori; Chen, Yi; Okada, Tatsuya; Noguchi, Takashi; Itoh, Taketsugu

    2010-12-01

    The microcrystalline phase obtained by adopting a two-step rapid thermal annealing (RTA) process for rf-sputtered silicon films deposited on thermally durable glass was characterized. The optical properties, surface morphology, and internal stress of the annealed Si films are investigated. As the thermally durable glass substrate allows heating of the deposited films at high temperatures, micro-polycrystalline silicon (micro-poly-Si) films of uniform grain size with a smooth surface and a low internal stress could be obtained after annealing at 750 °C. The thermal stress in the Si films was 100 times lower than that found in the films deposited on conventional glass. Uniform grains with an average grain size of 30 nm were observed by transmission electron microscopy (TEM) in the films annealed at 800 °C. These micro-poly-Si films have potential application for fabrication of uniform and reliable thin film transistors (TFTs) for large scale active-matrix organic light emitting diode (AMOLED) displays.

  15. Structurally Integrated Photoluminescence-Based Lactate Sensor Using Organic Light Emitting Devices (OLEDs) as the Light Source

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Chengliang [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    Multianalyte bio(chemical) sensors are extensively researched for monitoring analytes in complex systems, such as blood serum. As a step towards developing such multianalyte sensors, we studied a novel, structurally integrated, organic light emitting device (OLED)-based sensing platform for detection of lactate. Lactate biosensors have attracted numerous research efforts, due to their wide applications in clinical diagnosis, athletic training and food industry. The OLED-based sensor is based on monitoring the oxidation reaction of lactate, which is catalyzed by the lactate oxidase (LOX) enzyme. The sensing component is based on an oxygen-sensitive dye, Platinum octaethyl porphyrin (PtOEP), whose photoluminescence (PL) lifetime τ decreases as the oxygen level increases. The PtOEP dye was embedded in a thin film polystyrene (PS) matrix; the LOX was dissolved in solution or immobilized in a sol-gel matrix. τ was measured as a function of the lactate concentration; as the lactate concentration increases, τ increases due to increased oxygen consumption. The sensors performance is discussed in terms of the detection sensitivity, dynamic range, and response time. A response time of ~32 sec was achieved when the LOX was dissolved in solution and kept in a closed cell. Steps towards development of a multianalyte sensor array using an array of individually addressable OLED pixels were also presented.

  16. Fabrication of Photonic Crystal Structures on Flexible Organic Light-Emitting Diodes by Using Nano-Imprint and PDMS Mold

    Directory of Open Access Journals (Sweden)

    Ho Ting-Lin

    2016-01-01

    Full Text Available In this paper, nanoimprint lithography was used to create a photonic crystals structure film in organic light-emitting diode (OLED component, and then compare the efficiency of components whether with nanostructure or not. By using two different kinds of mold, such as silicon mold and PDMS mold, the nano structures in PMMA (molecular weight of 350K were fabricated. Nanostructures in period of 403.53nm with silicon mold and nano structures in period of 385.64nm with PDMS mold as photonic crystal films were fabricated and were integrated into OLED. In experimental results, the OLED without photonic crystal films (with packing behaves 193.3cd/m2 for luminous intensity, 3.481cd/A for lightening efficiency (ηL and 0.781 lm/W for lightening power (ηP where V is 14V and I is 5.5537mA; the OLED with photonic crystal films (with packing behaves 241.6cd/m2 for luminous intensity, 4.173cd/A for lightening efficiency (ηL and 0.936 lm/W for lightening power (ηP where voltage of 14V and current (I of 5.7891mA, which shows that the latter perform is well.

  17. Improved Efficiency of Flexible Organic Light-Emitting Diodes by Insertion of Ultrathin SiO2 Buffer Layers

    Directory of Open Access Journals (Sweden)

    Chien-Jung Huang

    2013-01-01

    Full Text Available An ultrathin hole-injection buffer layer (HBL using silicon dioxide (SiO2 by electron beam evaporation in flexible organic light-emitting diode (FOLED has been fabricated. While the current of the device at constant driving voltage decreases as increasing SiO2 thickness. Compared to the different thicknesses of the buffer layer, the FOLED with the buffer layer of 4 nm showed the highest luminous efficiency. The atomic force microscopy (AFM investigation of indium tin oxide (ITO/SiO2 topography reveals changes at the interface between SiO2 and N,N′-bis-(1-naphthl-diphenyl-1,1′-bipheny-4,4′-diamine (NPB, resulting in ultrathin SiO2 layers being a clear advantage for a FOLED. However, the SiO2 can be expected to be a good buffer layer material and thus enhance the emission performance of the FOLED.

  18. A Light Scattering Layer for Internal Light Extraction of Organic Light-Emitting Diodes Based on Silver Nanowires.

    Science.gov (United States)

    Lee, Keunsoo; Shin, Jin-Wook; Park, Jun-Hwan; Lee, Jonghee; Joo, Chul Woong; Lee, Jeong-Ik; Cho, Doo-Hee; Lim, Jong Tae; Oh, Min-Cheol; Ju, Byeong-Kwon; Moon, Jaehyun

    2016-07-13

    We propose and fabricate a random light scattering layer for light extraction in organic light-emitting diodes (OLEDs) with silver nanodots, which were obtained by melting silver nanowires. The OLED with the light scattering layer as an internal light extraction structure was enhanced by 49.1% for the integrated external quantum efficiency (EQE). When a wrinkle structure is simultaneously used for an external light extraction structure, the total enhancement of the integrated EQE was 65.3%. The EQE is maximized to 65.3% at a current level of 2.0 mA/cm(2). By applying an internal light scattering layer and wrinkle structure to an OLED, the variance in the emission spectra was negligible over a broad viewing angle. Power mode analyses with finite difference time domain (FDTD) simulations revealed that the use of a scattering layer effectively reduced the waveguiding mode while introducing non-negligible absorption. Our method offers an effective yet simple approach to achieve both efficiency enhancement and spectral stability for a wide range of OLED applications.

  19. Multiscale Micro-Nano Nested Structures: Engineered Surface Morphology for Efficient Light Escaping in Organic Light-Emitting Diodes.

    Science.gov (United States)

    Zhou, Lei; Dong, Xiaoxuan; Zhou, Yun; Su, Wenming; Chen, Xiaolian; Zhu, Yufu; Shen, Su

    2015-12-01

    Various micro-to-nanometer scale structures are extremely attractive for light escaping in organic light-emitting diodes. To develop and optimize such structures, an innovative approach was demonstrated for the first time to fabricate multiscale micro-nano nested structures by photolithography with a well-designed mask pattern followed by a controllable thermal reflow process. The experimental and theoretical characterizations verify that these unique nested structures hold the capability of light concentration, noticeable low haze, and efficient antireflection. As a proof-of-concept, the incorporation of this pattern onto the glass substrate efficiently facilitates light escaping from the device, resulting in current efficiency 1.60 times and external quantum efficiency 1.63 times that of a control flat device, respectively. Moreover, compared to a hexagonally arranged microlens array and quasi-random biomimetic moth eye nanostructures, the nested structures proposed here can magically tune the spatial emission profile to comply with the Lambertian radiation pattern. Hence, this novel structure is expected to be of great potential in related ubiquitous optoelectronic applications and provide scientific inspiration to other novel multiscale micro-nanostructure research.

  20. Phosphorescence lifetimes of organic light-emitting diodes from two-component time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Kühn, Michael [Institut für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstraße 12, 76131 Karlsruhe (Germany); Weigend, Florian, E-mail: florian.weigend@kit.edu [Institut für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstraße 12, 76131 Karlsruhe (Germany); Institut für Nanotechnologie, Karlsruher Institut für Technologie, Postfach 3640, 76021 Karlsruhe (Germany)

    2014-12-14

    “Spin-forbidden” transitions are calculated for an eight-membered set of iridium-containing candidate molecules for organic light-emitting diodes (OLEDs) using two-component time-dependent density functional theory. Phosphorescence lifetimes (obtained from averaging over relevant excitations) are compared to experimental data. Assessment of parameters like non-distorted and distorted geometric structures, density functionals, relativistic Hamiltonians, and basis sets was done by a thorough study for Ir(ppy){sub 3} focussing not only on averaged phosphorescence lifetimes, but also on the agreement of the triplet substate structure with experimental data. The most favorable methods were applied to an eight-membered test set of OLED candidate molecules; Boltzmann-averaged phosphorescence lifetimes were investigated concerning the convergence with the number of excited states and the changes when including solvent effects. Finally, a simple model for sorting out molecules with long averaged phosphorescence lifetimes is developed by visual inspection of computationally easily achievable one-component frontier orbitals.

  1. The effect of the hole injection layer on the performance of single layer organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wenjin, Zeng; Ran, Bi; Hongmei, Zhang, E-mail: iamhmzhang@njupt.edu.cn, E-mail: iamwhuang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays (KLOEID), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China); Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China); Wei, Huang, E-mail: iamhmzhang@njupt.edu.cn, E-mail: iamwhuang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays (KLOEID), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China)

    2014-12-14

    Efficient single-layer organic light-emitting diodes (OLEDs) were reported based on a green fluorescent dye 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7–tetramethyl-1H,5H,11H-(1) benzopyropyrano (6,7-8-I,j)quinolizin-11-one (C545T). Herein, poly(3,4-ethylenedioxy thiophene) poly(styrene sulfonate) were, respectively, applied as the injection layer for comparison. The hole transport properties of the emission layer with different hole injection materials are well investigated via current-voltage measurement. It was clearly found that the hole injection layers (HILs) play an important role in the adjustment of the electron/hole injection to attain transport balance of charge carriers in the single emission layer of OLEDs with electron-transporting host. The layer of tris-(8-hydroxyquinoline) aluminum played a dual role of host and electron-transporting materials within the emission layer. Therefore, appropriate selection of hole injection layer is a key factor to achieve high efficiency OLEDs with single emission layer.

  2. Image quality affected by diffraction of aperture structure arrangement in transparent active-matrix organic light-emitting diode displays.

    Science.gov (United States)

    Tsai, Yu-Hsiang; Huang, Mao-Hsiu; Jeng, Wei-de; Huang, Ting-Wei; Lo, Kuo-Lung; Ou-Yang, Mang

    2015-10-01

    Transparent display is one of the main technologies in next-generation displays, especially for augmented reality applications. An aperture structure is attached on each display pixel to partition them into transparent and black regions. However, diffraction blurs caused by the aperture structure typically degrade the transparent image when the light from a background object passes through finite aperture window. In this paper, the diffraction effect of an active-matrix organic light-emitting diode display (AMOLED) is studied. Several aperture structures have been proposed and implemented. Based on theoretical analysis and simulation, the appropriate aperture structure will effectively reduce the blur. The analysis data are also consistent with the experimental results. Compared with the various transparent aperture structure on AMOLED, diffraction width (zero energy position of diffraction pattern) of the optimize aperture structure can be reduced 63% and 31% in the x and y directions in CASE 3. Associated with a lenticular lens on the aperture structure, the improvement could reach to 77% and 54% of diffraction width in the x and y directions. Modulation transfer function and practical images are provided to evaluate the improvement of image blurs.

  3. Magnetic field enhanced electroluminescence in organic light emitting diodes based on electron donor-acceptor exciplex blends

    Science.gov (United States)

    Baniya, Sangita; Basel, Tek; Sun, Dali; McLaughlin, Ryan; Vardeny, Zeev Valy

    2016-03-01

    A useful process for light harvesting from injected electron-hole pairs in organic light emitting diodes (OLED) is the transfer from triplet excitons (T) to singlet excitons (S) via reverse intersystem crossing (RISC). This process adds a delayed electro-luminescence (EL) emission component that is known as thermally activated delayed fluorescence (TADF). We have studied electron donor (D)/acceptor(A) blends that form an exciplex manifold in which the energy difference, ΔEST between the lowest singlet (S1) and triplet (T1) levels is relatively small (field of 50 mT at ambient. Moreover the MEL response is activated with activation energy similar that of the EL emission. This suggests that the large magneto-EL originates from an additional spin-mixing channel between singlet and triplet states of the generated exciplexes, which is due to TADF. We will report on the MEL dependencies on the temperature, bias voltage, and D-A materials for optimum OLED performance. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

  4. Improving Light Extraction of Organic Light-Emitting Devices by Attaching Nanostructures with Self-Assembled Photonic Crystal Patterns

    Directory of Open Access Journals (Sweden)

    Kai-Yu Peng

    2014-01-01

    Full Text Available A single-monolayered hexagonal self-assembled photonic crystal (PC pattern fabricated onto polyethylene terephthalate (PET films by using simple nanosphere lithography (NSL method has been demonstrated in this research work. The patterned nanostructures acted as a scattering medium to extract the trapped photons from substrate mode of optical-electronic device for improving the overall external quantum efficiency of the organic light-emitting diodes (OLEDs. With an optimum latex concentration, the distribution of self-assembled polystyrene (PS nanosphere patterns on PET films can be easily controlled by adjusting the rotation speed of spin-coater. After attaching the PS nanosphere array brightness enhancement film (BEF sheet as a photonic crystal pattern onto the device, the luminous intensity of OLEDs in the normal viewing direction is 161% higher than the one without any BEF attachment. The electroluminescent (EL spectrum of OLEDs with PS patterned BEF attachment also showed minor color offset and superior color stabilization characteristics, and thus it possessed the potential applications in all kinds of display technology and solid-state optical-electronic devices.

  5. Improved hole-injection and power efficiency of organic light-emitting diodes using an ultrathin cerium fluoride buffer layer

    Science.gov (United States)

    Lu, Hsin-Wei; Kao, Po-Ching; Chu, Sheng-Yuan

    2016-09-01

    In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF3 film as an ultra-thin buffer layer between the ITO and NPB hole transport layer, with the structure configuration ITO/CeF3 (1 nm)/NPB (40 nm)/Alq3 (60 nm)/LiF (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The work function increased from 4.8 eV (standard ITO electrode) to 5.2 eV (1-nm-thick UV-ozone treated CeF3 film deposited on the ITO electrode). The turn-on voltage decreased from 4.2 V to 4.0 V at 1 mA/cm2, the luminance increased from 7588 cd/m2 to 10820 cd/m2, and the current efficiency increased from 3.2 cd/A to 3.5 cd/A when the 1-nm-thick UV-ozone treated CeF3 film was inserted into the OLEDs.

  6. Silver Nanowire-IZO-Conducting Polymer Hybrids for Flexible and Transparent Conductive Electrodes for Organic Light-Emitting Diodes

    Science.gov (United States)

    Yun, Ho Jun; Kim, Se Jung; Hwang, Ju Hyun; Shim, Yong Sub; Jung, Sun-Gyu; Park, Young Wook; Ju, Byeong-Kwon

    2016-01-01

    Solution-processed silver nanowire (AgNW) has been considered as a promising material for next-generation flexible transparent conductive electrodes. However, despite the advantages of AgNWs, some of their intrinsic drawbacks, such as large surface roughness and poor interconnection between wires, limit their practical application in organic light-emitting diodes (OLEDs). Herein, we report a high-performance AgNW-based hybrid electrode composed of indium-doped zinc oxide (IZO) and poly (3,4-ethylenediowythiophene):poly(styrenesulfonate) [PEDOT:PSS]. The IZO layer protects the underlying AgNWs from oxidation and corrosion and tightly fuses the wires together and to the substrate. The PEDOT:PSS effectively reduces surface roughness and increases the hybrid films’ transmittance. The fabricated electrodes exhibited a low sheet resistance of 5.9 Ωsq−1 with high transmittance of 86% at 550 nm. The optical, electrical, and mechanical properties of the AgNW-based hybrid films were investigated in detail to determine the structure-property relations, and whether optical or electrical properties could be controlled with variation in each layer’s thickness to satisfy different requirements for different applications. Flexible OLEDs (f-OLEDs) were successfully fabricated on the hybrid electrodes to prove their applicability; their performance was even better than those on commercial indium doped tin oxide (ITO) electrodes. PMID:27703182

  7. Effect of transparent film desiccant on the lifetime of top-emitting active matrix organic light emitting diodes

    Science.gov (United States)

    Lee, Byoung Duk; Cho, Yoon-Hyung; Kim, Won-Jong; Oh, Min Ho; Lee, Jong Hyuk; Zang, Dong Sik

    2007-03-01

    The effects of a transparent film desiccant on the lifetime of top-emitting active matrix organic light emitting diodes (AMOLEDs) were investigated. The transparent film desiccants were prepared by mixing solutions dispersed with calcium oxide powders and ultraviolet-curable resins. As the solid content in the solutions increased from 15to30wt%, the average particle size increased from 107to240nm, whereas the transmittance of the films decreased from 98% to 80% in the visible range. The devices encapsulated with the transparent film desiccants which contained 20wt% CaO exhibited no dark spots and 97% of the initial luminance, even after being stored for over 500h at 70°C and 90% relative humidity. Also, the operational lifetime of these devices was 1850h, ten times longer than that of a device without desiccant. These results confirmed that the transparent film desiccants, which absorbed the moisture that penetrated into the devices, could be applied to the encapsulation of top-emitting AMOLEDs.

  8. Improving efficiency of organic light-emitting devices by optimizing the LiF interlayer in the hole transport layer

    Institute of Scientific and Technical Information of China (English)

    Jiauo Zhi-Qiang; Wu Xiao-Ming; Hua Yu-Lin; Dong Mu-Sen; Su Yue-Ju; Shen Li-Ying; Yin Shou-Gen

    2011-01-01

    The efficiency of organic light-emitting devices (OLEDs) based on N,N'-bis(1-naphthyl)-N,N'-diphenyl-N,l' biphenyl-4,4'-diamine (NPB) (the hole transport layer) and tris(8-hydroxyquinoline) aluminum (Alq3) (both emission and electron transport layers) is improved remarkably by inserting a LiF interlayer into the hole transport layer.This thin LiF interlayer can effectively influence electrical performance and significantly improve the current efficiency of the device.A device with an optimum LiF layer thickness at the optimum position in NPB exhibits a maximum current efficiency of 5.96 cd/A at 215.79 mA/cm2,which is about 86% higher than that of an ordinary device (without a LiF interlayer,3.2 cd/A).An explanation can be put forward that LiF in the NPB layer can block holes and balance the recombination of holes and electrons.The results may provide some valuable references for improving OLED current efficiency.

  9. Energy level alignment at the interface of NPB/HAT-CN/graphene for flexible organic light-emitting diodes

    Science.gov (United States)

    Oh, Eonseok; Park, Soohyung; Jeong, Junkyeong; Kang, Seong Jun; Lee, Hyunbok; Yi, Yeonjin

    2017-01-01

    Graphene is highly promising as an electrode for flexible optoelectronic devices due to its excellent conductivity and transparency. However, it is necessary to tailor its work function with a charge injection layer in order to obtain favorable energy level alignment for efficient charge injection. An adequate charge injection layer can only be chosen with the understanding of the interfacial electronic structure between a charge transport layer and an electrode. In this study, we investigated the energy level alignment of N,N‧-diphenyl-1,1‧-biphenyl-4,4‧-diamine (NPB)/hexaazatriphenylene hexacarbonitrile (HAT-CN)/graphene using in situ ultraviolet and X-ray photoelectron spectroscopy measurements. The effective work function of graphene was significantly increased by 0.94 eV by the HAT-CN hole injection layer (HIL) due to the interface dipole formation. In addition, the charge generation barrier (CGB) between NPB and HAT-CN, which plays a decisive role in charge injection efficiency with a charge generation HIL, was measured to be 0.66 eV. This CGB on graphene is the same as the CGBs on other electrodes, and smaller than that of the widely-used MoO3 HIL. Therefore, HAT-CN could be a promising HIL for efficient flexible organic light-emitting diodes with a graphene anode.

  10. "Quasi-freestanding" graphene-on-single walled carbon nanotube electrode for applications in organic light-emitting diode.

    Science.gov (United States)

    Liu, Yanpeng; Jung, Eun; Wang, Yu; Zheng, Yi; Park, Eun Ji; Cho, Sung Min; Loh, Kian Ping

    2014-03-12

    An air-stable transparent conductive film with "quasi-freestanding" graphene supported on horizontal single walled carbon nanotubes (SWCNTs) arrays is fabricated. The sheet resistance of graphene films stacked via layer-by-layer transfer (LBL) on quartz, and modified by 1-Pyrenebutyric acid N-hydroxysuccinimide ester (PBASE), is reduced from 273 Ω/sq to about 76 Ω/sq. The electrical properties are stable to heat treatment (up to 200 ºC) and ambient exposure. Organic light-emitting diodes (OLEDs) constructed of this carbon anode (T ≈ 89.13% at 550 nm) exhibit ≈88% power efficiency of OLEDs fabricated on an ITO anode (low turn on voltage ≈3.1 eV, high luminance up to ≈29 490 cd/m(2) , current efficiency ≈14.7 cd/A). Most importantly, the entire graphene-on-SWCNT hybrid electrodes can be transferred onto plastic (PET) forming a highly-flexible OLED device, which continues to function without degradation in performance at bending angles >60°.

  11. Red phosphorescent organic light-emitting diodes (PhOLEDs) based on a heteroleptic cyclometalated Iridium (III) complex

    Energy Technology Data Exchange (ETDEWEB)

    Lepeltier, Marc [Institut Lavoisier de Versailles, UMR 8180 CNRS, Université de Versailles Saint-Quentin en Yvelines, 45 avenue des Etats-Unis, 78035 Versailles Cedex (France); Dumur, Frédéric, E-mail: frederic.dumur@univ-amu.fr [Aix-Marseille Université, CNRS, ICR, UMR 7273, F-13397 Marseille (France); Wantz, Guillaume, E-mail: guillaume.wantz@ims-bordeaux.fr [University of Bordeaux, IMS, UMR 5218, F-33400 Talence (France); CNRS, IMS, UMR 5218, F-33400 Talence (France); Vila, Neus; Mbomekallé, Israel [Institut Lavoisier de Versailles, UMR 8180 CNRS, Université de Versailles Saint-Quentin en Yvelines, 45 avenue des Etats-Unis, 78035 Versailles Cedex (France); Bertin, Denis; Gigmes, Didier [Aix-Marseille Université, CNRS, ICR, UMR 7273, F-13397 Marseille (France); Mayer, Cédric R., E-mail: cmayer@lisv.uvsq.fr [Laboratoire d’Ingénierie des Systèmes de Versailles LISV – EA 4048, Université de Versailles Saint Quentin en Yvelines, 10/12 avenue de l’Europe, 78140 Vélizy (France)

    2013-11-15

    Highly efficient red-emitting Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) based on a neutral vacuum-sublimatable heteroleptic iridium (III) complex have been designed and studied. Heteroleptic complex Ir(piq){sub 2}(acac) was prepared in one step with acetylacetone (acac) as the ancillary ligand. Electronic and spectroscopic properties of Ir(piq){sub 2}(acac) were investigated by UV–visible absorption, fluorescence spectroscopy and cyclic voltammetry. Electrophosphorescent devices comprising Ir(piq){sub 2}(acac) as dopant of TCTA exhibited outstanding electroluminescence performance with a current efficiency of 10.0 cd A{sup −1}, a maximum power efficiency of 7.2 lm W{sup −1} and a maximal brightness of 3540 cd m{sup −2} was reached at 8.0 V. CIE coordinates close to the standard red of the national television system committee were obtained (0.67, 0.33). -- Highlights: • A saturated red OLED has been prepared. • High power efficiency and brightness were obtained. • Thickness of the device was determined as a parameter determining the overall performance. • CIE coordinates close to the standard red of the national television system committee were obtained.

  12. Full phosphorescent white-light organic light-emitting diodes with improved color stability and efficiency by fine tuning primary emission contributions

    Directory of Open Access Journals (Sweden)

    Wang Hua

    2014-02-01

    Full Text Available In this paper, a novel type of white-light organic light emitting diode (OLED with high color stability was reported, in which the yellow-light emission layer of (4,4′-N,N′-dicarbazolebiphenyl (CBP : tris(2-phenylquinoline-C2,N′iridium(III (Ir(2-phq3 was sandwiched by double blue-light emission layers of 1,1-bis-[(di-4-tolylaminopheny1]cyclohexane (TAPC : bis[4,6-(di-fluorophenyl-pyridinato-N,C2′]picolinate (FIrpic and tris[3-(3-pyridylmesityl]borane (3TPYMB:FIrpic. And, it exhibited the maximum current efficiency of 33.1 cd/A, the turn-on voltage at about 3 V and the maximum luminance in excess of 20000 cd/m2. More important, it realized very stable white-light emission, and its CIE(x, y coordinates only shift from (0.34, 0.37 to (0.33, 0.37 as applied voltage increased from 5 V to 12 V. It is believed that the new scheme in emission layer of white-light OLED can fine tune the contribution of primary emission with applied voltage changed, resulting in high quality white-light OLED.

  13. BLUE LIGHT-EMITTING COIL-ROD-COIL BLOCK OLIGOMERS WITH RIGID p-HEXAPHENYL AS CHROMOPHORE

    Institute of Scientific and Technical Information of China (English)

    Jiang-feng Fan; Hai-feng He; Xin-hua Wan; Xiao-fang Chen; Qi-feng Zhou

    2006-01-01

    The synthesis and characterization of coil-rod-coil triblock oligomers, poly(ethylene oxide)-b-p-hexaphenyl-b-poly(ethylene oxide), are described. The number of repeating ethylene oxide units in each flexible block are 3 (EO3-PHP-EO3), 8 (EO8-PHP-EO8), 13 (EO13-PHP-EO13), and 17 (EO17-PHP-EO17), respectively. The structures of these oligomers are confirmed by 1H-NMR, 13C-NMR, EA, and MALDI-TOF mass spectrometry. The introduction of soluble poly(ethylene oxide) coils to the rigid p-hexaphenyl segment significantly improves the solubility of the oligomers, so they can form smooth thin films by spin-coating from their solutions. The oligomers are quite thermally stable and have 1% weight loss temperatures at above 340℃ under nitrogen. They can emit strong blue light in both solution and film state, and have fluorescence quantum yields of about 40% in chloroform. They are expected to have potential applications in optoelectronic devices.

  14. Organic light emitting devices with doped electron transport and hole blocking layers

    Energy Technology Data Exchange (ETDEWEB)

    Tardy, J. [Laboratoire d' Electronique, Optoelectronique et Microsystemes (LEOM, UMR CNRS no 5512) Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69134 Ecully Cedex (France)]. E-mail: jacques.tardy@ec-lyon.fr; Khalifa, M. Ben [Laboratoire d' Electronique, Optoelectronique et Microsystemes (LEOM, UMR CNRS no 5512) Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69134 Ecully Cedex (France); Vaufrey, D. [Laboratoire d' Electronique, Optoelectronique et Microsystemes (LEOM, UMR CNRS no 5512) Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69134 Ecully Cedex (France)

    2006-03-15

    This study reports on heterostructure OLEDs with n-type molecularly doped electron transport layer and hole blocking layer. The influence of doping on the operating voltage and on light emission performances was investigated. The n-type doping molecule is 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) dispersed into either an 8-(hydroquinoline) aluminum (Alq) electron transport layer (ETL) or a 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocuproine BCP) hole blocking layer (HBL). The typical device structure is glass substrate/indium tin oxide/PEDOT/TPD-F4-TCNQ/Alq-DCM/BCP/Alq/Mg-Ag where Poly(3,4)ethylenedioxythiophene/Polystyrenesulphonate (PEDOT/PSS) is a hole injecting layer, TPD-F4-TCNQ is a hole transport layer (HTL) made of N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) doped with 2 wt.% of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) and Alq-DCM is the emitting layer (EML) made of Alq doped with 2 wt.% of 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) orange dye. The modified cathode consists in a combination of a BCP HBL and an Alq ETL where BCP or/and Alq were doped with PBD. Lowest operating voltage (3 V for a luminance of 10 Cd/m{sup 2}) and brightest devices (6000 Cd/m{sup 2}) were obtained with a hole blocking bilayer made of BCP doped with 28 wt.% deposited onto an undoped BCP (each one being 5 nm thick). Adding an undoped Alq layer improved the device current efficiency (4 Cd/A) but is detrimental to the operating voltage (6 V for a luminance of 10 Cd/m{sup 2}). In the absence of real n-type doping with organic molecules, our results point out that the design of molecular doped injection layer at the cathode will need for a compromise between high luminance and efficiency on one hand and low operating voltage on the other hand.

  15. Comparison of the efficiency of titanium(IV) and iron(III) oxide nanoparticles as mediators in suppression of bacterial growth by radiation of a blue (405 nm) light-emitting diode

    Science.gov (United States)

    Petrov, P. O.; Tuchina, E. S.; Kulikova, M. V.; Kochubei, V. I.; Tuchin, V. V.

    2013-08-01

    The effect of blue (405 nm) radiation of a light-emitting diode in combination with titanium(IV) and iron(III) oxide nanoparticles on S. aureus 209 P, S. simulans, and D. hominis bacteria is studied. It is shown that, upon irradiation of bacteria by blue (405 nm) light, Fe2O3 nanoparticles have a stronger (by 5-30%) antibacterial effect than TiO2 nanoparticles.

  16. Use of a New Blue Emitter in Color-Stable, Flexible, Polymeric White Light-Emitting Diodes with a Simple Structure

    Science.gov (United States)

    Mohsennia, Mohsen; Bidgoli, Maryam Massah; Boroumand, Farhad Akbari; Khademi, Alireza

    2015-08-01

    New, polymeric white light-emitting diodes with the structure ITO/PEDOT:PSS/BFE + MEH-PPV/Al have been fabricated, in which poly(9,9-dioctylfluorene-co- N, N'-di(phenyl)- N, N'-di(3-carboethoxyphenyl) benzidine (BFE) was used as the blue emitter host and poly [2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene (MEH-PPV) as the red emitter guest. A poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) layer was spin-coated as the hole-injection layer (HIL) on a flexible poly(ethylene terephthalate)/indium tin oxide (PET/ITO) substrate; the cathode was aluminium (Al). The entire simple, low-cost fabrication process was performed without any need for a glove box. The effect of PEDOT:PSS films prepared from the PEDOT:PSS/water solution with two different volume ratios (1:3 and 1:6) as the HIL on the lifetime and output performance of devices was investigated. The device fabricated by using the volume ratio 1:3 emitted white light with high color quality and Commission Internationale de l'Eclairage (CIE) coordinates of (0.34, 0.38), and had a long operating lifetime.

  17. Effects of the electrode metal structure and the current blocking layer on the characteristics of blue GaN-based light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hee S. [Chonnam National University, Gwangju (Korea, Republic of); LG Innotek Co., Ltd., Paju (Korea, Republic of); Tawfik, Wael Z. [Chonnam National University, Gwangju (Korea, Republic of); Beni-Suef University, Beni-Suef (Egypt); Lee, June K. [Chonnam National University, Gwangju (Korea, Republic of)

    2014-03-15

    The influence of the electrode metal structure and the current blocking layer on the characteristics of blue GaN-based light-emitting diodes (LEDs) was investigated. The changes in the electrode metal structure, along with the current blocking layer (CBL) were found to enable control of the optical and the electrical properties of the fabricated LEDs. Thus, the light output power at an injection current of 90 mA was increased by about 8.5% for the LED with a Cr/Al/Ni/Au electrode metal and a SiO{sub 2} CBL and by about 9.0% for the LED with a Ti/Al/Ni/Au electrode metal and without a SiO{sub 2} CBL over the reference LED with only Cr/Ni/Au electrode metal. This was due to the reduction of the current-crowding effect and to the absorption of photons near the P/N pad by the metal electrode. Furthermore, the operating voltage under the same injection current of 90 mA was changed from 3.30 V for the reference LED to 3.37 V and 3.28 V for the LED with a SiO{sub 2} CBL and for the LED with Ti/Al/Ni/Au electrode metal, respectively. The results confirmed that the electrode metal structure and the CBL played critical roles in the improvement of the emission characteristics in GaN-based LEDs.

  18. Nitrogen-doped TiO2 modified with NH4F for efficient photocatalytic degradation of formaldehyde under blue light-emitting diodes.

    Science.gov (United States)

    Li, Yuexiang; Jiang, Yuan; Peng, Shaoqin; Jiang, Fengyi

    2010-10-15

    A nitrogen-doped TiO(2) (N-TiO(2)) photocatalyst was prepared by calcination of the hydrolysis precipitate of Ti(SO(4))(2) with aqueous ammonia. The prepared N-TiO(2) was treated with NH(4)F (F-N-TiO(2)) by an impregnation-calcination method. The photocatalyst (F-N-TiO(2)) was characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), UV-vis diffusive reflectance spectroscopy (DRS), BET and X-ray photoelectron spectroscopy (XPS). With blue light-emitting diode (LED) as the light source, its photocatalytic activity for the degradation of formaldehyde was investigated. NH(4)F treatment enhances markedly photocatalytic activity of N-TiO(2). The treatment increases the visible absorption of N-TiO(2), decreases its specific surface area and influences the concentration of oxygen vacancies in N-TiO(2). Photocatalytic activity of F-N-TiO(2) depends on the visible absorption, the specific surface area, and the concentration of oxygen vacancies. The preparation conditions, such as the calcination temperature and the initial molar ratio of NH(4)F to N-TiO(2), have a significant influence on the photocatalytic activity. The doping mechanism of NH(4)F was investigated.

  19. Effect of external tensile stress on blue InGaN/GaN multi-quantum-well light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Tawfik, Wael Z. [Interdisciplinary Program of Photonic Engineering, Chonnam National University, Yongbong 300, Gwangju 500-757 (Korea, Republic of); Department of Physics, Faculty of Science, Beni-Suef University, Beni-Suef 62511 (Egypt); Song, Juhui; Lee, Jung Ju; Ha, Jun Seok; Ryu, Sang-Wan [Interdisciplinary Program of Photonic Engineering, Chonnam National University, Yongbong 300, Gwangju 500-757 (Korea, Republic of); Choi, Hee Seok [Interdisciplinary Program of Photonic Engineering, Chonnam National University, Yongbong 300, Gwangju 500-757 (Korea, Republic of); LG Innotek Co., Ltd., 413-901 Paju (Korea, Republic of); Ryu, Bengso [Interdisciplinary Program of Photonic Engineering, Chonnam National University, Yongbong 300, Gwangju 500-757 (Korea, Republic of); Lee, June Key, E-mail: junekey@chonnam.ac.kr [Interdisciplinary Program of Photonic Engineering, Chonnam National University, Yongbong 300, Gwangju 500-757 (Korea, Republic of)

    2013-10-15

    The influence of external tensile stress on blue InGaN/GaN multi-quantum-well (MQW) light-emitting diodes (LEDs) is demonstrated. It was found that applying external tensile stress effectively compensates for the compressive strain developed in the InGaN active layer, thus reducing the quantum-confined Stark effect by attenuating the piezoelectric polarization from the InGaN layer. With 35 A/cm{sup 2} of current density (∼50 mA), the light output power could be improved by ∼40% when the LEDs were subjected to an external tensile stress. The blueshift in electroluminescence (EL) spectra was reduced by applying the external tensile stress. In contrast, when the LEDs were exposed to external compressive stress, the light output power intensity was decreased by ∼12% at a current density of 35 A/cm{sup 2}. The simulation results confirm that the relaxation of compressive strain in the InGaN/GaN MQW structure results in the reduction of the piezoelectric field and improves the overlap of electron and hole wave functions.

  20. The Histopathological Investigation of Red and Blue Light Emitting Diode on Treating Skin Wounds in Japanese Big-Ear White Rabbit.

    Directory of Open Access Journals (Sweden)

    Yanhong Li

    Full Text Available The biological effects of different wavelengths of light emitting diode (LED light tend to vary from each other. Research into use of photobiomodulation for treatment of skin wounds and the underlying mechanisms has been largely lacking. We explored the histopathological basis of the therapeutic effect of photobiomodulation and the relation between duration of exposure and photobiomodulation effect of different wavelengths of LED in a Japanese big-ear white rabbit skin-wound model. Skin wound model was established in 16 rabbits (three wounds per rabbit: one served as control, the other two wounds were irradiated by red and blue LED lights, respectively. Rabbits were then divided into 2 equal groups based on the duration of exposure to LED lights (15 and 30 min/exposure. The number of wounds that showed healing and the percentage of healed wound area were recorded. Histopathological examination and skin expression levels of fibroblast growth factor (FGF, epidermal growth factor (EGF, endothelial marker (CD31, proliferating cell nuclear antigen (Ki67 and macrophagocyte (CD68 infiltration, and the proliferation of skin collagen fibers was assessed. On days 16 and 17 of irradiation, the healing rates in red (15 min and 30 min and blue (15 min and 30 min groups were 50%, 37.5%, 25% and 37.5%, respectively, while the healing rate in the control group was 12.5%. The percentage healed area in the red light groups was significantly higher than those in other groups. Collagen fiber and skin thickness were significantly increased in both red light groups; expression of EGF, FGF, CD31 and Ki67 in the red light groups was significantly higher than those in other groups; the expression of FGF in red (30 min group was not significantly different from that in the blue light and control groups. The effect of blue light on wound healing was poorer than that of red light. Red light appeared to hasten wound healing by promoting fibrous tissue, epidermal and

  1. Rational Design and Characterization of Heteroleptic Phosphorescent Complexes for Highly Efficient Deep-Red Organic Light-Emitting Devices.

    Science.gov (United States)

    Li, Guomeng; Li, Ping; Zhuang, Xuming; Ye, Kaiqi; Liu, Yu; Wang, Yue

    2017-03-27

    Two new deep-red iridium(III) complexes, (fpiq)2Ir(dipba) (fIr1) and (f2piq)2Ir(dipba) (dfIr2), comprising two cyclometaling ligands of fluorophenyl-isoquinoline derivatives (fpiq and f2piq) and a N-heterocyclic carbene (NHC)-based ancillary ligand of N,N'-diisopropylbenzamidinate (dipba) are designed, synthesized, and characterized. Given the unique four-membered Ir-N-C-N backbone built by the metal center and the ancillary ligand, both phosphors achieve significant improvement for their comprehensive optoelectronic characteristics. Density function theory (DFT) calculations and electrochemical measurements support the genuine pure red phosphorescent emission of fIr1 and dfIr2 based on their clearly distinct electron density distributions of the HOMO/LUMO orbitals compared with other red-emitting Ir(III) derivatives. Both new phosphors show deep-red emission with λmax values in the region of 650-660 nm with high PLQYs and short excited-state lifetimes. The phosphorescent organic light emitting diodes (PhOLEDs) based on fIr1 and dfIr2 realize deep-red EL with the stable CIEx,y coordinates of (0.70, 0.30) and (0.69, 0.31), the peak EQE/PE values of 15.4%/9.3 lm W(-1) and 16.7%/10.4 lm W(-1), respectively, which maintain such high levels as 10.6%/3.5 lm W(-1) and 10.8%/3.6 lm W(-1) at the practical luminance of 1000 cd m(-2). They are the highest EL values reported for the OLEDs with such deep-red CIE coordinates.

  2. Analysis of the Electrical Properties of an Electron Injection Layer in Alq3-Based Organic Light Emitting Diodes.

    Science.gov (United States)

    Kim, Soonkon; Choi, Pyungho; Kim, Sangsub; Park, Hyoungsun; Baek, Dohyun; Kim, Sangsoo; Choi, Byoungdeog

    2016-05-01

    We investigated the carrier transfer and luminescence characteristics of organic light emitting diodes (OLEDs) with structure ITO/HAT-CN/NPB/Alq3/Al, ITO/HAT-CN/NPB/Alq3/Liq/Al, and ITO/HAT-CN/NPB/Alq3/LiF/A. The performance of the OLED device is improved by inserting an electron injection layer (EIL), which induces lowering of the electron injection barrier. We also investigated the electrical transport behaviors of p-Si/Alq3/Al, p-Si/Alq3/Liq/Al, and p-Si/Alq3/LiF/Al Schottky diodes, by using current-voltage (L-V) and capacitance-voltage (C-V) characterization methods. The parameters of diode quality factor n and barrier height φ(b) were dependent on the interlayer materials between Alq3 and Al. The barrier heights φ(b) were 0.59, 0.49, and 0.45 eV, respectively, and the diode quality factors n were 1.34, 1.31, and 1.30, respectively, obtained from the I-V characteristics. The built in potentials V(bi) were 0.41, 0.42, and 0.42 eV, respectively, obtained from the C-V characteristics. In this experiment, Liq and LiF thin film layers improved the carrier transport behaviors by increasing electron injection from Al to Alq3, and the LiF schottky diode showed better I-V performance than the Liq schottky diode. We confirmed that a Liq or LiF thin film inter-layer governs electron and hole transport at the Al/Alq3 interface, and has an important role in determining the electrical properties of OLED devices.

  3. The two-dimensional optical pattern of a five inch diagonal white organic light emitting diode by rapid rotating measurement

    Science.gov (United States)

    Yang, Henglong; Cheng, Yu-Hen; Chen, Ming-Hong; Lin, Yu-Hsuan

    2016-09-01

    The feasibility of applying a five-inch diagonal white organic light-emitting diode (WOLED) as a desk lamp was experimentally investigated by quantitatively comparing its two-dimensional (2D) optical intensity profile to that of a traditional 3M desk lamp equipped with optical diffuser. The 2D optical distribution patterns as the function of vertical distances to a surface of a five-inch diagonal WOLED were obtained by using rapid rotating measurement technique consisted of a sample holder on a rotational stage and a fixed photo detector with optical power meter. The 2D optical intensity profile on a surface can be rapidly established in a relatively small space by recording the reading from the fixed photo detector as rotating the sample holder. This rapid measurement technique is suitable for practical application in quality engineering without larger space. A WOLED is a compact and thin lighting source with planar device structure without additional optical components. Its optical intensity profile on a plane is expected to be different from traditional lighting sources. The optical distribution pattern of a desk lamp requires a relatively large area on a surface with relatively uniformed intensity distribution. The quantitative analysis of the similarity between WOLED and 3M desk lamp was conducted by comparing the optimal zones defined as the area within 75% of the maximum intensity in 2D optical distribution pattern. Our preliminary result showed that the optimal zone of a five-inch diagonal WOLED at 45cm vertical distance is highly similar to that of the 3M desk lamp with optical diffuser.

  4. Light-Emitting Pickles

    Science.gov (United States)

    Vollmer, M.; Mollmann, K-P.

    2015-01-01

    We present experiments giving new insights into the classical light-emitting pickle experiment. In particular, measurements of the spectra and temperatures, as well as high-speed recordings, reveal that light emission is connected to the polarity of the electrodes and the presence of hydrogen.

  5. Influence of active layer thickness on the performance of distyrylarylene derivative blue organic light-emitting device%发光层厚度对联苯乙烯衍生物蓝色有机发光器件性能的影响

    Institute of Scientific and Technical Information of China (English)

    吴有智; 张文林; 倪蔚德; 张材荣; 张定军

    2012-01-01

    Thickness of emissive layer in organic electroluminescent device is one of the important factors affecting the device performance. In this report, a blue electroluminescent device with an active layer of 4, 4'-bis(2, 2'-diphenylvinyl) -1, 1'- biphenyl (DPVBi) is fabricated. The device performance varies with the thickness of DPVBi. With the increase of the DPVBi thickness between 10-50 nm, the device luminance and efficiency at the same current density first increase and then decrease, the device with a DPVBi thickness of 40 nm exhibits the highest luminance of 15840 cd/m^2 and a maximum external quantum efficiency of 3.2%, with Commission Internationale de 1'Eclairage (CIE) co-ordinates being (0.15, 0.15). The luminescent spectral red shift and the color purity deteriorate when the thickness is over 40 nm, which can be attributed to a result of microcavity effect. In the meantime, the analysis from experimental results shows that the exciton diffusion length in DPVBi is between 20---30 nm%本文制备了联苯乙烯衍生物(4,4'-bis(2,2'-diphenylvinyl)-l,l'-biphenyl,DPVBi)为发光层的蓝色有机电致发光器件.器件性能随发光层厚度变化而变.在DPVBi厚度为10—50 nm范围内,同样电流密度下器件亮度及效率随DPVBi厚度增加先增后减,40 nm时最佳,最高亮度达到15840 cd/m~2,最高外量子效率达到3.2%,器件色坐标(Commission Internationale de l'Eclairage(CIE)co-ordinates)为(0.15,0.15).DPVBi厚度超过40 nm时器件发光光谱出现红移而致色度变差,其原因可归于微腔效应所致.同时,通过实验结果分析表明DPVBi中激子扩散长度位于20—30 nm范围.

  6. Top-Emitting Organic Light-Emitting Devices Based on Silicon Substrate with High Luminance and Low Turn-on Voltage

    Institute of Scientific and Technical Information of China (English)

    WU Zhi-Jun; CHEN Shu-Fen; YANG Hui-Shan; ZHAO Yi; LI Chuan-Nan; HOU Jing-Ying; LIU Shi-Yong

    2005-01-01

    @@ We have fabricated a top- emitting organic light-emitting device on silicon substrate with high yellow luminance based on 5,6,11,12-tetraphenylnaphthacene sub-monolayer. It consists of a thin layer of highly conductive silver as the semitransparent cathode and surfaced-modified Ag as the anode. The device turns on at 3 V with the luminance of 8.4 cd/m2. The maximum current efficiency is 1.3 cd/A at 6 V and the luminance reaches 14790 cd/m2at 14 V. The performance of the device is excellent in top-emitting organic light-emitting devices according to our knowledge.

  7. Effect of red and blue light emitting diodes "CRB-LED" on in vitro organogenesis of date palm (Phoenix dactylifera L.) cv. Alshakr.

    Science.gov (United States)

    Al-Mayahi, Ahmed Madi Waheed

    2016-10-01

    The objective of the present study is to determine the effect of light source on enhancement of shoot multiplication, phytochemicals, as well as, antioxidant enzyme activities of in vitro cultures of date palm cv. Alshakr. In vitro-grown buds were cultured on Murashige and Skoog (MS) medium and incubated under a conventional white fluorescent light (control), and combinations of red + blue light emitting diode (18:2) (CRB-LED). Results revealed that the treatment of CRB-LED showed a significant increase in the number of shoots compared with the white florescent light. Total soluble carbohydrate "TSCH" (7.10 mg g(-1) DW.), starch (1.63 mg g(-1) DW.) and free amino acids (2.90 mg g(-1) DW.) were significantly higher in CRB-LED (p < 0.05). Additionally, CRB-LED induced a higher peroxidase activity (25.50 U ml(-1)) compared with the white fluorescent light treatment (19.74 U ml(-1)) as control treatment. Potassium, magnesium and sodium contents in (3.62, 13.99 and 2.76 mg g(-1) DW.) were increased in in vitro shoots under CRB-LED treatment in comparison with fluorescent light (p < 0.05). Protein profile showed the appearance of newly bands with the molecular weight of 38 and 60 kDa at the treatment CRB-LED compared with control treatment. Our results demonstrate the positive effects of CRB-LED light during the course of date palm tissue cultures.

  8. Enhancing Optical Out-Coupling of Organic Light-Emitting Devices with Nanostructured Composite Electrodes Consisting of Indium Tin Oxide Nanomesh and Conducting Polymer.

    Science.gov (United States)

    Chen, Chien-Yu; Lee, Wei-Kai; Chen, Yi-Jiun; Lu, Chun-Yang; Lin, Hoang Yan; Wu, Chung-Chih

    2015-09-02

    A nanostructured composite electrode consisting of a high-index indium-tin-oxide nanomesh and low-index high-conductivity conducting polymer effectively enhances coupling of internal radiation of organic light-emitting devices into their substrates. When combining this internal extraction structure and the external extraction scheme, a very high external quantum efficiency of nearly 62% is achieved with a green phosphorescent device.

  9. Growth and properties of wide spectral white light emitting diodes

    Institute of Scientific and Technical Information of China (English)

    Xie Zi-Li; Shi Yi; Zheng You-Dou; Zhang Rong; Fu De-Yi; Liu Bin; Xiu Xiang-Qian; Hua Xue-Mei; Zhao Hong; Chen Peng; Han Ping

    2011-01-01

    Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system.Three quantum wells with blue-light-emitting,green-light-emitting and red-light-emitting structures were grown according to the design.The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction θ/2θ scan spectroscopy was carried out on the multi-quantum wells.The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region.The room temperature photolumineecence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained.The light spectrum covers 400-700 nm,which is almost the whole visible light spectrum.

  10. Light-Emission and Electricity-Generation Properties of Photovoltaic Organic Light-Emitting Diodes with Rubrene/DBP Light-Emission and Electron-Donating Layers

    Directory of Open Access Journals (Sweden)

    Mun Soo Choi

    2014-01-01

    Full Text Available We report the dependence of the characteristics of photovoltaic organic light-emitting diodes (PVOLEDs on the composition of the light-emission and electron-donating layer (EL-EDL. 5,6,11,12-Tetraphenylnaphthacene (rubrene: dibenzo{[f,f′]-4,4′,7,7′-tetraphenyl}diindeno[1,2,3-cd:1′,2′,3′-lm]perylene (DBP was used to form the EL-EDL, and C60 was used as an electron-accepting layer (EAL material. A half-gap junction was formed at the EAL/EL-EDL interface. As the rubrene ratio in the EL-EDL increased, the emission spectra became blue-shifted and the light-emission efficiency increased. The highest emission efficiency was achieved with an EL-EDL composed of 95% rubrene and 5% DBP. The short-circuit current decreased as the rubrene content increased up to 50% and then saturated, while the open-circuit voltage was almost unchanged regardless of the rubrene content. The power-conversion efficiency and fill factor increased as the composition of the EL-EDL approached that of pure materials. By controlling the rubrene : DBP ratio, the emission color could be adjusted. The emission efficiency of devices with mixed rubrene/DBP EL-EDLs could be greater than that of either pure rubrene or pure DBP devices. We obtained an overall power-conversion efficiency of 3% and a fill factor greater than 50%.

  11. Electroluminescence of a Multi-Layered Organic Light-Emitting Diode Utilizing Trans-4-[p-[Nmethyl-N-(hydroxymethyl)amino]styryl]-N-Methylphridinium Tetraphenylborate as the Active Layer

    Institute of Scientific and Technical Information of China (English)

    FENG Xue-Yuan; ZHANG Jia-Yu; XU Chun-Xiang; QIAO Yi; GUI Yi-Ping

    2006-01-01

    Employing an organic dye salt oftrans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-methylphridinium tetraphenylborate (ASPT) as the active layer, 8-hydrocyquinoline aluminium (Alqa) as the electron transporting layer and N,Nt-diphenyl-N,Nl-bis(3-methylphenyl)-[l,l'-biphenyl]-4,4'-diamine (TPD) as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence (EL). The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region.

  12. Solution-processable deep red-emitting supramolecular phosphorescent polymer with novel iridium complex for organic light-emitting diodes

    Science.gov (United States)

    Liang, Aihui; Huang, Gui; Wang, Zhiping; Wu, Wenjin; Zhong, Yu; Zhao, Shan

    2016-09-01

    A novel bis(dibenzo-24-crown-8)-functionalized iridium complex with an emission peak at 665 nm was synthesized. Several deep red-emitting supramolecualr phosphorescent polymers (SPPs) as a class of solutionprocessable electroluminescent (EL) emitters were formed by utilizing the efficient non-bonding self-assembly between the resulting iridium complex and bis(dibenzylammonium)-tethered monomers. These SPPs show an intrinsic glass transition with a T g of ca. 90 °C. The photophysical and electroluminescent properties are strongly dependent on the hosts' structures of the supramolecular phosphorescent polymers. The polymer light-emitting diode based on SPP3 displayed a maximal external quantum efficiency (EQE) of 2.14% ph·el-1 and the Commission Internationale de L'Eclairage (CIE) coordinates of (0.70, 0.29).

  13. MoO3/Ag/MoO3 anode for organic light-emitting diodes and its carrier injection property

    Science.gov (United States)

    Banzai, Kazuki; Naka, Shigeki; Okada, Hiroyuki

    2015-05-01

    We report on the application of the dielectric/metal/dielectric (DMD) structure consisting of a molybdenum trioxide (MoO3)/silver (Ag)/MoO3 stack as the transparent electrode in organic light-emitting diodes (OLEDs). Bright emission similar to that of the indium-tin-oxide anode (ITO) device was obtained from the OLEDs with the DMD anode. Also, the barrier height at the interface of DMD/bis[N-(1-naphthyl)-N-phenyl] benzidine (α-NPD) is similar to that at the ITO/α-NPD interface. The DMD electrode is a promising anode for OLEDs.

  14. Threshold-Voltage-Shift Compensation and Suppression Method Using Hydrogenated Amorphous Silicon Thin-Film Transistors for Large Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Oh, Kyonghwan; Kwon, Oh-Kyong

    2012-03-01

    A threshold-voltage-shift compensation and suppression method for active matrix organic light-emitting diode (AMOLED) displays fabricated using a hydrogenated amorphous silicon thin-film transistor (TFT) backplane is proposed. The proposed method compensates for the threshold voltage variation of TFTs due to different threshold voltage shifts during emission time and extends the lifetime of the AMOLED panel. Measurement results show that the error range of emission current is from -1.1 to +1.7% when the threshold voltage of TFTs varies from 1.2 to 3.0 V.

  15. Analysis of the current-voltage characteristics of polymer-based organic light-emitting diodes (OLEDs) deposited by spin coating

    OpenAIRE

    Ricardo Vera; Juan Carlos Salcedo-Reyes; Juan Pablo Cuéllar-Alvarado; Diana Rocío Pardo-Pardo; Henry Alberto Méndez-Pinzón; Beynor Antonio Páez-Sierra

    2010-01-01

    Polymer-based organic light-emitting diodes (OLEDs) with the structure ITO / PEDOT:PSS / MDMO-PPV / Metal were prepared by spincoating. It is known that electroluminescence of these devices is strongly dependent on the material used as cathode and on the depositionparameters of the polymer electroluminescent layer MDMO-PPV. Objective. In this work the effect of i) the frequency of the spin coater(1000-8000 rpm), ii) the concentration of the MDMO-PPV: Toluene solution, and iii) the material us...

  16. Electron-hole pair mechanism for the magnetic field effect in organic light emitting diodes based on poly(paraphenylene vinylene)

    Science.gov (United States)

    Bagnich, S. A.; Niedermeier, U.; Melzer, C.; Sarfert, W.; von Seggern, H.

    2009-12-01

    We investigated the magnetic field effect (MFE) on current and electroluminescence in organic light emitting diodes based on poly(paraphenylene vinylene). The MFE was strictly positive in the full range of device operation and showed nonmonotonic dependencies on applied voltage and temperature. Furthermore, the MFE on current obtained in bipolar devices was significantly larger than in hole-dominated devices. We discuss our results in the framework of an electron-hole pair model and show that the model can explain all functional dependencies observed in our devices.

  17. A europium(III) organic ternary complex applied in fabrication of near UV-based white light-emitting diodes

    Science.gov (United States)

    Wang, H.; He, P.; Liu, S.; Shi, J.; Gong, M.

    2009-10-01

    A β-diketone, 2-acetylfluorene-4,4,4-trifluorobutane-1,3-dione (HAFTFBD), and its three europium(III) complexes, Eu(AFTFBD)3ṡ2H2O, Eu(AFTFBD)3(TPPO)2 and Eu(AFTFBD)3phen, were designed and synthesized, where TPPO was triphenylphosphine oxide and phen was 1,10-phenanthroline. The complexes were characterized by IR, UV-visible, photoluminescence (PL) spectroscopy and thermogravimetric analysis (TGA). The results show that the Eu(III) complexes exhibit a high thermal stability,and wide and strong excitation bands when monitored at 613 nm. Excited by ˜395 nm near UV light, the complexes emitted strong and characteristic red light due to f- f transitions of the central Eu3+ ion, and no emission from the ligands was found. The photoluminescence mechanism of the europium(III) complexes was investigated and proposed as a ligand-sensitized luminescence process. Among the three europium(III) complexes, Eu(AFTFBD)3phen exhibits the highest thermal stability and the most excellent photoluminescence properties. A bright red light-emitting diode was fabricated by coating the Eu(AFTFBD)3phen complex onto an ˜395 nm-emitting InGaN chip, and the LED showed appropriate CIE chromaticity coordinates ( x=0.66, y=0.33). A white LED with CIE chromaticity coordinates ( x=0.32, y=0.32) was prepared with Eu(AFTFBD)3phen as red phosphor, indicating that Eu(AFTFBD)3phen can be applied as a red component for fabrication of near ultraviolet-based white light-emitting diodes.

  18. Efficiency of Blue Organic Light-emitting Diodes Enhanced by Employing an Exciton Feedback Layer

    Science.gov (United States)

    Yu, Qian-Qian; Zhang, Xu; Bi, Jing-Xuan; Liu, Guan-Ting; Zhang, Qi-Wen; Wu, Xiao-Ming; Hua, Yu-Lin; Yin, Shou-Gen

    2016-08-01

    Not Available Supported by the National Natural Science Foundation of China under Grant No 60906022, the Natural Science Foundation of Tianjin under Grant No 10JCYBJC01100, the Scientific Developing Foundation of Tianjin Education Commission under Grant No 2011ZD02, and the Key Science and Technology Support Program of Tianjin under Grant No 14ZCZDGX00006.

  19. Highly thermally stable single-component white-emitting silicate glass for organic-resin-free white-light-emitting diodes.

    Science.gov (United States)

    Zhang, Xuejie; Huang, Lin; Pan, Fengjuan; Wu, Mingmei; Wang, Jing; Chen, Yan; Su, Qiang

    2014-02-26

    Thermal management is still a great challenge for high-power phosphor-converted white-light-emitting diodes (pc-WLEDs) intended for future general lighting. In this paper, a series of single-component white-emitting silicate SiO2-Li2O-SrO-Al2O3-K2O-P2O5: Ce(3+), Tb(3+), Mn(2+) (SLSAKP: Ce(3+), Tb(3+), Mn(2+)) glasses that simultaneously play key roles as a luminescent convertor and an encapsulating material for WLEDs were prepared via the conventional melt-quenching method, and systematically studied using their absorption spectra, transmittance spectra, photoluminescence excitation and emission spectra in the temperature range 296-498 K, decay curves, and quantum efficiency. The glasses show strong and broad absorption in 250-380 nm region and exhibit intense white emission, produced by in situ mixing of blue-violet, green, and orange-red light from Ce(3+), Tb(3+), and Mn(2+) ions, respectively, in a single glass component. The quantum efficiency of SLSAKP: 0.3%Ce(3+), 2.0%Tb(3+), 2.0%Mn(2+) glass is determined to be 19%. More importantly, this glass shows good thermal stability, exhibiting at 373 and 423 K about 84.56 and 71.02%, respectively, of the observed room temperature (298 K) emission intensity. The chromaticity shift of SLSAKP: 0.3%Ce(3+), 2.0%Tb(3+), 2.0%Mn(2+) is 2.94 × 10(-2) at 498 K, only 57% of the commercial triple-color white-emitting phosphor mixture. Additionally, this glass shows no transmittance loss at the 370 nm emission of a UV-Chip-On-Board (UV-COB) after thermal aging for 240 h, compared with the 82% transmittance loss of epoxy resin. The thermal conductivity of the glass is about 1.07 W/mK, much larger than the 0.17 W/mK of epoxy resin. An organic-resin-free WLEDs device based on SLSAKP: 0.3%Ce(3+), 2.0%Tb(3+), 2.0%Mn(2+) glass and UV-COB is successfully demonstrated. All of our results demonstrate that the presented Ce(3+)/Tb(3+)/Mn(2+) tridoped lithium-strontium-silicate glass may serve as a promising candidate for high-power WLEDs.

  20. Large area inkjet printing for organic photovoltaics and organic light emitting diodes using non-halogenated ink formulations

    NARCIS (Netherlands)

    Eggenhuisen, T.M.; Coenen, M.J.J.; Slaats, M.W.L.; Groen, W.A.

    2014-01-01

    The transfer of laboratory scale solution processing of organic electronics to large area roll-to-roll production requires the use of up-scalable deposition techniques. Furthermore, industrial production demands the omission of halogenated and other harmful solvents. Here, the authors discuss large

  1. Highly stable three-band white light from an InGaN-based blue light-emitting diode chip precoated with (oxy)nitride green/red phosphors

    Science.gov (United States)

    Yang, Chih-Chieh; Lin, Chih-Min; Chen, Yi-Jung; Wu, Yi-Tsuo; Chuang, Shih-Ren; Liu, Ru-Shi; Hu, Shu-Fen

    2007-03-01

    A three-band white light-emitting diode (LED) was fabricated using an InGaN-based blue LED chip that emits 455nm blue light, and green phosphor SrSi2O2N2:Eu and red phosphor CaSiN2:Ce that emit 538nm green and 642nm red emissions, respectively, when excited by the 455nm blue light. The luminous efficacy of this white LED is about 30lm /W at a dc of 20mA. With increasing dc from 5.0to60mA, both the coordinates x and y of the white LED tend to be the same, and consequently the Tc is the same and the Ra increases to 92.2.

  2. The advantage of blue InGaN multiple quantum wells light-emitting diodes with p-AlInN electron blocking layer

    Institute of Scientific and Technical Information of China (English)

    Lu Tai-Ping; Wang Hai-Long; Yang Xiao-Dong; Li Shu-Ti; Zhang Kang; Liu Chao; Xiao Guo-Wei; Zhou Yu-Gang; Zheng Shu-Wen; Yin Yi-An; Wu Le-Juan

    2011-01-01

    InGaN based light-emitting diodes (LEDs) with different electron blocking layers have been numerically investigated using the APSYS simulation software. It is found that the structure with a p-AIInN electron blocking layer showes improved light output power,lower current leakage,and smaller efficiency droop. Based on numerical simulation and analysis,these improvements of the electrical and optical characteristics are mainly attributed to the efficient electron blocking in the InGaN/GaN multiple quantum wells (MQWs).

  3. Effect of different processing methods for the hole transporting layer on the performance of double layer organic light-emitting devices

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The hole transporting layer (HTL) of organic light-emitting device (OLED) was processed by vacuum deposition and spin coating method, respectively, where N,N'-biphenyl-N, N'-bis(3-methylphenyl)-1, 1'-biphenyl-4,4' -diamine (TPD) and poly (vinylcarbazole) (PVK) acted as the hole-transport materials. Tris-(8-hydroxyquinoline)- aluminum (Alq3) was utilized as both the light-emitting layer and the electron transporting layer. The basic structure of the device cell was: indium-tin-oxide (ITO)/PVK: TPD/Alq3/Mg:Ag. The electroluminescent (EL) characteristics of devices were characterized. The results showed that the peak of EL spectra was located at 530 nm, which conformed to the characterizing spectrum of Alq3.Compared with using vacuum deposition method, the green emission with a maximum luminance up to 26135 cd/m2 could be achieved at a drive voltage of 15 V by selecting proper solvent using spin-coating technique, and its maximum luminance efficiency was 2.56 lm/W at a drive voltage of 5.5 V.

  4. Molecularly Engineered Organic-Inorganic Hybrid Perovskite with Multiple Quantum Well Structure for Multicolored Light-Emitting Diodes

    Science.gov (United States)

    Hu, Hongwei; Salim, Teddy; Chen, Bingbing; Lam, Yeng Ming

    2016-01-01

    Organic-inorganic hybrid perovskites have the potential to be used as a new class of emitters with tunable emission, high color purity and good ease of fabrication. Recent studies have so far been focused on three-dimensional (3D) perovskites, such as CH3NH3PbBr3 and CH3NH3PbI3 for green and infrared emission. Here, we explore a new series of hybrid perovskite emitters with a general formula of (C4H9NH3)2(CH3NH3)n−1PbnI3n+1 (where n = 1, 2, 3), which possesses a multiple quantum well structure. The quantum well thickness of these materials is adjustable through simple molecular engineering which results in a continuously tunable bandgap and emission spectra. Deep saturated red emission was obtained with a peak external quantum efficiency of 2.29% and a maximum luminance of 214 cd/m2. Green and blue LEDs were also demonstrated through halogen substitutions in these hybrid perovskites. We expect these results to open up the way towards high performance perovskite LEDs through molecular-structure engineering of these perovskite emitters. PMID:27633084

  5. Molecularly Engineered Organic-Inorganic Hybrid Perovskite with Multiple Quantum Well Structure for Multicolored Light-Emitting Diodes.

    Science.gov (United States)

    Hu, Hongwei; Salim, Teddy; Chen, Bingbing; Lam, Yeng Ming

    2016-09-16

    Organic-inorganic hybrid perovskites have the potential to be used as a new class of emitters with tunable emission, high color purity and good ease of fabrication. Recent studies have so far been focused on three-dimensional (3D) perovskites, such as CH3NH3PbBr3 and CH3NH3PbI3 for green and infrared emission. Here, we explore a new series of hybrid perovskite emitters with a general formula of (C4H9NH3)2(CH3NH3)n-1PbnI3n+1 (where n = 1, 2, 3), which possesses a multiple quantum well structure. The quantum well thickness of these materials is adjustable through simple molecular engineering which results in a continuously tunable bandgap and emission spectra. Deep saturated red emission was obtained with a peak external quantum efficiency of 2.29% and a maximum luminance of 214 cd/m(2). Green and blue LEDs were also demonstrated through halogen substitutions in these hybrid perovskites. We expect these results to open up the way towards high performance perovskite LEDs through molecular-structure engineering of these perovskite emitters.

  6. Modifying the organic/electrode interface in Organic Solar Cells (OSCs) and improving the efficiency of solution-processed phosphorescent Organic Light-Emitting Diodes (OLEDs)

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Teng [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Organic semiconductors devices, such as, organic solar cells (OSCs), organic light-emitting diodes (OLEDs) and organic field-effect transistors (OFETs) have drawn increasing interest in recent decades. As organic materials are flexible, light weight, and potentially low-cost, organic semiconductor devices are considered to be an alternative to their inorganic counterparts. This dissertation will focus mainly on OSCs and OLEDs. As a clean and renewable energy source, the development of OSCs is very promising. Cells with 9.2% power conversion efficiency (PCE) were reported this year, compared to < 8% two years ago. OSCs belong to the so-called third generation solar cells and are still under development. While OLEDs are a more mature and better studied field, with commercial products already launched in the market, there are still several key issues: (1) the cost of OSCs/OLEDs is still high, largely due to the costly manufacturing processes; (2) the efficiency of OSCs/OLEDs needs to be improved; (3) the lifetime of OSCs/OLEDs is not sufficient compared to their inorganic counterparts; (4) the physics models of the behavior of the devices are not satisfactory. All these limitations invoke the demand for new organic materials, improved device architectures, low-cost fabrication methods, and better understanding of device physics. For OSCs, we attempted to improve the PCE by modifying the interlayer between active layer/metal. We found that ethylene glycol (EG) treated poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT: PSS) improves hole collection at the metal/polymer interface, furthermore it also affects the growth of the poly(3- hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) blends, making the phase segregation more favorable for charge collection. We then studied organic/inorganic tandem cells. We also investigated the effect of a thin LiF layer on the hole-collection of copper phthalocyanine (CuPc)/C70-based small molecular OSCs. A

  7. Novel red phosphorescent polymers bearing both ambipolar and functionalized Ir(III) phosphorescent moieties for highly efficient organic light-emitting diodes.

    Science.gov (United States)

    Zhao, Jiang; Lian, Meng; Yu, Yue; Yan, Xiaogang; Xu, Xianbin; Yang, Xiaolong; Zhou, Guijiang; Wu, Zhaoxin

    2015-01-01

    A series of novel red phosphorescent polymers is successfully developed through Suzuki cross-coupling among ambipolar units, functionalized Ir(III) phosphorescent blocks, and fluorene-based silane moieties. The photophysical and electrochemical investigations indicate not only highly efficient energy-transfer from the organic segments to the phosphorescent units in the polymer backbone but also the ambipolar character of the copolymers. Benefiting from all these merits, the phosphorescent polymers can furnish organic light-emitting diodes (OLEDs) with exceptional high electroluminescent (EL) efficiencies with a current efficiency (η L ) of 8.31 cd A(-1) , external quantum efficiency (η ext ) of 16.07%, and power efficiency (η P ) of 2.95 lm W(-1) , representing the state-of-the-art electroluminescent performances ever achieved by red phosphorescent polymers. This work here might represent a new pathway to design and synthesize highly efficient phosphorescent polymers.

  8. Metal Organic Vapor Phase Epitaxy of Monolithic Two-Color Light-Emitting Diodes Using an InGaN-Based Light Converter

    Science.gov (United States)

    Damilano, Benjamin; Kim-Chauveau, Hyonju; Frayssinet, Eric; Brault, Julien; Hussain, Sakhawat; Lekhal, Kaddour; Vennéguès, Philippe; De Mierry, Philippe; Massies, Jean

    2013-09-01

    Monolithic InGaN-based light-emitting diodes (LEDs) using a light converter fully grown by metal organic vapor phase epitaxy are demonstrated. The light converter, consisting of 10-40 InGaN/GaN quantum wells, is grown first, followed by a violet pump LED. The structure and growth conditions of the pump LED are specifically adapted to avoid thermal degradation of the light converter. Electroluminescence analysis shows that part of the pump light is absorbed by the light converter and reemitted at longer wavelength. Depending on the emission wavelength of the light converter, different LED colors are achieved. In particular, for red-emitting light converters, a color temperature of 2100 K corresponding to a tint between warm white and candle light is demonstrated.

  9. Amorphous In-Ga-Zn-O Thin Film Transistor Current-Scaling Pixel Electrode Circuit for Active-Matrix Organic Light-Emitting Displays

    Science.gov (United States)

    Chen, Charlene; Abe, Katsumi; Fung, Tze-Ching; Kumomi, Hideya; Kanicki, Jerzy

    2009-03-01

    In this paper, we analyze application of amorphous In-Ga-Zn-O thin film transistors (a-InGaZnO TFTs) to current-scaling pixel electrode circuit that could be used for 3-in. quarter video graphics array (QVGA) full color active-matrix organic light-emitting displays (AM-OLEDs). Simulation results, based on a-InGaZnO TFT and OLED experimental data, show that both device sizes and operational voltages can be reduced when compare to the same circuit using hydrogenated amorphous silicon (a-Si:H) TFTs. Moreover, the a-InGaZnO TFT pixel circuit can compensate for the drive TFT threshold voltage variation (ΔVT) within acceptable operating error range.

  10. Driving Method for Compensating Reliability Problem of Hydrogenated Amorphous Silicon Thin Film Transistors and Image Sticking Phenomenon in Active Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Shin, Min-Seok; Jo, Yun-Rae; Kwon, Oh-Kyong

    2011-03-01

    In this paper, we propose a driving method for compensating the electrical instability of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) and the luminance degradation of organic light-emitting diode (OLED) devices for large active matrix OLED (AMOLED) displays. The proposed driving method senses the electrical characteristics of a-Si:H TFTs and OLEDs using current integrators and compensates them by an external compensation method. Threshold voltage shift is controlled a using negative bias voltage. After applying the proposed driving method, the measured error of the maximum emission current ranges from -1.23 to +1.59 least significant bit (LSB) of a 10-bit gray scale under the threshold voltage shift ranging from -0.16 to 0.17 V.

  11. Driving Method Compensating for the Hysteresis of Polycrystalline Silicon Thin-Film Transistors for Active-Matrix Organic Light-Emitting Diode Displays

    Science.gov (United States)

    Jung, Myoung-Hoon; Kim, Ohyun; Kim, Byeong-Koo; Chung, Hoon-Ju

    2009-05-01

    A new driving method for active-matrix organic light-emitting diode displays is proposed and evaluated. The pixel structure of the proposed driving method is composed of three thin-film transistors (TFTs) and one capacitor. It inserts black data into display images to reset driving TFTs for the purpose of maintaining constant electrical characteristics of driving TFTs. The proposed driving scheme is less sensitive to the hysteresis of low-temperature polycrystalline silicon (LTPS) TFTs than the conventional pixel structure with two TFTs and one capacitor, and this scheme can virtually eliminate the recoverable residual image that occurs owing to the hysteresis characteristics of LTPS TFTs. In the proposed driving scheme, black data are inserted into displayed images so that the motion image quality is improved.

  12. Transparent Pixel Circuit with Threshold Voltage Compensation Using ZnO Thin-Film Transistors for Active-Matrix Organic Light Emitting Diode Displays

    Science.gov (United States)

    Yang, Ik-Seok; Kwon, Oh-Kyong

    2009-03-01

    A transparent pixel circuit with a threshold voltage compensating scheme using ZnO thin-film transistors (TFTs) for active-matrix organic light emitting diode (AMOLED) displays is proposed. This circuit consists of five n-type ZnO TFTs and two capacitors and can compensate for the threshold voltage variation of ZnO TFTs in real time. From simulation results, the maximum deviation of the emission current of the pixel circuit with a threshold voltage variation of ±1 V is determined to be less than 10 nA. From measurement results, it is verified that the maximum deviation of measured emission currents with measurement position in a glass substrate is less than 15 nA in a higher current range, and the deviation of emission current with time is less than 3%.

  13. Current-Sensing and Voltage-Feedback Driving Method for Large-Area High-Resolution Active Matrix Organic Light Emitting Diodes

    Science.gov (United States)

    In, Hai‑Jung; Choi, Byong‑Deok; Chung, Ho‑Kyoon; Kwon, Oh‑Kyong

    2006-05-01

    There is the problem of picture quality nonuniformity due to thin film transistor (TFT) characteristic variations throughout a panel of large-area high-resolution active matrix organic light emitting diodes. The current programming method could solve this issue, but it also requires very long charging time of a data line at low gray shades. Therefore, we propose a new driving method and a pixel circuit with emission-current sensing and feedback operation in order to resolve these problems. The proposed driving method and pixel circuit successfully compensate threshold voltage and mobility variations of TFTs and overcome the data line charging problem. Simulation results show that emission current deviations of the proposed driving method are less than 1.7% with ± 10.0% mobility and ± 0.3 V threshold voltage variations of pixel-driving TFTs, which means the proposed driving method is applicable to large-area high-resolution applications.

  14. Hole-exciton interaction induced high field decay of magneto-electroluminescence in Alq{sub 3}-based organic light-emitting diodes at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tingting; Holford, D. F.; Gu, Hang; Kreouzis, T. [Materials Research Institute and School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Zhang, Sijie, E-mail: Sijie.zhang@scu.edu.cn, E-mail: w.gillin@qmul.ac.uk [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Gillin, W. P., E-mail: Sijie.zhang@scu.edu.cn, E-mail: w.gillin@qmul.ac.uk [Materials Research Institute and School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China)

    2016-01-11

    The magnetic field effects on the electroluminescence of aluminium tris-(8-hydroxyqinoline) (Alq{sub 3}) based organic light emitting diodes have been investigated by varying the electron/hole ratio in the emissive layer. Experimental results reveal that a negative high field effect in the magneto-electroluminescence (MEL) can be found in devices with very low triplet exciton concentration at room temperature. This suggests triplet-triplet annihilation cannot be used to explain the negative high field MEL in the Alq{sub 3} system. Our results suggest that hole-exciton interaction may be the origin of the negative high field MEL and also, in parallel with this interaction, there is also the more common positive high field process occurring which has been tentatively attributed to electron-exciton interactions. The competition between these different processes decides the final shape of the MEL at high fields.

  15. Super color purity green organic light-emitting diodes with ZrO2/zircone nanolaminates as a distributed Bragg reflector deposited by atomic layer deposition

    Science.gov (United States)

    Zhang, Jianhua; Zhang, Hao; Zheng, Yanqiong; Wei, Mengjie; Ding, He; Wei, Bin; Zhang, Zhilin

    2017-01-01

    ZrO2/zircone nanolaminate thin films fabricated by atomic layer deposition were used for a distributed Bragg reflector (DBR) in green organic light-emitting diodes (OLEDs). It is found that the novel ZrO2/zircone DBR structure significantly improves the light purity of green OLEDs without interfering with intrinsic electroluminescence properties. The full width at half maximum (FWHM) of the EL spectral band for the green OLEDs decreases with respect to increasing the ZrO2/zircone pairs. The FWHMs of OLEDs with 0, 2, 4, and 6 pairs of ZrO2/zircone layers are 72 nm, 48 nm, 24 nm, and 12 nm, respectively. A super-narrow FWHM of 12 nm is achieved by using six pairs of the DBR structure. The EQE is increased from 10.7% to 16.1% with four pairs of ZrO2/zircone layers.

  16. Enhanced life time and suppressed efficiency roll-off in phosphorescent organic light-emitting diodes with multiple quantum well structures

    Directory of Open Access Journals (Sweden)

    Ja-Ryong Koo

    2012-03-01

    Full Text Available We demonstrate red phosphorescent organic light-emitting diodes (OLEDs with multiple quantum well structures which confine triplet exciton inside an emitting layer (EML region. Five types of OLEDs, from a single to five quantum wells, are fabricated with charge control layers to produce high efficiencies, and the performance of the devices is investigated. The improved quantum efficiency and lifetime of the OLED with four quantum wells, and its suppressed quantum efficiency roll-off of 17.6%, can be described by the increased electron–hole charge balance owing to the bipolar property as well as the efficient triplet exciton confinement within each EML, and by prevention of serious triplet–triplet and/or triplet–polaron annihilation as well as the Förster self-quenching due to charge control layers.

  17. Chlorinated indium tin oxide electrode by InCl3 aqueous solution for high-performance organic light-emitting diodes

    Science.gov (United States)

    Hu, Yun; Zhou, Dong-Ying; Wang, Bo; Wang, Zhao-Kui; Liao, Liang-Sheng

    2016-04-01

    The authors develop a facile and effective method to produce the chlorinated indium tin oxide (Cl-ITO) treated by InCl3 aqueous solution and UV/ozone. The work function of the Cl-ITO achieved by this treatment is as high as 5.69 eV, which is increased by 1.09 eV compared with that of the regular ITO without any treatment. Further investigation proved that the enhancement of the work function is attributed to the formation of In-Cl bonds on the Cl-ITO surface. Green phosphorescent organic light-emitting devices based on the Cl-ITO electrodes exhibit excellent electroluminescence performance, elongating lifetime due to the improvement in hole injection.

  18. Improvement in luminance efficiency of organic light emitting diodes by suppression of secondary electron bombardment of substrate during sputter deposition of top electrode films

    Science.gov (United States)

    Hamaguchi, Daichi; Kobayashi, Shin-ichi; Uchida, Takayuki; Sawada, Yutaka; Lei, Hao; Hoshi, Yoichi

    2016-10-01

    In this study, we investigated the degradation mechanisms of the luminance performance of organic light-emitting diodes (OLEDs) when their top electrode films were deposited by sputter deposition process. During the sputter deposition of the top electrode films, the suppression of the incidence of high-energy electrons on the substrate was attempted using various methods. As a result, we found that during electrode deposition, the incidence of the high-energy secondary electrons, which were emitted from the target surface, on the substrate was the main cause of the significant degradation of the luminance performance. It was also found that the application of a magnetic field by setting permanent magnets near the substrate holder and the insertion of a shield plate near the target cathode were effective in suppressing the incidence of secondary electrons on the substrate.

  19. Highly efficient and inverted tandem organic light-emitting devices using a MoO3/Al/MoO3 charge generation layer

    Science.gov (United States)

    Li, Ya-Ze; Lee, Chih-Chien; Li, Yan-De; Yeh, Tzu-Hung; Chang, Po-Chien; Biring, Sajal; Huang, Kuan-Chieh; Su, Chia-Hung; Liu, Shun-Wei

    2017-03-01

    We present bottom-emission, inverted, tandem phosphorescent organic light-emitting devices (PHOLEDs) using a multilayer charge generation layer (CGL) of MoO3/Al/MoO3 (MAM), which exhibits a maximum external quantum efficiency of 40% and current efficiency of 120 cd/A. In this inverted tandem structure, the feature of MAM shows a high optical transmittance (approximately 90%) in visible light, an efficient charge generation property, and a relatively smooth morphology (root mean square of ∼0.336 nm) providing an efficient CGL to connect the bottom and top display units. In addition, the device structure of ITO/LiF/TAPC/MAM/BPhen:CS2CO3/BPhen/LiF/Al was proposed to capacitance characterization, and the results demonstrated that using the ultrathin Al of ∼2 nm in a MAM structure exhibited a more efficient CGL for high performance inverted tandem PHOLEDs.

  20. Highly efficient orange and red organic light-emitting diodes with iridium(III) complexes bearing benzothiazole cyclometallate ligands as emitters

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ming [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Wang, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054 (China); Dai, Jun [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Lu, Zhi-yun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Huang, Yan [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Yu, Jun-sheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu, 610054 (China); Luo, Shuai [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Su, Shi-jian, E-mail: mssjsu@scut.edu.cn [State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640 (China)

    2012-12-30

    Two iridium complexes bearing benzothiazole cyclometallate ligands, bis[2-(3 Prime ,5 Prime -di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C{sup 2 Prime }]iridium(III) (acetylacetonate) [(tbpbt){sub 2}Ir(acac)] and bis[2-(9,9-dimethyl-9H-fluoren-2-yl)benzothiazolato-N,C{sup 2 Prime }]iridium(III) (acetylacetonate) [(fbt){sub 2}Ir(acac)], have been evaluated as orange and red electrophosphorescent materials. Both X-ray crystallographic analysis and photophysical results indicate that they possess alleviated self-quenching characteristics due to the existence of steric bulky ligands. As a result, phosphorescent organic light-emitting diodes (PhOLEDs) based on them show high performance even in heavily-doped level ({>=} 15 wt.%). The (tbpbt){sub 2}Ir(acac)-based PhOLED gives efficient orange emission with peak current efficiency of 26.9 cd/A (1280 cd/m{sup 2}) at doping ratio of 15 wt.%, while the 15 wt.% (fbt){sub 2}Ir(acac)-doped device emits efficient red light with Commission Internationale de l'Eclairage coordinates of (0.63, 0.36), and peak current and external quantum efficiency of 28.5 cd/A (1210 cd/m{sup 2}) and 15.6%, respectively. Moreover, all these heavily-doped PhOLEDs exhibit low efficiency roll-off at relatively high current density. - Highlights: Black-Right-Pointing-Pointer Two iridium complexes with bulky ligands are developed as orange/red emitter. Black-Right-Pointing-Pointer Organic light-emitting diodes using these phosphors show low efficiency roll-off. Black-Right-Pointing-Pointer High performance devices could be achieved under high doping ratio of {>=} 15 wt.%. Black-Right-Pointing-Pointer The high device efficiencies arise from the reduced self-quenching of the phosphors.

  1. Fluorometric flow-immunoassay for alkylphenol polyethoxylates on a microchip containing a fluorescence detector comprised of an organic light emitting diode and an organic photodiode.

    Science.gov (United States)

    Liu, Rong; Ishimatsu, Ryoichi; Yahiro, Masayuki; Adachi, Chihaya; Nakano, Koji; Imato, Toshihiko

    2015-03-01

    A compact fluorescence detector was constructed on a microchip from an organic light emitting diode (OLED) as the light source and an organic photodiode (OPD) as the photo-detector and was used in an immunoassay for alkylphenol polyethoxylates (APE). The OLED based on a terbium complex emitted a sharp light at the main wavelength of 546 nm with a full width at half maximum of 9 nm. The incident photo-to-current conversion efficiency (IPCE) of the OPD fabricated with Fullerene 70 (C70) and tris[4-(5-phenylthiopen-2-yl)phenyl]-amine (TPTPA) was approximately 44% for light at a wavelength of 586 nm. The performance of the fluorescence detector was evaluated for the determination of resorufin (λ(em)=586 nm) and the photocurrent of the OPD due to the fluorescence of resorufin was proportional to the concentration of resorufin in the range from 0 to 18 µM with a detection limit (S/N=3) of 0.6 µM. The fluorescence detector was successfully utilized in a competitive enzyme-linked immunosorbent assay for APE, where an anti-APE antibody was immobilized on the surface of the channel of the Polydimethylsiloxane (PDMS) microchip or on the surface of magnetic microbeads. After an immunoreaction with a sample solution of APE containing a horse radish peroxidase (HRP)-labeled APE, the fluorescence of resorufin generated just after introduction of a mixed solution of Amplex Red and H2O2 was measured using the fluorescence detector. The calibration curve for the photocurrent signals of the OPD due to the fluorescence of resorufin against the logarithmic concentration of APE was sigmoidal in shape. The detection limits defined as IC80 were ca. 1 ppb and ca. 2 ppb, respectively, for the methods using the anti-APE antibody immobilized on the surface of the microchannel and in the case where the antibody was immobilized on the surface of magnetic microbeads.

  2. Improving Electron Mobility of Tetraphenylethene-Based AIEgens to Fabricate Nondoped Organic Light-Emitting Diodes with Remarkably High Luminance and Efficiency.

    Science.gov (United States)

    Lin, Gengwei; Peng, Huiren; Chen, Long; Nie, Han; Luo, Wenwen; Li, Yinghao; Chen, Shuming; Hu, Rongrong; Qin, Anjun; Zhao, Zujin; Tang, Ben Zhong

    2016-07-01

    Robust light-emitting materials with strong solid-state fluorescence as well as fast and balanced carrier transporting ability are crucial to achieve high-performance organic light-emitting diodes (OLEDs). In this contribution, two linear tetraphenylethene (TPE) derivatives (TPE-TPAPBI and TPE-DPBI) that are functionalized with hole-transporting triphenylamine and/or electron-transporting 1,2-diphenyl-1H-benzimidazole groups are synthesized and fully characterized. Both TPE-TPAPBI and TPE-DPBI have aggregation-induced emission attributes and excellent photoluminescence quantum yields approaching 100% in vacuum deposited films. They also possess good thermal property, giving high decomposition temperatures (480 and 483 °C) and glass-transition temperatures (141 and 157 °C). TPE-TPAPBI and TPE-DPBI present high electron mobilities of 1.80 × 10(-5) and 1.30 × 10(-4) cm(2) V (-1) s(-1), respectively, at an electric field of 3.6 × 10(5) V cm(-1), which are comparable or even superior to that of 1,3,5-tri(1-phenylbenzimidazol-2-yl)benzene. The nondoped OLED device employing TPE-TPAPBI as active layer performs outstandingly, affording ultrahigh luminance of 125 300 cd m(-2), and excellent maximum external quantum, power and current efficiencies of 5.8%, 14.6 lm W(-1), and 16.8 cd A(-1), respectively, with very small roll-offs, demonstrating that TPE-TPAPBI is a highly promising luminescent material for nondoped OLEDs.

  3. One-Step Preparation of Blue-Emitting (La,Ca)Si3(O,N)5:Ce3+ Phosphors for High-Color Rendering White Light-Emitting Diodes

    Science.gov (United States)

    Yaguchi, Atsuro; Suehiro, Takayuki; Sato, Tsugio; Hirosaki, Naoto

    2011-02-01

    Highly phase-pure (La,Ca)Si3(O,N)5:Ce3+ blue-emitting phosphors were successfully synthesized via the one-step solid-state reaction from the system La2O3-CaO-CeO2-Si3N4. The synthesized (La,Ca)Si3(O,N)5:Ce3+ exhibits tunable blue broadband emission with the dominant wavelength of 466-479 nm and the external quantum efficiency up to ˜45% under 380 nm near-UV (NUV) excitation. Spectral simulations of the trichromatic white light-emitting diodes (LEDs) using (La,Ca)Si3(O,N)5:Ce3+ demonstrated markedly higher color rendering index Ra values of 93-95, compared to 76-90 attained by the systems using a conventional BAM:Eu2+ phosphor or InGaN blue LED. The present achievement indicates the promising applicability of (La,Ca)Si3(O,N)5:Ce3+ as a blue luminescent source for NUV-converting high-color rendering white LEDs.

  4. Luminescence properties of blue La1-xCexAl(Si6-zAlz)(N10-zOz) (z˜1) oxynitride phosphors and their application in white light-emitting diode

    Science.gov (United States)

    Takahashi, Kohsei; Hirosaki, Naoto; Xie, Rong-Jun; Harada, Masamichi; Yoshimura, Ken-ichi; Tomomura, Yoshitaka

    2007-08-01

    This letter reports blue oxynitride phosphors of La1-xCexAl(Si6-zAlz)(N10-zOz) (z˜1) (termed JEM crystal phase) and their application for the white light-emitting diodes (LEDs). The JEM phosphor can be excited by 405nm light efficiently, and its spectrum can be tuned widely by changing the Ce concentration. The emission spectrum of this phosphor is as wide as 110nm in full width at half maximum, which is convenient to solid state lighting. The preparation of white LED was attempted by using a 405nm InGaN chip and oxynitride phosphors in this work. High color rendering index >95 was achieved in white LED with various correlated color temperatures, indicating the suitability of the JEM phosphor in solid-state lightings.

  5. Recent advances in conjugated polymers for light emitting devices.

    Science.gov (United States)

    Alsalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.

  6. Recent Advances in Conjugated Polymers for Light Emitting Devices

    Directory of Open Access Journals (Sweden)

    Mohan Raja

    2011-03-01

    Full Text Available A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.

  7. Strong blue and white photoluminescence emission of BaZrO{sub 3} undoped and lanthanide doped phosphor for light emitting diodes application

    Energy Technology Data Exchange (ETDEWEB)

    Romero, V.H. [Centro de Investigaciones en Optica, A. P. 1-948, Leon Gto., 37160 (Mexico); De la Rosa, E., E-mail: elder@cio.mx [Centro de Investigaciones en Optica, A. P. 1-948, Leon Gto., 37160 (Mexico); Salas, P. [Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, A.P. 1-1010, Queretaro, Qro. 76000 (Mexico); Velazquez-Salazar, J.J. [Department of Physics and Astronomy, The University of Texas at San Antonio One UTSA Circle, San Antonio TX 78249 (United States)

    2012-12-15

    In this paper, we report the obtained strong broadband blue photoluminescence (PL) emission centered at 427 nm for undoped BaZrO{sub 3} observed after 266 nm excitation of submicron crystals prepared by hydrothermal/calcinations method. This emission is enhanced with the introduction of Tm{sup 3+} ions and is stronger than the characteristic PL blue emission of such lanthanide. The proposed mechanism of relaxation for host lattice emission is based on the presence of oxygen vacancies produced during the synthesis process and the charge compensation due to the difference in the electron valence between dopant and substituted ion in the host. Brilliant white light emission with a color coordinate of (x=0.29, y=0.32) was observed by combining the blue PL emission from the host with the green and red PL emission from Tb{sup 3+} and Eu{sup 3+} ions, respectively. The color coordinate can be tuned by changing the ratio between blue, green and red band by changing the concentration of lanthanides. - Graphical abstract: Strong blue emission from undoped BaZrO{sub 3} phosphor and white light emission by doping with Tb{sup 3+} (green) and Eu{sup 3+} (red) after 266 nm excitation. Highlights: Black-Right-Pointing-Pointer Blue emission from BaZrO{sub 3} phosphor. Black-Right-Pointing-Pointer Blue emission enhanced with Tm{sup 3+}. Black-Right-Pointing-Pointer White light from BaZrO{sup 3+} phosphor.

  8. Highly efficient and stable phosphorescent organic light-emitting diodes employing TADF materials as host (Conference Presentation)

    Science.gov (United States)

    Fukagawa, Hirohiko; Iwasaki, Yukiko; Shimizu, Takahisa

    2016-09-01

    The OLED is one of the key devices for realizing next-generation displays and lighting. The efficiency of OLEDs has been improved markedly by employing phosphorescent emitters. However, there are two main issues in the practical application of phosphorescent OLEDs (PHOLEDs): the relatively short operational lifetime of green/blue devices and the relatively high cost owing to the use of a costly emitter with a concentration of about 10% in the emitting layer. Here, we report on our success in resolving these issues by the utilization of thermally activated delayed fluorescent (TADF) materials as the host materials for phosphorescent emitters. Operationally stable green PHOLEDs are demonstrated by employing a TADF material as the host since the triplet excitons of the host, which are key elements in operational degradation, are transferred rapidly to the emitter following the Förster process via reverse intersystem crossing from the triplet to singlet states. In this case, the concentration of the emitter can be reduced to 1-3 wt%, similar to that in fluorescent OLEDs. Although an external quantum efficiency (EQE) of about 20% is obtained in many PHOLEDs regardless of the TADF host, the operational lifetime strongly depends on the host. Our optimized green PHOLED employing only 1 wt% phosphorescent emitter exhibits an EQE of over 20%, a small efficiency roll-off, and a long operational lifetime on the order of 10,000 h with an initial luminance of 1,000 cd/m2.

  9. Mulifunctional Dendritic Emitter: Aggregation-Induced Emission Enhanced, Thermally Activated Delayed Fluorescent Material for Solution-Processed Multilayered Organic Light-Emitting Diodes

    Science.gov (United States)

    Matsuoka, Kenichi; Albrecht, Ken; Yamamoto, Kimihisa; Fujita, Katsuhiko

    2017-01-01

    Thermally activated delayed fluorescence (TADF) materials emerged as promising light sources in third generation organic light-emitting diodes (OLED). Much effort has been invested for the development of small molecular TADF materials and vacuum process-based efficient TADF-OLEDs. In contrast, a limited number of solution processable high-molecular weight TADF materials toward low cost, large area, and scalable manufacturing of solution processed TADF-OLEDs have been reported so far. In this context, we report benzophenone-core carbazole dendrimers (GnB, n = generation) showing TADF and aggregation-induced emission enhancement (AIEE) properties along with alcohol resistance enabling further solution-based lamination of organic materials. The dendritic structure was found to play an important role for both TADF and AIEE activities in the neat films. By using these multifunctional dendritic emitters as non-doped emissive layers, OLED devices with fully solution processed organic multilayers were successfully fabricated and achieved maximum external quantum efficiency of 5.7%.

  10. Largely enhanced efficiency in ZnO nanowire/p-polymer hybridized inorganic/organic ultraviolet light-emitting diode by piezo-phototronic effect.

    Science.gov (United States)

    Yang, Qing; Liu, Ying; Pan, Caofeng; Chen, Jun; Wen, Xiaonan; Wang, Zhong Lin

    2013-02-13

    ZnO nanowire inorganic/organic hybrid ultraviolet (UV) light-emitting diodes (LEDs) have attracted considerable attention as they not only combine the high flexibility of polymers with the structural and chemical stability of inorganic nanostructures but also have a higher light extraction efficiency than thin film structures. However, up to date, the external quantum efficiency of UV LED based on ZnO nanostructures has been limited by a lack of efficient methods to achieve a balance between electron contributed current and hole contributed current that reduces the nonradiative recombination at interface. Here we demonstrate that the piezo-phototronic effect can largely enhance the efficiency of a hybridized inorganic/organic LED made of a ZnO nanowire/p-polymer structure, by trimming the electron current to match the hole current and increasing the localized hole density near the interface through a carrier channel created by piezoelectric polarization charges on the ZnO side. The external efficiency of the hybrid LED was enhanced by at least a factor of 2 after applying a proper strain, reaching 5.92%. This study offers a new concept for increasing organic LED efficiency and has a great potential for a wide variety of high-performance flexible optoelectronic devices.

  11. Simultaneously enhanced device efficiency, stabilized chromaticity of organic light emitting diodes with lambertian emission characteristic by random convex lenses

    Science.gov (United States)

    Lee, Keunsoo; Lee, Jonghee; Kim, Eunhye; Lee, Jeong-Ik; Cho, Doo-Hee; Lim, Jong Tae; Joo, Chul Woong; Kim, Joo Yeon; Yoo, Seunghyup; Ju, Byeong-Kwon; Moon, Jaehyun

    2016-02-01

    An optical functional film applicable to various lighting devices is demonstrated in this study. The phase separation of two immiscible polymers in a common solvent was used to fabricate the film. In this paper, a self-organized lens-like structure is realized in this manner with optical OLED functional film. For an OLED, there are a few optical drawbacks, including light confinement or viewing angle distortion. By applying the optical film to an OLED, the angular spectra distortion resulting from the designed organic stack which produced the highest efficiency was successfully stabilized, simultaneously enhancing the efficiency of the OLED. We prove the effect of the film on the efficiency of OLEDs through an optical simulation. With the capability to overcome the main drawbacks of OLEDs, we contend that the proposed film can be applied to various lighting devices.

  12. Photophysical processes and light extraction in organic light emitting devices; Photophysikalische Prozesse und Lichtextraktion in organischen Leuchtdioden

    Energy Technology Data Exchange (ETDEWEB)

    Reinke, Nils Andre

    2008-11-10

    Alq{sub 3} is the most commonly used material for electron transport and as an emission layer in organic LEDs. However many of its photophysical properties are still unknown. The phosphorescence - known as a low temperature effect - was measured at room temperature for the first time. A new experimental method is presented to identify and characterize a new molecular conversion process into an unknown dark state. This conversion process represents an additional fundamental energy loss channel which is especially important for the development of organic lasers. A physically intuitive model was developed, which allows the calculation of light emission from OLEDs. In addition, a new method for the quantification of optical losses in OLEDs based on an dipole approach has been implemented and verified experimentally. The use of OLEDs was demonstrated for the first time in a chemical sensor, which is based on the detection of the surface plasmon resonance. (orig.)

  13. Low-temperature remote plasma enhanced atomic layer deposition of ZrO2/zircone nanolaminate film for efficient encapsulation of flexible organic light-emitting diodes

    Science.gov (United States)

    Chen, Zheng; Wang, Haoran; Wang, Xiao; Chen, Ping; Liu, Yunfei; Zhao, Hongyu; Zhao, Yi; Duan, Yu

    2017-01-01

    Encapsulation is essential to protect the air-sensitive components of organic light-emitting diodes (OLEDs) such as active layers and cathode electrodes. In this study, hybrid zirconium inorganic/organic nanolaminates were fabricated using remote plasma enhanced atomic layer deposition (PEALD) and molecular layer deposition at a low temperature. The nanolaminate serves as a thin-film encapsulation layer for OLEDs. The reaction mechanism of PEALD process was investigated using an in-situ quartz crystal microbalance (QCM) and in-situ quadrupole mass spectrometer (QMS). The bonds present in the films were determined by Fourier transform infrared spectroscopy. The primary reaction byproducts in PEALD, such as CO, CO2, NO, H2O, as well as the related fragments during the O2 plasma process were characterized using the QMS, indicating a combustion-like reaction process. The self-limiting nature and growth mechanisms of the ZrO2 during the complex surface chemical reaction of the ligand and O2 plasma were monitored using the QCM. The remote PEALD ZrO2/zircone nanolaminate structure prolonged the transmission path of water vapor and smooth surface morphology. Consequently, the water barrier properties were significantly improved (reaching 3.078 × 10‑5 g/m2/day). This study also shows that flexible OLEDs can be successfully encapsulated to achieve a significantly longer lifetime.

  14. Photo- and electroluminescent properties of bithiophene disubstituted 1,3,4-thiadiazoles and their application as active components in organic light emitting diodes

    Science.gov (United States)

    Grykien, Remigiusz; Luszczynska, Beata; Glowacki, Ireneusz; Kurach, Ewa; Rybakiewicz, Renata; Kotwica, Kamil; Zagorska, Malgorzata; Pron, Adam; Tassini, Paolo; Maglione, Maria Grazia; Mauro, Anna De Girolamo Del; Fasolino, Tommaso; Rega, Romina; Pandolfi, Giuseppe; Minarini, Carla; Aprano, Salvatore

    2014-11-01

    Photo- and electroluminescence of five bithiophene disubstituted 1,3,4-thiadiazoles, constituting a new class of solution processable materials for organic opto-electronics, were studied. It was found that the introduction of alkyl solubilizing substituents bathochromically shifted the photo- and electroluminescence bands. The most pronounced effect was observed for the substitution at the Cα position which changed the emitting light color from bluish to green. All five derivatives were tested in host/guest type organic light emitting diodes (OLEDs) with either poly(N-vinylcarbazole) (PVK) or poly(N-vinylcarbazole) + 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PVK + PBD) matrices. The latter matrix turned out especially well suited for these guest molecules yielding devices of varying color coordinates. The best luminance (750 cd/m2) was measured for 2,5-bis(5‧-octyl-2,2‧-bithiophene-5-yl)-1,3,4-thiadiazole with the luminous efficiency exceeding 0.4 cd/A.

  15. Influence of PEDOT:PSS on the effectiveness of barrier layers prepared by atomic layer deposition in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wegler, Barbara, E-mail: barbara.wegler@siemens.com [Siemens AG, Corporate Technology, Guenther-Scharowsky-Strasse 1, 91058 Erlangen, Germany and Center for Medical Physics and Engineering, University of Erlangen-Nuremberg, Henkestrasse 91, 91052 Erlangen (Germany); Schmidt, Oliver [Siemens AG, Corporate Technology, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany); Hensel, Bernhard [Center for Medical Physics and Engineering, University of Erlangen-Nuremberg, Henkestrasse 91, 91052 Erlangen (Germany)

    2015-01-15

    Organic light emitting diodes (OLEDs) are well suited for energy saving lighting applications, especially when thinking about highly flexible and large area devices. In order to avoid the degradation of the organic components by water and oxygen, OLEDs need to be encapsulated, e.g., by a thin sheet of glass. As the device is then no longer flexible, alternative coatings are required. Atomic layer deposition (ALD) is a very promising approach in this respect. The authors studied OLEDs that were encapsulated by 100 nm Al{sub 2}O{sub 3} deposited by ALD. The authors show that this coating effectively protects the active surface area of the OLEDs from humidity. However, secondary degradation processes still occur at sharp edges of the OLED stack where the extremely thin encapsulation layer does not provide perfect coverage. Particularly, the swelling of poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate), which is a popular choice for the planarization of the bottom electrode and at the same time acts as a hole injection layer, affects the effectiveness of the encapsulation layer.

  16. ITO films realized at room-temperature by ion beam sputtering for high-performance flexible organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, B.; Rammal, W.; Moliton, A. [Limoges Univ., Faculte des Sciences et Techniques, CNRS, UMR 6172, Institut de Recherche XLIM, Dept. MINACOM, 87 - Limoges (France)

    2006-06-15

    Indium-tin oxide (ITO) thin layers are obtained by an IBS (Ion Beam Sputtering) deposition process. We elaborated ITO films on flexible substrates of polyethylene terephthalate (PET), under soft conditions of low temperatures and fulfilling the requirements of fabrication processes of the organic optoelectronic components. With a non thermally activated (20 Celsius degrees) ITO deposition assisted by an oxygen flow (1 cm{sup 3}/min), we got an optical transmittance of 90% in the visible range, a resistivity around 10{sup -3} {omega}.cm and a surface roughness lower than 1.5 mm. Thus we realized flexible organic light-emitting diodes (FOLEDs) with good performances: a maximum luminance of 12000 cd/m{sup 2} at a voltage of 19 V and a maximum luminous power efficiency around 1 lm/W at a voltage of 10 V (or a maximum current efficiency of 4 cd/A at 14 V) for the (PET(50 {mu}m) / ITO(200 nm) / TPD(40 nm) / Alq3(60 nm) / Ca / Al) structure. (authors)

  17. Electrochemical Light-Emitting Gel

    Directory of Open Access Journals (Sweden)

    Nobuyuki Itoh

    2010-06-01

    Full Text Available Light-emitting gel, a gel state electroluminescence material, is reported. It is composed of a ruthenium complex as the emitter, an ionic liquid as the electrolyte, and oxide nanoparticles as the gelation filler. Emitted light was produced via electrogenerated chemiluminescence. The light-emitting gel operated at low voltage when an alternating current was passed through it, regardless of its structure, which is quite thick. The luminescence property of the gel is strongly affected by nanoparticle materials. TiO2 nanoparticles were a better gelation filler than silica or ZnO was, with respect to luminescence stability, thus indicating a catalytic effect. It is demonstrated that the light-emitting gel device, with quite a simple fabrication process, flashes with the application of voltage.

  18. Charge generation layers for all-solution processed organic tandem light emitting diodes with regular device architecture

    Science.gov (United States)

    Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Colsmann, Alexander

    2015-10-01

    We present multi-photon OLEDs where enhanced light emission was achieved by stacking two OLEDs utilizing a regular device architecture (top cathode) and an intermediate charge carrier generation layer (CGL) for monolithic device interconnection. With respect to future printing processes for organic optoelectronic devices, all functional layers were deposited from solution. The CGL comprises a low-work function zinc oxide layer that was applied from solution under ambient conditions and at moderate processing temperatures and a high-work function interlayer that was realized from various solution processable precursor-based metal oxides, like molybdenum-, vanadium- and tungsten-oxide. Since every injected electron-hole pair generates two photons, the luminance and the current efficiency of the tandem OLED at a given device current are doubled while the power efficiency remains constant. At a given luminance, the lower operating current in the tandem device reduces electrical stress and improves the device life-time. ToF-SIMS, TEM/FIB and EDX analyses provided evidence of a distinct layer sequence without intermixing upon solution deposition.

  19. Efficient top-emitting white organic light emitting device with an extremely stable chromaticity and viewing-angle

    Institute of Scientific and Technical Information of China (English)

    Shao Ming; Guo Xu; Chen Shu-Fen; Fan Qu-Li; Huang Wei

    2012-01-01

    In this paper,we report on the fabrication of a top-emitting electrophosphorescent p-i- n white organic lightemitting diode on the basis of a low-reflectivity Sm/Ag semi-transparent cathode together with a thickness-optimized ZnS out-coupling layer.With a 24-nm out-coupling layer,the reflectivity of the cathode is reduced to 8% at 492 nm and the mean reflectivity is 24% in the visible area. By introducing an efficient electron blocking layer tris(1-phenylpyrazolato,N,C2')iridium(III) (Ir(ppz)3) to confine the exciton recombination area,the current efficiency and the colour stability of the device are effectively improved.A white emission with the Ir(ppz)3 layer exhibits a maximum current efficiency of 9.8 cd/A at 8 V,and the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates are almost constant during a large voltage change of 6 V-11 V.There is almost no viewing angular dependence in the spectrum when the viewing angle is no more than 45°,with a CIEx,y coordinate variation of only (±0.0025,±0.0008).Even at a large viewing angle (75°),the CIEx,y coordinate change is as small as (±0.0087,±0.0013).

  20. Affect of the electrical characteristics depending on the hole and electron injection materials of red organic light-emitting diodes

    Indian Academy of Sciences (India)

    Jong-Yeol Shin; Hyun-Min Choi; Hyeon-Seok Han; Jin-Woong Hong

    2011-10-01

    This study examined the electrical and optical properties of red OLEDs (organic lightemitting diodes) with a four-layer structure, ITO/amorphous fluoropolymer (AF)/,′--diphenyl,′-bis(3-methylphenyl)-1, 1-biphenyl-4,4′-diamine (TPD)/R-H:R-D/lithium fluoride (LiF)/Al, containing a hole injection material, AF (amorphous fluoropolymer) and an electron injection material, LiF. Compared to the basic structure (two-layer structure), the brightness and luminous efficiency of the four-layer structure, ITO/TPD/R-H:R-D/Al, increased approximately 100 times (30,000 lm/m2) and 150 times (51 lm/W), respectively, with an applied voltage. The excellent efficiency of the external proton was also increased 150 times (0.51%). That is, the hole and electron injection layers improved the surface roughness of ITO and Al, and the interfacial physical properties. In addition, these layers allowed the smooth injection of holes and electrons. The luminance, luminous efficiency and external quantum efficiency were attributed to an increase in the recombination rates.