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Sample records for blue organic light-emitting

  1. Blue fluorescent organic light emitting diodes with multilayered graphene anode

    International Nuclear Information System (INIS)

    As an innovative anode for organic light emitting devices (OLEDs), we have investigated graphene films. Graphene has importance due to its huge potential in flexible OLED applications. In this work, graphene films have been catalytically grown and transferred to the glass substrate for OLED fabrications. We have successfully fabricated 2 mm × 2 mm device area blue fluorescent OLEDs with graphene anodes which showed 2.1% of external quantum efficiency at 1000 cd/m2. This is the highest value reported among fluorescent OLEDs using graphene anodes. Oxygen plasma treatment on graphene has been found to improve hole injections in low voltage regime, which has been interpreted as oxygen plasma induced work function modification. However, plasma treatment also increases the sheet resistance of graphene, limiting the maximum luminance. In summary, our works demonstrate the practical possibility of graphene as an anode material for OLEDs and suggest a processing route which can be applied to various graphene related devices.

  2. Organic optocoupler consisting of an optimized blue organic light emitting diode and an organic photoconductor

    Science.gov (United States)

    El Amrani, A.; Lucas, B.; Antony, R.

    2015-09-01

    We present an optocoupler device based on a blue organic light-emitting diode (OLED) as input unit, and a pentacene photoconductor as output unit. The optocoupler was realized on a transparent glass substrate. The luminance was found larger than 103 cd/m2 with a blue peak emission at 450 nm for the optimized ZnO (120 nm)/ITO (150 nm)/α-NPB (40 nm)/BCP (15 nm)/Alq3 (20 nm)/Al structure. The Ids-Illum/Ids-Dark current ratio, the sensitivity and the current density transfer ratio of the optocoupler are of about 7, 10-1 A/W, and 10-1, respectively. The rise as well as full times were found faster for high bias voltages. The equilibrium regime with less persistent current was reached more quickly, as evidenced by the fast current response for higher bias voltage, indicating a more favorable recombination processes of the charge carriers. The organic optocoupler with a blue OLED reveals promising results; thus, it can be investigated as a good candidates for practical uses in organic optoelectronic circuits with high bias voltages.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Efficient red, green, blue and white organic light-emitting diodes with same exciplex host

    Science.gov (United States)

    Chang, Chih-Hao; Wu, Szu-Wei; Huang, Chih-Wei; Hsieh, Chung-Tsung; Lin, Sung-En; Chen, Nien-Po; Chang, Hsin-Hua

    2016-03-01

    Recently, exciplex had drawn attention because of its potential for efficient electroluminescence or for use as a host in organic light-emitting diodes (OLEDs). In this study, four kinds of hole transport material/electron transport material combinations were examined to verify the formation of exciplex and the corresponding energy bandgaps. We successfully demonstrated that the combination of tris(4-carbazoyl-9-ylphenyl)amine (TCTA) and 3,5,3‧,5‧-tetra(m-pyrid-3-yl)phenyl[1,1‧]biphenyl (BP4mPy) could form a stable exciplex emission with an adequate energy gap. Using exciplex as a host in red, green, and blue phosphorescent OLEDs with an identical trilayer architecture enabled effective energy transfer from exciplex to emitters, achieving corresponding efficiencies of 8.8, 14.1, and 15.8%. A maximum efficiency of 11.3% and stable emission was obtained in white OLEDs.

  8. Efficient white organic light-emitting devices based on blue, orange, red phosphorescent dyes

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ping; Duan Yu; Xie Wenfa; Zhao Yi; Hou Jingying; Liu Shiyong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Zhang Liying; Li Bin, E-mail: chenping0329@gmail.co, E-mail: syliu@jlu.edu.c [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, 130033 (China)

    2009-03-07

    We demonstrate efficient white organic light-emitting devices (WOLEDs) based on an orange phosphorescent iridium complex bis(2-(2-fluorphenyl)-1,3-benzothiozolato-N, C{sup 2'})iridium(acetylacetonate) in combination with blue phosphorescent dye bis[(4, 6-difluorophenyl)-pyridinato-N,C{sup 2})](picolinato) Ir(III) and red phosphorescent dye bis[1-(phenyl)isoquinoline] iridium (III) acetylanetonate. By introducing a thin layer of 4, 7-diphenyl-1,10-phenanthroline between blue and red emission layers, the diffusion of excitons is confined and white light can be obtained. WOLEDs with the interlayer all have a higher colour rendering index (>82) than the device without it (76). One device has the maximum current efficiency of 17.6 cd A{sup -1} and a maximum luminance of 39 050 cd m{sup -2}. The power efficiency is 8.7 lm W{sup -1} at 100 cd m{sup -2}. Furthermore, the device has good colour stability and the CIE coordinates just change from (0.394, 0.425) to (0.390, 0.426) with the luminance increasing from 630 to 4200 cd m{sup -2}.

  9. Electroluminescence enhancement in blue phosphorescent organic light-emitting diodes based on different hosts

    Science.gov (United States)

    Zhang, Wei; Zhang, Fang-hui; Huang, Jin; Zhang, Mai-li; Ma, Ying

    2013-09-01

    Blue phosphorescent organic light-emitting diodes (OLEDs) are fabricated by utilizing the hole transport-type host material of 1,3-bis(carbazol-9-yl)benzene (MCP) combined with the electron transport-type host material of 1,3-bis (triphenylsilyl) benzene (UGH3) with the ratios of 1:0, 8:2 and 6:4, and doping with blue phosphorescent dopant of bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium (FIrpic). The device with an optimum concentration proportion of MCP:UGH3 of 8:2 exhibits the maximum current efficiency of 19.18 cd/A at luminance of 35.71 cd/m2 with maintaining Commission Internationale de L'Eclairage (CIE) coordinates of (0.1481, 0.2695), which is enhanced by 35.7% compared with that of 1:0 with (0.1498, 0.2738). The improvements are attributed to the effective carrier injection and transport in emitting layer (EML) because of mixed host materials. In addition, electron and exciton are confined in the EML, and 4,4',4″-Tris(carbazol-9-yl)-triphenylamine (TCTA) and Di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC) have the high lowest unoccupied molecular orbital (LUMO) energy level and triplet exiton energy.

  10. 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.

  11. Improvement of operation voltage and efficiency in inverted blue phosphorescent organic light-emitting devices

    Science.gov (United States)

    Chang, Chih-Hao; Huang, Hao Siang; Su, Yu-De; Liang, Yi-Hu; Chang, Yu-Shuo; Chiu, Chuan-Hao; Chang, Hsin-Hua

    2013-09-01

    Inverted organic light-emitting diodes (IOLEDs) have drawn considerable attention for use in active-matrix OLED (AMOLED) displays because of their easy integration with n-channel metal-oxide-based thin film transistors (TFTs). The most crucial issue for IOLEDs is the poor electron injection caused by the bottom cathode. According to previous reports, the turn-on voltages of FIrpic-based IOLEDs are within a range from 4 to 8 V. In this study, we focus on developing bottom-emission IOLEDs with low operating voltages through the use of adequate-charge injection materials. We successfully demonstrate a turn-on voltage as low as 3.7 V for blue phosphorescent IOLEDs. The effective electron injection layers (EIL) were constructed by combining an ultrathin aluminum layer, an alkali metal oxide layer and an organic layer doped with alkali metal oxide, allowing for the effective adjustment of the carrier balance in IOLEDs. The peak efficiencies of the IOLEDs reached 15.6%, 31.8 cd/A and 23.4 lm/W. An external nanocomposite scattering layer was used to further improve light extraction efficiency. The IOLEDs equipped with the SiO2 nanocomposite scattering layer respectively provided performance improvements of 1.3 and 1.5 times that of pristine blue phosphorescent IOLEDs at practical luminance levels of 100 cd/m2 and 1000 cd/m2. Through sophisticated EIL and external light-extraction structures, we obtained blue phosphorescent IOLEDs with satisfactory efficiency and low operation voltages, thereby demonstrating the great potential of nanocomposite film for application in IOLEDs.

  12. High color rendering index white organic light-emitting diode using levofloxacin as blue emitter

    Science.gov (United States)

    Miao, Yan-Qin; Gao, Zhi-Xiang; Zhang, Ai-Qin; Li, Yuan-Hao; Wang, Hua; Jia, Hu-Sheng; Liu, Xu-Guang; Tsuboi, Taijuf

    2015-05-01

    Levofloxacin (LOFX), which is well-known as an antibiotic medicament, was shown to be useful as a 452-nm blue emitter for white organic light-emitting diodes (OLEDs). In this paper, the fabricated white OLED contains a 452-nm blue emitting layer (thickness of 30 nm) with 1 wt% LOFX doped in CBP (4,4’-bis(carbazol-9-yl)biphenyl) host and a 584-nm orange emitting layer (thickness of 10 nm) with 0.8 wt% DCJTB (4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran) doped in CBP, which are separated by a 20-nm-thick buffer layer of TPBi (2,2’,2”-(benzene-1,3,5-triyl)-tri(1-phenyl-1H-benzimidazole). A high color rendering index (CRI) of 84.5 and CIE chromaticity coordinates of (0.33, 0.32), which is close to ideal white emission CIE (0.333, 0.333), are obtained at a bias voltage of 14 V. Taking into account that LOFX is less expensive and the synthesis and purification technologies of LOFX are mature, these results indicate that blue fluorescence emitting LOFX is useful for applications to white OLEDs although the maximum current efficiency and luminance are not high. The present paper is expected to become a milestone to using medical drug materials for OLEDs. Project supported by the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-13-0927), the International Science & Technology Cooperation Program of China (Grant No. 2012DFR50460), the National Natural Science Foundation of China (Grant Nos. 21101111 and 61274056), and the Shanxi Provincial Key Innovative Research Team in Science and Technology, China (Grant No. 2012041011).

  13. 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.

  14. 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.

  15. Efficient white phosphorescent organic light-emitting diodes consisting of orange ultrathin and blue mixed host emission layers

    Science.gov (United States)

    Sheng, Ren; Zuo, Liangmei; Xue, Kaiwen; Duan, Yu; Chen, Ping; Cheng, Gang; Zhao, Yi

    2016-08-01

    We have successfully demonstrated highly efficient white phosphorescent organic light-emitting diodes (OLEDs) by inserting an ultrathin non-doped orange layer within blue mixed host emission layer. The key feature of the novel device is the employment of blue mixed host and orange ultrathin layers, resulting in an extended recombination region and more balanced charge carrier. The maximum efficiencies of 33.8 lm W‑1 and 32.2 cd A‑1 are obtained. Moreover, the resulting white device achieves a slight efficiency roll-off and a high luminance at low operating voltage. Our versatile concept suggests a promising simple method to achieve high performance white OLEDs.

  16. Highly efficient organic blue light emitting devices using doped transport layers

    Energy Technology Data Exchange (ETDEWEB)

    Seidler, Nico; Reineke, Sebastian; Walzer, Karsten; Luessem, Bjoern; Leo, Karl [Institut fuer Angewandte Physik/Photophysik, Technische Universitaet Dresden, D-01062 Dresden (Germany); Tomkeviciene, Ausra; Grazulevicius, Juozas V. [Department of Organic Technology, Kaunas University of Technology, Kaunas LT-50254 (Lithuania)

    2009-07-01

    In contrast to red and green OLEDs, blue light emitting devices are still far away from the theoretical limit of about 20 % external quantum efficiency. The best results so far have been achieved involving ultrahigh energy gap organosilicon compounds. Due to their poor transport properties, high efficiencies are obtained only at low current densities and high voltages. We used the blue phosphorescent emitter iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-N,C{sup 2{sup '}}]picolinate (FIrpic) as a dopant in the host material 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole, which possesses both a large triplet exciton energy and good charge carrier transport properties. It was therewith possible to efficiently confine the triplet excitons on the emitting molecules and keep the recombination zone away from the blocking layers. This results in a high external quantum efficiency of 13.1 % at a brightness of 1,000 cd/m{sup 2}. Due to the superior charge carrier injection properties provided by the doped transport layers, this brightness could be achieved at low voltages of only 4.0 V, resulting in a high power efficiency of 22.5 lm/W.

  17. Blue organic light-emitting diode as the electro-optical conversion device for high-speed switching applications

    International Nuclear Information System (INIS)

    Luminance of about 40 mW cm-2 with an emission peak at about 435 nm and the optical pulses of 100 MHz have been obtained from a blue organic light-emitting diode (OLED) based on the N,N'-di(naphtalen-1-yl)-N,N'- diphenylbenzidine emissive layer with the active area of 0.01 mm2. The performance of modulation speed was improved significantly by applying the positive offset voltage in the range of lower voltages. We demonstrate that the OLEDs can be applied to the electro-optical conversion device for high-speed switching applications. (author)

  18. 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.

  19. Organic Light-Emitting Transistors

    OpenAIRE

    Karg, Siegfried; Rost-Bietsch, Constance; Riess, Walter; Loi, Maria Antonietta; Murgia, Mauro; Muccini, Michele

    2005-01-01

    A light-emitting OFET with pronounced ambipolar current characteristic has been prepared by co-evaporation of α-quinquethiophene (α-5T) as hole-transport material and ditridecyl-perylene-tetracarboxylic diimide (P13) as electron-transport material. The light intensity is controlled by both the drain-source voltage VDS and the gate voltage VG. Here, we demonstrate the general concept of adjusting electron and hole mobilities by co-evaporation of two different organic semiconductors.

  20. A comparative study of blue, green and yellow light emitting diode structures grown by metal organic chemical vapor deposition

    Science.gov (United States)

    Ramaiah, Kodigala Subba; Su, Y. K.; Chang, S. J.; Chen, C. H.

    2006-02-01

    The blue, green and yellow light emitting diode (LED) structures have been fabricated by metal organic chemical vapor deposition (MOCVD), and characterized by using different techniques, in order to understand the mechanism between these LEDs. Atomic force microscopy (AFM) analysis revealed that the surface roughness value and density of etch pits were different in the blue, green and yellow LEDs. The threading, misfit dislocations, interfacial dislocations, nano-pipe-like structures and quantum dot-like structures, which determine quality of the structures, were observed by transmission electron microscope (TEM) in the LED structures. The reasons for their formation in the layers are now elucidated. The indium composition, period width such as well and barrier widths were determined by simulating experimental high resolution X-ray diffraction (HRXRD) spectra. The In composition obtained by HRXRD and photoluminescence (PL) measurements for the same LED structure was not one and the same due to several reasons. In fact, the InGaN quantum well emission peaks at 2.667 and 2.544 eV of the blue and green LEDs, respectively showed S-shaped character shift, whereas the quantum well peak at 2.219 eV of yellow LEDs did not show any shift in the PL spectra with decreasing temperature. The blue, green and yellow LEDs showed different activation energies.

  1. Rational design of charge transport molecules for blue organic light emitting devices

    Science.gov (United States)

    Padmaperuma, Asanga; Cosimbescu, Lelia; Koech, Phillip; Polikarpov, Evgueni; Swensen, James; Gaspar, Daniel

    2012-02-01

    The efficiency and stability of blue OLEDs continue to be the primary roadblock to developing organic solid-state white lighting as well as power efficient displays. It is generally accepted that such high quantum efficiency can be achieved with the use of organometallic phosphor doped OLEDs. The transport layers can be designed to increase the carrier density as a way to reduce the drive voltage. We have developed a comprehensive library of charge transporting molecules using combination of theoretical modeling and experimental evidence. Our work focuses on using chemical structure design and computational methods to develop host, transport, emitter, and blocking materials for high efficiency blue OLEDs, along with device architectures to take advantage of these new materials. Through chemical modification of materials we are able to influence both the charge balance and emission efficiency of OLEDs, and understand the influence of the location of photon emission in OLEDs as a function of minor chemical modifications of host and electron transport materials. Design rules, structure-property relationships and results from state of the art OLEDs will be presented.

  2. 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%.

  3. Approaches to blue light emitting polymers

    International Nuclear Information System (INIS)

    Blue-light emitting polymers are important for full colour displays. Blue- light emitting polymers, such as poly(fluorene)s have been reported, but tend to be soluble in the conjugated form. The aim of the project was to produce insoluble polymers, prepared via processible soluble precursor polymers, so that multilayer devices could be easily fabricated. Multilayer devices are often required for more efficient light emission. The target materials were derivatives of poly(p-phenylenevinylene) (PPV), a green-yellow emitting polymer. To blue shift the emission of PPV, bulky substituents, namely chloro, phenyl and alkyl, were attached to the vinylic linkage. These bulky substituents were incorporated to introduce steric interactions between the side group and the backbone phenyl protons, to shorten the effective conjugation length and increase the HOMO-LUMO energy gap. Chloro substituents quenched the fluorescence. Phenyl substituents resulted in highly conjugated precursor polymers with low molecular weights, showing blue- green to green emission in the conjugated form. Alkyl substituted PPV derivatives, prepared via chloro or xanthate precursors, were blue-light emitting conjugated polymers, which were electroluminescent in ITO/polymer/AI devices. The PL quantum yields were found to be up to 38%. The incorporation of electron withdrawing groups into the polymers was attempted, to lower the barrier to electron injection. Chloro groups quenched fluorescence and methylsulfone substituents resulted in insoluble polymers, probably due to cross-linking. However a copolymer containing methylsulfone electron withdrawing groups could be prepared. Phenylsulfone substituents were found to give fluorescent polymers which were soluble in the precursor form. (author)

  4. Solution Processable White Organic Light-Emitting Diodes Using New Blue Host Material Including Substituent Group.

    Science.gov (United States)

    Lee, Jaehyun; Shin, Hwangyu; Park, Jongwook

    2016-02-01

    New host material of T-TATa isomer substituted t-butyl group was investigated in solution process WOLED device compared with 4-(10-(3',5'-diphenylbiphenyl-4-yl)anthracen-9-yl)-N,N-diphenylaniline [TATa]. A two-color WOLED of a co-host system using solution process method was demonstrated. The device configuration was ITO/PEDOT:PSS (40 nm)/emitting layer (50 nm)/TPBi (20 nm)/LiF (1 nm)/AI. The emitting layer consisted of TATa or T-TATa isomer, NPB, DPAVBi (blue dopant), and rubrene (yellow dopant). NPB was used as not only blue host but also helping hole carrier transport. The device using T-TATa compound as a co-host exhibited a luminance efficiency of 3.39 cd/A, which is about twice higher than TATa device of 1.58 cd/A at 10 mA/cm2. PMID:27433738

  5. 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.

  6. 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.

  7. White organic light-emitting devices based on blue fluorescent dye combined with dual sub-monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Huishan, E-mail: yanghuishan1697@163.com

    2013-10-15

    White organic light-emitting devices have been realized by using highly blue fluorescent dye 4,4′-Bis(2,2-diphenyl-ethen-1-yl)-4,4′-di-(tert-butyl)phenyl(p-TDPVBi) and [2-methyl-6-[2-(2, 3,6,7-tetrahydro-1H, red fluorescent dye 5H-benzo[ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile(DCM2), together with well known green fluorescent dye quinacridone (QAD). The fabrication of multilayer WOLEDs did not involve the hard-to-control doping process. The structure of the device is ITO/m-MTDATA (45 nm)/NPB(8 nm)/p-TDPVBi(15 nm)/DCM2(x nm)/Alq{sub 3} (5 nm)/QAD(y nm)/Alq{sub 3}(55 nm)/LiF(1 nm)/Al, where 4,4′,4′′-tris{N,-(3-methylphenyl)-N-phenylamine}triphenylamine (m-MTDATA) acts as a hole injection layer, N,N′-bis-(1-naphthyl)-N, N′-diphenyl-1, 1′-biph-enyl-4, 4′-diamine (NPB) acts as a hole transport layer, p-TDPVBi acts as a blue emitting layer, DCM2 acts as a red emitting layer, QAD acts as a green emitting layer, tris-(8-hydroxyquinoline) aluminum (Alq{sub 3}) acts as an electron transport layer, and WOLEDs of devices A, B, C and D are different in layer thickness of DCM2 and QAD, respectively. To change the thickness of dual sub-monolayer DCM2 and QAD, the WOLEDs were obtained. When x, y=0.05, 0.1, the Commission Internationale de 1’Eclairage (CIE) coordinates of the device change from (0.4458, 0.4589) at 3 V to (0.3137, 0.3455) at 12 V that are well in the white region, and the color temperature and color rendering index were 5348 K and 85 at 8 V, respectively. Its maximum luminance was 35260 cd/m{sup 2} at 12 V, and maximum current efficiency and maximum power efficiency were 13.54 cd/A at 12 V and 6.68 lm/W at 5 V, respectively. Moreover, the current efficiency is largely insensitive to the applied voltage. The electroluminescence intensity of white EL devices varied only little at deferent dual sub-monolayer. Device D exhibited relatively high color rendering index (CRI) in the range of 88–90, which was essentially

  8. High-power-efficiency hybrid white organic light-emitting diodes with a single emitting layer doped with blue delayed fluorescent and yellow phosphorescent emitters

    International Nuclear Information System (INIS)

    High-efficiency hybrid white organic light-emitting diodes (HWOLEDs) with a blue thermally activated delayed fluorescent (TADF) emitter and a yellow phosphorescent emitter doped in a single emitting layer were developed. Exciton harvesting by the blue TADF and yellow phosphorescent emitters rendered both singlet and triplet excitons to contribute to the white emission, which leads to a high quantum efficiency of 22.4% and a power efficiency of 60.3 lm W−1 in the HWOLEDs. In addition, the electroluminescence spectra of the HWOLEDs were kept stable from 100 cd m−2 to 5, 000 cd m−2. (paper)

  9. Fine-tuning the thicknesses of organic layers to realize high-efficiency and long-lifetime blue organic light-emitting diodes

    Institute of Scientific and Technical Information of China (English)

    Yu Jian-Ning; Zhang Min-Yan; Li Chong; Shang Yu-Zhu; Lii Yan-Fang; Wei Bin; Huang Wei

    2012-01-01

    By using p-bis(p - N,N-diphenyl-aminostyryl)benzene doped 2-tert-butyl-9,10-bis-β-naphthyl)-anthracene as an emitting layer,we fabricate a high-efficiency and long-lifetime blue organic light emitting diode with a maximum external quantum efficiency of 6.19% and a stable lifetime at a high initial current density of 0.0375 A/cm2.We demonstrate that the change in the thicknesses of organic layers affects the operating voltage and luminous efficiency greater than the lifetime.The lifetime being independent of thickness is beneficial in achieving high-quality full-colour display devices and white lighting sources with multi-emitters.

  10. A single blue nanorod light emitting diode

    Science.gov (United States)

    Hou, Y.; Bai, J.; Smith, R.; Wang, T.

    2016-05-01

    We report a light emitting diode (LED) consisting of a single InGaN/GaN nanorod fabricated by a cost-effective top-down approach from a standard LED wafer. The device demonstrates high performance with a reduced quantum confined Stark effect compared with a standard planar counterpart fabricated from the same wafer, confirmed by optical and electrical characterization. Current density as high as 5414 A cm‑2 is achieved without significant damage to the device due to the high internal quantum efficiency. The efficiency droop is mainly ascribed to Auger recombination, which was studied by an ABC model. Our work provides a potential method for fabricating compact light sources for advanced photonic integrated circuits without involving expensive or time-consuming fabrication facilities.

  11. High efficiency blue phosphorescent organic light-emitting diode based on blend of hole- and electron-transporting materials as a co-host

    Science.gov (United States)

    Chen, Yonghua; Chen, Jiangshan; Zhao, Yongbiao; Ma, Dongge

    2012-05-01

    Highly efficient blue phosphorescent organic light-emitting diodes (PHOLEDs) were achieved by blending the same hole- and electron-transporting layer materials in device as the host in the emissive layer. The design of this kind of device structure not only decreases the amount of used organic materials but also greatly reduces the structural heterogeneities and effectively facilitates the charge injection into the emissive layer. The resulting blue PHOLEDs exhibit higher electroluminescent efficiency. The maximum external quantum efficiency and power efficiency reach 20.4% and 55.4 lm W-1, respectively, yet keep 19.5% and 49.9 lm W-1, 18.3% and 40.9 lm W-1, respectively, at a luminance of 100 and 1000 cd m-2, showing a low efficiency roll-off property. The mechanism studies fully demonstrate that the bipolar co-host system extends the lifetime of excitons, broadens the recombination zone, and improves the charge carrier injection and transport balance, which are of greatly critical to get the improved efficiency and efficiency roll-off at high luminance in the blue PHOLEDs.

  12. 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.

  13. Quinoline-Substituted 10-(naphthalene-7-yl)anthracene Derivatives for Blue Fluorescent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Kim, Chanwoo; Park, Soo Na; Lee, Seul Bee; Kim, Young Seok; Lee, Ho Won; Kim, Young Kwan; Yoon, Seung Soo

    2016-02-01

    In this study, we have designed and synthesized blue emitters based on quinoline-substituted 10-(naphthalene-7-yl)anthracene. Particularly, a material exhibited highly efficient blue electroluminescence with CIE coordinates of (0.15, 0.18). PMID:27433688

  14. Organic Fluorescent Dyes Supported on Activated Boron Nitride: A Promising Blue Light Excited Phosphors for High-Performance White Light-Emitting Diodes

    Science.gov (United States)

    Li, Jie; Lin, Jing; Huang, Yang; Xu, Xuewen; Liu, Zhenya; Xue, Yanming; Ding, Xiaoxia; Luo, Han; Jin, Peng; Zhang, Jun; Zou, Jin; Tang, Chengchun

    2015-02-01

    We report an effective and rare-earth free light conversion material synthesized via a facile fabrication route, in which organic fluorescent dyes, i.e. Rhodamine B (RhB) and fluorescein isothiocyanate (FITC) are embedded into activated boron nitride (αBN) to form a composite phosphor. The composite phosphor shows highly efficient Förster resonance energy transfer and greatly improved thermal stability, and can emit at broad visible wavelengths of 500-650 nm under the 466 nm blue-light excitation. By packaging of the composite phosphors and a blue light-emitting diode (LED) chip with transparent epoxy resin, white LED with excellent thermal conductivity, current stability and optical performance can be realized, i.e. a thermal conductivity of 0.36 W/mk, a Commission Internationale de 1'Eclairage color coordinates of (0.32, 0.34), and a luminous efficiency of 21.6 lm.W-1. Our research opens the door toward to the practical long-life organic fluorescent dyes-based white LEDs.

  15. Blue organic light-emitting diodes with low driving voltage and maximum enhanced power efficiency based on buffer layer MoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Khizar-ul-Haq, E-mail: khizar_bhr@yahoo.co [School of Materials Science and Engineering, Shanghai University, Jiading Shanghai 201800 (China); Khan, M.A.; Jiang, X.Y. [School of Materials Science and Engineering, Shanghai University, Jiading Shanghai 201800 (China); Zhang, Z.L. [School of Materials Science and Engineering, Shanghai University, Jiading Shanghai 201800 (China)] [Key Laboratories of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072 (China); Zhang, X.W. [School of Materials Science and Engineering, Shanghai University, Jiading Shanghai 201800 (China); Wei, Bin [School of Materials Science and Engineering, Shanghai University, Jiading Shanghai 201800 (China)] [Key Laboratories of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072 (China); Wei, J.M.; Zhang Liang; Li Jun [School of Materials Science and Engineering, Shanghai University, Jiading Shanghai 201800 (China)

    2009-10-15

    Blue organic light-emitting devices based on wide bandgap host material, 2-(t-butyl)-9, 10-di-(2-naphthyl) anthracene (TBADN), blue fluorescent styrylamine dopant, p-bis(p-N,N-diphenyl-amino-styryl)benzene (DSA-Ph) have been realized by using molybdenum oxide (MoO{sub 3}) as a buffer layer and 4,7-diphenyl-1,10-phenanthroline (BPhen) as the ETL. The typical device structure used was glass substrate/ITO/MoO{sub 3} (5 nm)/NPB (30 nm)/[TBADN: DSA-Ph (3 wt%)](35 nm)/BPhen (12 nm)/LiF (0.8 nm)/Al (100 nm). It was found that the MoO{sub 3}-parallel BPhen-based device shows the lowest driving voltage and highest power efficiency among the referenced devices. At the current density of 20 mA/cm{sup 2}, its driving voltage and power efficiency are 5.4 V and 4.7 Lm/W, respectively, which is independently reduced 46%, and improved 74% compared with those the m-MTDATA-parallel Alq{sub 3} is based on, respectively. The J-V curves of 'hole-only' devices reveal that a small hole injection barrier between MoO{sub 3}-parallel NPB leads to a strong hole injection, resulting low driving voltage and high power efficiency. The results strongly indicate that carrier injection ability and balance shows a key significance in OLED performance.

  16. 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.

  17. 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

  18. 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.

  19. High performance blue organic light-emitting devices fabricated by using the doped Alq3 in NPB hole transmistion layers

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We have designed a new structure blue emission device with doped Alq3 of 3% in hole transmission layers of NPB. The CIE coordination of the devices is (0.17,0.19). The maximum electroluminescence efficiency is 4.1 cd/A at 11V, the brightness is 118.8 cd/m2 at 7 V, and the maximum brightness is 10770 cd/m2 at 13V.

  20. 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).

  1. Multi-3,3'-Bicarbazole-Substituted Arylsilane Host Materials with Balanced Charge Transport for Highly Efficient Solution-Processed Blue Phosphorescent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Sun, Dianming; Zhou, Xiaokang; Li, Huihui; Sun, Xiaoli; Ren, Zhongjie; Ma, Dongge; Yan, Shouke

    2015-08-19

    A series of 3,3'-bicarbazole (mCP)-functionalized tetraphenylsilane derivatives (SimCPx), including bis(3,5-di(9H-carbazol-9-yl)phenyl)diphenylsilane (SimCP2), tris(3,5-di(9H-carbazol-9-yl)phenyl)methylsilane (SimCP3-CH3), tris(3,5-di(9H-carbazol-9-yl)phenyl)phenylsilane (SimCP3-Ph), and tetrakis(3,5-di(9H-carbazol-9-yl)phenyl)silane (SimCP4), serving as bipolar blue hosts for bis[2-(4,6-difluorophenyl)pyridyl-N,C2']iridium(III) (FIrpic), have been synthesized by incorporating different ratios of mCP subunits into a central silicon atom. All of the SimCPx derivatives have wide bandgaps and high triplet energies because of the indirect linkage by silicon between each mCP subunit. The good solubility and high thermal and morphological stability of SimCPx are beneficial for forming amorphous and homogeneous films through solution processing. Density functional theory simulations manifest the better bipolar characteristics for SimCPx using three and four mCP units rather than the represented bipolar host SimCP2. As a result, SimCP4 presents the best electron-transporting ability for charge balance. Consequently, the lowest driving voltage of 4.8 eV, and the favorable maximum efficiencies of 14.2% for external quantum efficiency (28.4 cd A(-1), 13.5 lm W(-1)), are achieved by solution-processed, SimCP4-based blue phosphorescent organic light-emitting diodes as the highest performance among SimCPx, in which 32% improved device efficiencies compared to that of SimCP2 are obtained. It is inspiring to develop efficient bipolar hosts for blue phosphors by just incorporating monopolar carbazole into arylsilanes in two steps. PMID:26252613

  2. 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...

  3. Blue light emitting diode internal and injection efficiency

    Directory of Open Access Journals (Sweden)

    Ilya E. Titkov

    2012-09-01

    Full Text Available A simple experimental method of light emitting diode (LED injection efficiency (IE determination was suggested. IE and internal quantum efficiency (IQE calculation is an actual and difficult problem in LED science. In this paper IE and IQE of blue LEDs were determined separately. The method is based on electroluminescence data fitting by the modified rate equation model. Efficiency droop caused by Auger recombination and poor injection were taken into account. Only one reasonable assumption was accepted during the calculations: IE tends to 1 at low current densities.

  4. Biologically Inspired Organic Light-Emitting Diodes.

    Science.gov (United States)

    Kim, Jae-Jun; Lee, Jaeho; Yang, Sung-Pyo; Kim, Ha Gon; Kweon, Hee-Seok; Yoo, Seunghyup; Jeong, Ki-Hun

    2016-05-11

    Many animal species employ highly conspicuous traits as courtship signals for successful mating. Fireflies utilize their bioluminescent light as visual courtship signals. In addition to efficient bioluminescent light emission, the structural components of the firefly lantern also contribute to the enhancement of conspicuous optical signaling. Recently, these firefly lantern ultrastructures have attracted much interest and inspired highly efficient light management approaches. Here we report on the unique optical function of the hierarchical ultrastructures found in a firefly (Pyrocoelia rufa) and their biological inspiration of highly efficient organic light-emitting diode (OLED) applications. The hierarchical structures are comprised of longitudinal nanostructures and asymmetric microstructures, which were successfully replicated using geometry-guided resist reflow, replica molding, and polydimethylsiloxane (PDMS) oxidation. The external quantum efficiency (EQE) of the bioinspired OLEDs was enhanced by up to 61%. The bioinspired OLEDs clearly showed side-enhanced super-Lambertian emission with a wide-viewing angle. The highly efficient light extraction and wide-angle illumination suggest how the hierarchical structures likely improve the recognition of firefly optical courtship signals over a wide-angle range. At the same time, the biologically inspired designs provide a new paradigm for designing functional optical surfaces for lighting or display applications. PMID:27014918

  5. Sensitized fluorescence in organic light emitting diodes

    Science.gov (United States)

    Nguyen, C.; Ingram, G.; Lu, Z. H.

    2014-10-01

    We have studied the effects of incorporating phosphorescent sensitizers into fluorescent organic-light emitting diode (OLED) devices. In the emissive layer of this system, the host material is co-doped at low concentrations with both a phosphorescent and a fluorescent dye. The purpose of the phosphorescent dopant is to capture both singlet and triplet excitons from the host material and to transfer them into the singlet state of the fluorescent dye. Ideally, recombination of excitons and the emission of light would occur solely on the fluorescent dye. This sensitized fluorescent system can potentially achieve 100% internal quantum efficiency as both triplet and singlet states are being harvested. We have observed an almost two-fold improvement in the quantum efficiency of a sensitized fluorescent system, utilizing rubrene as the fluorescent dye and Ir(ppy)2(acac) as the sensitizer, versus a standard rubrene-based host-guest system. By testing various dopant concentrations, the optimal emissive layer composition for this system was determine to be ~2 wt.% rubrene and ~7 wt.% Ir(ppy)2(acac) in a CBP host.

  6. 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.

  7. 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.

  8. Enhancement of efficiency in blue organic light-emitting devices with nanoscale barrier and trapping layers embedded in an emitting layer and a hole transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dea Uk [Division of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Choo, Dong Chul [Research Institute of Information Display, Department of Information Display Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, Tae Whan, E-mail: twk@hanyang.ac.k [Division of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Research Institute of Information Display, Department of Information Display Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Seo, Ji Hyun; Park, Jung Hyun; Kim, Young Kwan [Department of Information Display Engineering and COMID, Hong-ik University, Seoul 121-791 (Korea, Republic of)

    2009-07-01

    The electrical and the optical properties of the organic light-emitting diodes (OLEDs) utilizing a tetraphenylnaphthacene (rubrene) trapping layer and an 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) barrier layer with a nanoscale thickness were investigated. While the operating voltage of the OLED with a rubrene trapping layer in the HTL significantly increased because of a decrease in the hole mobility of the HTL, that of the OLED with a rubrene trapping layer in the EML slightly decreased resulting from an increase of the trapped electrons and holes in a rubrene trapping layer. The electroluminescence peak corresponding to the emission zone in the EML of OLEDs with a rubrene trapping layer and a TPBI barrier layer shifts to the EML center due to the existence of trapping layer in the EML.

  9. 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.

  10. Recent progress in solution processable organic light emitting devices

    Science.gov (United States)

    So, Franky; Krummacher, Benjamin; Mathai, Mathew K.; Poplavskyy, Dmitry; Choulis, Stelios A.; Vi, Choong-En

    2007-11-01

    Organic light emitting devices (OLEDs) have been the subject of intense research because of their potential for flat panel display and solid state lighting applications. While small molecule OLEDs with very high efficiencies have been demonstrated, solution processable devices are more desirable for large size flat panel display and solid state applications because they are compatible with low cost, large area roll-to-roll manufacturing process. In this review paper, we will present the recent progress made in solution processable OLEDs. The paper will be divided into three parts. In the first part of the paper, we will focus on the recent development of fluorescent polymer OLEDs based on conjugated polyfluorene copolymers. Specifically, we will present results of carrier transport and injection measurements, and discuss how the charge transport and injection properties affect the device performance. In the second part of the paper, we will focus on the recent progress on phosphorescent dye-dispersed nonconjugated polymer OLEDs. Specifically, we will present our recent results on high efficiency green and blue emitting devices based on the dye-dispersed polymer approach. Similar to fluorescent conjugated polymer OLEDs, charge transport and injection properties in dye-dispersed polymer OLEDs also play an important role in the device performance. In the third part of this paper, we will present our results on white emitting phosphorescent OLEDs. Two approaches have been used to demonstrate white emitting OLEDs. First, white emitting OLEDs were made using blue emitting OLEDs with downconversion phosphors. Second, white emitting OLEDs were made by dispersing red, green, and blue phosphorescent dyes into the light emitting layer. High efficiency devices have been demonstrated with both approaches.

  11. [A novel yellow organic light-emitting device].

    Science.gov (United States)

    Ma, Chen; Wang, Hua; Hao, Yu-Ying; Gao, Zhi-Xiang; Zhou, He-Feng; Xu, Bing-She

    2008-07-01

    The fabrication of a novel organic yellow-light-emitting device using Rhodamine B as dopant with double quantum-well (DQW) structure was introduced in the present article. The structure and thickness of this device is ITO/CuPc (6 nm) /NPB (20 nm) /Alq3 (3 nm)/Alq3 : Rhodamine B (3 nm) /Alq3 (3 nm) /Al q3 : Rhodamine B(3 nm) /Alq3 (30 nm) /Liq (5 nm)/Al (30 nm). With the detailed investigation of electroluminescence of the novel organic yellow-light-emitting device, the authors found that the doping concentration of Rhodamine B (RhB) had a very big influence on luminance and efficiency of the organic yellow-light-emitting device. When doping concentration of Rhodamine B (RhB) was 1.5 wt%, the organic yellow-light-emitting device was obtained with the maximum current efficiency of 1.526 cd x A(-1) and the maximum luminance of 1 309 cd x m(-2). It can be seen from the EL spectra of the devices that there existed energy transferring from Alq3 to RhB in the organic light-emitting layers. When the doping concentration of RhB increased, lambda(max) of EL spectra redshifted obviously. The phenomenon was attributed to the Stokes effect of quantum wells and self-polarization of RhB dye molecules. PMID:18844143

  12. 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.

  13. 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.  ……

  14. 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.

  15. Theoretical Design of Blue-light-emitting Material Based on 1,2,3-Benzotriazole-based Derivative

    Institute of Scientific and Technical Information of China (English)

    HU Bo; YAO Chan; HUANG Xu-Ri

    2011-01-01

    Theoretically,1,2,3-benzotriazole(BT)-based derivative is designed by the struc-tural tuning in 2,1,3-benzothiadiazole(BTD)-based derivative and presents potential for applications in organic light-emitting diodes(OLEDs).Calculations show that the emission spectrum of BT-based derivative is located at the blue scope,so it can act as a blue-light-emitting material.Importantly,the oscillator strength of emission spectrum is significantly enhanced by replacing BTD with BT,implying it possess large fluorescent intensity.Additionally,BT-based derivative exhibits improved hole transportation with respect to the BTD-based derivative.

  16. Proceedings of the 5th International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004)

    Science.gov (United States)

    Suh, Eun-Kyung; Yoon, Euijoon; Lee, Hyung Jae

    2004-09-01

    The 5th International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004) was held in Gyeongju, Korea, 15-19 March 2004. The purpose of the symposium was to provide a forum for scientists and engineers to discuss recent progress and future trends in the rapidly advancing wide band gap semiconductor science and technologies and their applications in blue laser and light emitting diodes.

  17. A Flexible Blue Light-Emitting Diode Based on ZnO Nanowire/Polyaniline Heterojunctions

    OpenAIRE

    Liu, Y Y; Wang, X. Y.; Cao, Y; X. D. Chen; Xie, S. F.; X. J. ZHENG; Zeng, H. D.

    2013-01-01

    An organic/inorganic light-emitting diode (LED) consisting of n-type vertically aligned ZnO nanowires (NWs) and p-type proton acid doped polyaniline (PANi) is reported. The device was fabricated on flexible indium-tin-oxide (ITO) coated polyethylene terephthalate (PET) substrate. A broad blue light emission band ranging from 390 nm to 450 nm was observed in the electroluminescence (EL) spectra of the device, which was related to the interface recombination of electrons in the conduction band ...

  18. White-blue electroluminescence from a Si quantum dot hybrid light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Xin, Yunzi; Nishio, Kazuyuki [Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-hiroshima 739-8526 (Japan); Saitow, Ken-ichi, E-mail: saitow@hiroshima-u.ac.jp [Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-hiroshima 739-8526 (Japan); Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, Higashi-hiroshima 739-8526 (Japan)

    2015-05-18

    A silicon (Si) quantum dot (QD)-based hybrid inorganic/organic light-emitting diode (LED) was fabricated via solution processing. This device exhibited white-blue electroluminescence at a low applied voltage of 6 V, with 78% of the effective emission obtained from the Si QDs. This hybrid LED produced current and optical power densities 280 and 350 times greater than those previously reported for such device. The superior performance of this hybrid device was obtained by both the prepared Si QDs and the optimized layer structure and thereby improving carrier migration through the hybrid LED and carrier recombination in the homogeneous Si QD layer.

  19. 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

  20. 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.

  1. 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...

  2. Transparent white organic light emitting diodes with improved cathode transparency

    Science.gov (United States)

    Lee, Jeong-Ik; Lee, Jonghee; Lee, Joowon; Shin, Jae-Heon; Hwang, Chi-Sun; Chu, Hye Yong

    2009-08-01

    We have fabricated transparent white organic light emitting diode (WOLED) for lighting application based on a hybrid white OLED and a phosphorescence white OLED. For the hybrid WOLED, a blue fluorescence emitting layer (FLEML) and green and red phosphorescence emitting layers (PH-EMLs) have been used in the device structure of ITO/hole transporting layer (HTL)/PH-EMLs/interlayer/FL-EML/ETL/LiF/Al. The balanced emissions from the FLEML and the PH-EMLs have been obtained by using appropriate carrier (hole) trapping effects in the PH-EMLs, which resulted in external and power efficiencies of 15 % and 27 lm/W, respectively, at a luminance of 1000 cd/m2 without any out-coupling enhancement. The Commission Internationale de L'Eclairage (CIE) coordinates of this hybrid WOLED is (0.43,0.44) with color rendering index (CRI) of 80 and correlated color temperature (CCT) of 3200 K, respectively, in the bottom emission structure. Based on this hybrid WOLED, we established highly efficient transparent WOLED by introduction of a transparent cathode, and obtained over 19 lm/W of power efficiency at a total luminance of 1000 cd/m2 as well as over 60 % of transmittance at 550 nm with the conventional glass encapsulation. Moreover, when the phosphorescent white OLED was combined with a transparent cathode, the power efficiency was reached up to 24 lm/W of power efficiency at a total luminance of 1000 cd/m2.

  3. 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

  4. High-efficiency organic light-emitting diodes with fluorescent emitters

    Science.gov (United States)

    Nakanotani, Hajime; Higuchi, Takahiro; Furukawa, Taro; Masui, Kensuke; Morimoto, Kei; Numata, Masaki; Tanaka, Hiroyuki; Sagara, Yuta; Yasuda, Takuma; Adachi, Chihaya

    2014-05-01

    Fluorescence-based organic light-emitting diodes have continued to attract interest because of their long operational lifetimes, high colour purity of electroluminescence and potential to be manufactured at low cost in next-generation full-colour display and lighting applications. In fluorescent molecules, however, the exciton production efficiency is limited to 25% due to the deactivation of triplet excitons. Here we report fluorescence-based organic light-emitting diodes that realize external quantum efficiencies as high as 13.4-18% for blue, green, yellow and red emission, indicating that the exciton production efficiency reached nearly 100%. The high performance is enabled by utilization of thermally activated delayed fluorescence molecules as assistant dopants that permit efficient transfer of all electrically generated singlet and triplet excitons from the assistant dopants to the fluorescent emitters. Organic light-emitting diodes employing this exciton harvesting process provide freedom for the selection of emitters from a wide variety of conventional fluorescent molecules.

  5. 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.

  6. A switched supply tunable red-green-blue light emitting diode driver.

    Science.gov (United States)

    Feng, Weifeng; Shi, Frank G; He, Yongzhi; Zhao, Bin

    2008-04-01

    This paper presents a new switched supply tunable red-green-blue (RGB) light emitting diode (LED) driver. The RGB LEDs act not only as light emitting devices but also as rectifying diodes in the presented driver circuit. The RGB LED color control is realized by controlling the switched supply voltage amplitude, frequency, and duty cycle. The driver efficiency is high since the only loss in the driver circuit is the switch and can be further reduced by direct alternate current supply.

  7. 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.

  8. 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. %.

  9. Organic Light-Emitting Devices with Tandem Structure.

    Science.gov (United States)

    Chiba, Takayuki; Pu, Yong-Jin; Kido, Junji

    2016-06-01

    Tandem organic light-emitting devices (OLEDs) have attracted considerable attention for solid-state lighting and flat panel displays because their tandem architecture enables high efficiency and long operational lifetime simultaneously. In the tandem OLED structure, plural light-emitting units (LEUs) are stacked in series through a charge generation layer (CGL) and an electron injection layer (EIL). In this chapter, we focus on the key features of tandem OLEDs for high efficiency and long operational lifetimes. We also demonstrate the effect of the CGL comprising a Lewis acid, an n-type semiconductor metal oxide, and an organic electron-accepting material. We discuss the two types of EILs in tandem OLEDs: alkali metals containing n-type compounds and ultra-thin metals. Finally, we focus on the recent progress of the state-of-the-art solution-processed tandem OLEDs. PMID:27573273

  10. 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").

  11. Novel Field Emission Organic Light Emitting Diodes with Dynode

    Institute of Scientific and Technical Information of China (English)

    Meiso YOKOYAMA; LI Chi-Shing; SU Shui-hsiang

    2011-01-01

    This work presents novel field emission organic light emitting diodes (FEOLEDs) with dynode, in which an organic EL light-emitting layer is used instead of an inorganic phosphor thin film in the field emission display (FED). The proposed FEOLEDs introduce field emission electrons into organic light emitting diodes (OLEDs),which exhibit a higher luminous efficiency than conventional OLED. The field emission electrons emitted from the carbon nanotubes (CNTs) cathode and to be amplified by impact the dynode in vacuum. These field emission electrons are injected into the multi-layer organic materials of OLED to increase the electron density. Additionally, the proposed FEOLED increase the luminance of OLED from 10 820 cd/m2 to 24 782 cd/m2 by raising the current density of OLED from an external electron source. The role of FEOLED is to add the quantity of electrons-holes pairs in OLED,which increase the exciton and further increase the luminous efficiency of OLED. Under the same operating current density, the FEOLED exhibits a higher luminous efficiency than that of OLED.

  12. 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...

  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. High saturated blue phosphorescent organic lighting emitting devices%高饱和度蓝色磷光有机发光器件

    Institute of Scientific and Technical Information of China (English)

    丁磊; 张方辉; 李艳飞; 梁田静; 张静

    2011-01-01

    使用典型天蓝色磷光材料FIrpic作为磷光金属微腔有机发光器件(OLED)的发光层,以高反射的Al膜作为阴极顶电极和半透明的Al膜作为阳极底电极,采用空穴和电子注入层MoO3和LiF,制备了结构glass/Al(15nm)/MoO3(znm)/NPD(40nm)/mCP:Flrpic(30Ftm,7%)/BCP(20nm)/Alqa(20nm)/LiF(1nm)/Al(150nm)的底发射磷光金属微腔OLED,微腔OLED正方向电致发光(EL)光谱的中心波长为468nm,半波宽(FWHM)约为24nm,色坐标为(0.14,0.15),其发光波长得到调制,光谱得到窄化。理论模拟得到微腔OLED的发光增强因子与实际光谱吻合。%The sky-blue phosphor Flrpic-based electrophosphorescent bottom-emitting metallic microcavity organic lighvemitting device (OLED) employs a structure of glass/Al(15 nm)/MoO3 (x nm)/NPD (40 nm)/ mCP:FIrpie(30 nm,7%)/13CP(20 nm)/Alq3 (20 nm)/LiF(1 nm)/Al(150 nm),using MoO3 and LiF as efficient hole and electron injection layers, respectively. The cavity structure consists of the highly reflective Al cathode and the semitransparent Al anode. The emission spectrum of the microcavity OLED is centered at 468 nm with a full width at half maximum (FWHM) of 24 nm,and CIE color coordinates are x=0. 14 and y=0.15. It's indicated that the spectrum is modulated and narrowed. Theoretical simulations of the enhancement factor of the microcavity OLED agree with experimented results well.

  15. N-(4-tert-Butylphenyl)-N-phenyl-4-(9,10-diphenylanthracen-3-yl)benzenamine for blue organic light-emitting diodes

    Science.gov (United States)

    Kim, Young Seok; Kim, Dong Young; Lee, Song Eun; Kim, Young Kwan; Yoon, Seung Soo

    2016-06-01

    In this study, we have synthesized two blue fluorescent materials based on anthracene derivatives with electron-donating diphenylamine moieties by Suzuki cross-coupling reactions. To explore their electroluminescent properties as blue emitting materials, multilayer devices were fabricated in following sequence: indium–tin-oxide (180 nm)/4,4‧-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (50 nm)/blue emitters (30 nm)/bathophenanthroline (30 nm)/lithium quinolate (2 nm)/Al (100 nm). Among them, a device using N-(4-tert-butylphenyl)-N-phenyl-4-(9,10-diphenylanthracen-3-yl)benzenamine exhibited efficient blue emission with a luminous, power and external quantum efficiency of 3.11 cd/A, 2.39 lm/W, and 1.82% at 20 mA/cm2, respectively. The Commission International de L’Eclairage coordinates of this device were (x,y) = (0.14,0.15) at 6.0 V.

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

    International Nuclear Information System (INIS)

    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. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  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. 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

  20. 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.

  1. 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.

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

    International Nuclear Information System (INIS)

    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/cm2, the optimal radiance R could reach 0.38 mW/cm2, and the quantum efficiency was 1.25%. using the delayed EL technique, electron mobilities in DPVBi and CBP were determined to be ∼ 10-5 cm2/Vs and ∼ 10-4 cm2/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

  3. 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.

  4. 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...

  5. 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.

  6. 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...

  7. 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.

  8. Exciton dynamics in organic light-emitting diodes

    Science.gov (United States)

    Kim, Kwangsik; Won, Taeyoung

    2012-11-01

    In this paper, we present a numerical simulation for the optoelectronic material and device characterization in organic light-emitting diodes (OLEDs). Our model includes a Gaussian density of states to account for the energetic disorder in the organic semiconductors and the Fermi-Dirac statistics to account for the charge-hopping process between uncorrelated sites. The motivation for this work is the extraction of the emission profile and the source spectrum of a given OLED structure. The physical model covers all the key physical processes in OLEDs: namely, charge injection, transport and recombination, exciton diffusion, transfer, and decay. The exciton model includes generation, diffusion, energy transfer, and annihilation. We assume that the light emission originates from an oscillation and is thus embodied as excitons and is embedded in a stack of multilayers. The outcoupled emission spectrum is numerically calculated as a function of viewing angle, polarization, and dipole orientation. We also present simulated current-voltage and transient results.

  9. Efficiency optimization of green phosphorescent organic light-emitting device

    International Nuclear Information System (INIS)

    Using a narrow band gap host of bis[2-(2-hydroxyphenyl)-pyridine]beryllium (Bepp2) and green phosphorescent Ir(ppy)3 [fac-tris(2-phenylpyridine) iridium III] guest concentration as low as 2%, high efficiency phosphorescent organic light-emitting diode (PHOLED) is realized. Current and power efficiencies of 62.5 cd/A (max.), 51.0 lm/W (max.), and external quantum efficiency (max.) of 19.8% are reported in this green PHOLED. A low current efficiency roll-off value of 10% over the brightness of 10,000 cd/m2 is noticed in this Bepp2 single host device. Such a high efficiency is obtained by the optimization of the doping concentration with the knowledge of the hole trapping and the emission zone situations in this host-guest system. It is suggested that the reported device performance is suitable for applications in high brightness displays and lighting.

  10. 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.

  11. Active differential optical absorption spectroscopy for NO2 gas pollution using blue light emitting diodes

    Science.gov (United States)

    Aljalal, Abdulaziz; Gasmi, Khaled; Al-Basheer, Watheq

    2015-05-01

    Availability of high intensity light emitting diodes in the blue region offer excellent opportunity for using them in active Differential Optical Absorption Spectroscopy (DOAS) to detect air pollution. Their smooth and relatively broad spectral emissions as well as their long life make them almost ideal light sources for active DOAS. In this study, we report the usage of a blue light emitting diode in an active DOAS setup to measure traces of NO2 gas and achieving few parts per billion detection limit for a path length of 300 m. Details of the setup will be presented along with the effects on measurement accuracy due to shifts in the measured spectra calibration and due to using theoretical instrument Gaussian function instead of the measured instrument function.

  12. White organic light-emitting diodes with 9, 10-bis (2-naphthyl) anthracene

    Energy Technology Data Exchange (ETDEWEB)

    Guan Yunxia; Niu Lianbin [Key Laboratory of Optical Engineering, College of Physics and Information Technology, Chongqing Normal University, Chongqing 400047 (China)], E-mail: gyxybsy@126.com, E-mail: niulb03@126.com

    2009-03-01

    White organic light-emitting diodes were fabricated by 9, 10-bis (2-naphthyl) anthracene (ADN) doped with Rubrene with a structure of ITO/copper phthalocyanine (CuPc) / NPB /ADN: Rubrene /Alq{sub 3} /CsF/Mg:Ag/Ag. Multilayer organic devices using AND and Rubrene as an emitting layer produced white emissions with good chromaticity and luminous efficiency as high as 5.93 cd/A. This performance can be explained by Foerster energy transfer from the blue-emitting host to the orange-emitting dopant.

  13. Adhesion in flexible organic and hybrid organic/inorganic light emitting device and solar cells

    International Nuclear Information System (INIS)

    This paper presents the results of an experimental study of the adhesion between bi-material pairs that are relevant to organic light emitting devices, hybrid organic/inorganic light emitting devices, organic bulk heterojunction solar cells, and hybrid organic/inorganic solar cells on flexible substrates. Adhesion between the possible bi-material pairs is measured using force microscopy (AFM) techniques. These include: interfaces that are relevant to organic light emitting devices, hybrid organic/inorganic light emitting devices, bulk heterojunction solar cells, and hybrid combinations of titanium dioxide (TiO2) and poly(3-hexylthiophene). The results of AFM measurements are incorporated into the Derjaguin-Muller-Toporov model for the determination of adhesion energies. The implications of the results are then discussed for the design of robust organic and hybrid organic/inorganic electronic devices

  14. [Effects of white organic light-emitting devices using color conversion films on electroluminescence spectra].

    Science.gov (United States)

    Hou, Qing-Chuan; Wu, Xiao-Ming; Hua, Yu-Lin; Qi, Qing-Jin; Li, Lan; Yin, Shou-Gen

    2010-06-01

    The authors report a novel white organic light-emitting device (WOLED), which uses a strategy of exciting organic/ inorganic color conversion film with a blue organic light-emitting diode (OLED). The luminescent layer of the blue OLED was prepared by use of CBP host blended with a blue highly fluorescent dye N-BDAVBi. The organic/inorganic color conversion film was prepared by dispersing a mixture of red pigment VQ-D25 and YAG : Ce3+ phosphor in PMMA. The authors have achieved a novel WOLED with the high color stability by optimizing the thickness and fluorescent pigment concentration of the color conversion film. When the driving voltage varied between 6 and 14 V, the color coordinates (CIE) varied slightly from (0.354, 0.304) to (0.357, 0.312) and the maximum current efficiency is about 5.8 cd x A(-1) (4.35 mA x cm(-2)), the maximum brightness is 16 800 cd x m(-2) at the operating voltage of 14 V. PMID:20707129

  15. 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)

  16. 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.

  17. High-efficiency white organic light-emitting diodes using thermally activated delayed fluorescence

    Science.gov (United States)

    Nishide, Jun-ichi; Nakanotani, Hajime; Hiraga, Yasuhide; Adachi, Chihaya

    2014-06-01

    White organic light-emitting diodes (WOLEDs) have attracted much attention recently, aimed for next-generation lighting sources because of their high potential to realize high electroluminescence efficiency, flexibility, and low-cost manufacture. Here, we demonstrate high-efficiency WOLED using red, green, and blue thermally activated delayed fluorescence materials as emissive dopants to generate white electroluminescence. The WOLED has a maximum external quantum efficiency of over 17% with Commission Internationale de l'Eclairage coordinates of (0.30, 0.38).

  18. 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.

  19. 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.

  20. 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

  1. Near-field photometry for organic light-emitting diodes

    Science.gov (United States)

    Li, Rui; Harikumar, Krishnan; Isphording, Alexandar; Venkataramanan, Venkat

    2013-03-01

    Organic Light Emitting Diode (OLED) technology is rapidly maturing to be ready for next generation of light source for general lighting. The current standard test methods for solid state lighting have evolved for semiconductor sources, with point-like emission characteristics. However, OLED devices are extended surface emitters, where spatial uniformity and angular variation of brightness and colour are important. This necessitates advanced test methods to obtain meaningful data for fundamental understanding, lighting product development and deployment. In this work, a near field imaging goniophotometer was used to characterize lighting-class white OLED devices, where luminance and colour information of the pixels on the light sources were measured at a near field distance for various angles. Analysis was performed to obtain angle dependent luminous intensity, CIE chromaticity coordinates and correlated colour temperature (CCT) in the far field. Furthermore, a complete ray set with chromaticity information was generated, so that illuminance at any distance and angle from the light source can be determined. The generated ray set is needed for optical modeling and design of OLED luminaires. Our results show that luminance non-uniformity could potentially affect the luminaire aesthetics and CCT can vary with angle by more than 2000K. This leads to the same source being perceived as warm or cool depending on the viewing angle. As OLEDs are becoming commercially available, this could be a major challenge for lighting designers. Near field measurement can provide detailed specifications and quantitative comparison between OLED products for performance improvement.

  2. Efficiency roll-off in organic light-emitting diodes.

    Science.gov (United States)

    Murawski, Caroline; Leo, Karl; Gather, Malte C

    2013-12-17

    Organic light-emitting diodes (OLEDs) have attracted much attention in research and industry thanks to their capability to emit light with high efficiency and to deliver high-quality white light that provides good color rendering. OLEDs feature homogeneous large area emission and can be produced on flexible substrates. In terms of efficiency, OLEDs can compete with highly efficient conventional light sources but their efficiency typically decreases at high brightness levels, an effect known as efficiency roll-off. In recent years, much effort has been undertaken to understand the underlying processes and to develop methods that improve the high-brightness performance of OLEDs. In this review, we summarize the current knowledge and provide a detailed description of the relevant principles, both for phosphorescent and fluorescent emitter molecules. In particular, we focus on exciton-quenching mechanisms, such as triplet-triplet annihilation, quenching by polarons, or field-induced quenching, but also discuss mechanisms such as changes in charge carrier balance. We further review methods that may reduce the roll-off and thus enable OLEDs to be used in high-brightness applications. PMID:24019178

  3. Carrier modulation layer-enhanced organic light-emitting diodes.

    Science.gov (United States)

    Jou, Jwo-Huei; Kumar, Sudhir; Singh, Meenu; Chen, Yi-Hong; Chen, Chung-Chia; Lee, Meng-Ting

    2015-01-01

    Organic light-emitting diode (OLED)-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML), also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI) for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance. PMID:26193252

  4. Carrier Modulation Layer-Enhanced Organic Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Jwo-Huei Jou

    2015-07-01

    Full Text Available Organic light-emitting diode (OLED-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML, also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance.

  5. Improved interconnecting structure for a tandem organic light emitting diode

    International Nuclear Information System (INIS)

    Two-unit tandem organic light emitting diodes (OLEDs) employing two kinds of interconnecting structures, i.e. 5 nm lithium carbonate doped PTCDA (1:2 Li2CO3:PTCDA)/5 nm MoO3 and 5 nm Li2CO3 doped BCP (1:4 Li2CO3:BCP)/5 nm MoO3, have been fabricated, where PTCDA and BCP stand for 3, 4, 9, 10 perylenetetracarboxylic dianhydride and bathocuproine, respectively. Compared to the tandem OLED using the interconnecting structure of 5 nm 1:4 Li2CO3:BCP/5 nm MoO3, the one utilizing 5 nm 1:2 Li2CO3:PTCDA/5 nm MoO3 showed nearly same power efficiency and decreased operating voltage, mainly attributed to the higher electron conductivity of 1:2 Li2CO3:PTCDA relative to 1:4 Li2CO3:BCP. The charge generation and electron injection processes based on the interconnecting structure of 5 nm 1:2 Li2CO3:PTCDA/5 nm MoO3 were also discussed. We provide a simple and effective connecting structure to enhance the current conduction for tandem OLEDs

  6. 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.

  7. Graphene electrodes for organic metal-free light-emitting devices

    OpenAIRE

    Robinson, Nathaniel D; Edman, Ludvig; Chhowalla, Manish

    2012-01-01

    In addition to its fascinating electrical and mechanical properties, graphene is also an electrochemically stable and transparent electrode material. We demonstrate its applicability as both anode and cathode in a light-emitting electrochemical cell (LEC), an electrochemical analogue to a polymer organic light-emitting diode. Specifically, we summarize recent progress in carbon-based metal-free light-emitting devices enabled by chemically derived graphene cathodes on quartz and plastic substr...

  8. Luminance Mechanisms of White Organic Light-Emitting Devices Fabricated Utilizing a Charge Generation Layer with a Light-Emitting Function.

    Science.gov (United States)

    Kim, K H; Jeon, Y P; Choo, D C; Kim, T W

    2015-07-01

    The luminance mechanisms of the white organic light-emitting devices (WOLEDs) with a charge generation layer (CGL) consisting of a tungsten oxide layer and a 5,6,11,12-tetraphenyltetracene (rubrene) doped N,N',-bis-(1-naphthyl)-N,N'-diphenyl1-1'-biphenyl-4,4'-diamine (NPB) layer were investigated. Current densities and luminances of the WOLEDs increased with increasing a rubrene doping concentration because the formation of excitons in the rubrene-doped NPB layer increased due to the more exciton trapping in rubrene molecules and the delay of the electron injection due to the insertion of the litium qunolate layer. The yellow light emitted from the rubrene-doped NPB layer in the CGL combined with the blue light from the main emitting layer of the WOLEDs, resulting in the emission of the white light. The ratio between the yellow and the blue color peak intensities of the electroluminescence spectra for the WOLEDs was controlled by the rubrene doping concentration. The Commission Internationale de l'Eclairage coordinates of the fabricated WOLED were (0.31, 0.42) at 740.7 cd/m2, indicative of white emission color. PMID:26373110

  9. Improved blue light-emitting polymeric device by the tuning of drift mobility and charge balance

    Science.gov (United States)

    Chin, Byung Doo; Suh, Min Chul; Lee, Seong Taek; Chung, Ho Kyoon; Lee, Chang Hee

    2004-03-01

    We have prepared blue polymer-small molecule hybrid electroluminescence devices with improved efficiency and lower driving voltage by the statistical design method. Analysis of time-of-flight measurement shows that amorphous small molecule hole-transporter blended with a blue light-emitting polymer increases the field-dependent hole mobility, with transition from nondispersive to dispersive transport induced by the charge-trapping effect. Moreover, at the electroluminescent devices with different electron injection/transport layer (LiF/Al, LiF/Ca/Al, and Alq3/LiF/Al), efficiency was further increased. We have analyzed that carrier mobility of a multilayered device can also be controlled by the change of electron injection and transport layers. We find that structural design and matching overall charge balance is an essential factor to improve both the operating voltage and efficiency of existing blue polymer devices.

  10. Highly efficient white organic light-emitting devices consisting of undoped ultrathin yellow phosphorescent layer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shengqiang [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); Yu, Junsheng, 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); Ma, Zhu; Zhao, Juan [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)

    2013-02-15

    High-efficiency white organic light-emitting devices (WOLEDs) based on an undoped ultrathin yellow light-emitting layer and a doped blue light-emitting layer were demonstrated. While the thickness of blue light-emitting layer, formed by doping a charge-trapping phosphor, iridium(III) bis(4 Prime ,6 Prime -difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6) in a wide bandgap host, was kept constant, the thickness of neat yellow emissive layer of novel phosphorescent material, bis[2-(4-tertbutylphenyl)benzothiazolato-N,C{sup 2 Prime }]iridium (acetylacetonate) [(t-bt){sub 2}Ir(acac)] was varied to optimize the device performance. The optimized device exhibited maximum luminance, current efficiency and power efficiency of 24,000 cd/m{sup 2} (at 15.2 V), 79.0 cd/A (at 1550 cd/m{sup 2}) and 40.5 lm/W (at 1000 cd/m{sup 2}), respectively. Besides, the white-light emission covered a wide range of visible spectrum, and the Commission Internationale de l'Eclairage coordinates were (0.32, 0.38) with a color temperature of 5800 K at 8 V. Moreover, high external quantum efficiency was also obtained in the high-efficiency WOLEDs. The performance enhancement was attributed to the proper thickness of (t-bt){sub 2}Ir(acac) layer that enabled adequate current density and enough phosphorescent dye to trap electrons. - Highlights: Black-Right-Pointing-Pointer Highly efficient WOLEDs based on two complementary layers were fabricated. Black-Right-Pointing-Pointer The yellow emissive layer was formed by utilizing undoping system. Black-Right-Pointing-Pointer The blue emissive layer was made by host-guest doping system. Black-Right-Pointing-Pointer The thickness of the yellow emissive layer was varied to make device optimization. Black-Right-Pointing-Pointer The optimized device achieved high power efficiency of 40.5 lm/W.

  11. 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

  12. 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).

  13. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    International Nuclear Information System (INIS)

    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 especially

  14. 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

  15. 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.

  16. 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.

  17. Horizontal molecular orientation in solution-processed organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, L.; Inoue, M. [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Komino, T. [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, c/o Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Education Center for Global Leaders in Molecular System for Devices, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Kim, J.-H. [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Ribierre, J. C., E-mail: ribierre@opera.kyushu-u.ac.jp, E-mail: adachi@cstf.kyushu-u.ac.jp [Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, c/o Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); and others

    2015-02-09

    Horizontal orientation of the emission transition dipole moments achieved in glassy vapor-deposited organic thin films leads to an enhancement of the light out-coupling efficiency in organic light-emitting diodes (OLEDs). Here, our combined study of variable angle spectroscopic ellipsometry and angle dependent photoluminescence demonstrates that such a horizontal orientation can be achieved in glassy spin-coated organic films based on a composite blend of a heptafluorene derivative as a dopant and a 4,4′-bis(N-carbazolyl)-1,1′-biphenyl as a host. Solution-processed fluorescent OLEDs with horizontally oriented heptafluorene emitters were then fabricated and emitted deep blue electroluminescence with an external quantum efficiency as high as 5.3%.

  18. Green-light supplementation for enhanced lettuce growth under red- and blue-light-emitting diodes

    Science.gov (United States)

    Kim, Hyeon-Hye; Goins, Gregory D.; Wheeler, Raymond M.; Sager, John C.

    2004-01-01

    Plants will be an important component of future long-term space missions. Lighting systems for growing plants will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue light was an effective light source for several crops. Yet the appearance of plants under red and blue lighting is purplish gray making visual assessment of any problems difficult. The addition of green light would make the plant leave appear green and normal similar to a natural setting under white light and may also offer a psychological benefit to the crew. Green supplemental lighting could also offer benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the leaves in the lower canopy. In this study, four light sources were tested: 1) red and blue LEDs (RB), 2) red and blue LEDs with green fluorescent lamps (RGB), 3) green fluorescent lamps (GF), and 4) cool-white fluorescent lamps (CWF), that provided 0%, 24%, 86%, and 51% of the total PPF in the green region of the spectrum, respectively. The addition of 24% green light (500 to 600 nm) to red and blue LEDs (RGB treatment) enhanced plant growth. The RGB treatment plants produced more biomass than the plants grown under the cool-white fluorescent lamps (CWF treatment), a commonly tested light source used as a broad-spectrum control.

  19. 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.

  20. Tandem white organic light-emitting diodes adopting a C60:rubrene charge generation layer

    Science.gov (United States)

    Bi, Wen-Tao; Wu, Xiao-Ming; Hua, Yu-Lin; Sun, Jin-E.; Xiao, Zhi-Hui; Wang, Li; Yin, Shou-Gen

    2014-01-01

    Organic bulk heterojunction fullerence (C60) doped 5, 6, 11, 12-tetraphenylnaphthacene (rubrene) as the high quality charge generation layer (CGL) with high transparency and superior charge generating capability for tandem organic light emitting diodes (OLEDs) is developed. This CGL shows excellent optical transparency about 90%, which can reduce the optical interference effect formed in tandem OLEDs. There is a stable white light emission including 468 nm and 500 nm peaks from the blue emitting layer and 620 nm peak from the red emitting layer in tandem white OLEDs. A high efficiency of about 17.4 cd/A and CIE coordinates of (0.40, 0.35) at 100 cd/m2 and (0.36, 0.34) at 1000 cd/m2 have been demonstrated by employing the developed CGL, respectively.

  1. 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...

  2. Blue resonant-cavity light-emitting diode with half milliwatt output power

    Science.gov (United States)

    Yeh, Pinghui S.; Chang, Chi-Chieh; Chen, Yu-Ting; Lin, Da-Wei; Wu, Chun Chia; He, Jhao Hang; Kuo, Hao-Chung

    2016-03-01

    GaN-based resonant-cavity light-emitting diode (RCLED) has a circular output beam with superior directionality than conventional LED and has power scalability by using two-dimensional-array layout. In this work, blue RCLEDs with a top reflector of approximately 50% reflectance were fabricated and characterized. An output power of more than 0.5 mW per diode was achieved before packaging under room-temperature continuous-wave (CW) operation. The full width at half maximum (FWHM) of the emission spectrum was approximately 3.5 and 4.5 nm for 10- and 20-μm-diameter devices, respectively. And the peak wavelength as well as the FWHM remained stable at various currents and temperatures.

  3. 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.

  4. Localized surface plasmon resonance effect in organic light-emitting devices with Ag islands

    Science.gov (United States)

    Shimazaki, Noritaka; Naka, Shigeki; Okada, Hiroyuki

    2014-04-01

    We report on luminescence enhancement of organic light-emitting devices (OLEDs) with silver islands (i-Ag) by a localized surface plasmon resonance (LSPR) effect. The devices were fabricated using tetraphenylporphyrin (TPP) as the red emission material, bis[N-(1-naphthyl)-N-phenyl] benzidine (α-NPD) as the blue emission and hole transport material, and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as the electron transport material. To clarify the position of emission enhancement by energy transfer from i-Ag, an ultrathin TPP layer located within the α-NPD layer. In the device with i-Ag and the TPP layer located over 10 nm from i-Ag, TPP emission was enhanced in comparison with the device without i-Ag. The enhancement of TPP emission was suggested to be the effect of the enhanced electric field resulting from LSPR excited by α-NPD emission.

  5. 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.

  6. Reduction in Power Consumption for Full-Color Active Matrix Organic Light-Emitting Devices

    Science.gov (United States)

    Kanno, Hiroshi; Hamada, Yuji; Nishimura, Kazuki; Okumoto, Kenji; Saito, Nobuo; Mameno, Kazunobu; Shibata, Kenichi

    2006-09-01

    The active matrix organic light-emitting diode (AMOLED) is expected to serve as next generation flat panels display with the outstanding features of wide viewing angle, vivid images, and quick response. For practical use of full-color AMOLEDs in mobile devices, it is essential to reduce the power consumption, which is generally higher than that of liquid crystal displays (LCDs). For this aim, a red, green, blue, and white (RGBW) pixel format combined with an RGB color filter array (RGBW format) with a common white emission layer (EML) has been developed. We find that the RGBW format can successfully reduce the power consumption of a full-color AMOLED by nearly half that of a conventionally filtered RGB pixel format. This improved power consumption is almost equal to the power consumption of a same-sized LCD. The RGBW format is a promising technique for the further reduction of the power consumption of a full-color AMOLED.

  7. 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.

  8. 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.

  9. Synthesis and blue light-emitting properties of 4,4'-bis(diphenylamino)-quinque(p-phenyl)s

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An excellent organic blue light-emitting diode based on 4,4'-bis(diphenylamino)-quinque(p-phenylene)s (OPP(5)-NPh) with a maximum luminance of up to 5000 cd/m2 and a luminanous efficiency of 1.3 cd/A was reported. This diode was made by using a wide band-gap hole-blocking layer, F-TBB instead of PBD in the OLED devices. We attribute the good performance to the one trade-off involved in the use of F-TBB to obtain higher luminance is the increased turn-on voltages and slightly decreased device efficiencies.(C) 2007 Zhong Hui Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

  10. 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.

  11. 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

    2016-01-01

    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. PMID:27484401

  12. 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.

  13. Candlelight style organic light-emitting diode: a plausibly human-friendly safe night light

    Science.gov (United States)

    Jou, Jwo-Huei; Hsieh, Chun-Yu; Chen, Po-Wei; Kumar, Sudhir; Hong, James H.

    2014-01-01

    Candles emit sensationally warm light with a very low color temperature, comparatively most suitable for use at night. In response to the need for such a human-friendly night light, we demonstrate the employment of a high number of candlelight complementary organic emitters to generate and mimic candlelight based on organic light emitting diode (OLED). One resultant candlelight style OLED shows a very-high color rendering index (CRI), with an efficacy at least 300 times that of a candle or at least two times that of an incandescent bulb. The device can be fabricated, for example, by using four candlelight complementary emitters: red, yellow, green, and sky-blue phosphorescent dyes. These dyes, in the present system, can be vacuum deposited into two emission layers that are separated by a nanolayer of carrier modulation material that is used to maximize very high CRI and energy efficiency. A nano carrier modulation layer also played a significant role in maintaining the low blue emission and high-red emission, the low color temperature of device was obtained. Importantly, a romantic sensation giving and supposedly physiologically friendly candlelight style emission can hence be driven by electricity in lieu of hydrocarbon burning and greenhouse gas-releasing candles that were invented 5000 years ago.

  14. 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.

  15. Cathodes incorporating thin fluoride layers for efficient injection in blue polymer light-emitting diodes

    Science.gov (United States)

    Brown, Thomas M.; Millard, Ian S.; Lacey, David; Burroughes, Jeremy H.; Friend, Richard H.; Cacialli, Franco

    2002-02-01

    Efficient blue Polymer Light-Emitting Diodes (PLEDs) were fabricated by evaporating thin LiF layers between Al or Ca cathodes. Electroabsorption measurements of the built-in potential across the diodes show that devices fabricated with LiF/Ca/Al cathodes exhibit the smallest average barrier height and operating voltage (compared to both Ca and LiF/Al currently amongst the most efficient electron injectors). The turn-on bias is essentially equivalent to the built-in potential (~2.7 V), indicating an effective minimisation of the barrier to electron injection. Results are also compared with devices incorporating CsF layers and are correlated with the electroluminescent characteristics of the LEDs. A very strong dependence (~ exponential) between the built-in potential and the current and luminance at a fixed electric field (0.5MV/cm) is observed and is explained with the reduction of the cathodic barrier height brought about by the different cathode multilayers.

  16. Improvement of white organic light emitting diode performances by an annealing process

    Energy Technology Data Exchange (ETDEWEB)

    Sepeai, Suhaila, E-mail: suhaila_sepeai@yahoo.co [Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor (Malaysia); Salleh, Muhamad Mat, E-mail: mms@pkrisc.cc.ukm.m [Institute Of Microengineering And Nanoelectronic, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor (Malaysia); Yahaya, Muhammad; Umar, Akrajas Ali [Institute Of Microengineering And Nanoelectronic, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor (Malaysia)

    2009-06-30

    White organic light emitting diode (OLED) devices with the structure ITO/PHF:rubrene/Al, in which PHF (poly(9,9-di-n-hexylfluorenyl-2,7-diyl)) is used as blue light emitting host and rubrene (5,6,11,12-tetraphenylnapthacene) as an orange dye dopant, have been fabricated. Indium tin oxide (ITO) coated-glass and aluminium were used as anode and cathode, respectively. The devices were fabricated with various rubrene-dopant to obtain a white light emission. The OLED device that composed of several concentrations of rubrene-doped PHF film was prepared in this study. It was found that the concentration of rubrene in the PHF-rubrene thin film matrix plays a key role in producing the white color emission. In a typical result, the device composed of 0.06 wt.% rubrene-dopant produced the white light emission with the Commission Internationale de L'Eclairage (CIE) coordinate of (0.30,0.33). The turn-on voltage and the brightness were found to be as low as 14.0 V and as high as 6540 cd/m{sup 2}, respectively. The annealing technique at relatively low temperature (50 {sup o}C, 100 {sup o}C, and 150 {sup o}C) was then used to optimize the performance of the device. In a typical result, the turn-on voltage of the device could be successfully reduced and the brightness could be increased using the annealing technique. At an optimum condition, for example, annealed at 150 {sup o}C, the turn-on voltage as low as 8.0 V and the brightness as high as 9040 cd/m{sup 2} were obtained. The mechanism for the improvement of the device performance upon annealing will be discussed.

  17. Low driving voltage in white organic light-emitting diodes using an interfacial energy barrier free multilayer emitting structure

    International Nuclear Information System (INIS)

    The driving voltage of white organic light-emitting diodes (WOLEDs) with blue fluorescent and red phosphorescent emitting materials was lowered by using a device architecture with little energy barrier between emitting layers. A mixed layer of hole and electron transport materials was used as a host material and an interlayer, reducing the driving voltage of WOLEDs. The driving voltage of WOLEDs was reduced by more than 4 V and power efficiency of WOLEDs was improved by more than 40% due to little energy barrier for holes and electrons injection in light-emitting layer. In addition, there was little change of electroluminescence spectra from 100 to 10,000 cd/m2.

  18. Red phosphorescent organic light-emitting diodes using pyridine based electron transport type triplet host materials

    International Nuclear Information System (INIS)

    Research highlights: → Pyridine based host material for red phosphorescent organic light emitting diode. → Device optimization at low doping concentration of 2%. → Simplified red phosphorescent organic light emitting diodes. - Abstract: Pyridine based electron transport type host materials were developed and their device performances were investigated according to doping concentration. The pyridine substituent was combined with a spirofluorenebenzofluorene core unit and a high quantum efficiency of 13.3% was achieved in red phosphorescent organic light-emitting diodes at a low doping concentration of 2%. A simple red device without any electron transport layer could be fabricated and a simple device without any electron transport layer showed better power efficiency than the standard device with an electron transport layer.

  19. 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...

  20. Dopant effects on charge transport to enhance performance of phosphorescent white organic light emitting diodes

    Science.gov (United States)

    Zhu, Liping; Chen, Jiangshan; Ma, Dongge

    2015-11-01

    We compared the performance of phosphorescent white organic light emitting diodes (WOLEDs) with red-blue-green and green-blue-red sequent emissive layers. It was found that the influence of red and green dopants on electron and hole transport in emissive layers leads to the large difference in the efficiency of fabricated WOLEDs. This improvement mechanism is well investigated by the current density-voltage characteristics of single-carrier devices based on dopant doped emissive layers and the comparison of electroluminescent and photoluminescence spectra, and attributed to the different change of charge carrier transport by the dopants. The optimized device achieves a maximum power efficiency, current efficiency, and external quantum efficiency of 37.0 lm/W, 38.7 cd/A, and 17.7%, respectively, which are only reduced to 32.8 lm/W, 38.5 cd/A, and 17.3% at 1000 cd/m2 luminance. The critical current density is as high as 210 mA/cm2. It can be seen that the efficiency roll-off in phosphorescent WOLEDs can be well improved by effectively designing the structure of emissive layers.

  1. 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.

  2. Nanostructured thin films for organic photovoltaic cells and organic light-emitting diodes

    Science.gov (United States)

    Zheng, Ying

    2009-12-01

    heterojunction device based on the same D -- A materials. We also show that the efficiency of a deep-blue phosphorescent OLED (PHOLED) can be significantly enhanced by improving the exciton and charge confinement in the multilayer organic stack. A peak external quantum efficiency of (20 +/- 1) % is achieved, which approaches the theoretical maximum of PHOLED without specific out-coupling mechanisms. We further demonstrate PHOLEDs with enhanced power efficiency by using the p-i- n device structures to reduce driving voltage and achieved a maximum of (14 +/- 1) lm/W and (12 +/- 1) lm/W at a luminance of 100 cd/m 2. Moreover, an ultra low turn-on voltage of ˜ 1.3 V is observed in an orange-emitting polymer light-emitting diode (PLED) using ZnO nanoparticles as the electron injection layer. An Auger-assisted electron injection mechanism is proposed to explain the low turn-on voltage. The novel ZnO nanoparicles electron injection layer opens a new way to reduce driving voltage in PLED. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

  3. Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films

    Science.gov (United States)

    Lin, Hoang-Yan; Lee, Jiun-Haw; Wei, Mao-Kuo; Dai, Ching-Liang; Wu, Chia-Fang; Ho, Yu-Hsuan; Lin, Hung-Yi; Wu, Tung-Chuan

    2007-07-01

    In this paper, we present and analyse the optical characteristics, such as spectral shift, CIE coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency, of an organic light-emitting device (OLED) with a commercial diffuser film or a brightness-enhancement film (BEF) attached. Compared to a planar green OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 29% and 23%, respectively. The overall luminous power efficiencies are enhanced by 28% and 7%. Compared to the planar green device, we observe blue shifts at different viewing angles when microstructured films are attached, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifts and the full width at the half maximum (FWHM) decrease with increasing viewing angles due to the microcavity effect. When the diffuser is attached, the spectral peak has a constant blue shift (6 nm) compared to that of the planar OLED. On the other hand, in the BEF case, the spectral shift depends on the viewing angle (2-12 nm blue shifts from 0 to 80°). This is due to the different operating principles (scattering and redirected light) of the diffuser and BEF. Since the transmittance spectra of both the diffuser film and the BEF are flat over the visible range, it is suitable for lighting applications by using white OLED. When attaching the films on a commercial white OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 34% and 31%, respectively. The overall luminous power efficiencies are enhanced by 42% and 8%.

  4. Multilayered Organic Light Emitting Diodes Based on Polyfluorenes

    Science.gov (United States)

    Bozano, Luisa; Marsitzky, Dirk; Carter, Kenneth; Swanson, Sally; Lee, Victor; Salem, Jesse; Miller, Robert; Scott, Campbell; Carter, Sue

    2001-03-01

    The electroluminescence of polyfluorene homopolymers and various arylene copolymers is in the deep blue, with peak emission wavelengths as small as 420 nm. These materials are therefore of great interest for use in full-color OLED displays both as emitters for blue subpixels and as hosts for red and green emitting dopants or comonomers. In this work, we compare the properties of single and multilayer diode structures based on dihexyl and di(2-ethylexyl) substituted polyfluorenes. A cross-linkable polymeric arylamine hole transport polymer and/or a polyquinoline electron transport layer are introduced to better balance the charge injection from the electrodes and optimize the recombination in the fluorene emitter layer. External quantum efficiencies increase from about 0.1layer devices to well over 1The electrical and optical response is determined by steady state and transient measurements. The effects on efficiency, emission spectrum and electrical response resulting from the introduction of dopant dyes into the emitter layer are also presented.

  5. Active Matrix Organic light Emitting Diode Display Based on “Super Top Emission” Technology

    Science.gov (United States)

    Ishibashi, Tadashi; Yamada, Jiro; Hirano, Takashi; Iwase, Yuichi; Sato, Yukio; Nakagawa, Ryo; Sekiya, Mitsunobu; Sasaoka, Tatsuya; Urabe, Tetsuo

    2006-05-01

    We developed an original “Super Top Emission” technology, which enables us to optimize the distinctive features of an organic light emitting diode (OLED) display. With this technology, the following characteristics can be obtained: (1) high color reproduction of a 100% NTSC gamut ratio, (2) wide viewing angle, (3) high contrast of 1000:1 maintaining high luminous efficiency with a color filter, (4) original all-solid sealing structure. In addition, Super Top Emission technology was demonstrated by developing a 3.8-type size half video graphics array (HVGA) active matrix organic light emitting diode (AM-OLED) display by the shadow mask patterning process.

  6. Enhanced out-coupling factor of microcavity organic light-emitting devices with irregular microlens array

    Science.gov (United States)

    Lim, Jongsun; Oh, Seung Seok; Youp Kim, Doo; Cho, Sang Hee; Kim, In Tae; Han, S. H.; Takezoe, Hideo; Choi, Eun Ha; Cho, Guang Sup; Seo, Yoon Ho; Oun Kang, Seung; Park, Byoungchoo

    2006-07-01

    We studied microcavity organic light-emitting devices with a microlens system. A microcavity for organic light-emitting devices (OLED) was fabricated by stacks of SiO2 and SiNx layers and a metal cathode together with the microlens array. Electroluminescence of the devices showed that color variation under the viewing angle due to the microcavity is suppressed remarkably by microlens arrays, which makes the use of devices acceptable in many applications. It was also demonstrated that the external out-coupling factor of the devise increases by a factor of ~1.8 with wide viewing angles compared to conventional OLEDs.

  7. 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.

  8. 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.

  9. Growth and Properties of Blue and Amber Complex Light Emitting InGaN/GaN Multi-Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    XIE Zi-Li; HAN Ping; SHI Yi; ZHENG You-Dou; ZHANG Rong; LIU Bin; XIU Xiang-Qian; SU Hui; LI Yi; HUA Xue-Mei; ZHAO Hong; CHEN Peng

    2011-01-01

    @@ Blue-red complex light emitting InGaN/GaN multi-quantum well(MQW) structures are fabricated by metal organic chemical vapor deposition(MOCVD).The structures are grown on a 2-inch diameter(0001) oriented (c-face) sapphire substrate, which consists of an approximately 2-Etm-thick GaN template and a five-period layer consisting of a 4.9-nm-thick In0.18Ga0.82N well layer and a GaN barrier layer.The surface morphology of the MQW structures is observed by an atomic force microscope(AFM), which indicates the presence of islands of several tens of nanometers in height on the surface.The high resolution x-ray diffraction(XRD)θ/2θ scan is carried out on the symmetric(0002) of the InGaN/GaN MQW structures.At least four order satellite peaks presented in the XRD spectrum indicate that the thickness and alloy compositions of the individual quantum wells are repeatable throughout the active region.Besides the 364 nm GaN band edge emission, two main emissions of blue and amber light from these MQWs are found, which possibly originate from the carrier recombinations in the InGaN/GaN QWs and InGaN quasi-quantum dots embedded in the QWs.

  10. 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.

  11. 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%.

  12. Effects of doping dyes on the electroluminescent characteristics of multilayer organic light-emitting diodes

    Science.gov (United States)

    Suzuki, Hiroyuki; Hoshino, Satoshi

    1996-06-01

    We report the effects of dyes doped in the emitting layer on the electroluminescent characteristics of multilayer organic light-emitting diodes (LEDs) using a polysilane polymer, poly(methylphenylsilane) (PMPS), as the hole transporting material. We formed the emitting layer by dispersing in poly(styrene) (PS), one of four dyes whose fluorescence ranged from blue to orange. Two- or three-layer LEDs were prepared by combining PMPS and dye doped PS layers with the indium tin oxide and aluminum used for the hole and electron injecting electrodes, respectively. The three-layer LEDs had an additional vacuum-deposited tris-(8-hydroxyquinoline) aluminum layer. The electroluminescent (EL) characteristics of these multilayer organic LEDs, such as the current-voltage-EL intensity curve, the relative EL efficiency, and the EL emitting species, exhibit a marked dependence on the emitting dye. The observed dependence can be described consistently in terms of the dependence of the charge carrier trapping efficiency on the emitting dyes.

  13. 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.

  14. Management of singlet and triplet excitons for efficient white organic light-emitting devices

    Science.gov (United States)

    Sun, Yiru; Giebink, Noel C.; Kanno, Hiroshi; Ma, Biwu; Thompson, Mark E.; Forrest, Stephen R.

    2006-04-01

    Lighting accounts for approximately 22 per cent of the electricity consumed in buildings in the United States, with 40 per cent of that amount consumed by inefficient (~15lmW-1) incandescent lamps. This has generated increased interest in the use of white electroluminescent organic light-emitting devices, owing to their potential for significantly improved efficiency over incandescent sources combined with low-cost, high-throughput manufacturability. The most impressive characteristics of such devices reported to date have been achieved in all-phosphor-doped devices, which have the potential for 100 per cent internal quantum efficiency: the phosphorescent molecules harness the triplet excitons that constitute three-quarters of the bound electron-hole pairs that form during charge injection, and which (unlike the remaining singlet excitons) would otherwise recombine non-radiatively. Here we introduce a different device concept that exploits a blue fluorescent molecule in exchange for a phosphorescent dopant, in combination with green and red phosphor dopants, to yield high power efficiency and stable colour balance, while maintaining the potential for unity internal quantum efficiency. Two distinct modes of energy transfer within this device serve to channel nearly all of the triplet energy to the phosphorescent dopants, retaining the singlet energy exclusively on the blue fluorescent dopant. Additionally, eliminating the exchange energy loss to the blue fluorophore allows for roughly 20 per cent increased power efficiency compared to a fully phosphorescent device. Our device challenges incandescent sources by exhibiting total external quantum and power efficiencies that peak at 18.7 +/- 0.5 per cent and 37.6 +/- 0.6lmW-1, respectively, decreasing to 18.4 +/- 0.5 per cent and 23.8 +/- 0.5lmW-1 at a high luminance of 500cdm-2.

  15. 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

  16. 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

  17. Lamination of organic solar cells and organic light emitting devices: Models and experiments

    Energy Technology Data Exchange (ETDEWEB)

    Oyewole, O. K. [Department of Theoretical and Applied Physics, African University of Science and Technology, Km 10 Airport Road, Galadimawa, Abuja, Federal Capital Territory (Nigeria); Department of Materials Science and Engineering, Kwara State University, P.M.B 1530, Ilorin, Kwara State (Nigeria); Yu, D. [Department of Mechanical and Aerospace Engineering, Princeton University, Olden Street, Princeton, New Jersey 08544 (United States); Princeton Institute of Science and Technology of Materials, Princeton University, 70 Prospect Street, Princeton, New Jersey 08544 (United States); Du, J. [Department of Mechanical and Aerospace Engineering, Princeton University, Olden Street, Princeton, New Jersey 08544 (United States); Princeton Institute of Science and Technology of Materials, Princeton University, 70 Prospect Street, Princeton, New Jersey 08544 (United States); Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 137 Reber Building, University Park, Pennsylvania (United States); Asare, J.; Fashina, A. [Department of Theoretical and Applied Physics, African University of Science and Technology, Km 10 Airport Road, Galadimawa, Abuja, Federal Capital Territory (Nigeria); Anye, V. C. [Department of Materials Science and Engineering, African University of Science and Technology, Km 10 Airport Road, Galadimawa, Abuja, Federal Capital Territory (Nigeria); Zebaze Kana, M. G. [Department of Materials Science and Engineering, Kwara State University, P.M.B 1530, Ilorin, Kwara State (Nigeria); Soboyejo, W. O., E-mail: soboyejo@princeton.edu [Department of Mechanical and Aerospace Engineering, Princeton University, Olden Street, Princeton, New Jersey 08544 (United States); Princeton Institute of Science and Technology of Materials, Princeton University, 70 Prospect Street, Princeton, New Jersey 08544 (United States); Department of Materials Science and Engineering, African University of Science and Technology, Km 10 Airport Road, Galadimawa, Abuja, Federal Capital Territory (Nigeria)

    2015-08-21

    In this paper, a combined experimental, computational, and analytical approach is used to provide new insights into the lamination of organic solar cells and light emitting devices at macro- and micro-scales. First, the effects of applied lamination force (on contact between the laminated layers) are studied. The crack driving forces associated with the interfacial cracks (at the bi-material interfaces) are estimated along with the critical interfacial crack driving forces associated with the separation of thin films, after layer transfer. The conditions for successful lamination are predicted using a combination of experiments and computational models. Guidelines are developed for the lamination of low-cost organic electronic structures.

  18. Lamination of organic solar cells and organic light emitting devices: Models and experiments

    International Nuclear Information System (INIS)

    In this paper, a combined experimental, computational, and analytical approach is used to provide new insights into the lamination of organic solar cells and light emitting devices at macro- and micro-scales. First, the effects of applied lamination force (on contact between the laminated layers) are studied. The crack driving forces associated with the interfacial cracks (at the bi-material interfaces) are estimated along with the critical interfacial crack driving forces associated with the separation of thin films, after layer transfer. The conditions for successful lamination are predicted using a combination of experiments and computational models. Guidelines are developed for the lamination of low-cost organic electronic structures

  19. Organic Light Emitting Diodes with an Organic Acceptor/Donor Interface Involved in Hole Injection

    Institute of Scientific and Technical Information of China (English)

    CAO Guo-Hua; QIN Da-Shan; GUAN Min; CAO Jun-Song; ZENG Yi-Ping; LI Jin-Min

    2007-01-01

    Organic light emitting diodes with an interface of organic acceptor 3-,4-,9-,10-perylenetetracarboxylic dianhydride (PTCDA) and donor copper phthalocyanine (CuPc) involved in hole injection are fabricated. As compared to the conventional device using a 5nm CuPc hole injection layer, the device using an interface of 10 nm PTCDA and 5nm CuPc layers shows much lower operating voltage with an increase of about 46% in the maximum power efficiency. The enhanced device performance is attributed to the efficient hole generation at the PTCDA/CuPc interface. This study provides a new way of designing hole injection.

  20. Flexible white phosphorescent organic light emitting diodes based on multilayered graphene/PEDOT:PSS transparent conducting film

    Science.gov (United States)

    Wu, Xiaoxiao; Li, Fushan; Wu, Wei; Guo, Tailiang

    2014-03-01

    A double-layered graphene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conductive film was prepared, in which the PEDOT:PSS layer was obtained by using spray-coating technique. A flexible white phosphorescent organic light-emitting devices based on the graphene/PEDOT:PSS conductive film was fabricated. Phosphorescent material tris(2-phenylpyridine) iridium (Ir(ppy)3) and the fluorescent dye 5,6,11,12-tetraphenylnapthacene (Rubrene) were co-doped into 4,4‧-N,N‧-dicarbazole-biphenyl (CBP) host. N,N‧-diphenyl-N,N‧-bis(1-naphthyl)-(1,1‧-biphenyl)-4,4‧-diamine (NPB) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were used as hole-transporting and electron-transporting layer, respectively, and 4,4‧-bis(2,2‧-diphenylvinyl)-1,1‧-biphenyl (DPVBi) was used as blue light-emitting layer. The device presented pure white light emission with a Commission Internationale De I'Eclairage coordinates of (0.31, 0.33) and exhibited an excellent light-emitting stability during the bending cycle test with a radius of curvature of 10 mm.

  1. Angular Dependence of the Sharply Directed Emission in Organic Light Emitting Diodes with a Microcavity Structure

    Science.gov (United States)

    Juang, Fuh-Shyang; Laih, Li-Hong; Lin, Chia-Ju; Hsu, Yu-Jen

    2002-04-01

    An optical microcavity structure was used in organic light emitting diodes. We succeeded in fabricating a device with sharply directed emission vertical to an emission surface. The device shows green emission (bright green) at normal position which turns red (bright red) at the 30° position. The angular dependences of the electroluminescence and the emission patterns versus viewing angle in the microcavity OLED were studied. The resonance wavelength λ decreases with viewing angle. The emission peak at 490 nm is directed vertically to the device surface more sharply than that at 632 nm. The microcavity structure shows non-Lambertian emission. The spectra appear more blue off-axis and the intensity of the green-like emission decreases rapidly with increasing viewing angle. A significantly narrow linewidth of 7.4 nm in the 0° direction for the 490 nm peak was observed. The full-widths at half maximum (FWHM) of the green-like spectra are much smaller than those of the red-like ones, indicating better cavity quality.

  2. Organic white-light-emitting devices based on a multimode resonant microcavity

    Science.gov (United States)

    Zhang, Hongmei; You, Han; Wang, Wei; Shi, Jiawei; Guo, Shuxu; Liu, Mingda; Ma, Dongge

    2006-08-01

    Organic white-light-emitting devices (OLEDs) based on a multimode resonant microcavity defined by a pair of dielectric mirrors and metal mirrors were presented. By selective effects of the quarter-wave dielectric stack mirror on mode, white light emission containing three individual narrow peaks of red, green and blue was achieved, and showed weak dependence on the viewing angle. The Commission Internationale De L'Eclairage (CIE) chromaticity coordinates changed from (0.29, 0.37) at 0° to (0.31, 0.33) at 40°. Furthermore, the brightness and electroluminescence efficiency of the microcavity OLEDs were enhanced compared with noncavity OLEDs. The maximum brightness reached 1940 cd m-2 at a current density of 200 mA cm-2, and the maximum current efficiency and power efficiency are 1.6 cd A-1 at a current density of 12 mA cm-2 and 0.41 lm W-1 at a current density of 1.6 mA cm-2, which are over 1.6 times higher than that of a noncavity OLED.

  3. 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.

  4. Synthesis and Electroluminescent Property of New Orange Iridium Compounds for Flexible White Organic Light Emitting Diodes.

    Science.gov (United States)

    Lee, Ho Won; Jeong, Hyunjin; Kim, Young Kwan; Ha, Yunkyoung

    2015-10-01

    Recently, white organic light-emitting diodes (OLEDs) have aroused considerable attention because they have the potential of next-generation flexible displays and white illuminated applications. White OLED applications are particularly heading to the industry but they have still many problems both materials and manufacturing. Therefore, we proposed that the new iridium compounds of orange emitters could be demonstrated and also applied to flexible white OLEDs for verification of potential. First, we demonstrated the chemical properties of new orange iridium compounds. Secondly, conventional two kinds of white phosphorescent OLEDs were fabricated by following devices; indium-tin oxide coated glass substrate/4,4'-bis[N-(napthyl)-N-phenylamino]biphenyl/N,N'-dicarbazolyl-3,5-benzene doped with blue and new iridium compounds for orange emitting 8 wt%/1,3,5-tris[N-phenylbenzimidazole-2-yl]benzene/lithium quinolate/aluminum. In addition, we fabricated white OLEDs using these emitters to verify the potential on flexible substrate. Therefore, this work could be proposed that white light applications can be applied and could be extended to additional research on flexible applications. PMID:26726407

  5. Spectral Characteristics of White Organic Light-emitting Diodes Based on Novel Phosphorescent Sensitizer

    Institute of Scientific and Technical Information of China (English)

    Xiao-qing Tang; Jun-sheng Yu; Lu Li; Wen Wen; Ya-dong Jiang

    2008-01-01

    White organic light-emitting diodes were fabricated by using a novel phosphorescence bis(1,2-diphenyl-1H-benzoimidazole)iridium(acetylacetonatc)[(pbi)2Ir(acac)] as sensitizer and a fluorescent dye of 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramcthyljulolidyl-9-enyl)-4H-pyran (DCJTB) codoped into a car-bazole polymcr of poly(N-vinylcarbazole) (PVK). Through characterizing the UV-Vis absorption spectra, the photoluminesccncc spectra of (pbi)2Ir(acac) and DCJTB, and the electrolumincscence spectral proper-ties of the WOLEDs, the energy transfer mechanisms of the codoped polymer system were deduced. The results demonstrate that the luminescent spectra with different intensity of (pbi)2Ir(acac) and DCJTB were co-existent in the EL spectra of the blended system, which is ascribed to an incomplete energy transfer process in the EL process. The efficient FSrster and Dexter energy transfer between the host and the guests enabled a strong yellow emission from (pbi)2Ir(acac) and DCJTB, where (pbi)2Ir(acac) plays an important role as a phosphorescent sensitizer for DCJTB. With the blue emitting-layer of N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine, the codoped system device achieved white emission. The codoped system showed that its Commissions Internationale de l'Eclairage coordinates were more independent of the variation of bias voltage than those of phosphorescent doped PVK systems.

  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. 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.

  8. Optical Properties of Blue-Light-Emitting (Ca,Sr)Mg2Si3O9:Eu2+ Phosphor

    Science.gov (United States)

    Lee, Hyun Ju; Choi, Sung Hwan; Kim, Kyung Pil; Shin, Hyun Ho; Yoo, Jae Soo

    2010-10-01

    For light-emitting diode (LED) excitation at 400 nm, the optical properties of a Eu2+-activated CaO-SrO-MgO-SiO2 material system were investigated. All the materials were synthesized by solid state reaction. In particular, (Ca,Sr)Mg2Si3O9:Eu2+, which has the same crystal structure as CaMgSi2O6, was found to be promising as a blue-light-emitting phosphor for near UV LED application. The luminance intensity was optimized by controlling the Eu2+ concentration and the composition of the host lattice. The ratio of calcium ions to strontium ions was a convenient parameter for adjusting the maximum excitation peak to 400 nm, which is favorable for near UV LED excitation. The highest luminance intensity of Ca1-x-ySryMg2Si3O9:Eux2+ under 405 nm excitation was achieved at the Eu2+ concentration of x=0.01 and a Sr2+ concentration of y=0.3. The luminance intensity of (Ca,Sr)Mg2Si3O9:Eu2+ was found to be superior to that of a commercial blue-light-emitting BaMgAl10O17:Eu2+ phosphor, which is used for near-UV LED excitation.

  9. Transparent organic light-emitting diodes with different bi-directional emission colors using color-conversion capping layers

    International Nuclear Information System (INIS)

    We report a study on transparent organic light-emitting diodes (OLEDs) with different bi-directional emission colors, enabled by color-conversion organic capping layers. Starting from a transparent blue OLED with an uncapped Ag top electrode exhibiting an average transmittance of 33.9%, a 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM)-doped tris-(8-hydroxy-quinolinato)-aluminum (Alq3) capping layer is applied to achieve color-conversion from blue to orange-red on the top side while maintaining almost unchanged device transmittance. This color-conversion capping layer does not only change the color of the top side emission, but also enhances the overall device efficiency due to the optical interaction of the capping layer with the primary blue transparent OLED. Top white emission from the transparent bi-directional OLED exhibits a correlated color temperature around 6000–7000 K, with excellent color stability as evidenced by an extremely small variation in color coordinate of Δ(x,y)=(0.002, 0.002) in the forward luminance range of 100–1000 cd m−2. At the same time, the blue emission color of bottom side is not influenced by the color conversion capping layer, which finally results in different emission colors of the two opposite sides of our transparent OLEDs. - Highlights: • We report transparent organic light-emitting diodes (OLEDs) with different bi-directional emission colors. • Transparent blue OLED with color-conversion organic capping layers (CCL) shows orange top side emission. • Top white emission exhibits a CCT around 7000 K, with excellent color stability on a driving voltage

  10. Highly efficient broad-area blue and white light-emitting diodes on bulk GaN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Vampola, Kenneth J.; Fellows, Natalie N.; Masui, Hisashi; Chung, Roy B.; Sato, Hitoshi; Sonoda, Junichi; Hirasawa, Hirohiko; Iza, Michael; Nakamura, Shuji [Materials Department, University of California, Santa Barbara, California (United States); Brinkley, Stuart E.; Furukawa, Motoko [Electrical and Computer Engineering Department, University of California, Santa Barbara, California (United States); DenBaars, Steven P. [Materials Department, University of California, Santa Barbara, California (United States)]|[Electrical and Computer Engineering Department, University of California, Santa Barbara, California (United States)

    2009-02-15

    Highly efficient light emitting diodes (LEDs) with peak emission wavelengths of nominally 450 nm were grown, fabricated and tested. The growth was performed by metal organic chemical vapour deposition. The LEDs were grown on c-plane (0001) bulk GaN substrates and fabricated into broad-area devices with active area 0.01 cm{sup 2}. Considerations were made to improve extraction efficiency, including transparent contacts, suspended mirror-less packaging and encapsulation in a truncated pyramid optic. These factors resulted in LEDs with high peak external quantum efficiency and reduced efficiency droop. The output power and external quantum efficiency at 20 mA were 38.5 mW and 68.9%. At 100 mA, they were 170 mW and 60.9%. White LEDs were fabricated by application of a yellow phosphor to the blue LEDs. The white LED luminous flux and efficacy at 20 mA was 9.6 lm and 128 lm/W. The chromaticity coordinates and correlated colour temperature were (0.348 K, 0.378 K) and 4998 K. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Synthesis and ordered aggregation in water of a blue light-emitting PEO-PHP-PEO triblock oligomer

    Institute of Scientific and Technical Information of China (English)

    HE Haifeng; CAO Hongqing; WAN Xinhua; TU Yingfeng; CHEN Xiaofang; ZHOU Qifeng

    2003-01-01

    A novel blue light-emitting coil-rod-coil triblock oligomer, PEO-PHP-PEO, which consists of para-hexaphenyl (PHP) as the rigid rod and poly(ethylene oxide) (PEO, M w = 750) as the flexible coil, has been synthesized. It is the first soluble poly(para-phenylene) molecule containing no lateral substituent, which can dissolve not only in organic solvents such as chloroform and THF, but also in water. The critical micelle concentration (CMC) of PEO-PHP-PEO in water is 5.25×10-4 mol@L-1 and the surface tension at CMC, γCMC, is 61.29 mN@m-1. The absorption peak of the molecularly dissolved PEO-PHP-PEO in water is centered at 323 nm and the fluorescence spectrum has a maximum at 432 nm and shows the vibronic fine structure typical of molecular dissolution. The photoluminescence spectrum of the aggregate solution is similar to that of the PHP polycrystal film, indicating that the ordered packing of PHP block has taken place due to a combination of hydrophobic interaction and π-π Stacking. The oligomer self-assembles into cotton-like nanofibers with diameter of about 20 nm in 5.0×10-3 mol@L-1 aqueous solution.

  12. 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…

  13. Mask-less patterning of organic light emitting diodes using electrospray and selective biasing on pixel electrodes

    Science.gov (United States)

    Lee, Sangyeob; Koo, Hyun; Cho, Sunghwan

    2015-04-01

    Wet process of soluble organic light emitting diode (OLED) materials has attracted much attention due to its potential as a large-area manufacturing process with high productivity. Electrospray (ES) deposition is one of candidates of organic thin film formation process for OLED. However, to fabricate red, green, and blue emitters for color display, a fine metal mask is required during spraying emitter materials. We demonstrate a mask-less color pixel patterning process using ES of soluble OLED materials and selective biasing on pixel electrodes and a spray nozzle. We show red and green line patterns of OLED materials. It was found that selective patterning can be allowed by coulomb repulsion between nozzle and pixel. Furthermore, we fabricated blue fluorescent OLED devices by vacuum evaporation and ES processes. The device performance of ES processed OLED showed nearly identical current-voltage characteristics and slightly lower current efficiency compared to vacuum processed OLED.

  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. 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.

  17. 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.

  18. The performance enhancement in organic light-emitting diode using a semicrystalline composite for hole injection

    Institute of Scientific and Technical Information of China (English)

    Cao Jun-Song; Guan Min; Cao Guo-Hua; Zeng Yi-Ping; Li Jin-Min; Qin Da-Shan

    2008-01-01

    A semicrystalline composite, 3, 4, 9, 10 perylenetetracarboxylic dianhydride (PTCDA) doped N, N'-di (1-naphthyl)-N, N'-diphenylbenzidine (NPB), has been fabricated and characterized. An organic light-emitting diode using such a composite in hole injection exhibits the improved performance as compared with the reference device using neat NPB in hole injection. For example, at a luminance of 2000 cd/m2, the former device gives a current efficiency of 2.0cd/A, higher than 1.6cd/A obtained from the latter device. Furthermore, the semicrystalline composite has been shown thermally to be more stable than the neat NPB thin film, which is useful for making organic light emitting diodes with a prolonged lifetime.

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

    OpenAIRE

    Gather, M.C.; Reineke, S.

    2015-01-01

    M.C.G. is grateful to the Scottish Funding Council (via SUPA) for financial support. 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...

  20. Organic light emitting diodes with environmentally and thermally stable doped graphene electrodes

    DEFF Research Database (Denmark)

    Kuruvila, Arun; Kidambi, Piran R.; Kling, Jens;

    2014-01-01

    We present a comparative study of the environmental and thermal stability of graphene charge transfer doping using molybdenum– trioxide (MoO3), vanadium–pentoxide (V2O5) and tungsten–trioxide (WO3). Our results show that all these metal oxides allow a strong and stable p-type doping of graphene, ......, as well as functioning as effective hole-injection layers for highly efficient organic light emitting diodes...

  1. Improved light extraction from white organic light-emitting devices using a binary random phase array

    Energy Technology Data Exchange (ETDEWEB)

    Inada, Yasuhisa, E-mail: inada.yasuhisa@jp.panasonic.com; Nishiwaki, Seiji; Hirasawa, Taku; Nakamura, Yoshitaka; Hashiya, Akira; Wakabayashi, Shin-ichi; Suzuki, Masa-aki [R and D Division, Panasonic Corporation, 1006 Kadoma, Kadoma City, Osaka 571-8501 (Japan); Matsuzaki, Jumpei [Device Development Center, Eco Solutions Company, Panasonic Corporation, 1048 Kadoma, Osaka 571-8686 Japan (Japan)

    2014-02-10

    We have developed a binary random phase array (BRPA) to improve the light extraction performance of white organic light-emitting devices (WOLEDs). We demonstrated that the scattering of incoming light can be controlled by employing diffraction optics to modify the structural parameters of the BRPA. Applying a BRPA to the substrate of the WOLED leads to enhanced extraction efficiency and suppression of angle-dependent color changes. Our systematic study clarifies the effect of scattering on the light extraction of WOLEDs.

  2. 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.

  3. Organic light-emitting device with a phosphor-sensitized fluorescent emission layer

    Science.gov (United States)

    Forrest, Stephen; Kanno, Hiroshi

    2009-08-25

    The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters. The emissive region of the devices of the present invention comprise at least one phosphor-sensitized layer which has a combined emission from a phosphorescent emitter and a fluorescent emitter. In preferred embodiments, the invention relates to white-emitting OLEDS (WOLEDs).

  4. Effect of Triplet Harvesting on the Lifetime Based on Fluorescence and Phosphorescence in Hybrid White Organic Light Emitting Diodes.

    Science.gov (United States)

    Lee, Eun; Lee, Ho Won; Yang, Hyung Jin; Sun, Yong; Lee, Jae Woo; Hwang, Kyo Min; Kim, Woo Young; Kim, Young Kwan

    2016-03-01

    We investigated efficient hybrid white organic light emitting diodes (WOLEDs) apply to triplet harvesting (TH) concept based on three complementary colors by mixing containing blue fluorescent emitter with phosphorescent emitters. The TH is to transfer these triplet excitons from a fluorescence to a phosphorescence, where they can decay radiatively. We fabricated several hybrid WOLEDs, having various emitting layer structures with blue fluorescent emitter and red, green phosphorescent emitter. The WOLED exhibited maximum luminous efficiency of 9.02 cd/A, and a maximum external quantum efficiency of 4.17%. The WOLED showed a highly color-stable white emission with the Commission International de L'Éclairage chromaticity of (0.38, 0.36) at 1,000 cd/m2. PMID:27455693

  5. Enhanced light extraction from organic light-emitting devices using a sub-anode grid

    Science.gov (United States)

    Qu, Yue; Slootsky, Michael; Forrest, Stephen R.

    2015-11-01

    We demonstrate the highly effective extraction of waveguided light from the active region of organic light-emitting devices using a non-diffractive dielectric grid layer placed between the transparent anode and the substrate. The sub-anode grid couples out all waveguide mode power into the substrate without changing the device electrical properties, resulting in an increase in both the external quantum efficiency and luminous efficacy for green phosphorescent organic light-emitting devices from 15 ± 1% and 36 ± 2 lm W-1 to 18 ± 1% and 43 ± 2 lm W-1. These characteristics are further increased to 40 ± 2% and 95 ± 4 lm W-1 when all glass modes are also extracted. The use of a thick electron transport layer further reduces surface plasmon modes, resulting in an increase in the substrate and air modes by 50 ± 8% compared with devices lacking the grids. The sub-anode grid has minimal impact on organic light-emitting device emission wavelength and viewing angle, and is likely to prove beneficial for a broad range of display and lighting applications.

  6. White organic light-emitting devices with high color purity and stability

    Science.gov (United States)

    Bai, Yajie; Liu, Su; Li, Hairong; Liu, Chunjuan; Wang, Jinshun; Chang, Jinxian

    2014-04-01

    A white organic light-emitting device (WOLED) with dual-emitting layers was presented, in which the blue fluorescent dye 2,5,8,11-terta-tertbutylperylene (TBPe) was doped in 2-methyl-9, 10-di(2-naphthyl)-anthracene (MADN) as a blue-emitting layer, while 5,6,11,12-tetraphenylnaphthacene (rubrene, Rb) was doped in the above-mentioned materials as a yellow-emitting layer. The fabricated monochromatic devices using the blue- and yellow-emitting layer have demonstrated that the direct charge trapping mechanism is the dominant emission mechanism in the yellow OLED. Studies on the WOLEDs with dual-emitting layers have shown that the performances of these devices are strongly susceptible to the thickness of the emitting layer and the stack order of two emitting layers. Structure of ITO(160 nm)/NPB(30 nm)/MADN: 5 wt%TBPe: 3 wt%Rb(10 nm)/MADN: 5 wt%TBPe(20 nm)/BCP (10 nm)/Alq3(20 nm)/Al(100 nm) was determined to be the most favorable WOLED. The maximum luminance of 16 000 cd cm-2 at the applied voltage of 13.4 V and Commission International de 1‧Eclairage (CIE) coordinates of (0.3263, 0.3437) which is closer to the standard white light (CIE (0.33, 0.33)) than the most recent reported WOLEDs were obtained. Moreover, there is just slight variation of CIE coordinates (ΔCIEx, y = 0.0171, 0.0167; corresponding Δu‧v‧ = 0.0119) when the current density increases from 10 to 100 mA cm-2. It reveals that the emissive dopant Rb acts as charge traps to improve electron-hole balance, provides sites for electron-hole recombination and thus makes carriers distribute more evenly in the dual-emitting layers which broaden the recombination zone and improve the stability of the CIE coordinates.

  7. Polarization-matched quaternary superlattice electron blocking layer in blue InGaN light-emitting diodes

    Science.gov (United States)

    Kuo, Yen-Kuang; Chen, Fang-Ming; Chang, Jih-Yuan; Lin, Bing-Cheng

    2016-05-01

    The effect of polarization-matched AlInGaN/AlGaN superlattice (SL) electron blocking layer (EBL) on the physical characteristics of blue InGaN light-emitting diodes (LEDs) is investigated numerically. Simulation results show that the optical performance of the LEDs with polarization-matched SL EBL can be markedly improved due to the effectively suppressed polarization effect, enhanced hole injection efficiency, and reduced electron overflow. Comparing to the LEDs with conventional AlGaN EBL, an improvement of 53% in light output power is achieved for the proposed LED structure.

  8. Transparent stacked organic light emitting devices. II. Device performance and applications to displays

    Science.gov (United States)

    Gu, G.; Parthasarathy, G.; Tian, P.; Burrows, P. E.; Forrest, S. R.

    1999-10-01

    Vertical stacking of organic light emitting devices (OLEDs) that emit the three primary colors is shown to be a means for achieving efficient and bright full-color displays. In Paper I, we addressed stacked OLED (SOLED) design and fabrication principles to optimize emission colors, operating voltage, and efficiency. Here, we present results on two different (metal-containing and metal-free cathode) SOLED structures that exhibit performance suitable for many full-color display applications. The operating voltages at 10 mA/cm2 (corresponding to video display brightnesses) are 6.8, 8.5, and 12.1 V for the red (R), green (G), and blue (B) elements of the metal-containing SOLED, respectively. The respective subpixel luminous efficiencies are 0.53, 1.44, and 1.52 cd/A, and the Commission Internationale de L'Éclairage (CIE) chromaticity coordinates are (0.72, 0.28), (0.42, 0.56), and (0.20, 0.22). In the high transparency metal-free SOLED, an insulating layer was inserted between the two upper subpixels to allow for independent grounding of all color emitters in the stack. At operating voltages of 12-14 V, video display brightnesses were achieved with luminous efficiencies of 0.35, 1.36, and 1.05 cd/A for the R, G, and B subpixels, respectively. The respective CIE coordinates for R, G, and B emissions are (0.72, 0.28), (0.26, 0.63), and (0.17, 0.28) in the normal viewing direction, shifting inperceptibly as the viewing angle is increased to as large as 60°. Finally, we discuss addressing schemes of SOLED displays, and compare them with other strategies for achieving full-color, OLED-based displays.

  9. 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.

  10. Fabrication of flexible organic light-emitting diodes with Alq3 as emitting layer

    Institute of Scientific and Technical Information of China (English)

    SUN Yuan-yuan; HUA Yu-lin; XU Feng; YIN Shou-gen; ZHENG Jia-jin; WANG Shu-guo; FENG Xiu-lan

    2005-01-01

    Fabrication of flexible organic light-emitting diodes(FOLEDs) with ITO/PVK:TPD/Alq3/Al configuration prepared on PET substrates is reported.Alq3 is used as the light-emitting material.The curves of the current density vs.voltage,optical current vs.voltage and quantum efficiency vs.current density of the devices are investigated.Compared the devices with the ones that have the same configuration and are fabricated under the same conditions but on glass substrates,the characteristics of the two kinds of devices are very similar except that the threshold voltage of the flexible FOLEDs is a little higher.Under the driving voltage of 20V,the corresponding brightness and the external quantum efficiency are 1000 cd/m2 and 0.27%,respectively.In addition,the anti-bend ability of the devices is tested and the reasons of failure of the devices are analyzed.

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

    International Nuclear Information System (INIS)

    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/m2. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq)3 as phosphorescent red dopant in electron transport layer

  12. Temperature-dependent efficiency droop of blue InGaN micro-light emitting diodes

    International Nuclear Information System (INIS)

    Temperature-dependent trends in radiative and Auger recombination coefficients have been determined at different injection carrier concentrations using InGaN micro-light emitting diodes 40 μm in diameter. The differential lifetime was obtained first from the measured modulation bandwidth and was then employed to calculate the carrier concentration in the quantum well active region. When the temperature increases, the carrier concentration increases, but both the radiative and Auger recombination coefficients decrease. In addition, the temperature dependence of radiative and Auger recombination coefficients is weaker at a higher injection carrier concentration, which is strongly related to phase space filling.

  13. Fabrication and optimization of phosphorescent organic light emitting diodes for solid-state lighting applications

    Science.gov (United States)

    Bhansali, Unnat S.

    Organic Light Emitting Diodes (OLEDs) have made tremendous progress over the last decade and are under consideration for use as solid-state lighting sources to replace the existing incandescent and fluorescent technology. Use of metal-organic phosphorescent complexes as bright emitters and efficient charge transporting organic semiconductors has resulted in OLEDs with internal quantum efficiency ˜ 100% and power efficiency ˜100 lm/W (green OLEDs) at 1000 cd/m2. For lighting applications, white OLEDs (WOLEDs) are required to have a color rendering index (CRI) > 80, correlated color temperature (CCT) (2700 ≤ WOLEDs ≤ 6500 °K), power efficiency > 100 lm/W and a lifetime > 25,000 hrs (at 70% of its original lumen value) at a brightness of 1000 cd/m2. Typically, high CRIs and high power efficiencies are obtained by either a combination of a blue fluorescent emitter with green and red phosphorescent emitters or a stack of blue, green and red phosphorescent emitters doped in a host material. In this work, we implement a single-emitter WOLEDs (SWOLEDs) approach by using monomer (blue) and broad excimer emissions (green and orange) from a self-sensitizing Pt-based phosphorescent complex, designed and synthesized by Prof. M.A. Omary's group. We have optimized and demonstrated high efficiency turquoise-blue OLEDs from monomer emission of Pt(ptp)2-bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) doped in a phosphine-oxide based host molecule and an electron transport molecule. The device peak power efficiency and external quantum efficiency were maintained >40 lm/W and >11%, respectively throughout the wide range of dopant concentrations (1% to 10%). A monotonic increase in the excimer/monomer emission intensity ratio is observed at the higher doping concentrations within 1%-10%, causing a small green-shift in the color. The peak performance of 60 -- 70 lm/W for the best optimized device represents the highest power efficiency known to date for blue OLEDs. Typically

  14. Quasi-homoepitaxial GaN-based blue light emitting diode on thick GaN template

    International Nuclear Information System (INIS)

    The high power GaN-based blue light emitting diode (LED) on an 80-μm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapor-phase epitaxial (HVPE), and laser lift-off (LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Rutherford back-scattering (RBS), photoluminescence, current-voltage and light output-current measurements. The width of (0002) reflection in XRD rocking curve, which reaches 173″ for the thick GaN template LED, is less than that for the conventional one, which reaches 258″. The HRTEM images show that the multiple quantum wells (MQWs) in 80-μm-thick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-μm-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80-μm-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation. (condensed matter: structural, mechanical, and thermal properties)

  15. 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.

  16. 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.

  17. Flexible white phosphorescent organic light emitting diodes based on multilayered graphene/PEDOT:PSS transparent conducting film

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaoxiao; Li, Fushan, E-mail: fushanli@hotmail.com; Wu, Wei; Guo, Tailiang, E-mail: gtl_fzu@hotmail.com

    2014-03-01

    Highlights: • A double-layered graphene/PEDOT:PSS film was fabricated by spray-coating. • A white flexible phosphorescent OLED was fabricated based on this film. • The white flexible OLED presented pure white light emission. • The flexible OLEDs showed a stable white emission during bending test. - Abstract: A double-layered graphene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conductive film was prepared, in which the PEDOT:PSS layer was obtained by using spray-coating technique. A flexible white phosphorescent organic light-emitting devices based on the graphene/PEDOT:PSS conductive film was fabricated. Phosphorescent material tris(2-phenylpyridine) iridium (Ir(ppy){sub 3}) and the fluorescent dye 5,6,11,12-tetraphenylnapthacene (Rubrene) were co-doped into 4,4′-N,N′-dicarbazole-biphenyl (CBP) host. N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were used as hole-transporting and electron-transporting layer, respectively, and 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) was used as blue light-emitting layer. The device presented pure white light emission with a Commission Internationale De I’Eclairage coordinates of (0.31, 0.33) and exhibited an excellent light-emitting stability during the bending cycle test with a radius of curvature of 10 mm.

  18. 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.

  19. 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.

  20. Experimental Study of Red-, Green-, and Blue-Based Light Emitting Diodes Visible Light Communications for Micro-Projector Application

    Science.gov (United States)

    Chou, H.-H.; Liaw, S.-K.; Jiang, J.-S.; Teng, C.

    2016-05-01

    In this research, an experimental short-range visible light communication link using red-, green-, and blue-based light-emitting diodes (LEDs) for portable micro-projector applications is presented. A Reconfigurable design of a post-equalizer aimed to improve the inherent narrow modulation bandwidth of red-, green-, and blue-based LEDs has been experimentally implemented, and its effectiveness with optical filters at the receiver is investigated. Reflective liquid-crystal-on-silicon-based micro-projection architecture, widely used in portable micro-projectors, was set up to evaluate the proposed visible light communication system. The measurement results demonstrated that a significant aggregative bandwidth improvement of 162 MHz as well as an aggregative data transmission rate of nearly 400 Mb/s can be achieved by using a non-return-to-zero-on-off keying (NRZ-OOK) modulation scheme based on only one polarization state of incident light without any offline signal processing.

  1. High-efficiency blue multilayer polymer light-emitting diode based on poly(9,9-dioctylfluorene)

    Science.gov (United States)

    Tseng, Shin-Rong; Li, Shiuan-Yi; Meng, Hsin-Fei; Yu, Yi-Hsiang; Yang, Chia-Ming; Liao, Hua-Hsien; Horng, Sheng-Fu; Hsu, Chian-Shu

    2007-04-01

    A highly efficient blue polymer light-emitting diode based exclusively on commercial poly(9,9-dioctylfluorene) and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-s-butylphenyl)) diphenylamine)] is demonstrated. High electroluminescent efficiency is achieved by enhancing electron currents and making devices in multilayered structures. CsF/Al is used as the efficient electron injection cathode, and the fabrication process is in the glove box to enhance electron mobility by reducing oxygen adsorption. The multilayer structure is prepared by the liquid buffer layer technique. The maximum efficiency is 2.5 cd/A at deep blue with the corresponding external quantum efficiency of 2%.

  2. 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.

  3. 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.

  4. 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.

  5. All solution processed blue multi-layer light emitting diodes realized by thermal layer stabilization and orthogonal solvent processing

    Science.gov (United States)

    Nau, Sebastian; Trattnig, Roman; Pevzner, Leonid; Jäger, Monika; Schlesinger, Raphael; Nardi, Marco V.; Ligorio, Giovanni; Christodoulou, Christos; Schulte, Niels; Winkler, Stefanie; Frisch, Johannes; Vollmer, Antje; Baumgarten, Martin; Sax, Stefan; Koch, Norbert; Müllen, Klaus; List-Kratochvil, Emil J. W.

    2013-09-01

    Herein we report on the fabrication and the properties of two highly efficient blue light emitting multilayer polymer light emitting diodes (PLEDs). The first device structure combines a thermally stabilized polymer with a material processed from an orthogonal solvent, allowing for the fabrication of a triple layer structure from solution. The well known poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), which can be stabilized in a bake-out procedure, was used as a hole transporting layer. A novel pyrene - triphenylamine (PPyrTPA) copolymer was used as emissive layer. The stack was finalized by a poly(fluorene) - derivative with polar side-chains, therefore being soluble in a polar solvent which allows for the deposition onto PPyrTPA without redissolving. The resulting PLED showed bright-blue electroluminescence (CIE1931 coordinates x=0.163; y=0.216) with a high efficiency of 1.42 cd/A and a peak luminescence of 16500 cd/m². The second presented device configuration comprises a thermally stabilized indenofluorene - triphenylamine copolymer acting as hole transporter, and an emissive copolymer with building blocks specifically designed for blue light emission, effective charge carrier injection and transport as well as for exciton generation. This multilayer PLED led to deep-blue emission (CIE1931 x=0.144; y=0.129) with a remarkably high device efficiency of 9.7 cd/A. Additionally, atomic force microscopy was carried out to investigate the film morphology of the components of the stack and x-ray photoemission spectroscopy was performed to ensure a full coverage of the materials on top of each other. Ultraviolet photoemission spectroscopy confirmed the desired type-II band level offsets on the individual interfaces.

  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. Organic Light-Emitting Devices with Extended Operating Lifetimes on Plastic Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, Michael (Universal Display Corporation); Michalski, L (Universal Display Corporation); Rajan, K (Universal Display); Rothman, M A.(Universal Display); Silvernail, J A.(Universal Display); Brown, Julie J.(Universal Display Corporation); Burrows, Paul E.(BATTELLE (PACIFIC NW LAB)); Graff, Gordon L.(BATTELLE (PACIFIC NW LAB)); Gross, Mark E.(BATTELLE (PACIFIC NW LAB)); Martin, Peter M.(BATTELLE (PACIFIC NW LAB)); Hall, Michael G.(BATTELLE (PACIFIC NW LAB)); Mast, Eric S.(BATTELLE (PACIFIC NW LAB)); Bonham, Charles C.(BATTELLE (PACIFIC NW LAB)); Bennett, Wendy D.(BATTELLE (PACIFIC NW LAB)); Zumhoff, Mac R.(BATTELLE (PACIFIC NW LAB))

    2001-11-01

    We fabricate long-lived organic light emitting devices using a 175-micrometer thick polyethylene terephthalte substrate coated with an organic-inorganic multilayered barrier film. To assess the permeability of the plastic substrate, a glass lid and epoxy seal are used to encapsulate the display in order to compare the rate of degradation to glass-based devices. The observed permeating rate of water vapor through the plastic substrate was estimated to be 2 x 10-6 g/m squared/day. Driven at 2.5 mA/cm squared, we measure a device lifetime of 3800 hours from an initial luminance of 425 cd/m squared.

  8. Organic light emitting diodes the use of rare earth and transition metals

    CERN Document Server

    Pereira, Luiz F R

    2012-01-01

    The Organic Light Emitting Diode (OLED) world is one of the most fascinated fields of research with an enormous technological application market. Besides the actual use in displays, the intrinsic and unique properties of that electroluminescent devices opens new potential applications since efficient lighting to decorative environments, with a very simple incorporation in architectural design. This book addresses the development of OLEDs based on rare-earth and transition-metal complexes, focusing in special the Europium, Terbium, Ruthenium and Rhenium. The idea is to explain how these organic

  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. 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.

  11. 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. PMID:27411203

  12. 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.

  13. Weak-microcavity organic light-emitting diodes with improved light-extraction and wide viewing-angle

    Science.gov (United States)

    Cho, Sang-Hwan; Lee, Yong-Hee; Song, Young-Woo; Kim, Yoon-Chang; Lee, Joon-Gu; Lee, Jong Hyuk; Hwang, Kyu Hwan; Zang, Dong-Sik

    2009-02-01

    We propose and demonstrate weak-microcavity organic light-emitting diode (OLED) displays that deliver both a high light-extraction efficiency and wide viewing-angle characteristics. A single pair of low- and high-index layers is inserted between indium tin oxide (ITO) and a glass substrate. The electroluminescent (EL) efficiencies of discrete red, green, and blue weak-microcavity OLEDs (WMOLEDs) are enhanced by 56%, 107%, and 26%, respectively with minimal changes viewing angle and EL spectra characteristics. The color purity is also improved for all three colors. Moreover, we fabricated full-color 128×160 passive-matrix bottom-emitting WMOLED displays to prove their manufacturability. This design is realized by simple one-step 20-nm etching of the low-index layer of red/green subpixels. The EL efficiency of white color in the WMOLED display is 27% higher than that of a conventional OLED display.

  14. 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.

  15. 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.

  16. 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.

  17. Origin of Sub-Bandgap Electroluminescence in Organic Light-Emitting Diodes.

    Science.gov (United States)

    Xiang, Chaoyu; Peng, Cheng; Chen, Ying; So, Franky

    2015-10-28

    Sub-bandgap electroluminescence in organic light emitting diodes is a phenomenon in which the electroluminescence turn-on voltage is lower than the bandgap voltage of the emitter. Based on the results of transient electroluminescence (EL) and photoluminescence and electroabsorption spectroscopy measurements, it is concluded that in rubrene/C60 devices, charge transfer excitons are generated at the rubrene/C60 interface under sub-bandgap driving conditions, leading to the formation of triplet excitons, and sub-bandgap EL is the result of the subsequent triplet-triplet annihilation process. PMID:26312783

  18. 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.

  19. A non-doped phosphorescent organic light-emitting device with above 31% external quantum efficiency.

    Science.gov (United States)

    Wang, Qi; Oswald, Iain W H; Yang, Xiaolong; Zhou, Guijiang; Jia, Huiping; Qiao, Qiquan; Chen, Yonghua; Hoshikawa-Halbert, Jason; Gnade, Bruce E

    2014-12-23

    The demonstrated square-planar Pt(II)-complex has reduced triplet-triplet quenching and therefore a near unity quantum yield in the neat thin film. A non-doped phosphorescent organic light-emitting diode (PhOLED) based on this emitter achieves (31.1 ± 0.1)% external quantum efficiency without any out-coupling, which shows that a non-doped PhOLED can be comparable in efficiency to the best doped devices with very complicated device structures. PMID:25219957

  20. High luminance organic light-emitting diodes with efficient multi-walled carbon nanotube hole injectors

    OpenAIRE

    Shi, S; Silva, SRP

    2012-01-01

    We report high luminance organic light-emitting diodes by use of acid functionalized multi-walled carbon nanotube (o-MWCNTs) as efficient hole injector electrodes with a simple and solution processable device structure. At only 10 V, the luminance can reach nearly 50,000 cd/m2 with an external quantum efficiency over 2% and a current efficiency greater than 21 cd/A. The investigation of hole-only devices shows that the mechanism for hole injection is changed from injection limited to bulk lim...

  1. Collimated Light Source Using Patterned Organic Light-Emitting Diodes and Microlens

    Science.gov (United States)

    Sukekazu Aratani,; Masaya Adachi,; Masao Shimizu,; Tatsuya Sugita,; Toshinari Shibasaki,; Katsusuke Shimazaki,

    2010-04-01

    We developed for the first time a collimated organic light-emitting diode (OLED) light source using a patterned OLED and a microlens. The structure of the collimated OLED light source was designed by conventional ray-tracking simulation. We demonstrated that the collimated OLED light source enhanced the luminance of a liquid crystal display (LCD) with a low aperture ratio by a factor of more than two compared with a conventional OLED light source, which was not patterned. The collimated OLED light source with the patterned OLED and microlens is thus very effective for achieving a highly efficient LCD with OLED backlight.

  2. 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.

  3. Flexible organic light-emitting diodes with ITO/Ag/ITO multi-layers as anodes

    Institute of Scientific and Technical Information of China (English)

    LI Yang; WANG Liduo; CHANG Chun; DUAN Lian; QIU Yong

    2004-01-01

    The transparent ITO/Ag/ITO multi-layers are developed as anodes on flexible PET (poly(ethylene terephthalate)) substrates. The influence of these anodes on FOLED (Flexible Organic Light-emitting Diodes) is investigated. From the results of research, it can be seen that the multi-layer anode has optimum characteristics, whose sheet resistance is 11 Ω and optical transmittance is about 80%,when the thickness of Ag sandwiched by two ITO layers is in the range of 14-18 nm. It is demonstrated that the OLED devices with multi-layer anodes give better luminescence and higher efficiency compared with those with single ITO an odes.

  4. 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.

  5. Large white organic light-emitting diode lighting panel on metal foils

    OpenAIRE

    Guaino, Philippe; Mazeri, Fabrizo; Hofmann, Michael; Birnstock, Jan; Avril, Ludovic; Viville, Pascal; Kanaan, Hani; Lazzaroni, Roberto; Loicq, Jerôme; Rotheudt, Frank; Pans, Christian

    2011-01-01

    Large-area top-emitting PIN structure (highly p- and n- type doped transport layers for electrons and holes and an undoped emitter layer)–organic light-emitting diode (OLED) on advanced metal foils were fabricated for lighting applications. ArcelorMittal has developed a new surface treatment on metal foils, suitable for roll-to-roll production and dedicated to large-area device integration. Both monochromatic and white devices are realized on advanced metal foils. Power efficiencies at 1000 c...

  6. Improved AC pixel electrode circuit for active matrix of organic light-emitting display

    Science.gov (United States)

    Si, Yujuan; Lang, Liuqi; Chen, Wanzhong; Liu, Shiyong

    2004-05-01

    In this paper, a modified four-transistor pixel circuit for active-matrix organic light-emitting displays (AMOLED) was developed to improve the performance of OLED device. This modified pixel circuit can provide an AC driving mode to make the OLED working in a reversed-biased voltage during the certain cycle. The optimized values of the reversed-biased voltage and the characteristics of the pixel circuit were investigated using AIM-SPICE. The simulated results reveal that this circuit can provide a suitable output current and voltage characteristic, and little change was made in luminance current.

  7. 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.

  8. Organic Light Emitting Devices with Linearly-Graded Mixed Host Architecture

    Science.gov (United States)

    Lee, Sang Min

    Organic Light Emitting Devices (OLEDs) with a linearly-graded mixed (LGM) host architecture in the emissive layer (EML) were studied by the application of a newly-developed thermal deposition boat. A new thermal deposition boat, featuring indirect deposition control and fast rate response, was developed in order to make an evaporation coater of high space utilization and to achieve a real time linearly-graded rate control during the device fabrication process. A new design of dual-hole boat, based on the reduced wall resistance of the side hole toward the vapor flow, enabled the indirect deposition rate control with sufficient control accuracy by using the feature of the stable ratio of rates from top and side holes. Minimizing the thermal mass of the body and designing a direct heat transfer with a coil placed inside the boat resulted in the realization of the linearly-graded deposition rate within acceptable deviation range. Thanks to the feature of fast rate response, it was possible to control the linearly-graded rate of each host material during the process and to apply the architecture to some of the fluorescent and phosphorescent OLED devices. The reported efficiency improvement of a fluorescent OLED, based on step-graded junction in the literature, was well reproduced in an OLED with a LGM architecture, demonstrating that charge balance in the emissive layer can be further improved using the LGM architecture. By minimizing the internal energy barrier in the LGM device, a higher EL efficiency was well demonstrated over the uniformly-mixed (UM) host device, where residual internal interfaces were present as additional quenching sites in the EML. Similar effects were observed in blue phosphorescent OLED devices, where the mobility of the hole transport material (HTM) was usually much higher than that of the electron transport material (ETM) such that the recombination zone was more localized at the EML/ETL interface. It was found that the main effect of the

  9. 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.

  10. Improving spinach, radish, and lettuce growth under red light-emitting diodes (LEDs) with blue light supplementation

    Science.gov (United States)

    Yorio, N. C.; Goins, G. D.; Kagie, H. R.; Wheeler, R. M.; Sager, J. C.

    2001-01-01

    Radish (Raphanus sativus L. cv. Cherriette), lettuce (Lactuca sativa L. cv. Waldmann's Green), and spinach (Spinacea oleracea L. cv. Nordic IV) plants were grown under 660-nm red light-emitting diodes (LEDs) and were compared at equal photosynthetic photon flux (PPF) with either plants grown under cool-white fluorescent lamps (CWF) or red LEDs supplemented with 10% (30 micromoles m-2 s-1) blue light (400-500 nm) from blue fluorescent (BF) lamps. At 21 days after planting (DAP), leaf photosynthetic rates and stomatal conductance were greater for plants grown under CWF light than for those grown under red LEDs, with or without supplemental blue light. At harvest (21 DAP), total dry-weight accumulation was significantly lower for all species tested when grown under red LEDs alone than when grown under CWF light or red LEDs + 10% BF light. Moreover, total dry weight for radish and spinach was significantly lower under red LEDs + 10% BF than under CWF light, suggesting that addition of blue light to the red LEDs was still insufficient for achieving maximal growth for these crops.

  11. 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.

  12. Tri-Metal Layered Semitransparent Electrode for Red Phosphorescent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Lee, Jae Woo; Lee, Ho Won; Lee, Song Eun; Yang, Hyung Jin; Lee, Sung Kyu; Hwang, Kyo Min; Park, Soo Na; Yoon, Seung Soo; Kim, Young Kwan

    2015-10-01

    In this paper, we fabricated tri-metal layered thin film semitransparent electrodes consisting of a thin conductive metal layer, sandwiched between two nickel layers. An equal red phosphorescent organic light-emitting diode (PHOLED) structure was deposited on the anodes of indium tin oxide (ITO) and three types of tri-metal layers (Ni/Al/Ni, Ni/Cu/Ni, and Ni/Ag/Ni, thickness of 3/7/3 nm in common) on a glass substrate. The optical and electrical performances of the device using Ni/Ag/Ni were improved more than the performances of the other devices due to the micro-cavity effect in accordance with the various electrode characteristics. Moreover, we fabricated the same red PHOLED structures on a flexible substrate, as a consequence, showed competitive emission characteristics compared to the devices fabricated on a glass substrate. Therefore, this study could succeed to additional research on flexible display panel and light-emitting devices with ITO-free electrodes. PMID:26726477

  13. 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.

  14. 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.

  15. 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...

  16. Integration of silk protein in organic and light-emitting transistors.

    Science.gov (United States)

    Capelli, R; Amsden, J J; Generali, G; Toffanin, S; Benfenati, V; Muccini, M; Kaplan, D L; Omenetto, F G; Zamboni, R

    2011-07-01

    We present the integration of a natural protein into electronic and optoelectronic devices by using silk fibroin as a thin film dielectric in an organic thin film field-effect transistor (OFET) ad an organic light emitting transistor device (OLET) structures. Both n- (perylene) and p-type (thiophene) silk-based OFETs are demonstrated. The measured electrical characteristics are in agreement with high-efficiency standard organic transistors, namely charge mobility of the order of 10(-2) cm(2)/Vs and on/off ratio of 10(4). The silk-based optolectronic element is an advanced unipolar n-type OLET that yields a light emission of 100nW. PMID:22899899

  17. Solution-Processed Small Molecular Organic Light-Emitting Devices with a Mixed Single Layer

    Science.gov (United States)

    Wang, Zhaokui; Naka, Shigeki; Okada, Hiroyuki

    2011-01-01

    We investigated the characteristics of solution-processed mixed-single-layer organic light-emitting devices (OLEDs) by mixing an electron injection material, a hole transport material, and a dopant material based on 5,6,11,12-tetraphenylnaphthacene (rubrene). The mixed-single-layer OLEDs showed better performance by optimizing the solution concentration and mixing ratio of organic materials. The performance was further improved by mixing chloroform (95 wt %) and toluene (5 wt %) as a solvent. The maximum luminance and power efficiency obtained were 12,400 cd/m2 and 1.1 lm/W, respectively. The mixed-single-layer OLEDs by solution process can be expected as an alternative route to the fabrication of small-molecular OLEDs with reduced cost of devices and avoiding the complexities of the co-evaporation of multiple organic materials in the vacuum deposition process.

  18. 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.

  19. 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.

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

    Science.gov (United States)

    Shi, Hongying; Deng, Lingling; Chen, Shufen; Xu, Ying; Zhao, Xiaofei; Cheng, Fan; Huang, Wei

    2014-04-01

    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/m2. 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.

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

    Directory of Open Access Journals (Sweden)

    Hongying Shi

    2014-04-01

    Full Text Available 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/m2. 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.

  2. 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.

  3. Above 20% external quantum efficiency in novel hybrid white organic light-emitting diodes having green thermally activated delayed fluorescent emitter

    Science.gov (United States)

    Kim, Bo Seong; Yook, Kyoung Soo; Lee, Jun Yeob

    2014-08-01

    High efficiency hybrid type white organic light-emitting diodes (WOLEDs) combining a green thermally activated delayed fluorescent (TADF) emitting material with red/blue phosphorescent emitting materials were developed by manipulating the device architecture of WOLEDs. Energy transfer between a blue phosphorescent emitting material and a green TADF emitter was efficient and could be managed by controlling the doping concentration of emitters. A high quantum efficiency above 20% was achieved in the hybrid WOLEDs by optimizing the device structure of the hybrid type WOLEDs for the first time and the device performances of the hybrid WOLEDs were comparable to those of all phosphorescent WOLEDs.

  4. Color stability of white organic light emitting devices with a color conversion layer utilizing CdSe/ZnS quantum dots and phosphors dispersed in polymethylmethacrylate.

    Science.gov (United States)

    Kwon, W J; Kim, S H; Lee, K S; Choo, D C; Kim, S W; Kim, S W; Yoo, T W; Kwon, M S; Yoo, K H; Kim, T W

    2013-06-01

    White organic light-emitting devices (WOLEDs) were fabricated by combining a blue emitting organic light-emitting devices (OLEDs) and a color conversion layer made of yttrium aluminum garnet phosphors and CdSe/ZnS quantum dots (QDs) embedded into polymethylmethacrylate. When the ratio of phosphors and QDs changed, a good color balance was achieved at a ratio of 1:5, and the maximum luminance of 18.21 cd/m2 was obtained. As the applied voltage varied from 12 to 16 V, Commission Internationale de l'Eclairage coordinates shifted only slightly from (0.32, 0.34) to (0.30, 0.33), indicating a good color stability. PMID:23862508

  5. 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.

  6. 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

  7. A blue-emitting Sc silicate phosphor for ultraviolet excited light-emitting diodes.

    Science.gov (United States)

    Wang, Qian; Zhu, Ge; Xin, Shuangyu; Ding, Xin; Xu, Ju; Wang, Yuansheng; Wang, Yuhua

    2015-11-01

    A blue-emitting phosphor BaSc2Si3O10:Eu(2+) was synthesized using the conventional solid-state reaction. The crystallographic occupancy of Eu(2+) in the BaSc2Si3O10 matrix was studied based on the Rietveld refinement results and the photoluminescence properties. BaSc2Si3O10 exhibits blue emission ascribed to (3)T2-(1)A1 and (3)T1-(1)A1 charge transfer of SiO4(4-) excited by 360 nm. All the phosphors of BaSc2Si3O10:Eu(2+) exhibit strong broad absorption bands in the near ultraviolet range, and give abnormal blue emission upon 330 nm excitation. The abnormal phenomenon was explored in detail through many pieces of experimental evidence. The concentration of Eu(2+) is optimized to be 3 mol% according to emission intensity and the quenching mechanism is verified to be a quadrupole-quadrupole interaction. The CIE coordinates of BaSc2Si3O10:0.03Eu(2+) are calculated to be (0.15, 0.05) and BaSc2Si3O10:0.03Eu(2+) shows similar thermal stability to commercial BaMgAl10O17:Eu(2+). PMID:26242881

  8. 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.

  9. 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.

  10. Efficiency improvement and image quality of organic light-emitting display by attaching cylindrical microlens arrays.

    Science.gov (United States)

    Lee, Jiun-Haw; Ho, Yu-Hsuan; Chen, Kuan-Yu; Lin, Hoang-Yan; Fang, Jheng-Hao; Hsu, Sheng-Chih; Lin, Jia-Rong; Wei, Mao-Kuo

    2008-12-22

    In this paper, cylindrical microlens arrays with two different alignments were proposed to be applied in a commercial mobile phone having an organic light-emitting diode (OLED) panel. It was found that the parallel-aligned cylindrical array had better performance than the vertical-aligned one for the OLED panel. The parallel-aligned cylindrical microlens array can increase the luminous current efficiency at surface normal and the luminous power efficiency of the OLED panel by 45% and 38%, respectively. Besides, it can also make the spectrum of the OLED panel more insensitive to the viewing angle. Though it can slightly blur the image on the OLED panel, the universal image quality index can be maintained at a level of 0.8630. PMID:19104547

  11. Emiflective Display with Integration of Reflective Liquid Crystal Display and Organic Light Emitting Diode

    Science.gov (United States)

    Yang, Bo-Ru; Liu, Kang-Hung; Shieh, Han-Ping D.

    2007-01-01

    A novel emi-flective display which integrates a reflective liquid crystal display (R-LCD) and an organic light emitting diode (OLED) was demonstrated, whose OLED achieved a gain factor of 8 in contrast ratio (CR) compared with the conventional OLED. Under the high light ambience, the R-LCD is sustained with the CR of 10:1 at the viewing angle between ± 55°; while in the dim ambience, the OLED is operated with the CR of 5000:1 at ± 50°. By replacing the backlight system with OLED, emi-flective display has the benefits of lighter weight (<90%), thinner form factor (<40%), and lower power consumption (<2%, under sunlight) compared with the conventional LCD; therefore, to be very applicable for mobile products.

  12. Very low color-temperature organic light-emitting diodes for lighting at night

    Science.gov (United States)

    Jou, Jwo-Huei; Tang, Ming-Chun; Chen, Pin-Chu; Chen, Szu-Hao; Shen, Shih-Ming; Chen, Chien-Chih; Wang, Ching-Chiun; Chen, Chien-Tien

    2011-12-01

    Light sources with low color temperature (CT) are essential for their markedly less suppression effect on the secretion of melatonin, and high power efficiency is crucial for energy-saving. To provide visual comfort, the light source should also have a reasonably high color rendering index (CRI). In this report, we demonstrate the design and fabrication of low CT and high efficiency organic light-emitting diodes. The best resultant device exhibits a CT of 1,880 K, much lower than that of incandescent bulbs (2,000-2,500 K) and even as low as that of candles, (1,800-2,000 K), a beyond theoretical limit external quantum efficiency 22.7 %, and 36.0 lm/W at 100 cd/m 2. The high efficiency of the proposed device may be attributed to its interlayer, which helps effectively distribute the entering carriers into the available recombination zones.

  13. Electroluminescence from colloidal semiconductor CdSe nanoplatelets in hybrid organic-inorganic light emitting diode

    Science.gov (United States)

    Vitukhnovsky, A. G.; Lebedev, V. S.; Selyukov, A. S.; Vashchenko, A. A.; Vasiliev, R. B.; Sokolikova, M. S.

    2015-01-01

    We report on the fabrication of a hybrid light-emitting-diode based on colloidal semiconductor CdSe nanoplatelets as emitters and organic TAZ [3-(Biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole] and TPD [N, N‧-bis (3-methylphenyl)-N, N‧-bis (phenyl)-benzidine] materials as the electron and hole transporting layers. Electroluminescent and current-voltage characteristics of the developed hybrid device with the turn-on voltage of 5.5 V and the radiation wavelength of 515 nm have been obtained. Semiconductor nanoplatelets like CdSe are attractive for the fabrication of hybrid LEDs with low operating voltages, spectrally pure color and short-wavelength electroluminescence, which is required for RGB devices.

  14. Nondoped Electrophosphorescent Organic Light-Emitting Diodes Based on Platinum Complexes

    Institute of Scientific and Technical Information of China (English)

    YANG Gang; ZHANG Di; WANG Jun; JIANG Quan; ZHONG Jian; YU Jun-Sheng; ZHU Feng-Zhi; LUO Kai-Jun; XIE Yun; XU Ling-Ling

    2009-01-01

    An undoped electrophosphorescent organic light-emitting diode is fabricated using a pure platinum(Ⅱ)(2-phenylpyridinato-N, C2) (3-benzoyl-camphor) [(ppy)pt(bcam)] phosphorescent layer acting as the emitting layer. A maximum power efficiency ηp of 6.62lm/W and current efficiency of 14.78cd/A at 745 cd/m2 are ob-tained from the device. The roll-off percentage of ηp of the pure phosphorescent phosphor layer device is reduced to 5% at a current density of 20 mA/cm2, which is about 11% for conventional phosphorescent devices. The low roll-off efficiency is attributed to the phosphorescent material, which has the molecular structure of a strong steric hindrance effect.

  15. Enhancement and Quenching of Fluorescence by Silver Nanoparticles in Organic Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Ying-Chung Chen

    2013-01-01

    Full Text Available The influence of silver nanoparticles (SNPs on the performance of organic light-emitting diodes (OLEDs is investigated in this study. The SNPs are introduced between the electron-transport layers by means of thermal evaporation. SNPs are found to have the surface plasmon resonance at wavelength 525 nm when the mean particle size of SNPs is 34 nm. The optimized OLED, in terms of the spacing between the emitting layer and SNPs, is found to have the maximum luminance 2.4 times higher than that in the OLED without SNPs. The energy transfer between exciton and surface plasmons with the different spacing distances has been studied.

  16. 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.

  17. Degradation of Bilayer Organic Light-Emitting Diodes Studied by Impedance Spectroscopy.

    Science.gov (United States)

    Sato, Shuri; Takata, Masashi; Takada, Makoto; Naito, Hiroyoshi

    2016-04-01

    The degradation of bilayer organic light-emitting diodes (OLEDs) with a device structure of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) (hole transport layer) and tris-(8-hydroxyquinolate)aluminum (Alq3) (emissive layer and electron transport layer) has been studied by impedance spectroscopy and device simulation. Two modulus peaks are found in the modulus spectra of the OLEDs below the electroluminescence threshold. After aging of the OLEDs, the intensity of electroluminescence is degraded and the modulus peak due to the Alq3 layer is shifted to lower frequency, indicating that the resistance of the Alq3 layer is increased. Device simulation reveals that the increase in the resistance of the Alq3 layer is due to the decrease in the electron mobility in the Alq3 layer. PMID:27451634

  18. Ultra-thin fluoropolymer buffer layer as an anode stabilizer of organic light emitting devices

    International Nuclear Information System (INIS)

    We have investigated the effect of thin fluoro-acrylic polymer as an anode stabilizer on the lifetime of an organic light emitting device (OLED). Surface chemical properties of commercial fluoropolymer, FC-722 (Fluorad(TM) of 3M), on indium-tin oxide (ITO) were characterized by x-ray photoemission spectroscopy. An OLED with 1 nm thick fluoropolymeric film showed identical brightness and efficiency behaviour and improved operational stability compared with the reference device with UV-O3 treated ITO. The improvement in the lifetime was accompanied by the suppression of the voltage increase at the initial stage of constant-current driving, which can be attributed to the action of the FC-722 layer by smoothing the ITO surface. Fluoropolymer coating, therefore, improves the lifetime of the small molecular OLED by the simple and reliable anode-stabilizing process

  19. Ultra-thin fluoropolymer buffer layer as an anode stabilizer of organic light emitting devices

    Science.gov (United States)

    Yang, Nam Chul; Lee, Jaeho; Song, Myung-Won; Ahn, Nari; Kim, Mu-Hyun; Lee, Songtaek; Doo Chin, Byung

    2007-08-01

    We have investigated the effect of thin fluoro-acrylic polymer as an anode stabilizer on the lifetime of an organic light emitting device (OLED). Surface chemical properties of commercial fluoropolymer, FC-722 (Fluorad™ of 3M), on indium-tin oxide (ITO) were characterized by x-ray photoemission spectroscopy. An OLED with 1 nm thick fluoropolymeric film showed identical brightness and efficiency behaviour and improved operational stability compared with the reference device with UV-O3 treated ITO. The improvement in the lifetime was accompanied by the suppression of the voltage increase at the initial stage of constant-current driving, which can be attributed to the action of the FC-722 layer by smoothing the ITO surface. Fluoropolymer coating, therefore, improves the lifetime of the small molecular OLED by the simple and reliable anode-stabilizing process.

  20. 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.

  1. 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.

  2. 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.

  3. Improved Quantum Efficiency of Organic Light Emitting Diodes with Gradiently Doped Double Emitting Zone

    Institute of Scientific and Technical Information of China (English)

    高文宝; 姜文龙; 孙家鑫; 冯晶; 侯晶莹; 刘式墉

    2003-01-01

    We investigate electroluminescent characteristics of gradiently doped organic light-emitting diodes, which were gradiently doped in both the hole and the electron-transporting layer to form a double emitting zone. The device structure was ITO/(15nm) CuPc/(60nm)NPB:rubrene/(30nm)Alqs:rubrene/(20nm)Alqs/(0.5nm)LiF/Al. We observed that charge carriers were well trapped by the dopant molecules and the main emitting zone was localized at the NPB:rubrene side close to the interface of NPB:rubrene/Alqs:rubrene. The quantum efficiency (cd/A) was enhanced to 5.89 cd/A at 6 V. We attributed this improvement to the charge carriers trapping and the emitting of the double emitting zone.

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

    International Nuclear Information System (INIS)

    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.

  5. 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.

  6. Cold welding of organic light emitting diode: Interfacial and contact models

    Science.gov (United States)

    Asare, J.; Adeniji, S. A.; Oyewole, O. K.; Agyei-Tuffour, B.; Du, J.; Arthur, E.; Fashina, A. A.; Zebaze Kana, M. G.; Soboyejo, W. O.

    2016-06-01

    This paper presents the results of an analytical and computational study of the contacts and interfacial fracture associated with the cold welding of Organic Light Emitting diodes (OLEDs). The effects of impurities (within the possible interfaces) are explored for contacts and interfacial fracture between layers that are relevant to model OLEDs. The models are used to study the effects of adhesion, pressure, thin film layer thickness and dust particle modulus (between the contacting surfaces) on contact profiles around impurities between cold-welded thin films. The lift-off stage of thin films (during cold welding) is then modeled as an interfacial fracture process. A combination of adhesion and interfacial fracture theories is used to provide new insights for the design of improved contact and interfacial separation during cold welding. The implications of the results are discussed for the design and fabrication of cold welded OLED structures.

  7. 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.

  8. 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.

  9. 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.

  10. 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.)

  11. Glare-Tunable Transparent Electrochemical Smart Window Coupled with Transparent Organic Light-Emitting Diode

    Science.gov (United States)

    Uchida, Takayuki; Shibasaki, Masaaki; Matsuzaki, Tatsuya; Nagata, Yujiro

    2013-04-01

    We fabricated a novel device assembled by coupling a transparent organic light-emitting diode (TOLED) and a glare-tunable transparent electrochemical device. This device could be operated in six different states, namely, (1) transparent, (2) mirror, (3) black, (4) dual emission, (5) single-side emission with mirror, and (6) single-side emission with black. Switching between each of these states could be tuned by varying/selecting the applied DC bias voltage. The device showed 63.8% transmittance in the transparent state, and 42.1% reflectance in the mirror state at 700 nm. Transmittance in both the mirror and black states was less than 0.1% in the visible range.

  12. 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.

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

    Science.gov (United States)

    Ito, Hiroyuki; Ogawa, Masaki; Sunaga, Shoji

    2013-01-01

    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. PMID:23757510

  14. Front-Light Source Using Inverted Organic Light-Emitting Diodes with Microcathode Arrays

    Science.gov (United States)

    Urata, Kohei; Naka, Shigeki; Okada, Hiroyuki

    2010-04-01

    We have demonstrated an organic light-emitting diode (OLED) front-light source with a blinding microcathode array on a transparent electrode and a top-emission structure. Contrast ratio was improved by inserting MoO3 at the indium-tin-oxide (ITO)/Al interface. In a device of glass substrate/ITO/MoO3/meshed Al/lithium fluoride (LiF)/tris(8-hydroxyquinolinato) aluminum(III) (Alq3)/bis[N-(1-naphthyl)-N-phenyl] benzidine (α-NPD)/MoO3/semitransparent Au structure, the maximum luminance of top-side emission was 1,140 cd/m2, and the contrast ratio was 19:1. The transmittance was 44% at 555 nm.

  15. 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.

  16. Polarized electroluminescence from organic light-emitting devices using photon recycling.

    Science.gov (United States)

    Park, Byoungchoo; Huh, Yoon Ho; Jeon, Hong Goo

    2010-09-13

    We present results that show highly polarized electroluminescence (EL) from an organic light-emitting device (OLED) by using a quarter-wave (λ/4) retardation plate (QWP) film and a giant birefringent optical (GBO) photonic reflective polarizer. Polarized EL light of 13,400 cd/m(2) with high peak efficiencies (greater than 10 cd/A and 3.5 lm/W) was obtained from an OLED in this way. These values are almost double those of a polarized OLED that only uses a polarizer. The direction of polarization of the emitted EL light from the polarized OLED corresponded to the passing axis of the GBO reflective polarizer. Furthermore, the degree of linear polarization obtained, i.e. the ratio between the brightness of two linearly polarized EL emissions parallel and perpendicular to the passing axis, is greater than 40 over the whole range of emitted luminance. PMID:20940874

  17. Current-Voltage Characteristics of Organic Light-Emitting Diodes with a Variation of Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.K.; Hong, J.W. [Kwangwoon University, Seoul (Korea); Kim, T.W. [Hongik University, Seoul (Korea)

    2002-07-01

    Temperature-dependent current-voltage characteristics of organic light-emitting diodes(OLEDs) were studied in a device structure of ITO/TPD/Alq{sub 3}/Al to understand conduction mechanism. The current-voltage characteristics were measured in the temperature range of 8K {approx} 300K. We analyzed an electrical conduction mechanism of the OLEDs using space-charge-limited current(SCLC) and Fowler-Nordheim tunneling. In the temperature range above 150K, the conduction mechanism could be explained by space charge limited current from the inversely proportional temperature dependence of exponent m. The characteristic trap energy is found to be about 0.15eV. At low temperatures below 150K, the Fowler-Nordheim tunneling conduction mechanism is dominant. We have obtained a zero field barrier height to be about 0.6{approx}o.8eV. (author). 12 refs., 9 figs.

  18. 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.

  19. 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.

  20. 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.

  1. Multi-spectral imaging with infrared sensitive organic light emitting diode.

    Science.gov (United States)

    Kim, Do Young; Lai, Tzung-Han; Lee, Jae Woong; Manders, Jesse R; So, Franky

    2014-01-01

    Commercially available near-infrared (IR) imagers are fabricated by integrating expensive epitaxial grown III-V compound semiconductor sensors with Si-based readout integrated circuits (ROIC) by indium bump bonding which significantly increases the fabrication costs of these image sensors. Furthermore, these typical III-V compound semiconductors are not sensitive to the visible region and thus cannot be used for multi-spectral (visible to near-IR) sensing. Here, a low cost infrared (IR) imaging camera is demonstrated with a commercially available digital single-lens reflex (DSLR) camera and an IR sensitive organic light emitting diode (IR-OLED). With an IR-OLED, IR images at a wavelength of 1.2 µm are directly converted to visible images which are then recorded in a Si-CMOS DSLR camera. This multi-spectral imaging system is capable of capturing images at wavelengths in the near-infrared as well as visible regions. PMID:25091589

  2. Enhanced performance for organic light-emitting diodes by embedding an aerosol jet printed conductive grid

    International Nuclear Information System (INIS)

    A simple and low-cost method for improving organic light-emitting diode (OLED) performance by printing poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) grids on the anode is demonstrated. The PEDOT : PSS grids were printed by an aerosol jet printer on the ITO anode surface. The maximum current efficiency of the OLED modified with the PEDOT : PSS grids is 1.92 times higher than a conventional device. The power efficiency enhancement factor is 2.3 at the current density of 740 mA cm−2. The enhancement in performance can be attributed to the light extraction and conductivity of the embedded low-index grids. (paper)

  3. 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.

  4. 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%).

  5. 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.

  6. Multi-spectral imaging with infrared sensitive organic light emitting diode

    Science.gov (United States)

    Kim, Do Young; Lai, Tzung-Han; Lee, Jae Woong; Manders, Jesse R.; So, Franky

    2014-08-01

    Commercially available near-infrared (IR) imagers are fabricated by integrating expensive epitaxial grown III-V compound semiconductor sensors with Si-based readout integrated circuits (ROIC) by indium bump bonding which significantly increases the fabrication costs of these image sensors. Furthermore, these typical III-V compound semiconductors are not sensitive to the visible region and thus cannot be used for multi-spectral (visible to near-IR) sensing. Here, a low cost infrared (IR) imaging camera is demonstrated with a commercially available digital single-lens reflex (DSLR) camera and an IR sensitive organic light emitting diode (IR-OLED). With an IR-OLED, IR images at a wavelength of 1.2 µm are directly converted to visible images which are then recorded in a Si-CMOS DSLR camera. This multi-spectral imaging system is capable of capturing images at wavelengths in the near-infrared as well as visible regions.

  7. 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.

  8. 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.

  9. 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.

  10. Operating organic light-emitting diodes imaged by super-resolution spectroscopy

    Science.gov (United States)

    King, John T.; Granick, Steve

    2016-06-01

    Super-resolution stimulated emission depletion (STED) microscopy is adapted here for materials characterization that would not otherwise be possible. With the example of organic light-emitting diodes (OLEDs), spectral imaging with pixel-by-pixel wavelength discrimination allows us to resolve local-chain environment encoded in the spectral response of the semiconducting polymer, and correlate chain packing with local electroluminescence by using externally applied current as the excitation source. We observe nanoscopic defects that would be unresolvable by traditional microscopy. They are revealed in electroluminescence maps in operating OLEDs with 50 nm spatial resolution. We find that brightest emission comes from regions with more densely packed chains. Conventional microscopy of an operating OLED would lack the resolution needed to discriminate these features, while traditional methods to resolve nanoscale features generally cannot be performed when the device is operating. This points the way towards real-time analysis of materials design principles in devices as they actually operate.

  11. Research data supporting "Bright and efficient blue polymer light emitting diodes with reduced operating voltages processed entirely at low-temperature"

    OpenAIRE

    Hoye, R. L. Z.; Musselman, K.P.; Chua, M. R.; Sadhanala, A.; Raninga, R. D.; MacManus-Driscoll, J. L.; Friend, R. H.; Credgington, D.

    2015-01-01

    Raw data for all figures and ESI from manuscript "Bright and efficient blue polymer light emitting diodes with reduced operating voltages processed entirely at low-temperature" published in Journal of Materials Chemistry C (http://dx.doi.org/10.1039/C5TC01581B).

  12. Topical and Intradermal Efficacy of Photodynamic Therapy with Methylene Blue and Light-Emitting Diode in the Treatment of Cutaneous Leishmaniasis Caused by Leishmania braziliensis

    OpenAIRE

    Sbeghen, Mônica Raquel; Voltarelli, Evandra Maria; Campois, Tácito Graminha; Kimura, Elza; Aristides, Sandra Mara Alessi; Hernandes, Luzmarina; Caetano, Wilker; Hioka, Noboru; Lonardoni, Maria Valdrinez Campana; Silveira, Thaís Gomes Verzignassi

    2015-01-01

    Introduction: The topical and intradermal photodynamic therapy (PDT) effect of methylene blue (MB) using light-emitting diode (LED) as light source (MB/LED-PDT) in the treatment of lesions of American cutaneous leishmaniasis (ACL) caused by Leishmania braziliensis in hamsters were investigated.

  13. 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.

  14. 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.

  15. 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

    2014-08-01

    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.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. Electronic supplementary information (ESI) available: Simulation results of total (bottom and top) radiance of TOLEDs with the RSL depending on HTL and ETL thicknesses. See DOI: 10.1039/c4nr01520g

  16. 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.

  17. 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

  18. Efficiency improvement and spectral shift of an organic light-emitting device by attaching a hexagon-based microlens array

    Science.gov (United States)

    Wei, Mao-Kuo; Lee, Jiun-Haw; Lin, Hoang-Yan; Ho, Yu-Hsuan; Chen, Kuan-Yu; Lin, Ciao-Ci; Wu, Chia-Fang; Lin, Hung-Yi; Tsai, Jen-Hui; Wu, Tung-Chuan

    2008-05-01

    In this paper, we present and analyze the influences of the fill factor and the sag of hexagon-based microlenses on the optical characteristics of an organic light-emitting device (OLED), such as spectral shift, CIE (abbreviation of the French 'Commission internationale de l'éclairage') coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency. Both the luminous current efficiency and luminous power efficiency of the OLED were found to increase linearly on increasing the fill factor of the microlenses. It is also found that the full width at half maximum (FWHM) of the OLED spectra and CIE coordinates decreased linearly on increasing the fill factor of the microlenses. Besides, the efficiency improvement of the OLED increased with the height ratio of attached microlenses. Compared to the OLED, the luminous current efficiency and luminous power efficiency of the device can be enhanced by 35% and 40%, respectively, by attaching a microlens array having a fill factor of 0.90 and a height ratio of 0.56. We also observed blue shifts at different viewing angles when microlens arrays were attached to the OLED, which is evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifted and the FWHM decreased on increasing the viewing angles, due to the microcavity effect.

  19. 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...

  20. High-efficiency diphenylsulfon derivative-based organic light-emitting diode exhibiting thermally-activated delayed fluorescence

    Science.gov (United States)

    Lee, Geon Hyeong; Kim, Young Sik

    2016-08-01

    A 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 was investigated theoretically for a blue organic light emitting diode (OLED) emitter. We calculated the energies of the first singlet (S1) and the first triplet (T1) excited states of the TADF materials by using the dependence on the charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT to perform density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations on the ground state. The calculated Δ E ST value, where Δ E ST is the difference in energy between the S1 and T1 states, of TMC-DPS (0.094 eV) was smaller than DMOC-DPS (0.386 eV) because of the large dihedral angles between the donor and the accepter moieties. We show that TMC-DPS would be a suitable blue OLED emitter because it has a large dihedral angle that creates a small spatial overlap between the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO), consequently, it has a small value of Δ E ST and an emission wavelength of 2.82 eV and 439.9 nm, respectively.

  1. Solution-processed white organic light-emitting diodes with mixed-host structures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xinwen [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210046 (China); Wu Zhaoxin, E-mail: zhaoxinwu@mail.xjtu.edu.cn [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Jiao Bo; Wang Dongdong; Wang Dawei; Hou Xun [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Huang Wei [Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210046 (China)

    2012-03-15

    Efficient white light-emitting diodes (WOLEDs) were fabricated with a solution-processed single emission layer composed of a molecular and polymeric material mixed-host (MH). The main host used was a blue-emitting molecular material of 4,4 Prime -bis(2,2 Prime -diphenylvinyl)-1,1 Prime -biphenyl (DPVBi) and the assisting host used was a hole-transport-type polymer of poly(9-vinylcarbazole) (PVK). By co-doping 4,4 Prime -bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl and 5,6,11,12-tetraphenylnaphacene into the MH, the performances of the fabricated devices made with different mixing ratio of host materials were investigated, and were to depend on the mixing ratios. Under the optimal PVK:DPVBi ratio (3:7), we achieved a maximum luminance of 14 110 cd/m{sup 2} and a maximum current efficiency of 9.5 cd/A. These improvements were attributed to the MH structure, which effectively improved the thermal stability of spin-coated film and enhanced the hole-injection/transporting properties of WOLEDs. - Highlights: Black-Right-Pointing-Pointer Efficient WOLEDs with solution-processed mixed-host (MH) structures. Black-Right-Pointing-Pointer Dependence of performances of WOLEDs on the mixing ratios. Black-Right-Pointing-Pointer The MH structure effectively improved the thermal stability of spin-coated films and hole-injection of WOLEDs.

  2. Enhanced luminous efficiency and brightness using DNA electron blocking layers in bio-organic light emitting diodes

    Science.gov (United States)

    Hagen, Joshua A.

    The biopolymer deoxyribonucleic acid (DNA) has been extracted from salmon (saDNA) and used successfully as an electron blocking layer (EBL) in multiple structures of Organic Light Emitting Diodes (OLED). Water soluble saDNA was complexed with a cationic surfactant hexadecytrimethylammonium chloride (CTMA) which makes the resulting DNA-CTMA molecule water insoluble, and soluble in common organic media such as alcohols. Solutions of DNA-CTMA and butanol make uniform thin films from 20nm to 5 microns in thickness by varying spin coating parameters and molecular weight. The optical properties of DNA-CTMA thin films include high transparency and low optical loss for applications at wavelengths above 400nm. The DNA-CTMA films have an electrical resistivity on the order of 107 O*cm. All of these properties combined made DNA-CTMA a candidate as an EBL in OLEDs, and this resulting device was termed a Bio-organic Light Emitting Diode (BioLED). Enhanced electroluminescent efficiency has been demonstrated in both green and blue emitting BioLEDs. The resulting green and blue BioLEDs showed a maximum luminous efficiency of 8.2 and 0.8 cd/A, respectively. The DNA based BioLEDs were as much as 10x more efficient and 30x brighter than their OLED counterparts. The enhancement in performance is due to the electron blocking action with the 0.9 eV (lowest unoccupied molecular orbital) value, allows hole injection to proceed with a 5.6eV (highest occupied molecular orbital) value. DNA-CTMA has also been successfully deposited in thin film form via molecular beam deposition (MBD). The growth was achieved at 160°C at vacuum levels of 10-5 Torr at a deposition rate of 0.8A/s. MBD grown DNA-CTMA thin films were highly uniform, optically transparent, and adhere to silicon, quartz and glass substrates more strongly than spin coated films. The material deposited was verified as DNA-CTMA through optical absorption, energy dispersive X-ray analysis, and using a DNA indicating fluorescent dye

  3. In vitro and in vivo Efficacy of New Blue Light Emitting Diode Phototherapy Compared to Conventional Halogen Quartz Phototherapy for Neonatal Jaundice

    OpenAIRE

    Chang, Yun Sil; Hwang, Jong Hee; Kwon, Hyuk Nam; Choi, Chang Won; Ko, Sun Young; Park, Won Soon; Shin, Son Moon; Lee, Munhyang

    2005-01-01

    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 i...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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。

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

    Energy Technology Data Exchange (ETDEWEB)

    Kwang-Ohk Cheon

    2003-08-05

    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 layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance.

  11. 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.

  12. Performance improvement of rubrene-based organic light emitting devices with a mixed single layer

    Science.gov (United States)

    Wang, Zhaokui; Naka, Shigeki; Okada, Hiroyuki

    2010-09-01

    We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by using 4,4'-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl ( α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the J - V characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower than Al/Alq3 interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed single-layer device.

  13. Magnetic field enhancement of generation-recombination and shot noise in organic light emitting diodes

    Science.gov (United States)

    Djidjou, T. K.; Chen, Ying; Basel, Tek; Shinar, J.; Rogachev, A.

    2015-03-01

    We have studied the effect of magnetic field on noise in series of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene-based organic light emitting diodes with dominant hole injection, dominant electron injection, and balanced electron and hole injection. The noise spectra of the balanced devices revealed the generation-recombination (g-r) noise term, which we associated with bimolecular electron-hole recombination. The presence of the g-r noise term is correlated with the strong organic magnetoresistance (up to 25%) observed in the balanced devices. The noise spectra also have the shot noise contribution with the Fano factor 0.25-0.4. We found that time constant of the g-r term decreases and the magnitude of shot noise increases when magnetic field is applied. This behavior can be consistently explained within the polaron-polaron model of organic magnetoresistance. We have not found any evidence that the magnetoresistance in studied devices is affected by traps.

  14. Magnetic field enhancement of generation-recombination and shot noise in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Djidjou, T. K.; Basel, Tek; Rogachev, A. [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States); Chen, Ying; Shinar, J. [Ames Laboratory-USDOE, and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    2015-03-21

    We have studied the effect of magnetic field on noise in series of 2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene-based organic light emitting diodes with dominant hole injection, dominant electron injection, and balanced electron and hole injection. The noise spectra of the balanced devices revealed the generation-recombination (g-r) noise term, which we associated with bimolecular electron-hole recombination. The presence of the g-r noise term is correlated with the strong organic magnetoresistance (up to 25%) observed in the balanced devices. The noise spectra also have the shot noise contribution with the Fano factor 0.25–0.4. We found that time constant of the g-r term decreases and the magnitude of shot noise increases when magnetic field is applied. This behavior can be consistently explained within the polaron-polaron model of organic magnetoresistance. We have not found any evidence that the magnetoresistance in studied devices is affected by traps.

  15. Active-matrix organic light-emitting displays on flexible metal foils

    Science.gov (United States)

    Chuang, T. K.; Jamshidi Roudbari, A.; Troccoli, M. N.; Chang, Y. L.; Reed, G.; Hatalis, M.; Spirko, J.; Klier, K.; Preis, S.; Pearson, R.; Najafov, H.; Biaggio, I.; Afentakis, T.; Voutsas, A.; Forsythe, E.; Shi, J.; Blomquist, S.

    2005-05-01

    This paper describes the development of a 3.5 inch diagonal Active Matrix Organic Light Emitting Diode Display on flexible metal foils. The active matrix array had the VGA format and was fabricated using the polysilicon TFT technology. The advantages that the metal foil substrates offer for flexible display applications will first be discussed, followed by a discussion on the multilayer coatings that were investigated in order to achieve a high quality insulating layer on the metal foil substrate prior to TFT fabrication. Then the polysilicon TFT device performance will be presented as a function of the polysilicon crystallization method. Both laser crystallized polysilicon and solid phased crystallized polysilicon films were investigated for the TFT device fabrication. Due to the opaque nature of the metal foil substrates the display had a top emission structure. Both small molecule and polymer based organic material were investigated for the display emissive part. The former were evaporated while the latter were applied by spin-cast. Various transparent multi-layer metal films were investigated as the top cathode. The approach used to package the finished AMOLED display in order to protect the organic layers from environmental degradation will be described. The display had integrated polysilicon TFT scan drivers consisting of shift registers and buffers but external data drivers. The driving approach of the display will be discussed in detail. The performance of the finished display will be discussed as a function of the various materials and fabrication processes that were investigated.

  16. Fabrication of an organic light-emitting diode inside a liquid crystal display

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jiun-Haw; Chang, Wei-Fu; Wu, Cheng-Che [Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan, ROC (China); Lin, Chi-Feng [Department of Electro-Optical Engineering, National United University, Miaoli 36003, Taiwan, ROC (China); Lee, Jiunn-Yih [Department of Materials Science and Engineering, National Taiwan University Science and Technology, Taipei 10617, Taiwan, ROC (China); Chiu, Tien-Lung, E-mail: tlchiu@saturn.yzu.edu.tw [Department of Photonics Engineering, Yuan Ze University, Chungli, Taoyuan 32003, Taiwan, ROC (China)

    2013-10-31

    The fabrication of a hybrid device architecture fully integrating a transparent organic light-emitting diode (OLED) and a liquid crystal display (LCD) within two glass substrates is reported in this study. The transparent OLED was fabricated on the inner surface of the glass substrate. Twisted nematic liquid crystal (LC) materials were used to fill the space between the two glass substrates. The OLED was driven by an indium-tin oxide (ITO) anode on the glass substrate and a thin bi-metal (Al/Ag) cathode, which also served as the electrode of the LCD. The other electrode for the LCD-mode operation was the ITO on the other glass substrate. A commercially available ultraviolet (UV)-curable resin was spun onto the thin Al/Ag as the passivation layer to protect the OLED from attacks by the following polyimide layer (serving as the alignment layer of the LCD), rubbing process and LC materials. In this device structure, the electrical characteristic of the OLED-mode operation was almost the same as that of the control device. Current efficiency (in terms of cd/A) of the hybrid device from top-emission (towards the LCD) decreased by 26.5% due to optical interference effect, whereas efficiency from bottom-emission remained the same. The driving voltage of the LCD-mode operation increased by 1.6 V due to the insertion of the passivation layer between the two electrodes. The contrast ratio decreased from 150 to 25 due to the reflection of the thin Al/Ag layer. Compared with that of the control device, the storage lifetime of the OLED increased as a result of filling the encapsulated cavity with LC materials, which helped repel ambient water and oxygen. - Highlights: • Organic light emitting device (OLED) was fabricated inside liquid crystal device (LCD). • LCD protected OLED from the attack of ambient oxygen and moisture. • OLED functions were not affected by LCD process with suitable treatment.

  17. Efficient blue-green and green electroluminescent devices obtained by doping iridium complexes into hole-block material as supplementary light-emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Liang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zheng, Youxuan, E-mail: yxzheng@mail.nju.edu.cn [State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Deng, Ruiping; Feng, Jing; Song, Mingxing; Hao, Zhaomin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang, Hongjie, E-mail: hongjie@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zuo, Jinglin; You, Xiaozeng [State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

    2014-04-15

    In this work, organic electroluminescent (EL) devices with dominant and supplementary light-emitting layers (EMLs) were designed to further improve the EL performances of two iridium{sup III}-based phosphorescent complexes, which have been reported to provide EL devices with slow EL efficiency roll-off. The widely used hole-block material 2,2′,2''-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) was selected as host material to construct the supplementary EML. Compared with single-EML devices, double-EMLs devices showed higher EL efficiencies, higher brightness, and lower operation voltage attributed to wider recombination zone and better balance of carriers. In addition, the insertion of supplementary EML is instrumental in facilitating carriers trapping, thus improving the color purity. Finally, high performance blue-green and green EL devices with maximum current efficiencies of 35.22 and 90.68 cd/A, maximum power efficiencies of 26.36 and 98.18 lm/W, and maximum brightness of 56,678 and 112,352 cd/m{sup 2}, respectively, were obtained by optimizing the doping concentrations. Such a device design strategy extends the application of a double EML device structure and provides a chance to simplify device fabrication processes. -- Highlights: • Electroluminescent devices with supplementary light-emitting layer were fabricated. • Doping concentrations and thicknesses were optimized. • Better balance of holes and electrons causes the enhanced efficiency. • Improved carrier trapping suppresses the emission of host material.

  18. 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.

  19. 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.

  20. 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.

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

    Science.gov (United States)

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

    2008-07-17

    Patterned organic light-emitting diodes are fabricated by using microcontact- printed 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 direct handle on charge injection and enabling local modification of the light emission. PMID:25213893

  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. 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.

  4. 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.

  5. 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.

  6. 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.

  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. 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.

  10. 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.

  11. 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.

  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 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. PMID:25503083

  13. 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.

  14. 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.

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

    International Nuclear Information System (INIS)

    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 2Ag 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 1Bu/2Ag 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 (Duschinsky rotation

  16. 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.

  17. 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...

  18. 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.

  19. Non-doped phosphorescent white organic light-emitting devices with a quadruple-quantum-well structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Juan [State Key Laboratory of Electronic Thin Film and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Yu Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Film and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zhang Lei; Wang Jun [State Key Laboratory of Electronic Thin Film and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2012-07-15

    Non-doped white organic light-emitting devices (WOLEDs) with a quadruple-quantum-well structure were fabricated. An alternate layer of ultrathin blue and yellow iridium complexes was employed as the potential well layer, while potential barrier layers (PBLs) were chosen to be 2,2',2''-(1,3,5-benzenetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) or N,N'-dicarbazolyl-3,5-benzene (mCP) combined TPBi. On adjusting the PBLs for device performance comparison, the results showed that the device with all-TPBi PBLs exhibited a yellow emission with the color coordinates of (0.50,0.47) at a luminance of 1000 cd/m{sup 2}, while stable white emission with the color coordinates of (0.36,0.44) was observed in the device using mCP combined TPBi as the PBLs. Meanwhile, for the WOLED, with a reduced efficiency roll-off, a maximum luminance, luminous efficiency, and external quantum efficiency of 12,610 cd/m{sup 2}, 10.2 cd/A, and 4.4%, respectively, were achieved. The performance improvement by the introduction of mCP PBL was ascribed to the well confined exciton and the reduced exciton quenching effect in the multiple emission regions.

  20. Light Emitting Diode-Generated Blue Light Modulates Fibrosis Characteristics: Fibroblast Proliferation, Migration Speed, and Reactive Oxygen Species Generation

    Science.gov (United States)

    Mamalis, Andrew; Garcha, Manveer; Jagdeo, Jared

    2016-01-01

    Background and Objective Blue light is part of the visible light spectrum that does not generate harmful DNA adducts associated with skin cancer and photoaging, and may represent a safer therapeutic modality for treatment of keloid scars and other fibrotic skin diseases. Our laboratory previously demonstrated that light-emitting diode (LED) red and infrared light inhibits proliferation of skin fibroblasts. Moreover, different wavelengths of light can produce different biological effects. Furthermore, the effects of LED blue light (LED-BL) on human skin fibroblasts are not well characterized. This study investigated the effects of LED-BL on human skin fibroblast proliferation, viability, migration speed, and reactive oxygen-species (ROS) generation. Methods and Materials Irradiation of adult human skin fibroblasts using commercially-available LED-BL panels was performed in vitro, and modulation of proliferation and viability was quantified using the trypan blue dye exclusion assay, migratory speed was assessed using time-lapse video microscopy, and intracellular ROS generation was measured using the dihydrorhodamine flow cytometry assay. Statistical differences between groups were determined by ANOVA and Student s t-test. Results Human skin fibroblasts treated with LED-BL fluences of 5, 30, 45, and 80 J/cm2 demonstrated statistically significant dose-dependent decreases in relative proliferation of 8.4%, 29.1%, 33.8%, 51.7%, and 55.1%, respectively, compared to temperature and environment matched bench control plates, respectively. LED-BL fluences of 5, 30, 45 and 80 J/cm2 decreased fibroblast migration speed to 95 ± 7.0% (p = 0.64), 81.3 ± 5.5% (p = 0.021), 48.5 ± 2.7% (p migration speed, and is associated with increased reactive oxygen species generation in a dose-dependent manner without altering viability. LED-BL has the potential to contribute to the treatment of keloids and other fibrotic skin diseases and is worthy of further translational and clinical

  1. Efficient organic light-emitting diodes fabricated on cellulose nanocrystal substrates

    Science.gov (United States)

    Najafabadi, E.; Zhou, Y. H.; Knauer, K. A.; Fuentes-Hernandez, C.; Kippelen, B.

    2014-08-01

    Organic light-emitting diodes (OLEDs) fabricated on recyclable and biodegradable substrates are a step towards the realization of a sustainable OLED technology. We report on efficient OLEDs with an inverted top-emitting architecture on recyclable cellulose nanocrystal (CNC) substrates. The OLEDs have a bottom cathode of Al/LiF deposited on a 400 nm thick N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-(1,1'-biphenyl)-4,4'-diamine (α-NPD) layer and a top anode of Au/MoO3. They achieve a maximum luminance of 74 591 cd/m2 with a current efficacy of 53.7 cd/A at a luminance of 100 cd/m2 and 41.7 cd/A at 1000 cd/m2. It is shown that the α-NPD layer on the CNC substrate is necessary for achieving high performance OLEDs. The electroluminescent spectra of the OLEDs as a function of viewing angle are presented and show that the OLED spectra are subject to microcavity effects.

  2. Organic light-emitting diode (OLED) and its application to lighting devices

    Science.gov (United States)

    Ide, Nobuhiro; Komoda, Takuya; Kido, Junji

    2006-08-01

    Organic Light Emitting Diode (OLED) is an emerging technology as one of the strong candidates for next generation solid state lighting with various advantages such as thin flat shape, no UV emission and environmental benefits. At this moment, OLED still has a lot of issues to be solved before widely used as lighting devices. Nonetheless, typical properties of OLED, such as efficiency and lifetime, have been recently made great progress. For example, a green phosphorescent OLED with over 100 lm/W and a red fluorescent OLED with an estimated half decay time of over 100,000 h at 1,000 cd/m2 were reported. Large area, white OLEDs with long lifetime were also demonstrated. In this way, some of the issues are going to be steadily overcome. In this publication, we will present a phosphorescent white OLED with a high luminous efficiency of 46 lm/W and an external quantum efficiency of 20.6 percent observed at 100 cd/m2. This device achieves a luminous efficiency of 62.8 lm/W with a light-outcoupling film attached on the glass substrate. This is one of the highest values so far reported for white OLEDs. And we will also show a color-tunable stacked OLED with improved emission characteristics. This device minimizes a viewing angle dependence of the emission spectra and has color tunability from white to reddish-white. These technologies will be applied to OLED lighting.

  3. 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.

  4. 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.

  5. 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...

  6. 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.

  7. 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.

  8. Top-Emission Organic Light Emitting Diode Fabrication Using High Dissipation Graphite Substrate

    Directory of Open Access Journals (Sweden)

    Yu-Sheng Tsai

    2014-01-01

    Full Text Available This study uses a synthetic graphite fiber as the heat dissipation substrate for top-emission organic light emitting diode (TEOLED to reduce the impact from joule heat. UV glue (YCD91 was spin coated onto the substrate as the insulation layer. The TEOLED structure is (glass; copper; graphite substrate/YCD91 glue/Al/Au/EHI608/TAPC/Alq3/LiF/Al/Ag. The proposed graphite fiber substrate presents better luminous performance compared with glass and copper substrate devices with luminance of 3055 cd/m2 and current efficiency of 6.11 cd/A at 50 mA/cm2. When lighting period of different substrates TEOLED, the substrate case back temperature was observed using different lighting periods. A glass substrate element operating from 5 to 25 seconds at 3000 cd/m2 luminance produced a temperature rate of 1.207°C/sec. Under 4000 cd/m2 luminance the copper and graphite substrate temperature rates were 0.125°C/sec and 0.088°C/sec. Graphite component lifetime was determined to be 1.875 times higher than the glass components and 1.125 times higher than that of copper.

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

    International Nuclear Information System (INIS)

    A novel solution processable charge generating layer (CGL) that consists of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HATCN6)/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 HATCN6 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/m2. - Highlights: • A solution processable tandem OLED is built using a novel charge generating layer. • HATCN6 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

  10. Triplets contribute to both an increase and loss in fluorescent yield in organic light emitting diodes.

    Science.gov (United States)

    Zhang, Yifan; Forrest, Stephen R

    2012-06-29

    Nonradiative triplets in fluorescent organic light emitting diodes (OLEDs) can lead to increased efficiency through triplet-triplet annihilation, or to decreased efficiency due to singlet-triplet annihilation. We study the tradeoff between the two processes from the electroluminescence transients of an OLED comprising a tetraphenyldibenzoperiflanthene (DBP) doped rubrene emissive layer, whose emission spectrum peaks at a wavelength of 610 nm. The electroluminescent transients in the current density range, 4 mA/cm(2)

  11. Electroluminescence of organic light-emitting diodes with an ultra-thin layer of dopant

    Energy Technology Data Exchange (ETDEWEB)

    Li Weizhi [State Key Lab of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Yu Junsheng [State Key Lab of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)], E-mail: jsyu@uestc.edu.cn; Wang, Tao [State Key Lab of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Jiang, Yadong [State Key Lab of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)], E-mail: jiangyd@uestc.edu.cn; Wei, Bangxiong [State Key Lab of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

    2008-03-15

    Conventional fluorescent dyes, i.e., 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), 5,12-dihydro-5,12-dimethylquino [2,3-b]acridine-7,14-dione (DMQA) and 5,6,11,12-tetraphenylnaphthacene (Rubrene), were used to investigate the performance of organic light-emitting diodes (OLEDs) based on indium tin oxide (ITO)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB)/tris-(8-hydroxyquinolate)-aluminum (Alq{sub 3})/MgAg. The dyes were either inserted into devices as an ultra-thin film at the NPB/Alq{sub 3} interface by sequential evaporation, or doped into the Alq{sub 3} emission layer by co-evaporation with the doping ratio about 2%. Electroluminescence (EL) spectra of devices indicated that concentration quenching effect (CQE) of the dye-dopant was slightly bigger in the former than in the latter, while the degrees of CQE for three dopants are in the order of DMQA > DCJTB > Rubrene suggested by the difference in EL spectra and performances of devices. In addition, EL process of device with an ultra-thin layer of dopant is dominated by direct carrier trapping (DCT) process due to almost no holes recombine with electrons in Alq{sub 3}-host layer.

  12. Study on electroluminescence processes in dye-doped organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Li Weizhi [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)], E-mail: leewz@uestc.edu.cn; Jiang Yadong; Wang Tao [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)

    2008-07-15

    Electroluminescence (EL) mechanism of dye-doped organic light-emitting diodes (OLEDs) was investigated by using three familiar fluorescent dyes, i.e., 5,12-Dihydro-5,12-dimethylquino [2,3-b]acridine-7,14-dione (DMQA), 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran(DCJTB), and 5,6,11,12-tetraphenylnaphthacene (Rubrene). EL spectra of the doped devices with structure of indium tin oxide (ITO)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'- diamine (NPB) (40 nm)/tris-(8-hydroxyquinolate)-aluminum (Alq{sub 3}) (x nm, x=0-40 nm)/dye: Alq{sub 3} (weight ratio{approx}1%, 2 nm)/Alq{sub 3} (48-x nm)/MgAg indicated that direct carrier trapping (DCT) process dominated light emission of devices. As a result, investigation of carrier-recombination site via doping, which is conventionally applied in OLEDs, is questionable since the doping site and the dopant itself may significantly influence the carrier-recombination process in the doped devices.

  13. Doping in the Mixed Layer to Achieve High Brightness and Efficiency Organic Light Emitting Devices

    Institute of Scientific and Technical Information of China (English)

    高文宝; 杨开霞; 刘宏宇; 冯晶; 刘式墉

    2002-01-01

    Doping in the mixed layer was introduced to fabricate high brightness and high efficiency organic light emitting devices. In these devices, a copper phthalocyanine (CuPc) film acts as the buffer layer, a naphthylphenybiphenyl amine (NPB) film as the hole transport layer and a tris(8-hydroxyquinolinolate)aluminium (Alq3) film as the electron transport layer. The luminescent layer consists of the mixture of NPB, Alq3 (to be called the mixed layer), and an emitting dopant 5,6,11,12-petraphenylnaphthacene (rubrene), where the concentration of NPB declined and the concentration of Alq3 was increased gradually in the deposition process. Adopting this doping mixed layer, the device exhibits the maximum emission of 49300cd/m2 at 35 V and the maximum efficiency of 7.96cd/A at 10.5 V, which have been improved by two times in comparison with conventional doped devices. We attribute this improvement to the effective confinement of carriers in the mixed layer, which leads to the increase of the recombination efficiency of carriers.

  14. 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.

  15. 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.

  16. Enhanced electroluminescence of organic light-emitting diodes by using halloysite nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mondragón, Margarita, E-mail: mmondragon@ipn.mx [Instituto Politécnico Nacional, ESIME Azcapotzalco, Av. de las Granjas 682, 02250 México D.F. (Mexico); Moggio, Ivana; León, Arxel de; Arias, Eduardo [Centro de Investigación en Química Aplicada, CIQA, Blvd. Enrique Reyna 140, 25253 Saltillo, Coahuila (Mexico)

    2013-12-15

    The effect of halloysite clay nanotubes (HNTs) on the optical and electronic properties of poly(2-methoxy-5-[2′-ethylhexyloxy]-1,4-phenylenevinylene) (MEH-PPV) have been investigated. The UV–vis absorption band of the conjugated polymer remains unchanged upon the incorporation of halloysite nanotubes (HNTs). Photoluminescence (PL) measurements reveal a decreased quantum yield in the MEH-PPV/HNTs nanocomposites, compared with bulk MEH-PPV. Improvement of the electroluminescence of organic light-emitting diodes (OLEDs) was achieved by incorporating high contents of HNTs. The nanotubes act to enhanced polymer aggregates, as revealed by AFM analysis, thus increasing charge transport and therefore electroluminescence but also decreasing PL quantum yield. -- Highlights: • Thin films of nanocomposites of MEH-PPV/HNTs were prepared by spin coating. • Quantum yield in the nanocomposites was decreased compared with bulk MEH-PPV. • Improvement of the EL of OLEDs was achieved by incorporating high contents of HNTs. • The HNTs act to enhanced polymer aggregates, as revealed by AFM.

  17. 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.

  18. 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.

  19. 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.

  20. 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.)

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. An anode with aluminum doped on zinc oxide thin films for organic light emitting devices

    International Nuclear Information System (INIS)

    Doped zinc oxides are attractive alternative materials as transparent conducting electrode because they are nontoxic and inexpensive compared with indium tin oxide (ITO). Transparent conducting aluminum-doped zinc oxide (AZO) thin films have been deposited on glass substrates by DC reactive magnetron sputtering method. Films were deposited at a substrate temperature of 150-bar oC in 0.03 Pa of oxygen pressure. The electrical and optical properties of the film with the Al-doping amount of 2 wt% in the target were investigated. For the 300-nm thick AZO film deposited using a ZnO target with an Al content of 2 wt%, the lowest electrical resistivity was 4x10-4Ωcm and the average transmission in the visible range 400-700 nm was more than 90%. The AZO film was used as an anode contact to fabricate organic light-emitting diodes. The device performance was measured and the current efficiency of 2.9 cd/A was measured at a current density of 100 mA/cm2

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

    International Nuclear Information System (INIS)

    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. (paper)

  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. The effect of Indium metal nanoparticles on the electronic properties of organic light emitting diodes (OLEDs)

    Energy Technology Data Exchange (ETDEWEB)

    Kalhor, Davood, E-mail: d_kalhor@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 1983963113 (Iran, Islamic Republic of); Department of Physics, Damghan University, POB 3671941167, Damghan (Iran, Islamic Republic of); Mohajerani, Ezeddin, E-mail: e-mohajerani@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran 1983963113 (Iran, Islamic Republic of); Hashemi Pour, Omid, E-mail: HashemiPour@sbu.ac.ir [Department of Electrical and Computer Engineering, Shahid Beheshti University, G.C., Tehran 1983963113 (Iran, Islamic Republic of)

    2015-11-15

    In this paper the effect of Indium nanoparticles (NPs) on the electronic properties of organic light emitting diodes (OLEDs) is experimentally investigated. The metal NPs which are added to the hole transfer layer can be considered as a blocker layer for injected electrons. By optimizing hole and electron ratio, current density and voltage can be decreased. In order to study this effect, among various fabricated devices, a specific structure, namely ITO/PEDOT:PSS (50 nm)/TPD (45 nm)/NPs (x nm)/Alq{sub 3} (50 nm)/Ag (80 nm) has been used. Also, the experiment is investigated for Au and Cu as different cathode the results of structures are compared with Ag cathode. A manually controllable shutter was used for vacuum deposition process to prepare the same structures and to avoid any disturbing effects. It is observed that specific Indium NPs reduce current density and turn on voltage of the device. - Highlights: • The effect of In NPs on the electronic properties of OLEDs is investigated. • Current density and voltage may be reduced by optimizing electron hole ratio. • In NPs reduce the current density and turn on voltage of the device.

  9. 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.

  10. 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.

  11. 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.

  12. Thin film passivation of organic light emitting diodes by inductively coupled plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han-Ki [Department of Information and Nano Materials Engineering, Kumoh National Institute of Technology (KIT), 1 Yangho-dong, Gumi, Gyeongbuk, 730-701 (Korea, Republic of)]. E-mail: hkkim@kumoh.ac.kr; Kim, Sang-Woo [Department of Information and Nano Materials Engineering, Kumoh National Institute of Technology (KIT), 1 Yangho-dong, Gumi, Gyeongbuk, 730-701 (Korea, Republic of); Kim, Do-Geun [Surface Technology Research Center, Korea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon-si, Gyeongnam, 641-831 (Korea, Republic of); Kang, Jae-Wook [Organic Light Emitting Diodes (OLED) Center, Seoul National University, Silim-dong, Seoul 151-741 (Korea, Republic of); Kim, Myung Soo [Core Technology Laboratory, Samsung SDI, Co., LTD., 575 Shin-dong, Youngtong-Gu, Suwon, Gyeonggi-Do, 442-391 (Korea, Republic of); Cho, Woon Jo [Nano Device Research Center, Korea Institute of Science and Technology, 39-1, Haweolgok-Dong, Seongbuk-Gu, Seoul, 136-791 (Korea, Republic of)

    2007-04-09

    The characteristics of an SiN {sub x} passivation layer grown by a specially designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system with straight antennas for the top-emitting organic light emitting diodes (TOLEDs) are investigated. Using a high-density plasma on the order of {approx} 10{sup 11} electrons/cm{sup 3} formed by nine straight antennas connected in parallel, a high-density SiN {sub x} passivation layer was deposited on a transparent Mg-Ag cathode at a substrate temperature of 40 deg. C. Even at a low substrate temperature, single SiN {sub x} passivation layer prepared by ICP-CVD showed a low water vapor transmission rate of 5 x 10{sup -2} g/m{sup 2}/day and a transparency of {approx} 85% respectively. In addition, current-voltage-luminescence results of the TOLED passivated by the SiN {sub x} layer indicated that the electrical and optical properties of the TOLED were not affected by the high-density plasma during the SiN {sub x} deposition process.

  13. Characterization of phosphorescent organic light-emitting diodes using current noise cross-correlated spectroscopy

    Science.gov (United States)

    Kamdem Djidjou, Thaddee; Li, Sergey; Rogachev, Andrey

    2014-03-01

    Carrier injection and transport mechanism in small-molecule phosphorescent organic light-emitting diodes (PhOLED) have been investigated using current noise spectroscopy. The PhOLED devices studied consist of multilayers having the structure ITO / NPB / NPB:Irphq / Balq / Bpen:CsCO3/ Al. We found that in high bias regime, the noise spectral density can be described by two terms, 1/ f1.3 and 1/f2.8. The first term disappears below 2.5 V, as does the luminance; this suggests that this term is related to bimolecular recombination in the devices. The second term is more pronounced al low frequencies and its magnitude is linearly proportional to the current in the device. This term, which exists in all bias range, is likely related to the presence of traps with a distributed time constant. For applied voltages greater than 2.4 V, the frequency-independent noise is dominated by the shot noise. The Fano factor is one in the range 2.4 - 2.5 V, and decreases to a constant value of 0.4 at higher biases. This indicates the presence of a barrier for carrier injection into the device. Our overall results confirm the utility of noise measurements for OLED characterization.

  14. 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.

  15. 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.

  16. 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.

  17. 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)

  18. 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.

  19. 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.

  20. Inverted organic light-emitting diodes using different transparent conductive oxide films as a cathode

    Science.gov (United States)

    Takada, Makoto; Kobayashi, Takashi; Nagase, Takashi; Naito, Hiroyoshi

    2016-03-01

    We report on poly(dioctylfluorene-alt-benzothiadiazole) (F8BT) based inverted organic light-emitting diodes (iOLEDs) using commercially available transparent conductive oxide (TCO) films as a cathode, indium tin oxide (ITO), Ga doped ZnO (GZO), and Al doped ZnO (AZO). The ITO, GZO, and AZO glasses work as an electron-injecting layer (EIL) and cathode. The device configuration that we prepared is ITO, GZO, or AZO/F8BT/MoO3/Au. The device characteristics of these iOLEDs are almost comparable to those of conventional iOLEDs with ZnO films prepared by spray pyrolysis as an EIL, indicating that the electron injection properties of ITO, GZO, or AZO as a cathode are similar to those of ZnO layer in conventional iOLEDs. These results demonstrate the low-cost fabrication of iOLEDs utilizing commercially available TCO glasses as a cathode without deposition of ZnO layers on ITO glass.

  1. Electroluminescence efficiency in bilayer organic light-emitting devices with LiF/Al cathode

    Institute of Scientific and Technical Information of China (English)

    LI HongJian; ZHU RuHui; YAN LingLing; ZHANG HaiYan

    2007-01-01

    An analytical model to calculate electroluminescence (EL) efficiency of bilayer organic light-emitting devices,considering the influence of introducing LiF insulating buffer layer at metal/organic interface on the barrier height for electron injection,was presented.The relations of EL efficiency versus the applied voltage and injection barrier or internal interfacial barrier or the thickness of organic layer were discussed.The results indicate that: (1) when δ e/δ h < 2,metal/organic (M/O) interface is ohmic contact; when δ e/δ h > 2,M/O becomes contact limited; and when δ e/δ h = 2 (Ф h ~ 0.2 eV,Ф e~ 0.3 eV),there is a transition from ohmic contact to contact limited; (2) η EL decreases with the increase of d ′e / d ′h; however,when δ ′e / δ′h > 2.5 (H ′h ~0.2 eV,H ′e ~ 0.4 eV),the changes of η EL are very small,which shows that ηEL is dominated by the carrier's injection; (3) when increasing Lh/L,ηR has a descending trend at low voltage and a rising one at higher voltage.For a given Lh/L,η EL first increases and then decreases with the increasing applied voltage,and as Lh/L further increases,the variation tendency of η EL is more obvious.These conclusions are in agreement with the reported theoretic and experimental results.

  2. Electroluminescence efficiency in bilayer organic light-emitting devices with LiF/Al cathode

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An analytical model to calculate electroluminescence (EL) efficiency of bilayer organic light-emitting devices, considering the influence of introducing LiF insulating buffer layer at metal/organic interface on the barrier height for electron injection, was presented. The relations of EL efficiency versus the applied voltage and injection barrier or internal interfacial barrier or the thickness of organic layer were discussed. The results indicate that: (1) when δ e/δ h < 2, metal/organic (M/O) interface is ohmic contact; when δ e/δ h > 2, M/O becomes contact limited; and when δ e/δ h = 2 (Φ h ~ 0.2 eV, Φ e ~ 0.3 eV), there is a transition from ohmic contact to contact limited; (2) η EL decreases with the increase of δ′e / δ′h; however, when δ′e / δ′h > 2.5 (H ′h~ 0.2 eV, H ′e~ 0.4 eV), the changes of η EL are very small, which shows that η EL is dominated by the carrier’s injection; (3) when increasing Lh/L, η R has a descending trend at low voltage and a rising one at higher voltage. For a given Lh/L, η EL first increases and then decreases with the increasing applied voltage, and as Lh/L further increases, the variation tendency of η EL is more obvious. These conclusions are in agreement with the reported theoretic and experimental results.

  3. A new design mixing RGB LED (red, green, blue light-emitting diode) for a modern LCD (liquid crystal display) backlight system

    Science.gov (United States)

    Chang, Che-Ming; Fang, Yi-Chin; Lee, Chen-Rong

    2006-08-01

    The paper proposes a newly developed light source module mixing R.G.B. LED (Red, Green, Blue, Light Emitting Diode) for a modern LED backlight system, which might replace the white light LED and traditional CCFL (Cold Cathode Fluorescent Lamp). This system consists of three parts, a newly designed symmetric mirror for complete color mixing, a R.G. B LED (Red, Green, Blue Light Emitting Diode) light source and a diffusion plate with a newly designed microstructure for the improvement of light uniformity. The light module is designed and simulated by an ASAP (Advanced Systems Analysis Program), in which a sample with 160mm×90mm( around 7-inch panel) is presented with sixteen LEDs light source. Good color saturation and excellent light uniformity are reached in this research.

  4. Prospects for light-emitting diodes made of porous silicon from the blue to beyond 1.5 {micro}m

    Energy Technology Data Exchange (ETDEWEB)

    Fauchet, P.M.; Peng, C.; Tsybeskov, L. [Univ. of Rochester, NY (United States). Dept. of Electrical Engineering] [and others

    1994-12-31

    Since the discovery in 1990 that porous silicon emits bright photoluminescence in the red part of the spectrum, light-emitting devices (LEDs) made of light-emitting porous silicon (LEPSi) have been demonstrated, which could be used for optical displays, sensors or optical interconnects. In this paper, the authors discuss their work on the optical properties of LEPSi and progress towards commercial devices. LEPSi photoluminesces not only in the red-orange, but also throughout the entire visible spectrum, from the blue to the deep red, and in the infrared, well past 1.5 {micro}m. The intense blue and infrared emissions are possible only after treatments such as high temperature oxidation or low temperature vacuum annealing. These new bands have quite different properties from the usual red-orange band and their possible origins are discussed. Different LED structures are then presented and compared and the prospects for commercial devices are examined. 54 refs., 18 figs.

  5. 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 %.

  6. Influence of Dopant Concentration on Electroluminescent Performance of Organic White-Light-Emitting Device with Double-Emissive-Layered Structure

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-Ming; HUA Yu-Lin; YIN Shou-Gen; ZHANG Li-Juan; WANG Yu; HOU Qing-Chuan; ZHANG Jun-Mei

    2008-01-01

    A novel phosphorescent organic white-light-emitting device(WOLED)with configuration of ITO/NPB/CBP:TBPe:rubrene/Zn(BTZ)2:Ir(piq)2(acac)/Zn(BTZ)2/Mg:Ag is fabricated successfully,where the phosphorescent dye bis(1-(phenyl)isoquinoline)iridium(Ⅲ)acetylanetonate(Ir(piq)2(acac))doped into bis-(2-(2-hydroxyphenyl)benzothiazole)zinc(Zn (BTZ)2)(greenish-blue emitting material with electron transport character)as the red emitting layer,and fluorescent dye2,5,8,11-tetra-tertbutylperylene(TBPe)and5,6,11,12-tetraphenyl-naphthacene(rubrene)together doped into 4,4'-N,N'-dicarbazole-biphenyl(CBP)(ambipolar conductivity material)as the blue-orange emitting layer,respectively.The two emitting layers are sandwiched between the hole-transport layer N,N'-biphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine(NPB)and electron-transport layer(Zn(BTZ)2).The optimum device turns on at the driving voltage of 4.5V.A maximum external quantum efficiency of 1.53%and brightness 15000 cd/m2 are presented.The best point of the Commission Internationale de l'Eclairage(CIE)coordinates locates at (0.335,0.338)at about 13 V. Moreover,we also discuss how to achieve the bright pure white light through optimizing the doping concentration of each dye from the viewpoint of energy transfer process.

  7. High-efficiency polymer light-emitting devices using organic salts: A multilayer structure to improve light-emitting electrochemical cells

    Science.gov (United States)

    Lee, Tae-Woo; Lee, Ho-Chul; Park, O. Ok

    2002-07-01

    Balanced charge injection in polymer light-emitting devices is very important for high brightness and quantum efficiency. To improve the well-known light-emitting electrochemical cells (LECs), we fabricated multilayer electroluminescent devices employing an ammonium salt-containing poly(ethylene oxide) blend as hole- or electron-injecting materials. The charge injection can be greatly promoted due to the ionic space charges near both electrodes. The current-voltage-optical output characteristics of the triple-layer device using both the hole- and the electron-injecting layers are very similar to the well-known LEC devices. We obtained high quantum efficiencies of 0.9% and 1.5% photons/electron in forward- and reverse-bias field of the triple-layer device, respectively.

  8. 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.

  9. 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

  10. Active-matrix organic light-emitting diode displays on flexible metal foil substrates

    Science.gov (United States)

    Chuang, Ta-Ko

    This dissertation presents the research efforts that deal with the development of polysilicon thin film transistors (TFTs) on stainless-steel-foil substrates, the implementation of high-resolution flexible active-matrix backplanes, and the integration of the flexible polysilicon TFT backplanes with polymer light-emitting diodes. This research investigated the preparation of the steel foil substrates, the fabrication of flexible polysilicon TFT backplanes and polymer light emitting diodes (PLEDs), and the encapsulation of the flexible Active Matrix Polymer Light Emitting Diode displays. The first successful integration of polysilicon TFT backplane with PLEDs onto light-weight, robust, and flexible stainless-steel-foil substrates is presented. A top-emitting, monochrome active-matrix polymer light-emitting diode (AM-PLED) display, having the VGA (640x480) format and a 230 dpi resolution, is demonstrated for the first time on flexible stainless-steel-foil substrates. This work validates the compatibility of the polysilicon technology for high-resolution flexible AM-PLED displays. Furthermore, this work shows that a variety of other large-area microelectronics could also be implemented onto flexible metal foils, benefiting by the metal oil dimensional stability and ability to withstand high process temperature. In conclusion, the polysilicon TFT technology combining with metal-foil substrates opens up a new road for flexible displays as well as large-area flexible electronic applications.

  11. 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

  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. New double graded structure for enhanced performance in white organic light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Peng Yu Chen [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan (China); Herng Yih Ueng, E-mail: hueng@ee.nsysu.edu.t [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, 80424 Taiwan (China); Yokoyama, Meiso [Department of Electronic Engineering, I-Shou University, Kaohsiung County, Taiwan (China)

    2010-10-15

    This study presents a new design that uses a combination of a graded hole transport layer (GH) structure and a gradually doped emissive layer (GE) structure as a double graded (DG) structure to improve the electrical and optical performance of white organic light-emitting diodes (WOLEDs). The proposed structure is ITO/m-MTDATA (15 nm)/NPB (15 nm)/NPB: 25% BAlq (15 nm)/NPB: 50% BAlq (15 nm)/BAlq: 0.5% Rubrene (10 nm)/BAlq: 1% Rubrene (10 nm)/BAlq: 1.5% Rubrene (10 nm)/Alq{sub 3} (20 nm)/LiF (0.5 nm)/Al (200 nm). (m-MTDATA: 4,4',4'' -tris(3-methylphenylphenylamino)triphenylamine; NPB: N,N'-diphenyl-N,N'-bis(1-naphthyl-phenyl)-(1,1'-biphenyl)-4,4'-diamine; BAlq: aluminum (III) bis(2-methyl-8-quinolinato) 4-phenylphenolate; Rubrene: 5,6,11,12-tetraphenylnaphthacene; Alq{sub 3}: tris-(8-hydroxyquinoline) aluminum). By using this structure, the best performance of the WOLED is obtained at a luminous efficiency at 11.8 cd/A and the turn-on voltage of 100 cd/m{sup 2} at 4.6 V. The DG structure can eliminate the discrete interface, and degrade surplus holes, the electron-hole pairs are efficiently injected and balanced recombination in the emissive layer, thus the spectra are unchanged under various drive currents and quenching effects can be significantly suppressed. Those advantages can enhance efficiency and are immune to drive current density variations.

  14. Luminescence of Rubrene and DCJTB molecules in organic light-emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Chang-Bum, E-mail: cbmoon@hoseo.edu [Department of Display Engineering, Hoseo University, Sechul-Ri 160, Baebang, Asan, Chung-Nam 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S4L7 (Canada); Song, Wook; Meng, Mei; Kim, Nam Ho; Yoon, Ju-An [Department of Display Engineering, Hoseo University, Sechul-Ri 160, Baebang, Asan, Chung-Nam 336-795 (Korea, Republic of); Kim, Woo Young, E-mail: wykim@hoseo.edu [Department of Display Engineering, Hoseo University, Sechul-Ri 160, Baebang, Asan, Chung-Nam 336-795 (Korea, Republic of); Wood, Richard; Mascher, Peter [Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S4L7 (Canada)

    2014-02-15

    We investigated the optical properties of light emission based on the resonance energy transfer mechanism between two molecules in the host–dopant systems. For this purpose, we fabricated the organic light-emitting devices with the different doped emissive layers. The host matrices were made of 4,4′,4″-tris(carbasol-l-nyl)triphenylamine (TCTA) and 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) molecules and the doped molecules were 5,6,11,12-tetraphenylnaphtacene (Rubrene) and 4-(Dicyanomethylene)-2-tert-butyl-6- (1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB). The concentrations of the doped molecules were 0.1%, 0.3%, 0.5%, and 0.8%. Through spectroscopic analysis using multi-peak fits with a Gaussian function to the emission spectra, we obtained the relative light intensity of the two dopants according to the doping concentrations and examined the relations between the molecular excited energy states and the nature of energy transfer in the host and dopant systems. We show that the luminous efficiency of the devices has a strong correlation between the energy transfer owing to the individual molecular intrinsic properties and the electrical characteristics associated with the bulky properties in the devices. -- Highlights: • Fabrication and characterization of the OLEDs with a host–dopant system in the emissive layer. • Investigation of the optical properties of light emission based on the resonance energy transfer mechanism between the dopant molecules. • EL and PL spectroscopic study for the structure of the molecular energy levels in the dopant molecules.

  15. Studies on organic light-emitting diodes based on rubrene-doped zinc quinolate

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Dalip Singh [Instrument Design Development Centre, Indian Institute of Technology Delhi, New Delhi (India); Rai, Virender Kumar; Srivastava, Ritu; Chauhan, Gayatri; Kamalasanan, M.N. [Center for Organic Electronics, National Physical Laboratory, New Delhi (India); Jain, V.K. [AIARS (Materials and Devices), Amity University, Noida, U.P (India); Saxena, Kanchan

    2009-07-15

    We report on the fabrication and performance of organic light-emitting diodes (OLEDs) employing rubrene-doped metal chelate namely, zinc quinolate (Znq{sub 2}) as emissive layer. Different OLED architectures were carried out to improve the device performance by doping varying concentrations (by wt%) of rubrene dye into Znq{sub 2} host. Enhanced electroluminescence (EL) intensity was achieved using oxygen-plasma-treated indium tin oxide as anode, N,N'-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-4,4'diamine ({alpha}-NPD) as hole-transport layer, 10 weight percent rubrene-doped Znq{sub 2} as emission layer, Znq{sub 2} as electron-transport layer, LiF as electron-injection layer and aluminum as cathode. It has been demonstrated that by using Znq{sub 2} as electron-transport layer and host for dopant (rubrene) is the most suitable device structure for achieving low drive voltage and high efficiency. Electroluminescence spectra of rubrene-doped OLED devices were also studied. The EL spectral peak was found to be shifted to 565 nm and spectral full-width at half maximum (FWHM) of rubrene-doped device was found to be 58 nm, while it was 95 nm in the case of a pure Znq{sub 2}-based OLED device. No further significant changes in EL spectra, such as, spectral broadening, narrowing or peak shifting were observed on changing the concentration of the rubrene dye. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Effects of parylene buffer layer on flexible substrate in organic light emitting diode

    International Nuclear Information System (INIS)

    Parylene was deposited on a bare polyethylene terephthalate (PET) and poly carbonate (PC) film surface to enhance the oxygen and water barrier properties at room temperature. The deposition rate of the parylene was observed to have increased linearly as the working pressure was increased. The oxygen plasma pre-treatment of the PET for the adhesion between bare film and parylene was mostly effective to 5B, while the treatment of N-(2-Aminoethyl)-3-Aminopropylmethyldimethoxysilane solution at PC film resulted in 3B. Surface morphology and roughness were observed by atomic force microscopy and the barrier property was measured by oxygen transmission rate and water vapor permeation test equipments. The oxygen transmission rate (OTR) and water vapor transmission rate (WTR) of the PET film were reduced from 13.2 to 11.3 cc/m2 day and from 4.6 to 2.0 g/m2 day, respectively. When the parylene layer was coated onto the PC film, however, the barrier effects were significant from out of detection limit to 53.9 cc/m2 day for the OTR, and from 24.7 to 3.5 g/m2 day for the WTR. The real organic light emitting diode (OLED) device was fabricated with a parylene coated flexible substrate, which was subsequently deposited by transparent conducting layer and scratch-resistant layer. The initial brightness of the OLED device with a parylene buffer layer was 173 cd/cm2, and 70% of its initial brightness was maintained after 40,000 s

  17. AC quantum efficiency harmonic analysis of exciton annihilation in organic light emitting diodes (Presentation Recording)

    Science.gov (United States)

    Giebink, Noel C.

    2015-10-01

    Exciton annihilation processes impact both the lifetime and efficiency roll-off of organic light emitting diodes (OLEDs), however it is notoriously difficult to identify the dominant mode of annihilation in operating devices (exciton-exciton vs. exciton-charge carrier) and subsequently to disentangle its magnitude from competing roll-off processes such as charge imbalance. Here, we introduce a simple analytical method to directly identify and extract OLED annihilation rates from standard light-current-voltage (LIV) measurement data. The foundation of this approach lies in a frequency domain EQE analysis and is most easily understood in analogy to impedance spectroscopy, where in this case both the current (J) and electroluminescence intensity (L) are measured using a lock-in amplifier at different harmonics of the sinusoidal dither superimposed on the DC device bias. In the presence of annihilation, the relationship between recombination current and light output (proportional to exciton density) becomes nonlinear, thereby mixing the different EQE harmonics in a manner that depends uniquely on the type and magnitude of annihilation. We derive simple expressions to extract different annihilation rate coefficients and apply this technique to a variety of OLEDs. For example, in devices dominated by triplet-triplet annihilation, the annihilation rate coefficient, K_TT, is obtained directly from the linear slope that results from plotting EQE_DC-EQE_1ω versus L_DC (2EQE_1ω-EQE_DC). We go on to show that, in certain cases it is sufficient to calculate EQE_1ω directly from the slope of the DC light versus current curve [i.e. via (dL_DC)/(dJ_DC )], thus enabling this analysis to be conducted solely from common LIV measurement data.

  18. 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

    OpenAIRE

    Ching-Lin Fan; Hao-Wei Chen; Hui-Lung Lai; Bo-Liang Guo; Bohr-Ran Huang

    2014-01-01

    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 v...

  19. Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5 kA cm−2

    International Nuclear Information System (INIS)

    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. (paper)

  20. 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.

  1. Operation voltage behavior of organic light emitting diodes with polymeric buffer layers doped by weak electron acceptor

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Hyeon Soo; Cho, Sang Hee [Department of Information Display and Advanced Display Research Center, Kyung Hee University, Seoul 130-701 (Korea, Republic of); Seo, Jaewon; Park, Yongsup [Department of Physics, Kyung Hee University, Seoul 130-701 (Korea, Republic of); Suh, Min Chul, E-mail: mcsuh@khu.ac.kr [Department of Information Display and Advanced Display Research Center, Kyung Hee University, Seoul 130-701 (Korea, Republic of)

    2013-11-01

    We present polymeric buffer materials based on poly[2,7-(9,9-dioctyl-fluorene)-co-(1,4-phenylene -((4-sec-butylphenyl)imino)-1,4-phenylene)] (TFB) for highly efficient solution processed organic light emitting diodes (OLEDs). Doped TFB with 9,10-dicyanoanthracene, a weak electron acceptor results in significant improvement of current flow and driving voltage. Maximum current- and power-efficiency value of 12.6 cd/A and 18.1 lm/W are demonstrated from phosphorescent red OLEDs with this doped polymeric anode buffer system. - Highlights: • Polymeric buffer materials for organic light emitting diodes (OLEDs). • Method to control hole conductivity of polymeric buffer layer in OLED device. • Enhanced current density of buffer layers upon 9,10-dicyanoanthracene (DCA) doping. • Comparison of OLED devices having polymeric buffer layer with or without DCA. • Effect on operating voltage by doping DCA in the buffer layer.

  2. Chemically Compatible Sacrificial Layer-Assisted Lift-Off Patterning Method for Fabrication of Organic Light-Emitting Displays

    Science.gov (United States)

    Choi, Wonsuk; Kim, Min-Hoi; Lee, Sin-Doo

    2011-08-01

    We developed a generic platform to pattern combinatorial functional layers composed of different classes of organic materials using a repetitive lift-off method based on a chemically compatible sacrificial layer (SL) for organic light-emitting diodes (OLEDs). The essential features come from the chemically compatible SL of a fluorous-polymer that can be generated by laser-inscription or transfer-printing. The precise registration of lateral patterns of different materials was achieved on a single substrate through a series of SL-assisted lift-off processes. The chemical compatibility of the SL and the stability of the light-emitting characteristics were shown in a fluorous-solvent treated monochrome OLEDs.

  3. Dependence of light-emitting and photovoltaic properties of dual-function organic diodes on carrier-transporting layers

    Science.gov (United States)

    Lee, Ho-Nyeon; Choi, Mun Soo

    2013-10-01

    Dual-function photovoltaic organic light-emitting diodes (PVOEDs) have been investigated in this work. The PVOLEDs emit light when forward biased and generate electricity when backward biased. This dual function is based on the half-gap junction composed of 5,6,11,12-tetraphenylnaphthacene (rubrene) and C 60. The device structure was optimized through experiments using various organic materials for the electron-transporting layer (ETL) and electron-injection layer (EIL). Through this work, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), C 60 and LiF were selected as the ETL, electron-accepting layer and EIL, respectively. Using this device structure, we obtained a current efficiency of 0.27 cd/A for the light-emitting mode and a power-conversion efficiency of 1.95% for the photovoltaic mode.

  4. 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.

  5. 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.

  6. Operation voltage behavior of organic light emitting diodes with polymeric buffer layers doped by weak electron acceptor

    International Nuclear Information System (INIS)

    We present polymeric buffer materials based on poly[2,7-(9,9-dioctyl-fluorene)-co-(1,4-phenylene -((4-sec-butylphenyl)imino)-1,4-phenylene)] (TFB) for highly efficient solution processed organic light emitting diodes (OLEDs). Doped TFB with 9,10-dicyanoanthracene, a weak electron acceptor results in significant improvement of current flow and driving voltage. Maximum current- and power-efficiency value of 12.6 cd/A and 18.1 lm/W are demonstrated from phosphorescent red OLEDs with this doped polymeric anode buffer system. - Highlights: • Polymeric buffer materials for organic light emitting diodes (OLEDs). • Method to control hole conductivity of polymeric buffer layer in OLED device. • Enhanced current density of buffer layers upon 9,10-dicyanoanthracene (DCA) doping. • Comparison of OLED devices having polymeric buffer layer with or without DCA. • Effect on operating voltage by doping DCA in the buffer layer

  7. [Influence of MnO3 on Photoelectric Performance in Organic Light Emitting Diodes].

    Science.gov (United States)

    Guan, Yun-xia; Chen, Li-jia; Chen, Ping; Fu, Xiao-qiang; Niu, Lian-bin

    2016-03-01

    Organic Light Emitting Diodes (OLEDs) has been a promising new research point that has received much attention recently. Emission in a conventional OLED originates from the recombination of carriers (electrons and holes) that are injected from external electrodes. In the device, Electrons, on the other hand, are injected from the Al cathode to an electron-transporting layer and travel to the same emissive zone. Holes are injected from the transparent ITO anode to a hole-transporting layer and holes reach an emitting zone through the holetransporting layer. Electrons and holes recombine at the emissive film to formsinglet excited states, followed by emissive light. It is because OLED is basically an optical device and its structure consists of organic or inorganic layers of sub-wavelength thickness with different refractive indices. When the electron and holes are injected through the electrodes, they combine in the emission zone emitting the photons. These photons will have the reflection and transmission at each interface and the interference will determine the intensity profile. The emissive light reflected at the interfaces or the metallic electrode returns to the emissive layer and affects the radiation current efficiency. Microcavity OLED can produce saturated colors and narrow the emission spetrum as a new kind of technique. In the paper, we fabricate microcavity OLED using glass substrate. Ag film acts as the anode reflector mirror; NPB serves as the hole-transporting material; Alq3 is electron-transporting material and organic emissive material; Ag film acts as cathode reflector mirror. The microcavity OLED structures named as A, B, C and D are glass/Ag(15 nm)/MoO3 (x nm)/NPB(50 nm)/Alq3 (60 nm)/A1(100 nm). Here, A, x = 4 nm; B, x = 7 nm; C, x = 10 nm; D, x = 13 nm. The characteristic voltage, brightness and current of these devices are investigated in the electric field. The luminance from the Devices A, B, C and D reaches the luminance of 928, 1 369, 2

  8. 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.

  9. 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 .

  10. Molecular beam deposition and polymerization of parylene-N ultrathin films: Effective buffers in organic light emitting diodes

    International Nuclear Information System (INIS)

    Highlights: • Parylene-N (PPXN) films prepared by using a home-made Knudsen Cell were identified and characterized. • 1 nm PPXN thin films were inserted at different locations in the hole transport layers of organic light emitting diodes. • For an optimized PPXN inserted organic light emitting diodes, current efficiency improvement of 11% was achieved. • The device current efficiency improvement and the current density variation under operation were discussed. - Abstract: Ultrathin Parylene-N (PPXN) films were prepared by using a home-made Knudsen Cell (KC). The PPXN films were identified by infrared (IR) spectra. The morphology and insulativity of PPXN films were measured by atomic force microscope (AFM) and current density versus voltage (j–V) characteristics. Well controlled 1-nm-thick PPXN thin films were inserted at different locations in the N′-bis(naphthalene-1-yl)-N, N′-bis(phenyl) benzidine (NPB) layers of organic light emitting diodes (OLEDs) with the structure of ITO/NPB/tris (8-hydroxyquinolato) aluminum (Alq3)/LiF/Al. For an optimized PPXN inserted structure, current efficiency of 6.27 cd/A was achieved, 11% higher than the 5.64 cd/A of the control one with 1-nm-thick PPXN buffer inserted at the anode interface. The device current efficiency improvement is due to the electron blocking of PPXN buffers, and the current density variation of devices under operation was explained by tunneling barrier reduction

  11. 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.

  12. 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.

  13. Integration of Multiple Organic Light Emitting Diodes and a Lens for Emission Angle Control

    Science.gov (United States)

    Rahadian, Fanny; Masada, Tatsuya; Fujieda, Ichiro

    We propose to integrate a single lens on top of multiple OLEDs. Angular distribution of the light emitted from the lens surface is altered by turning on the OLEDs selectively. We can use such a light source as a backlight for a liquid crystal display to switch its viewing angle range and/or to display multiple images in different directions. Pixel-level integration would allow one to construct an OLED display with a similar emission angle control.

  14. 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.

  15. 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.

  16. 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

  17. Spatially Resolved Cathodoluminescence in the Vicinity of Defects in the High-Efficiency InGaN/GaN Blue Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Manh-Ha Doan

    2014-01-01

    Full Text Available In addition to the standard 447 nm blue emission from the InGaN/GaN multiple quantum wells, a high-energy shoulder is clearly observed in cathodoluminescence spectra of the high-efficiency InGaN/GaN blue light emitting diodes grown on sapphire substrates by metalorganic chemical vapor deposition. Monochromatic cathodoluminescence images of the samples measured at low temperature reveal a competition between the two emissions in the vicinity of the dislocations. The high-energy emission is dominant at the regions near the dislocation cores, while the blue emission is enhanced around the dislocation edges. The high-energy emission region is considered as a potential barrier that prevents the carriers for the blue emission from nonradiatively recombining at the dislocations.

  18. 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.

  19. Organic Light-Emitting Diodes Based on New Oxadiazole and Pyrazoline Derivatives

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Ming; ZHANG Rui-Feng; WU Fang; MA Yu-Guang; LI Guo-Wen; TIAN Wen-Jing; SHEN Jia-Cong

    2000-01-01

    The bilayer heterojunction devices were fabricated successfully by using a novel oxadiazole derivative: 2, 2-(2,5-thiophenediyl) bis (5-(4-methyl) phenyl-1,3, 4-oxadiazole) (T-OXD) as the electron-transporting layer (ETL)and a pyrazoline derivative:1-phenyl-3-(dimethylamino)styryl-5-(p-(dimethylamino) phenyl)pyrazoline (PDP) as the light-emitting layer and the hole-transporting layer. The emission at 500nm was derived from PDP layer.In comparison with the bilayer device of tris (8-hydroxyquinoline) aluminum (Alq) as the ETL, the luminous efficiency of the PDP/T-OXD heterojunction device was enhanced by 104 times.

  20. 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.

  1. 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.

  2. Light-Emitting-Diodes based on ordered InGaN nanocolumns emitting in the blue, green and yellow spectral range.

    OpenAIRE

    Bengoechea Encabo, Ana; Albert, Steven; López-Romero Moraleda, David; Lefebvre, P.; Barbagini, Francesca; Torres Pardo, Almudena; González Calbet, José María; Sánchez García, Miguel Angel; Calleja Pardo, Enrique

    2014-01-01

    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 layers (planar) of similar composition and thickness. The devices are driven under pulsed operation up ...

  3. 2,4-Dicyano-3-diethylamino-9,9-diethylfluorene Based Blue Light-emitting Star-shaped Compounds: Synthesis and Properties

    Institute of Scientific and Technical Information of China (English)

    CHEN,Xiaohang; CHEN,Xiaopeng; ZHAO,Zujin; L(U),Ping; WANG,Yanguang

    2009-01-01

    Two new star-shaped molecules 1 and 2 containing a triphenylamine/benzene moiety as the central core and three 2,4-dicyano-3-diethylamino-9,9-diethylfluorene moieties as the peripheral functional groups were synthesized and characterized. Charge transfer properties for these compounds were observed in photophysical experiments due to their D-A molecular structure. Compound 1 presented dual fluorescence in high polar solvents. Moreover, these compounds exhibited moderate fluorescence and high thermal stabilities, indicating their potential application to blue light emitting materials.

  4. 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.

  5. 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

  6. Using an organic radical precursor as an electron injection material for efficient and stable organic light-emitting diodes.

    Science.gov (United States)

    Bin, Zhengyang; Liu, Ziyang; Wei, Pengcheng; Duan, Lian; Qiu, Yong

    2016-04-29

    Materials with strong reducibility have been used as electron injection layers (EILs) to lower the work function of cathodes and reduce the driving voltage of organic light-emitting diodes (OLEDs). However, the most prominent electron injection materials presented so far are high-temperature-evaporable inorganic salts based on alkaline metals, which suffer from a high tendency of metal diffusion throughout the organic layer and thus reduce the device efficiency and stability. Here, we introduce a new kind of EIL based on a stable precursor of a strongly reducing organic radical. By using an organic precursor, we are able to take the advantage of the low-evaporation-temperature and avoid the problem of metal diffusion, thus improving the device efficiency and stability. Ultraviolet photoelectron spectroscopy (UPS) study indicates that inserting a thin layer of organic radical between the electron transport layer and cathode could greatly reduce the electron injection barrier due to the strong interaction of radical with cathode and the electron transporting material. As a result, OLEDs with an organic radical as the EIL showed a 25.2% higher efficiency and 2.2 times longer lifetime than the control device with conventional LiF as the EIL. PMID:26988713

  7. A study on single-layered white organic light-emitting diodes based on Co-host system using solution process.

    Science.gov (United States)

    Kim, Beomjin; Park, Youngil; Shin, Hwangyu; Lee, Jiwon; Park, Jongwook

    2011-08-01

    Two color white organic light-emitting diode (WOLED) that used a co-host system in a solution process method was prepared. A device configuration is ITO/PEDOT:PSS (40 nm)/emitting layer (50 nm)/TPBi (20 nm)/LiF (1 nm)/Al. The emitting layer consists of TATa+ alpha-NPB or beta-NPB + DPAVBi (blue dopant) + Rubrene (yellow dopant). The device using alpha-NPB or beta-NPB showed white color of CIE (0.30, 0.40) and (0.29, 0.39), respectively. Device efficiency of alpha-NPB was 3.85 cd/A at 100 mA/cm2, which is about 15% higher than beta-NPB's. PMID:22103231

  8. 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.

  9. 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.

  10. Solution-processed photonic crystals to enhance the light outcoupling efficiency of organic light-emitting diodes.

    Science.gov (United States)

    Cho, Hwan-Hee; Park, Boik; Kim, Hyong-Jun; Jeon, Sohee; Jeong, Jun-Ho; Kim, Jang-Joo

    2010-07-20

    We report an effective solution process to fabricate planarized photonic crystal substrates to enhance the outcoupling efficiency of organic light-emitting diodes (OLEDs). The photonic crystal structure was fabricated using nanoimprint lithography using a UV-curable acrylate and was planarized by using a ZnO layer formed by the solgel process. The solgel process resulted in a smooth surface, and OLEDs have been successfully integrated on the planarized photonic crystal layer with a low leakage current. The resulting light outcoupling efficiency was enhanced by 38% compared with that of conventional OLEDs, which is well matched with a theoretical prediction. PMID:20648184

  11. Enhanced light extraction efficiency in organic light emitting diodes using a tetragonal photonic crystal with hydrogen silsesquioxane.

    Science.gov (United States)

    Kim, Yang Doo; Han, Kyeong-Hoon; Park, Sang-Jun; Kim, Jung-Bum; Shin, Ju-Hyeon; Kim, Jang Joo; Lee, Heon

    2014-10-15

    We report an organic light emitting diode (OLED) with a hydrogen silsesquioxane as a scattering material, for enhancing light extraction efficiency. A tetragonal photonic crystal was used as pattern type, and fabricated using a direct printing technique. Planarization was accomplished using TiO₂ solgel solution, having a refractive index identical to that of the indium zinc oxide transparent electrode. The current efficiency and power efficiency of the OLED increased by 17.3% and 43.4% at 10  mA/cm², respectively, without electric degradation. PMID:25361115

  12. 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.

  13. Efficient textured colour conversion layer of a down-converted white organic light-emitting diode by transfer imprinting

    International Nuclear Information System (INIS)

    In this paper, we demonstrated an efficient textured colour conversion layer (CCL) of a down-converted white organic light-emitting diode (WOLED), which was fabricated by a very simple transfer imprinting method based on silicon wafer. The textured CCL not only helped to extract wave-guided light in the device, but also had an outstanding performance in enhancing the colour conversion rate, which was 1.75 times greater than that of flat CCL. Compared to flat CCL, the lower-doped textured CCL produced better white emission and higher efficiency simultaneously. Moreover, the WOLED with textured CCL also exhibited good colour stability at various voltages. (paper)

  14. 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.

  15. 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.

  16. 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 (Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

  17. Efficiency enhancement of organic light emitting diodes by NaOH surface treatment of the ITO anode

    Science.gov (United States)

    Cusumano, P.

    2009-09-01

    Organic light emitting diodes (OLEDs) based on tris-(8-idroxyquinoline)aluminum (Alq 3) with enhanced efficiency are reported here. This is obtained by improving the charge carrier balance, through a preliminary NaOH surface treatment of the indium tin oxide (ITO) anode, in order to decrease its work function and, consequently, reduce the hole injection. The obtained devices exhibit a 1.36% external quantum efficiency and a 1.2 lm/W power efficiency at a current density of 60 mA/cm 2. These values are more than double as compared with those of identical reference devices fabricated without the preliminary NaOH surface treatment.

  18. 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%.

  19. Flexible white top-emitting organic light-emitting diode with a MoOx roughness improvement layer

    International Nuclear Information System (INIS)

    In this paper, an MoOx film is deposited on a polyethylene terephthalate (PET) substrate as a buffer layer to improve the surface roughness of the flexible PET substrate. With an optimized MoOx thickness of 100 nm, the surface roughness of the PET substrate can be reduced to a very small value of 0.273 nm (much less than 0.585 nm of the pure PET). Flexible white top-emitting organic light-emitting diodes (TEOLEDs) with red and blue dual phosphorescent emitting layers are constructed based on a low-reflectivity Sm/Ag semi-transparent cathode. The flexible white emission exhibits the best luminance and current injection characteristics with the 100-nm-thick MoOx buffer layer and this result indicates that a smooth substrate is beneficial to the enhancement of device electrical and electroluminescence performances. However, the white TEOLED with a 50-nm-thick MoOx buffer layer exhibits a maximum current efficiency of 4.64 cd/A and a power efficiency of 1.9 lm/W, slightly higher than those with a 100-nm MoOx buffer layer, which is mainly due to an obvious intensity enhancement but limited current increases in 50-nm MoOx-based white TEOLED. The change amplitudes of the Commission International de l'Eclairage (CIE) chromaticity coordinates are less than (0.016, 0.005) for all devices in a wide luminance range over 100 cd/m2, indicating an excellent color stability in our white flexible TEOLEDs. Additionally, the flexible white TEOLED with an MoOx buffer layer shows excellent flexibility to withstand more than 500 bending times under a curvature radius of approximately 9 mm. Research demonstrates that it is mainly attributed to the high surface energy of the MoOx buffer layer, which is conducible to the improvement of the surface adhesion to the PET substrate and the Ag anode. (interdisciplinary physics and related areas of science and technology)

  20. Charge Carrier Transport Through the Interface Between Hybrid Electrodes and Organic Materials in Flexible Organic Light Emitting Diodes.

    Science.gov (United States)

    Zhou, Huanyu; Cheong, Hahn-Gil; Park, Jin-Woo

    2016-05-01

    We investigated the electronic properties of composite-type hybrid transparent conductive electrodes (h-TCEs) based on Ag nanowire networks (AgNWs) and indium tin oxide (ITO). These h-TCEs were developed to replace ITO, and their mechanical flexibility is superior to that of ITO. However, the characteristics of charge carriers and the mechanism of charge-carrier transport through the interface between the h-TCE and an organic material are not well understood when the h-TCE is used as the anode in a flexible organic light-emitting diode (f-OLED). AgNWs were spin coated onto polymer substrates, and ITO was sputtered atop the AgNWs. The electronic energy structures of h-TCEs were investigated by ultraviolet photoelectron spectroscopy. f-OLEDs were fabricated on both h-TCEs and ITO for comparison. The chemical bond formation at the interface between the h-TCE and the organic layer in f-OLEDs was investigated by X-ray photoelectron spectroscopy. The performances of f-OLEDs were compared based on the analysis results. PMID:27483896

  1. Numerical simulation of optical and electronic properties for multilayer organic light-emitting diodes and its application in engineering education

    Science.gov (United States)

    Chang, Shu-Hsuan; Chang, Yung-Cheng; Yang, Cheng-Hong; Chen, Jun-Rong; Kuo, Yen-Kuang

    2006-02-01

    Organic light-emitting diodes (OLEDs) have been extensively developed in the past few years. The OLED displays have advantages over other displays, such as CRT, LCD, and PDP in thickness, weight, brightness, response time, viewing angle, contrast, driving power, flexibility, and capability of self-emission. In this work, the optical and electronic properties of multilayer OLED devices are numerically studied with an APSYS (Advanced Physical Model of Semiconductor Devices) simulation program. Specifically, the emission and absorption spectra of the Alq 3, DCM, PBD, and SA light-emitting layers, and energy band diagrams, electron-hole recombination rates, and current-voltage characteristics of the simulated OLED devices, typically with a multilayer structure of metal/Alq 3/EML/TPD/ITO constructed by Lim et al., are investigated and compared to the experimental results. The physical models utilized in this work are similar to those presented by Ruhstaller et al. and Hoffmann et al. The simulated results indicate that the emission spectra of the Alq 3, DCM, PBD, and SA light-emitting layers obtained in this study are in good agreement with those obtained experimentally by Zugang et al. Optimization of the optical and electronic performance of the multilayer OLED devices are attempted. In order to further promote the research results, the whole numerical simulation process for optimizing the design of OLED devices has been applied to a project-based course of OLED device design to enhance the students' skills in photonics device design at the Graduate Institute of Photonics of National Changhua University of Education in Taiwan. In the meantime, the effectiveness of the course has been proved by various assessments. The application of the results is a useful point of reference for the research on photonics device design and engineering education. Therefore, it proffers a synthetic effect between innovation and practical application.

  2. 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.

  3. Characterization of an Optical Device with an Array of Blue Light Emitting Diodes LEDS for Treatment of Neonatal Jaundice.

    Science.gov (United States)

    Sebbe, Priscilla Fróes; Villaverde, Antonio G. J. Balbin; Nicolau, Renata Amadei; Barbosa, Ana Maria; Veissid, Nelson

    2008-04-01

    Phototherapy is a treatment that consists in irradiating a patient with light of high intensity, which promotes beneficial photochemical transformations in the irradiated area. The phototherapy for neonates is applied to break down the bilirubin, an organic pigment that is a sub product of the erythrocytes degradation, and to increase its excretion by the organism. Neonates should be irradiated with light of wavelength that the bilirubin can absorb, and with spectral irradiances between 4 and 16 μW/cm2/nm. The efficiency of the treatment depends on the irradiance and the area of the body that is irradiated. A convenient source of light for treatment of neonatal jaundice is the blue Light Emitter Diode (LED), emitting in the range of 400 to 500 nm, with power of the order of 10-150 mW. Some of the advantages for using LEDS are: low cost, operating long lifetime (over 100,000 hours), narrow emission linewith, low voltage power supply requirement and low heating. The aim of this work was to build and characterize a device for phototherapy treatment of neonatal jaundice. This consists of a blanket with 88 blue LEDs (emission peak at 472 nm), arranged in an 8×11 matrix, all connected in parallel and powered by a 5V-2A power supply. The device was characterized by using a spectroradiometer USB2000 (Ocean Optics Inc, USA), with a sensitivity range of 339-1019 nm. For determination of light spatial uniformity was used a calibrated photovoltaic sensor for measuring light intensity and mapping of the light intensity spatial distribution. Results indicate that our device shows a uniform spatial distribution for distances from the blanket larger than 10 cm, with a maximum of irradiance at such a distance. This device presenting a large and uniform area of irradiation, efficient wavelength emission and high irradiance seems to be promising for neonates' phototherapy treatment.

  4. 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.

  5. Investigation of carrier injection mechanism in small molecular organic light emitting device with a mixed single organic layer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhaokui; Naka, Shigeki; Okada, Hiroyuki [University of Toyama, Graduate School of Science and Technology, Toyama (Japan)

    2011-03-15

    Injection properties of electrons and holes in a mixed single layer organic light emitting device with mixed small molecules tris-(8-hydroxy-quinoline) aluminum (Alq{sub 3}), 2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), 4'-bis[N-(1-napthyl)-N-phenyl-amino]biphenyl ({alpha}-NPD), and 5,6,11,12-tetraphenylnaphthacene (rubrene) were investigated using Au/MoO{sub 3} as hole and Al alloy as electron injection electrodes. On the basis of measuring the temperature dependence of currents through the interface between the electrodes and the mixed single organic layer, the carrier injection mechanism was primarily ascribed to the Schottky thermionic emission with the barrier height of 0.25 eV for holes and 0.67 eV for electrons. By adding the dopant material rubrene and the electron transport material PyPySPyPy into the mixed single layer, the barrier height of electrons could be reduced. The interfacial state analysis demonstrated that the electron barrier height was also dependent on the interfacial conditions of the device. (orig.)

  6. Effect of Reactive Self-Assembled Monolayer at the Anode Interface of Organic Light-Emitting Diode.

    Science.gov (United States)

    Ono, Sotaro; Usui, Satoshi; Kim, Seong-Ho; Tanaka, Kuniaki; Advincula, Rigoberto C; Usuil, Hiroaki

    2016-04-01

    Organic light-emitting diodes (OLEDs) were prepared on-indium-tin oxide (ITO) substrates that were modified with various self-assembled monolayers (SAMs) including those which have reactive terminal units. The OLED performance was analyzed in terms of molecular length, dipole moment and HOMO level of SAM molecules estimated by the density functional theory calculation. It was suggested that the current efficiency of OLED is partly improved by controlling the carrier balance, interfacial dipole moment, and electron energy level by SAM modification. More importantly, remarkable improvement in OLED efficiency was achieved by chemically tethering the inorganic/organic interface via benzophenone-terminated SAM. The reactive SAM having benzophenone terminal group can be a promising tool to control the inorganic/organic interface for organic devices. PMID:27451642

  7. 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.

  8. 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.

  9. Nondoped-type White Organic Light-Emitting Diode Using Star-Shaped Hexafluorenylbenzene as an Energy Transfer Layer

    Institute of Scientific and Technical Information of China (English)

    Jun-sheng Yu; Tao Ma; Shuang-ling Lou; Ya-dong Jiang; Qing Zhang

    2008-01-01

    White organic light-emitting diodes (WOLEDs) with a structure of indium-tin-oxide (ITO)/N,N'-bis(1-naphthyl)-N,N'-diphenyl-(1, 1'-biphenyl)-4,4'-diamine (NPB) / 1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene (HKEthFLYPh)/5,6,11,12-tetraphenylnaphtacene (rubrene)/tris(8-hydroxyquinoline) aluminum (Alq3)/Mg:Ag were fabricated by vacuum deposition method, in which a novel star-shaped hexafluorenyl-benzene HKEthFLYPh was used as an energy transfer layer, and an ultrathin layer of rubrene was inserted between HKEthFLYPh and Alq3 layers as a yellow light-emitting layer instead of using a time-consuming doping process. A fairly pure WOLED with Commissions Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.33) was obtained when the thickness of rubrene was 0.3 nm, and the spectrum was insensitive to the applied voltage. The device yielded a maximum luminance of 4816 cd/m2 at 18 V.

  10. Transmission electron microscope observation of organic-inorganic hybrid thin active layers of light-emitting diodes

    Science.gov (United States)

    Jitsui, Yusuke; Ohtani, Naoki

    2012-10-01

    We performed transmission electron microscope (TEM) observation of organic-inorganic hybrid thin films fabricated by the sol-gel reaction and used as the active layers of organic light-emitting diodes. The cross-sectional TEM images show that the films consist of a triple-layer structure. To evaluate the composition of these layers, the distribution of atoms in them was measured by energy-dispersive X-ray fluorescence spectroscopy. As a result, most of the organic emissive material, poly(9,9-dioctyl-fluorene-co- N-4-butylphenyl-diphenylamine (TFB), was found to be distributed in the middle layer sandwiched by SiO and SiO2 layers. The surface SiO layer was fabricated due to the lack of oxygen. This means that the best sol-gel condition was changed due to the TFB doping; thus, the novel best condition should be found.

  11. 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%.

  12. Damage of photoreceptor-derived cells in culture induced by light emitting diode-derived blue light

    OpenAIRE

    Kuse, Yoshiki; Ogawa, Kenjiro; Tsuruma, Kazuhiro; Shimazawa, Masamitsu; Hara, Hideaki

    2014-01-01

    Our eyes are increasingly exposed to light from the emitting diode (LED) light of video display terminals (VDT) which contain much blue light. VDTs are equipped with televisions, personal computers, and smart phones. The present study aims to clarify the mechanism underlying blue LED light-induced photoreceptor cell damage. Murine cone photoreceptor-derived cells (661 W) were exposed to blue, white, or green LED light (0.38 mW/cm2). In the present study, blue LED light increased reactive oxyg...

  13. A novel theoretical model for broadband blue InGaN/GaN superluminescent light emitting diodes

    International Nuclear Information System (INIS)

    A broadband superluminescent light emitting diode with In0.2Ga0.8N/GaN multiple quantum wells (MQWs) active region is investigated. The investigation is based on a theoretical model which includes the calculation of electronic states of the structure, rate equations, and the spectral radiation power. Two rate equations corresponding to MQW active region and separate confinement heterostructures layer are solved self-consistently with no-k selection wavelength dependent gain and quasi-Fermi level functions. Our results show that the superluminescence started in a current of ∼120 mA (∼7.5 kA/Cm2) at 300 K. The range of peak emission wavelengths for different currents is 423–426 nm and the emission bandwidth is ∼5 nm in the superluminescence regime. A maximum light output power of 7.59 mW is obtained at 600 mA and the peak modal gain as a function of current indicates logarithmic behavior. Also, the comparison of our calculated results with published experimental data is shown to be in good agreement

  14. ZnO nanowire-based light-emitting diodes with tunable emission from near-UV to blue

    Science.gov (United States)

    Pauporté, Thierry; Lupan, Oleg; Viana, Bruno; le Bahers, T.

    2013-03-01

    Nanowires (NWs)-based light emitting diodes (LEDs) have drawn large interest due to many advantages compared to thin film based devices. We have successfully prepared epitaxial n-ZnO(NW)/p-GaN heterojunctions using low temperature soft electrochemical techniques. The structures have been used in LED devices and exhibited highly interesting performances. Moreover, the bandgap of ZnO has been tuned by Cu or Cd doping at controlled atomic concentration. A result was the controlled shift of the LED emission in the visible spectral wavelength region. Using DFT computing calculations, we have also shown that the bandgap narrowing has two different origins for Zn1-xCdxO (ZnO:Cd) and ZnO:Cu. In the first case, it is due to the crystal lattice expansion, whereas in the second case Cu-3d donor and Cu-3d combined to O-2p acceptor bands appear in the bandgap which broadnesses increase with the dopant concentration. This leads to the bandgap reduction.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. A new interpretation for performance improvement of high-efficiency vertical blue light-emitting diodes by InGaN/GaN superlattices

    International Nuclear Information System (INIS)

    The effect of InGaN/GaN superlattices (SLs) on quantum efficiency and forward voltage of vertical blue InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LED) grown on Si substrate has been experimentally and theoretically investigated. We have prepared two LED samples, in which the 30 and 45 periods of SLs are inserted between MQW active layers and n-GaN layer, respectively. Electroluminescence measurement shows that the LED with 45 periods of SLs has higher quantum efficiency but lower forward voltage. It is observed that V-shaped pits grow up in size with an increase in SLs period number by means of scan transmission electron microscope and secondary ion mass spectrometry. Further numerical simulations confirm that the performance improvement of LED by SLs is mainly ascribed to enhancing hole injection from the V-shaped pits

  3. 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.

  4. 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.

  5. 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.)

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. High ambient-contrast-ratio display using tandem reflective liquid crystal display and organic light-emitting device

    Science.gov (United States)

    Lee, Jiun-Haw; Zhu, Xinyu; Lin, Yi-Hsin; Kit Choi, Wing; Lin, Tien-Chun; Hsu, Sheng-Chih; Lin, Hoang-Yan; Wu, Shin-Tson

    2005-11-01

    A high ambient-contrast-ratio (A-CR) and large aperture-ratio display is conceptually demonstrated and experimentally validated by stacking a normally black reflective liquid crystal display (NB-RLCD) and an organic light-emitting device (OLED). Such a tandem device can be switched between the NB-RLCD mode and the OLED mode under bright and dark ambient light, respectively. The normally black characteristic of the RLCD also helps to boost the A-CR under OLED-mode operation. To obtain a better image quality in the RLCD mode, a bumpy and transmissive structure is used to eliminate the specular reflection and to increase the viewing angle performance that results in CR>2:1 over 55° viewing cone. Besides, such a structure can also increase the external quantum efficiency of the OLED by 49.4%. In our experiments, regardless of the ambient intensity the A-CR is kept higher than 100:1.

  11. A spectrum-adjusted white organic light-emitting diode for the optimization of luminous efficiency and color rendering index

    Science.gov (United States)

    Chen, Wei; Chen, Shu-ming

    2015-01-01

    High luminous efficiency and high color rendering index (CRI) are both the foremost factors for white organic light-emitting diodes (WOLEDs) to serve as next generation solid-state lighting sources. In this paper, we show that both luminous efficiency and CRI can be improved by adjusting the green/red spectra of WOLEDs. With green emission spectra matching with the human photopic curve, the WOLEDs exhibit higher luminous efficiency and higher CRI. Theoretical calculation shows that by tuning the white emission spectra to maximally match with the human photopic curve, the luminous efficiency can be improved by 41.8% without altering the color coordinates, the color correlated temperature (CCT) and the external quantum efficiency (EQE) of the WOLEDs.

  12. Tetra-methyl substituted copper (II) phthalocyanine as a hole injection enhancer in organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu-Long; Xu, Jia-Ju; Lin, Yi-Wei; Chen, Qian; Shan, Hai-Quan; Xu, Zong-Xiang, E-mail: xu.zx@sustc.edu.cn, E-mail: val.roy@cityu.edu.hk [Department of Chemistry, South University of Science and Technology of China, Shenzhen, Guangdong, P. R. China, 518055 (China); Yan, Yan; Roy, V. A. L., E-mail: xu.zx@sustc.edu.cn, E-mail: val.roy@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (Hong Kong)

    2015-10-15

    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.

  13. Improvement of Efficiency and Brightness of Red Organic Light-Emitting Devices Using Double-Quantum-Well Configuration

    Science.gov (United States)

    Mi, Rui; Cheng, Gang; Zhao, Yi; Xie, Wen-Fa; Hou, Jing-Ying; Ding, Tao; Liu, Shi-Yong

    2004-03-01

    We present red double-quantum-well organic light-emitting devices (DQW-OLEDs), in which N,N-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyo-4,4'-diamine (NPB) is used as potential barriers and hole transport layer, 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-thtramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped tris (8-hydroxyquinoline) aluminium (Alq3) as potential wells and emitter, undoped Alq3 as electron transport layer, respectively. The turn-on voltage is about 4 V. The maximum brightness and electroluminescent (EL) efficiency of the DQW device can reach 5916 cd m-2 at 16 V and 2.85 cd A-1 at 7 V, respectively. In addition, the EL efficiency of the DQW device is relatively independent of the drive voltage in the range from 5 V to 16 V.

  14. Improvement of Efficiency and Brightness of Red Organic Light-Emitting Devices Using Double-Quantum-Well Configuration

    Institute of Scientific and Technical Information of China (English)

    MI Rui; CHENG Gang; ZHAO Yi; XIE Wen-Fa; HOU Jing-Ying; DING Tao; LIU Shi-Yong

    2004-01-01

    @@ We present red double-quantum-well organic light-emitting devices (DQW-OLEDs), in which N,N-bis-(1-naphthyl)N,N′-diphenyl-1,1′-biphenyo-4,4'-diamine (NPB) is used as potential barriers and hole transport layer, 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7, 7-thtramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped tris (8-hydroxyquinoline) aluminum (Alq3) as potential wells and emitter, undoped Alq3 as electron transport layer, respectively. The turn-on voltage is about 4 V. The maximum brightness and electroluminescent (EL) efficiency of the DQW device can reach 5916cd m-2 at 16 V and 2.85cd A-1 at 7 V, respectively. In addition, the EL efficiency of the DQW device is relatively independent of the drive voltage in the range from 5 V to 16 V.

  15. 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.

  16. Improving the stability of organic light-emitting devices using a solution-processed hole-injecting layer

    International Nuclear Information System (INIS)

    The stability of organic light-emitting devices with a spin-coated film of 4,4',4''-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA) as hole-injection layer (HIL) was investigated. The lifetime of this device is increased to 40 900 h (with an initial luminance of 100 cd/m2), which is 2.7 times as large as that of the control device with a vacuum-deposited film of m-MTDATA as HIL. A significant feature with this method is that the performance and the operational stability of the device with spin-coated HIL are little attenuated by the rough substrate coated by the indium-tin oxide film. The surface morphology of the solution-processed m-MTDATA thin film is quite even and uniform, and it acts as a smoothing layer in the device, which leads to the stability enhancement of the device.

  17. 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.

  18. 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.

  19. Enhanced out-coupling efficiency of organic light-emitting diodes using an nanostructure imprinted by an alumina nanohole array

    Energy Technology Data Exchange (ETDEWEB)

    Endo, Kuniaki [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Yokohama Research Laboratories, Mitsubishi Rayon Co., Ltd., 10-1 Daikoku, Tsurumi, Yokohama 230-0053 (Japan); Adachi, Chihaya [Center for Organic Photonics and Electronics Research, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan); Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)

    2014-03-24

    We demonstrate organic light-emitting diodes (OLEDs) with enhanced out-coupling efficiency containing nanostructures imprinted by an alumina nanohole array template that can be applied to large-emitting-area and flexible devices using a roll-to-roll process. The nanostructures are imprinted on a glass substrate by an ultraviolet nanoimprint process using an alumina nanohole array mold and then an OLED is fabricated on the nanostructures. The enhancement of out-coupling efficiency is proportional to the root-mean-square roughness of the nanostructures, and a maximum improvement of external electroluminescence quantum efficiency of 17% is achieved. The electroluminescence spectra of the OLEDs indicate that this improvement is caused by enhancement of the out-coupling of surface plasmon polaritons.

  20. 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.

  1. 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.

  2. 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.

  3. 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...

  4. Impact of electric fields on the emission from organic light-emitting diodes based on polyvinylcarbazole (PVK)

    International Nuclear Information System (INIS)

    Influences of electric fields on the emission from organic light-emitting diodes (OLEDs) based on 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and polyvinylcarbazole (PVK) are studied. Electroluminescence (EL) spectra are very different from its photoluminescence (PL) for blend of PVK and BCP in the weight ratio M PVK:M BCP=1:3. EL spectrum of device ITO/Blend/BCP(20 nm)/Alq3(12 nm)/Al maximizes at 500 nm. For trilayer device ITO/PVK/BCP(10 nm)/Alq 3(10 nm)/Al, the relative emission intensity of PVK to BCP, initially increases and then decreases with increasing electric field. Under high electric fields, holes can transport through thinner BCP layer and recombine with electrons in Alq 3 layer

  5. New dual-curvature microlens array with a high fill-factor for organic light emitting diode modules

    Science.gov (United States)

    Lin, Tsung-Hung; Yang, Hsiharng; Chao, Ching-Kong; Shui, Hung-Chi

    2013-09-01

    A new method for fabricating a novel dual-curvature microlens array with a high fill-factor using proximity printing in a lithography process is reported. The lens shapes include dual-curvature, which is a novel shape composed of triangles and hexagons. We utilized UV proximity printing by controlling a printing gap between the mask and substrate. The designed high density microlens array pattern can fabricate a dual-curvature microlens array with a high fill-factor in a photoresist material. It is due to the UV light diffraction which deflects away from the aperture edges and produces a certain exposure in the photoresist material outside the aperture edges. A dual-curvature microlens array with a height ratio of 0.48 can boost axial luminance up to 22%. Therefore, the novel dual-curvature microlens array offers an economical solution for increasing the luminance of organic light emitting diodes.

  6. Use of space interlayer in phosphorescent organic light-emitting diodes to improve efficiency and reduce efficiency roll-off

    Science.gov (United States)

    Guo, Kunping; Chen, Changbo; Sun, Chang; Peng, Cuiyun; Yang, Lianqiao; Cai, Miao; Zhang, Xiaowen; Wei, Bin

    2016-06-01

    Typical phosphorescent organic light-emitting diodes (PhOLEDs) encounter efficiency roll-off problems and detrimentally degrades the device performance for practical applications particularity at high-brightness lightening. Here, we report high efficiency and reduced efficiency roll-off PhOLEDs by employing both 4,4‧,4″-tris-(N-carbazolyl)-triphenylamine (TCTA) and 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBi) as transporting, hosting and space interlayer (SIL) materials. The use of SIL blending TCTA into TPBi enables the current efficiency roll-up from 57.8 to 60.1 cd A‑1 with luminance increasing from 10.0 to 1143.0 cd m‑2. In particular, the current efficiency drops  ratio of the two materials in the SIL.

  7. 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.

  8. 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.

  9. 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.

  10. Remarkable improvement in electroluminescence benefited from appropriate electron injection and transporting in ultraviolet organic light-emitting diode

    Science.gov (United States)

    You, Fengjiao; Mo, Bingjie; Liu, Liming; Wang, Honghang; Bin Wei; Xu, Jiwen; Zhang, Xiaowen

    2016-08-01

    Suitable thickness of LiF and 4,7-diphenyl-1, 10-phenanthroline with slightly weakened electron injection and transporting is proposed to match the intractable hole injection capacity in ultraviolet organic light-emitting diode (UV OLED). By using this strategy, the device performance is remarkably improved. With 4,4‧-bis(carbazol-9-yl)biphenyl (CBP) and 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ) as emitters, the UV OLED shows maximum radiance of 5.8 mW/cm2 and external quantum efficiency of 2.1% with emission peak of ~380 nm predominantly from TAZ and noticeable shoulder emission of ~410 nm from CBP. The retarded electron injection and transporting contribute to optimizing hole-electron recombination zone and balance within the emitting layers, which accounts for the improved electroluminescent intensity. The detailed mechanism is further clarified with impedance spectroscopy.

  11. 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.

  12. A study of interfaces between organic and metal materials and their application in polymer light-emitting diodes and polymer photovoltaic solar cells

    Science.gov (United States)

    Li, Juo-Hao

    2009-12-01

    In the past few decades, it attracts a lot of attention for the researches of organic semiconductor due to its new and interesting properties, compared with conventional soft material and inorganic semiconductor. Several kinds of electronic devices such as light emitting diodes, thin film transistors and photovoltaic solar cell based on these organic semiconductors are also proposed and studied. This dissertation will focus on interface between organic and metal, which is one of the mysteries and critical issues remaining in the material properties and limiting the device performance. In the first chapter, a brief review and introduction of the organic semiconductor and organic electronics will be described. The purpose is to introduce the research background, motivation and methodology. Chapter two demonstrates the concept of top-emitting light-emitting diodes and the research focus on the interfaces between the light-emitting polymer and electrodes. An interfacial layer is introduced to improve the hole-injection from the anode. Except for alternating the electrode architecture, surface treatment or modification also have significant influences on interfacial electronic structure. Chapter three describes the discovery of solvent treatment on top of the light-emitting polymer and its application on organic electrophosphorescent devices. To further study the interfaces in organic electronics, an interface layer of sol-gel processed titanium oxide is introduced into organic electronic devices. Chapter four describes the amorphous titanium oxide and its application on polymer light-emitting diodes, while Chapter five demonstrates nanocrystalline titanium dioxide and its application in both light-emitting devices and polymer photovoltaic solar cells.

  13. 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).

  14. Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting

    Science.gov (United States)

    Goins, G. D.; Yorio, N. C.; Sanwo, M. M.; Brown, C. S.; Sager, J. C. (Principal Investigator)

    1997-01-01

    Red light-emitting diodes (LEDs) are a potential light source for growing plants in spaceflight systems because of their safety, small mass and volume, wavelength specificity, and longevity. Despite these attractive features, red LEDs must satisfy requirements for plant photosynthesis and photomorphogenesis for successful growth and seed yield. To determine the influence of gallium aluminium arsenide (GaAlAs) red LEDs on wheat photomorphogenesis, photosynthesis, and seed yield, wheat (Triticum aestivum L., cv. 'USU-Super Dwarf') plants were grown under red LEDs and compared to plants grown under daylight fluorescent (white) lamps and red LEDs supplemented with either 1% or 10% blue light from blue fluorescent (BF) lamps. Compared to white light-grown plants, wheat grown under red LEDs alone demonstrated less main culm development during vegetative growth through preanthesis, while showing a longer flag leaf at 40 DAP and greater main culm length at final harvest (70 DAP). As supplemental BF light was increased with red LEDs, shoot dry matter and net leaf photosynthesis rate increased. At final harvest, wheat grown under red LEDs alone displayed fewer subtillers and a lower seed yield compared to plants grown under white light. Wheat grown under red LEDs+10% BF light had comparable shoot dry matter accumulation and seed yield relative to wheat grown under white light. These results indicate that wheat can complete its life cycle under red LEDs alone, but larger plants and greater amounts of seed are produced in the presence of red LEDs supplemented with a quantity of blue light.

  15. A New Blue-Emitting Mg2Al4Si5O18:Ce3+ Phosphor for White Light Emitting Diodes.

    Science.gov (United States)

    Chen, Jian; Ma, Hongyun; Liu, Yangai

    2016-04-01

    A series of blue-emitting Mg2Al4Si5O18:Ce3+ phosphors were prepared via the conventional high temperature solid-state reaction method. The phase structure, photoluminescence (PL) properties, PL thermal stability, and fluorescence decay curves of the samples were investigated for the first time. Under excitation at 365 nm, the phosphor exhibited a broad band blue emission with peak at 440 nm, which was ascribed to the 4f --> 5d transition of Ce3+, and the color coordinate was (0.1602, 0.0849). When the temperature increased to 150 °C, the luminescence intensity of the Mg2Al4Si5O18:0.06Ce3+ phosphor was 55.73% of the initial value at room temperature. The activation energy ΔE was calculated to be 0.25 eV, which proved the good thermal stability of the sample. The energy transfer critical distance between Ce3+ ions in Mg2Al4Si5O18 host were also calculated. The above results indicate that the Mg2Al4Si5O18:Ce3+ is a promising candidate as a blue-emitting near ultraviolet convertible phosphor for application in white light emitting diodes (WLEDs). PMID:27451657

  16. 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.

  17. 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.

  18. White organic light-emitting diodes with single active layer using a solution process based on a co-host emitter system.

    Science.gov (United States)

    Kim, Beomjin; Park, Youngil; Park, Jongwook

    2014-11-01

    A two-color white organic light-emitting diode (WOLED) with a co-host system in solution process method was demonstrated. The device configuration was ITO/PEDOT:PSS (40 nm)/emitting layer (50 nm)/TPBi (20 nm)/LiF (1 nm)/Al. The emitting layer consisted of TAT, (α- or β-) NPB, DPAVBi (blue dopant), and Rubrene (yellow dopant). The device using α-NPB or β-NPB showed a white color of CIE (0.29, 0.40) and (0.28, 0.39). The device using the α-NPB co-host showed a luminance efficiency of 3.39 cd/A, which is 21% higher than β-NPB (2.80 cd/A). Power efficiency was increased by 16% in α-NPB (2.34 Im/W) compared to β-NPB (2.02 Im/W). The Co-host emitter system of HTL and single blue emitter using a solution process for WOLED was shown before, but the HTL role was not understood clearly. From this study, the WOLED device efficiency can be attributed to the HTL's energy transfer property in the emitter mixing system. PMID:25958544

  19. 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.

  20. Adhesion and Interfacial Fracture: From Organic Light Emitting Devices and Photovoltaic Cells to Solar Lanterns for Developing Regions

    Science.gov (United States)

    Tong, Tiffany Michelle

    From that “ah-ha!” moment when a new technology is first conceived until the time that it reaches the hands of consumers, products undergo numerous iterations of research, development, testing, and redesign in order to create an end-product that is relevant, desirable, functional, and affordable. One crucial step, particularly for electronic devices, is a rigorous testing stage to ensure that a product will be able to withstand regular wear-and-tear. An understanding of how, when, and under what conditions a technology will fail is important in improving device performance and creating high quality products that consumers trust. Understanding that success is inherently tied to failure, this thesis focuses on studies of mechanical failure related to two types of electronic devices: solar cells and light emitting devices. By considering the interfaces that are relevant to the next generation of solar cells and light emitting devices that are built using organic conducting polymers, an atomic force microscopy test is introduced to characterize and rank the relative interfacial adhesion between layers at the nano-scale. These results have implications for material selection that can enhance device processing and performance. This method is then linked to fracture mechanics techniques that determine critical loading forces that induce separation and, hence, mechanical failure between layers of these devices. These results demonstrate the effect of nano-scale interactions on macro-scale behavior, and are particularly valuable in product testing as flexible electronics gain interest. Finally, a case study is conducted in Rural Kenya that measures the impact of commercially-available LED lanterns that are charged by solar panels on a community that is disconnected from the power grid. By demonstrating the value of these lanterns for the community, the role of device reliability and lifetime is examined in underscoring the critical need for proper device testing before