WorldWideScience

Sample records for light emitting layers

  1. Hybrid fluorescent layer emitting polarized light

    Directory of Open Access Journals (Sweden)

    Mohammad Mohammadimasoudi

    2017-07-01

    Full Text Available Semiconductor nanorods have anisotropic absorption and emission properties. In this work a hybrid luminescent layer is produced based on a mixture of CdSe/CdS nanorods dispersed in a liquid crystal that is aligned by an electric field and polymerized by UV illumination. The film emits light with polarization ratio 0.6 (polarization contrast 4:1. Clusters of nanorods in liquid crystal can be avoided by applying an AC electric field with sufficient amplitude. This method can be made compatible with large-scale processing on flexible transparent substrates. Thin polarized light emitters can be used in LCD backlights or solar concentrators to increase the efficiency.

  2. Efficient white organic light emitting devices with dual emitting layers

    International Nuclear Information System (INIS)

    Wu Yaoshan; Hwang Shiaowen; Chen Hsianhung; Lee Mengting; Shen Wenjian; Chen, C.H.

    2005-01-01

    In this paper, a new white organic light-emitting device (OLED) with the structure of indium tin oxide / CF x / 1,4-bis[N-(1-naphthyl)-N'-phenylamino]-biphenyl (NPB) (30 nm)/NPB: 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (20 nm; 1.6 %) / 2-methyl-9,10-di(2-naphthyl) anthracene: p-bis(p-N,N-di-phenyl-aminostyryl)benzene (40 nm, 3%) / aluminum tris(8-hydroxyquinoline) (20 nm) / LiF (1 nm) / Al (200 nm) has been investigated. The device showed white emission with a high-luminous yield of 9.75 cd/A at 20 mA/cm 2 , but its Commission Internationale de l'Eclairage chromaticity coordinates appeared to change from (0.34, 0.42) at 6 mA/cm2 to (0.27, 0.37) at 200 mA/cm 2 due to the shift of recombination zone. The change of color with drive current was suppressed by introduction of an electron-blocking layer of NPB along with a hole-blocking layer of aluminum (III) bis(2-methyl-8-quinolinato)4-phenylphenolato to the white OLED which successfully confined the recombination site and achieved a luminous yield of 9.9 cd/A at 20 mA/cm 2

  3. Efficient white organic light emitting devices with dual emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yaoshan [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Hwang Shiaowen [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China)]. E-mail: jesse@faculty.nctu.edu.tw; Chen Hsianhung [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Lee Mengting [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Shen Wenjian [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Chen, C.H. [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China)

    2005-09-22

    In this paper, a new white organic light-emitting device (OLED) with the structure of indium tin oxide / CF {sub x} / 1,4-bis[N-(1-naphthyl)-N'-phenylamino]-biphenyl (NPB) (30 nm)/NPB: 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (20 nm; 1.6 %) / 2-methyl-9,10-di(2-naphthyl) anthracene: p-bis(p-N,N-di-phenyl-aminostyryl)benzene (40 nm, 3%) / aluminum tris(8-hydroxyquinoline) (20 nm) / LiF (1 nm) / Al (200 nm) has been investigated. The device showed white emission with a high-luminous yield of 9.75 cd/A at 20 mA/cm{sup 2}, but its Commission Internationale de l'Eclairage chromaticity coordinates appeared to change from (0.34, 0.42) at 6 mA/cm2 to (0.27, 0.37) at 200 mA/cm{sup 2} due to the shift of recombination zone. The change of color with drive current was suppressed by introduction of an electron-blocking layer of NPB along with a hole-blocking layer of aluminum (III) bis(2-methyl-8-quinolinato)4-phenylphenolato to the white OLED which successfully confined the recombination site and achieved a luminous yield of 9.9 cd/A at 20 mA/cm{sup 2}.

  4. Organic light emitting diode with surface modification layer

    Science.gov (United States)

    Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

    2017-09-12

    An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

  5. Organic light emitting diode with light extracting layer

    Science.gov (United States)

    Lu, Songwei

    2016-06-14

    A light extraction substrate includes a glass substrate having a first surface and a second surface. A light extraction layer is formed on at least one of the surfaces. The light extraction layer is a coating, such as a silicon-containing coating, incorporating nanoparticles.

  6. Efficient white organic light emission by single emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Young Wook; Chung, Choong-Heui; Lee, Jin Ho; Kim, Yong-Hae; Sohn, Choong-Yong; Kim, Bong-Chul; Hwang, Chi-Sun; Song, Yoon-Ho; Lim, Jongtae; Ahn, Young-Joo; Kang, Gi-Wook; Lee, Namheon; Lee, Changhee

    2003-02-24

    Stable organic white light-emitting diodes are successfully fabricated by a single organic white emitting layer, which is Bis (2-methyl-8-quinolinato) (triphenylsiloxy) aluminum (III) (SAlq) doped red fluorescent dye of 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)- 4H-pyran (DCJTB). The incomplete energy transfer from blue-emitting SAlq to red-emitting DCJTB enables to obtain a stable white balanced light-emission by the DCJTB doping concentration of 0.5%. A device with the structure of ITO/TPD (50 nm)/SAlq:DCJTB (30 nm, 0.5%)/Alq{sub 3} (20 nm)/LiF (0.5 nm)/Al (110 nm) shows maximum luminance of 20 400 cd/m{sup 2} at 810 mA/cm{sup 2}, external quantum efficiency of 2% at 200 cd/m{sup 2} ({approx}3 mA/cm{sup 2}), power efficiency of 2.3 lm/W at 67 cd/m{sup 2} ({approx}1 mA/cm{sup 2}), and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.34, 0.39) at 1.8 mA/cm{sup 2} to (0.31, 0.38) at 36 mA/cm{sup 2}.

  7. Efficient light emitting devices based on phosphorescent partially doped emissive layers

    KAUST Repository

    Yang, Xiaohui; Jabbour, Ghassan E.

    2013-01-01

    We report efficient organic light emitting devices employing an ultrathin phosphor emissive layer. The electroluminescent spectra of these devices can be tuned by introducing a low-energy emitting phosphor layer into the emission zone. Devices

  8. 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.

  9. White organic light-emitting diodes from three emitter layers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M.S. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Lim, J.T. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Jeong, C.H. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Lee, J.H. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Yeom, G.Y. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of)]. E-mail: gyyeom@skku.edu

    2006-11-23

    Three-wavelength white organic light-emitting diodes (WOLEDs) were fabricated using two doped layers, which were obtained by separating the recombination zones into three emitter layers. A sky blue emission originated from the 4,4'-bis(2,2'-diphenylethen-1-yl)biphenyl (DPVBi) layer. A green emission originated from a tris(8-quinolinolato)aluminum (III) (Alq{sub 3}) host doped with a green fluorescent 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1] benz opyrano [6,7,8-ij]-quinolizin-11-one (C545T) dye. An orange emission was obtained from the N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) host doped with a red fluorescent dye, 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4 H-pyran (DCJTB). A white light resulted from the partial excitations of these three emitter layers by controlling the layer thickness and concentration of the fluorescent dyes in each emissive layer simultaneously. The electroluminescent spectrum of the device was not sensitive to the driving voltage of the device. The white light device showed a maximum luminance of approximately 53,000 cd/m{sup 2}. The external quantum and power efficiency at a luminance of approximately 100 cd/m{sup 2} were 2.62% and 3.04 lm/W, respectively.

  10. Simple single-emitting layer hybrid white organic light emitting with high color stability

    Science.gov (United States)

    Nguyen, C.; Lu, Z. H.

    2017-10-01

    Simultaneously achieving a high efficiency and color quality at luminance levels required for solid-state lighting has been difficult for white organic light emitting diodes (OLEDs). Single-emitting layer (SEL) white OLEDs, in particular, exhibit a significant tradeoff between efficiency and color stability. Furthermore, despite the simplicity of SEL white OLEDs being its main advantage, the reported device structures are often complicated by the use of multiple blocking layers. In this paper, we report a highly simplified three-layered white OLED that achieves a low turn-on voltage of 2.7 V, an external quantum efficiency of 18.9% and power efficiency of 30 lm/W at 1000 cd/cm2. This simple white OLED also shows good color quality with a color rendering index of 75, CIE coordinates (0.42, 0.46), and little color shifting at high luminance. The device consists of a SEL sandwiched between a hole transport layer and an electron transport layer. The SEL comprises a thermally activated delayer fluorescent molecule having dual functions as a blue emitter and as a host for other lower energy emitters. The improved color stability and efficiency in such a simple device structure is explained as due to the elimination of significant energy barriers at various organic-organic interfaces in the traditional devices having multiple blocking layers.

  11. White emission from nano-structured top-emitting organic light-emitting diodes based on a blue emitting layer

    International Nuclear Information System (INIS)

    Hyun, Woo Jin; Park, Jung Jin; Park, O Ok; Im, Sang Hyuk; Chin, Byung Doo

    2013-01-01

    We demonstrated that white emission can be obtained from nano-structured top-emitting organic light-emitting diodes (TEOLEDs) based on a blue emitting layer (EML). The nano-structured TEOLEDs were fabricated on nano-patterned substrates, in which both optical micro-cavity and scattering effects occur simultaneously. Due to the combination of these two effects, the electroluminescence spectra of the nano-structured device with a blue EML exhibited not only blue but also yellow colours, which corresponded to the intrinsic emission of the EML and the resonant emission of the micro-cavity effect. Consequently, it was possible to produce white emission from nano-structured TEOLEDs without employing a multimode micro-cavity. The intrinsic emission wavelength can be varied by altering the dopant used for the EML. Furthermore, the emissive characteristics turned out to be strongly dependent on the nano-pattern sizes of the nano-structured devices. (paper)

  12. Optimization of white organic light emitting diodes based on emitting layer charge carrier conduction properties

    International Nuclear Information System (INIS)

    Baek, H I; Lee, C H

    2008-01-01

    We have fabricated white organic light emitting diodes (OLEDs) with multi-emitting layer (EML) structures in which 4,4'-N,N'-dicarbazole-biphenyl (CBP) layers doped with the phosphorescent dopants fac-tris(2-phenylpyridine) iridium (Ir(ppy) 3 ) and bis(2-(2'-benzo[4,5-a]thienyl)pyridinato-N,C3')iridium(acetylacetonate) (btp 2 Ir(acac)) and the fluorescent dopant 4,4'-bis[2-{4-(N,N-diphenylamino) phenyl}vinyl]biphenyl (DPAVBi) were used as green (G), red (R) and blue (B) EMLs, respectively. A higher efficiency was expected with the R/G/B EML sequence from the hole transport layer interface than with the G/R/B sequence because of the differences in the charge carrier conduction properties of the EMLs doped with phosphorescent dopants and the luminance balance between the phosphorescent and fluorescent emissions. A high efficiency of 18.3 cd A -1 (an external quantum efficiency of 8.5%) at 100 cd m -2 and good colour stability were achieved with the R/G/B EML sequence as expected, with an additional non-doped CBP interlayer used between the G and B EMLs. In addition, the OLED with this sequence was found to have the longest lifetime of the white devices we tested

  13. Optimization of white organic light emitting diodes based on emitting layer charge carrier conduction properties

    Energy Technology Data Exchange (ETDEWEB)

    Baek, H I; Lee, C H [School of Electrical Engineering and Computer Science and Inter-University Semiconductor Research Center, Seoul National University, Seoul 151-744 (Korea, Republic of)], E-mail: hibaek75@snu.ac.kr

    2008-05-21

    We have fabricated white organic light emitting diodes (OLEDs) with multi-emitting layer (EML) structures in which 4,4'-N,N'-dicarbazole-biphenyl (CBP) layers doped with the phosphorescent dopants fac-tris(2-phenylpyridine) iridium (Ir(ppy){sub 3}) and bis(2-(2'-benzo[4,5-a]thienyl)pyridinato-N,C3')iridium(acetylacetonate) (btp{sub 2}Ir(acac)) and the fluorescent dopant 4,4'-bis[2-{l_brace}4-(N,N-diphenylamino) phenyl{r_brace}vinyl]biphenyl (DPAVBi) were used as green (G), red (R) and blue (B) EMLs, respectively. A higher efficiency was expected with the R/G/B EML sequence from the hole transport layer interface than with the G/R/B sequence because of the differences in the charge carrier conduction properties of the EMLs doped with phosphorescent dopants and the luminance balance between the phosphorescent and fluorescent emissions. A high efficiency of 18.3 cd A{sup -1} (an external quantum efficiency of 8.5%) at 100 cd m{sup -2} and good colour stability were achieved with the R/G/B EML sequence as expected, with an additional non-doped CBP interlayer used between the G and B EMLs. In addition, the OLED with this sequence was found to have the longest lifetime of the white devices we tested.

  14. White top-emitting organic light-emitting diodes using one-emissive layer of the DCJTB doped DPVBi layer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M.S.; Jeong, C.H.; Lim, J.T. [Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Yeom, G.Y. [Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); The National Program for Tera-level Devices, Hawolgok-dong, Sungbuk-gu, Seoul, 136-791 (Korea, Republic of)], E-mail: gyyeom@skku.edu

    2008-04-01

    White top-emitting organic light-emitting diodes (TEOLEDs) composed of one doped emissive layer which emits two-wavelength light though the radiative recombination were fabricated. As the emissive layer, 4,4-bis(2,2-diphenylethen-1-yl)biphenyl (DPVBi) was used as the host material and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (DCJTB) was added as the dopant material. By optimizing the DCJTB concentration (1.2%) and the thickness of the DPVBi layer (30 nm), the intensity ratio of the two wavelengths could be adjusted for balanced white light emission. By using the device composed of glass/Ag (100 nm)/ITO (90 nm)/2-TNATA (60 nm)/NPB (15 nm)/DPVBi:DCJTB (1.2%, 30 nm)/Alq{sub 3} (20 nm)/Li (1.0 nm)/Al (2.0 nm)/Ag (20 nm)/ITO (63 nm)/SiO{sub 2} (42 nm), the Commission Internationale d'Eclairage (CIE) chromaticity coordinate of (0.32, 0.34) close to the ideal white color CIE coordinate could be obtained at 100 cd/m{sup 2}.

  15. [Performance dependence of organic light-emitting devices on the thickness of Alq3 emitting layer].

    Science.gov (United States)

    Lian, Jia-rong; Liao, Qiao-sheng; Yang, Rui-bo; Zheng, Wei; Zeng, Peng-ju

    2010-10-01

    The dependence of opto-electronical characteristics in organic light-emitting devices on the thickness of Alq3 emitter layer was studied, where MoO3, NPB, and Alq3 were used as hole injector, hole transporter, and emitter/electron transporter, respectively. By increasing the thickness of Alq3 layer from 20 to 100 nm, the device current decreased gradually, and the EL spectra of devices performed a little red shift with an obvious broadening in long wavelength range but a little decrease in intensity of short wavelength range. The authors simulated the EL spectra using the photoluminescence (PL) spectra of Alq3 as Alq3 intrinsic emission, which coincided with the experimental EL spectra well. The simulated results suggested that the effect of interference takes the major role in broadening the long wavelength range of EL spectra, and the distribution of emission zone largely affects the profile of EL spectra in short wavelength range.

  16. Efficient light emitting devices based on phosphorescent partially doped emissive layers

    KAUST Repository

    Yang, Xiaohui

    2013-05-29

    We report efficient organic light emitting devices employing an ultrathin phosphor emissive layer. The electroluminescent spectra of these devices can be tuned by introducing a low-energy emitting phosphor layer into the emission zone. Devices with the emissive layer consisting of multiple platinum-complex/spacer layer cells show a peak external quantum efficiency of 18.1%, which is among the best EQE values for platinum-complex based light emitting devices. Devices with an ultrathin phosphor emissive layer show stronger luminance decay with the operating time compared to the counterpart devices having a host-guest emissive layer.

  17. Organic light-emitting diodes with direct contact-printed red, green, blue, and white light-emitting layers

    Science.gov (United States)

    Chen, Sun-Zen; Peng, Shiang-Hau; Ting, Tzu-Yu; Wu, Po-Shien; Lin, Chun-Hao; Chang, Chin-Yeh; Shyue, Jing-Jong; Jou, Jwo-Huei

    2012-10-01

    We demonstrate the feasibility of using direct contact-printing in the fabrication of monochromatic and polychromatic organic light-emitting diodes (OLEDs). Bright devices with red, green, blue, and white contact-printed light-emitting layers with a respective maximum luminance of 29 000, 29 000, 4000, and 18 000 cd/m2 were obtained with sound film integrity by blending a polymeric host into a molecular host. For the red OLED as example, the maximum luminance was decreased from 29 000 to 5000 cd/m2 as only the polymeric host was used, or decreased to 7000 cd/m2 as only the molecular host was used. The markedly improved device performance achieved in the devices with blended hosts may be attributed to the employed polymeric host that contributed a good film-forming character, and the molecular host that contributed a good electroluminescence character.

  18. Recombination zone in white organic light emitting diodes with blue and orange emitting layers

    Science.gov (United States)

    Tsuboi, Taiju; Kishimoto, Tadashi; Wako, Kazuhiro; Matsuda, Kuniharu; Iguchi, Hirofumi

    2012-10-01

    White fluorescent OLED devices with a 10 nm thick blue-emitting layer and a 31 nm thick orange-emitting layer have been fabricated, where the blue-emitting layer is stacked on a hole transport layer. An interlayer was inserted between the two emitting layers. The thickness of the interlayer was changed among 0.3, 0.4, and 1.0 nm. White emission with CIE coordinates close to (0.33, 0.33) was observed from all the OLEDs. OLED with 0.3 nm thick interlayer gives the highest maximum luminous efficiency (11 cd/A), power efficiency (9 lm/W), and external quantum efficiency (5.02%). The external quantum efficiency becomes low with increasing the interlayer thickness from 0 nm to 1.0 nm. When the location of the blue- and orange-emitting layers is reversed, white emission was not obtained because of too weak blue emission. It is suggested that the electron-hole recombination zone decreases nearly exponentially with a distance from the hole transport layer.

  19. Efficient and bright organic light-emitting diodes on single-layer graphene electrodes

    Science.gov (United States)

    Li, Ning; Oida, Satoshi; Tulevski, George S.; Han, Shu-Jen; Hannon, James B.; Sadana, Devendra K.; Chen, Tze-Chiang

    2013-08-01

    Organic light-emitting diodes are emerging as leading technologies for both high quality display and lighting. However, the transparent conductive electrode used in the current organic light-emitting diode technologies increases the overall cost and has limited bendability for future flexible applications. Here we use single-layer graphene as an alternative flexible transparent conductor, yielding white organic light-emitting diodes with brightness and efficiency sufficient for general lighting. The performance improvement is attributed to the device structure, which allows direct hole injection from the single-layer graphene anode into the light-emitting layers, reducing carrier trapping induced efficiency roll-off. By employing a light out-coupling structure, phosphorescent green organic light-emitting diodes exhibit external quantum efficiency >60%, while phosphorescent white organic light-emitting diodes exhibit external quantum efficiency >45% at 10,000 cd m-2 with colour rendering index of 85. The power efficiency of white organic light-emitting diodes reaches 80 lm W-1 at 3,000 cd m-2, comparable to the most efficient lighting technologies.

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

    Energy Technology Data Exchange (ETDEWEB)

    Rothberg, Lewis

    2012-11-30

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

  1. The use of ionic salt dyes as amorphous, thermally stable emitting layers in organic light-emitting diodes

    Science.gov (United States)

    Chondroudis, Konstantinos; Mitzi, David B.

    2000-01-01

    The conversion of two neutral dye molecules (D) to ionic salts (H2N-D-NH2ṡ2HX) and their utilization as emitting layers in organic light-emitting diodes (OLEDs) is described. The dye salts, AEQTṡ2HCl and APTṡ2HCl, can be deposited as amorphous films using conventional evaporation techniques. X-ray diffraction and scanning electron microscopy analysis, coupled with thermal annealing studies, demonstrate the resistance of the films to crystallization. This stability is attributed to strong ionic forces between the relatively rigid molecules. OLEDs incorporating such salts for emitting layers exhibit better thermal stability compared with devices made from the corresponding neutral dyes (H2N-D-NH2). These results suggest that ionic salts may more generally enable the formation of thermally stable, amorphous emitting, and charge transporting layers.

  2. Current Spreading Layer with High Transparency and Conductivity for near-ultraviolet light emitting diodes

    DEFF Research Database (Denmark)

    Lin, Li; Jensen, Flemming; Herstrøm, Berit

    Transparent conductive aluminum-doped zinc oxide (AZO) layer was deposited on GaN-based near-ultraviolet (NUV) light emitting epitaxial wafers as current spreading layer by a sputtering process. Efforts were made to improve the electrical properties of AZO in order to produce ohmic contact....

  3. Characteristics of organic light emitting diodes with copper iodide as injection layer

    Energy Technology Data Exchange (ETDEWEB)

    Stakhira, P., E-mail: stakhira@polynet.lviv.u [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Cherpak, V.; Volynyuk, D.; Ivastchyshyn, F. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Hotra, Z. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Rzeszow University of Technology, W. Pola 2, Rzeszow, 35-959 (Poland); Tataryn, V. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Luka, G. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2010-09-30

    We have studied the use of a thin copper iodide (CuI) film as an efficient injection layer of holes from indium tin oxide (ITO) anode in a light-emitting diode structure based on tris-8-hydroxyquinoline aluminium (Alq3). The results of impedance analysis of two types of diode structures, ITO/CuI/Alq3/poly(ethylene glycol) dimethyl ether/Al and ITO/Alq3/poly(ethylene glycol) dimethyl ether/Al, are presented. Comparative analysis of their current density-voltage, luminance-voltage and impedance characteristics shows that presence of CuI layer facilitates injection of holes from ITO anode into the light-emitting layer Alq3 and increases electroluminescence efficiency of the organic light emitting diodes.

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

    International Nuclear Information System (INIS)

    Coenen, Michiel J.J.; Slaats, Thijs M.W.L.; Eggenhuisen, Tamara M.; Groen, Pim

    2015-01-01

    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

  5. Blue and white phosphorescent organic light emitting diode performance improvement by confining electrons and holes inside double emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Yu-Sheng; Hong, Lin-Ann; Juang, Fuh-Shyang; Chen, Cheng-Yin

    2014-09-15

    In this research, complex emitting layers (EML) were fabricated using TCTA doping hole-transport material in the front half of a bipolar 26DCzPPy as well as PPT doping electron-transport material in the back half of 26DCzPPy. Blue dopant FIrpic was also mixed inside the complex emitting layer to produce a highly efficient blue phosphorescent organic light emitting diode (OLED). The hole and electron injection and carrier recombination rate were effectively increased. The fabricated complex emitting layers exhibited current efficiency of 42 cd/A and power efficiency of 30 lm/W when the luminance was 1000 cd/m{sup 2}, driving voltage was 4.4 V, and current density was 2.4 mA/cm{sup 2}. A white OLED component was then manufactured by doping red dopant [Os(bpftz){sub 2}(PPh{sub 2}Me){sub 2}] (Os) in proper locations. When the Os dopant was doped in between the complex emitting layers, excitons were effectively confined within, increasing the recombination rate and therefore reducing the color shift. The resulting Commission Internationale de L’Eclairage (CIE) coordinates shifted from 4 to 10 V is (Δx=−0.04, Δy=+0.01). The component had a current efficiency of 35.7 cd/A, a power efficiency of 24 lm/W, driving voltage of 4.6 V and a CIE{sub x,y} of (0.31,0.35) at a luminance of 1000 cd/m{sup 2}, with a maximum luminance of 15,600 cd/m{sup 2} at 10 V. Attaching an outcoupling enhancement film was applied to increase the luminance efficiency to 30 lm/W. - Highlights: • Used the complex double emitting layers. • Respectively doped hole and electron transport material in the bipolar host. • Electrons and holes are effectively confined within EMLs to produce excitons.

  6. Blue and white phosphorescent organic light emitting diode performance improvement by confining electrons and holes inside double emitting layers

    International Nuclear Information System (INIS)

    Tsai, Yu-Sheng; Hong, Lin-Ann; Juang, Fuh-Shyang; Chen, Cheng-Yin

    2014-01-01

    In this research, complex emitting layers (EML) were fabricated using TCTA doping hole-transport material in the front half of a bipolar 26DCzPPy as well as PPT doping electron-transport material in the back half of 26DCzPPy. Blue dopant FIrpic was also mixed inside the complex emitting layer to produce a highly efficient blue phosphorescent organic light emitting diode (OLED). The hole and electron injection and carrier recombination rate were effectively increased. The fabricated complex emitting layers exhibited current efficiency of 42 cd/A and power efficiency of 30 lm/W when the luminance was 1000 cd/m 2 , driving voltage was 4.4 V, and current density was 2.4 mA/cm 2 . A white OLED component was then manufactured by doping red dopant [Os(bpftz) 2 (PPh 2 Me) 2 ] (Os) in proper locations. When the Os dopant was doped in between the complex emitting layers, excitons were effectively confined within, increasing the recombination rate and therefore reducing the color shift. The resulting Commission Internationale de L’Eclairage (CIE) coordinates shifted from 4 to 10 V is (Δx=−0.04, Δy=+0.01). The component had a current efficiency of 35.7 cd/A, a power efficiency of 24 lm/W, driving voltage of 4.6 V and a CIE x,y of (0.31,0.35) at a luminance of 1000 cd/m 2 , with a maximum luminance of 15,600 cd/m 2 at 10 V. Attaching an outcoupling enhancement film was applied to increase the luminance efficiency to 30 lm/W. - Highlights: • Used the complex double emitting layers. • Respectively doped hole and electron transport material in the bipolar host. • Electrons and holes are effectively confined within EMLs to produce excitons

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

    International Nuclear Information System (INIS)

    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 (C 60 ) 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/m 2 and (0.36, 0.34) at 1000 cd/m 2 have been demonstrated by employing the developed CGL, respectively. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  8. White emission from organic light-emitting diodes with a super-thin BCP layer

    Energy Technology Data Exchange (ETDEWEB)

    Hao Jingang [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Deng Zhenbo [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)]. E-mail: zbdeng@center.njtu.edu.cn; Yang Shengyi [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)

    2007-01-15

    We report a method to achieve white emission from organic light-emitting diodes (OLEDs) in which a super-thin (3 nm) hole blocking layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), was inserted between electron-transport layer 8-hydroxyquinoline aluminum (Alq{sub 3}) and 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (DCJTB) doped poly-vinlycarbazole (PVK) layer. The BCP layer can not only confine exciton in the emitting layer but also control energy transfer proportion from PVK to Alq{sub 3} and then from Alq{sub 3} to DCJTB through BCP layer. In this way, pure white emission with CIE coordinate of (0.32, 0.32) was obtained and it was voltage independent. The brightness reached 270 cd/m{sup 2} at 18 V with an efficiency of 0.166 cd/A.

  9. White emission from organic light-emitting diodes with a super-thin BCP layer

    International Nuclear Information System (INIS)

    Hao Jingang; Deng Zhenbo; Yang Shengyi

    2007-01-01

    We report a method to achieve white emission from organic light-emitting diodes (OLEDs) in which a super-thin (3 nm) hole blocking layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), was inserted between electron-transport layer 8-hydroxyquinoline aluminum (Alq 3 ) and 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (DCJTB) doped poly-vinlycarbazole (PVK) layer. The BCP layer can not only confine exciton in the emitting layer but also control energy transfer proportion from PVK to Alq 3 and then from Alq 3 to DCJTB through BCP layer. In this way, pure white emission with CIE coordinate of (0.32, 0.32) was obtained and it was voltage independent. The brightness reached 270 cd/m 2 at 18 V with an efficiency of 0.166 cd/A

  10. III-V group compound semiconductor light-emitting element having a doped tantalum barrier layer

    International Nuclear Information System (INIS)

    Oanna, Y.; Ozawa, N.; Yamashita, M.; Yasuda, N.

    1984-01-01

    Disclosed is a III-V Group compound semiconductor light-emitting element having a III-V Group compound semiconductor body with a p-n junction and including a p-type layer involved in forming the p-n junction; and a multi-layer electrode mounted on the p-type layer of the semiconductor body. The electrode comprises a first layer of gold alloy containing a small amount of beryllium or zinc and formed in direct contact with the p-type layer of the semiconductor body and an uppermost layer formed of gold or aluminum. A tantalum layer doped with carbon, nitrogen and/or oxygen is formed between the first layer and the uppermost layer by means of vacuum vapor deposition

  11. 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.

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

    KAUST Repository

    Yang, Xiaohui; Wu, Fang-Iy; Haverinen, Hanna; Li, Jian; Cheng, Chien-Hong; Jabbour, Ghassan E.

    2011-01-01

    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.

  13. Phosphorescence white organic light-emitting diodes with single emitting layer based on isoquinolinefluorene-carbazole containing host.

    Science.gov (United States)

    Koo, Ja Ryong; Lee, Seok Jae; Hyung, Gun Woo; Kim, Bo Young; Shin, Hyun Su; Lee, Kum Hee; Yoon, Seung Soo; Kim, Woo Young; Kim, Young Kwan

    2013-03-01

    We have demonstrated a stable phosphorescent white organic light-emitting diodes (WOLEDs) using an orange emitter, Bis(5-benzoyl-2-(4-fluorophenyl)pyridinato-C,N) iridium(III)acetylacetonate [(Bz4Fppy)2Ir(III)acac] doped into a newly synthesized blue host material, 2-(carbazol-9-yl)-7-(isoquinolin-1-yl)-9,9-diethylfluorene (CzFliq). When 1 wt.% (Bz4Fppy)2Ir(III)acac was doped into emitting layer, it was realized an improved EL performance and a pure white color in the OLED. The optimum WOLED showed maximum values as a luminous efficiency of 10.14 cd/A, a power efficiency of 10.24 Im/W, a peak external quantum efficiency 4.07%, and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39) at 8 V.

  14. 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.

  15. White-light-emitting diode based on a single-layer polymer

    Science.gov (United States)

    Wang, B. Z.; Zhang, X. P.; Liu, H. M.

    2013-05-01

    A broad-band light-emitting diode was achieved in a single-layer device based on pure poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB). Electromer emission was observed in the red with a center wavelength of about 620 nm in electroluminescence (EL) spectrum. This kind of emission exhibits strong dependence on the thickness of the PFB layer, so that the shape of the EL spectrum may be adjusted through changing the thickness of the active polymer layer to balance between the intrinsic PFB emission in the blue and the electromer emission in the red. Thus, white light emission may be achieved from such a single-layer single-material diode.

  16. Trap effect of an ultrathin DCJTB layer in organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yuanmin [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Teng Feng [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China)]. E-mail: advanced9898@126.com; Xu Zheng [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Hou Yanbing [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Yang Shengyi [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Xu Xurong [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China)

    2005-08-15

    An improved performance of organic light-emitting diodes has been obtained by using 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) -4Hpyran (DCJTB) as an ultrathin emitting layer. When 0.1 nm DCJTB was inserted between the hole-transporting layer and electron-transporting layer, for an unoptimized device indium-tin oxide (ITO)/naphtylphenyliphenyl diamine (NPB)/DCJTB (0.1 nm)/8-hydroxyquinoline aluminum (Alq{sub 3})/Al, the maximum brightness was 1531 cd m{sup -2} at 15 V. Compared with doped devices ITO/NPB/Alq{sub 3}:DCJTB (1%)/Alq{sub 3}/LiF/Al, a higher efficiency has been achieved. Compared with the conventional device ITO/NPB/Alq{sub 3}/Al, the inserted device has a slightly higher current efficiency and lower turn-on voltage. We suggest the ultrathin DCJTB layer acts as trap for carriers, and the accumulated holes at the hole-transport layer/electron-transport layer interface have enhanced the electric field in the electron-transport layer and improved the electron injection at the cathode.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-27

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

  18. Highly efficient single-layer dendrimer light-emitting diodes with balanced charge transport

    Science.gov (United States)

    Anthopoulos, Thomas D.; Markham, Jonathan P. J.; Namdas, Ebinazar B.; Samuel, Ifor D. W.; Lo, Shih-Chun; Burn, Paul L.

    2003-06-01

    High-efficiency single-layer-solution-processed green light-emitting diodes based on a phosphorescent dendrimer are demonstrated. A peak external quantum efficiency of 10.4% (35 cd/A) was measured for a first generation fac-tris(2-phenylpyridine) iridium cored dendrimer when blended with 4,4'-bis(N-carbazolyl)biphenyl and electron transporting 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene at 8.1 V. A maximum power efficiency of 12.8 lm/W was measured also at 8.1 V and 550 cd/m2. These results indicate that, by simple blending of bipolar and electron-transporting molecules, highly efficient light-emitting diodes can be made employing a very simple device structure.

  19. Graphene as current spreading layer on AlGaInP light emitting diodes

    Science.gov (United States)

    Guo, Xia; Feng, Yajie; Liu, Qiaoli; Hu, Anqi; He, Xiaoying; Hu, Zonghai

    2018-05-01

    Due to high transmittance and high mobility, graphene is one of the promising candidates for a current spreading layer, which is crucial to light emitting diode (LED) performance. In this paper, improved AlGaInP LED performance was reported after graphene was applied on the GaP surface. Due to its lowered work function difference than with the GaN material, the electrical properties remain the same without additional voltage bias. The light output power is enhanced by about 40% under the current injection of 5 mA at room temperature, which was confirmed by the light emission profile analysis in this study. Such results indicate that raphene is a promising candidate as a current spreading layer under low current injection.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-05-21

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

  1. 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.

  2. Ultrathin nondoped emissive layers for efficient and simple monochrome and white organic light-emitting diodes.

    Science.gov (United States)

    Zhao, Yongbiao; Chen, Jiangshan; Ma, Dongge

    2013-02-01

    In this paper, highly efficient and simple monochrome blue, green, orange, and red organic light emitting diodes (OLEDs) based on ultrathin nondoped emissive layers (EMLs) have been reported. The ultrathin nondoped EML was constructed by introducing a 0.1 nm thin layer of pure phosphorescent dyes between a hole transporting layer and an electron transporting layer. The maximum external quantum efficiencies (EQEs) reached 17.1%, 20.9%, 17.3%, and 19.2% for blue, green, orange, and red monochrome OLEDs, respectively, indicating the universality of the ultrathin nondoped EML for most phosphorescent dyes. On the basis of this, simple white OLED structures are also demonstrated. The demonstrated complementary blue/orange, three primary blue/green/red, and four color blue/green/orange/red white OLEDs show high efficiency and good white emission, indicating the advantage of ultrathin nondoped EMLs on constructing simple and efficient white OLEDs.

  3. Organic Light Emitting Diodes with Opal Photonic Crystal Layer and Carbon Nanotube Anode

    Science.gov (United States)

    Ovalle Robles, Raquel; Del Rocio Nava, Maria; Williams, Christopher; Zhang, Mei; Fang, Shaoli; Lee, Sergey; Baughman, Ray; Zakhidov, Anvar

    2007-03-01

    We report electroluminescence intensity and spectral changes in light emission from organic light emitting diode (OLEDs) structures, which have thin transparent films of opal photonic crystal (PC). The anode in such PC-OLED is laminated on opal layer from free standing optically transparent multiwall carbon nanotubes (T-CNT) sheets made by dry spinning from CVD grown forests. Silica and polystyrene opal films were grown on glass substrates by vertical sedimentation in colloids in thermal baths and the particle size of opal spheres ranges from 300 nm to 450 nm. The use of T-CNTs, (coated by PEDOT-PSS to avoid shorting) as hole injector, allows to eliminate the use of vacuum deposition of metals and permits to achieve tunneling hole injection regime from CNT tips into Alq^3 emission layer

  4. Stacking layered structure of polymer light emitting diodes prepared by evaporative spray deposition using ultradilute solution for improving carrier balance

    International Nuclear Information System (INIS)

    Aoki, Youichi; Shakutsui, Masato; Fujita, Katsuhiko

    2009-01-01

    Polymer light-emitting diodes (PLEDs) with staking layered structures are prepared by the evaporative spray deposition using ultradilute solution (ESDUS) method, which has enabled forming a polymer layer onto another polymer layer even if both polymers are soluble in a solvent used for the preparation. By this method, polymers having various HOMO and LUMO levels can be stacked as a hole transport layer, an emitting layer and an electron transport layer as commonly employed in small molecule-based organic light emitting diodes. Here we demonstrated that a PLED having a tri-layer structure using three kinds of polymers showed significant improvement in quantum efficiency compared with those having a single or bi-layer structure of corresponding polymers.

  5. Steady full colour white organic light-emitting devices consisting of an ultrathin red fluorescent layer

    International Nuclear Information System (INIS)

    Wen Wen; Yu Junsheng; Li Lu; Wang Jun; Jiang Yadong

    2009-01-01

    White organic light-emitting devices were fabricated using an ultrathin red fluorescent dye of 3-(dicyanomethylene)-5, 5-dimethyl-1-(4-dimethylamino-styryl)cyclohexene inserted in tris(8-quinolinolato) aluminium layer as a red and green emitting layer (EML) and a thin 4, 4'-bis(2, 2'-diphenylvinyl)-1, 1'-diphenyl (DPVBi) layer as blue EML. A maximum power efficiency of 2.4 lm W -1 at 5.5 V and a maximum luminance of 16 690 cd m -2 at 18.5 V were obtained. Pure white emission with a good colour rendering index of 80 was achieved as low as 5 V. The Commission Internationale de l'Eclairage (CIE) coordinates near (0.330, 0.300) show a slight variation of (-0.020, +0.002) in a wide range of voltages. The achievement of full colour white emission at low-operation voltages and high-colour stability is attributed to the confining emission zone function of the thin EML and direct carrier trapping in the ultrathin layer.

  6. Steady full colour white organic light-emitting devices consisting of an ultrathin red fluorescent layer

    Energy Technology Data Exchange (ETDEWEB)

    Wen Wen; Yu Junsheng; Li Lu; Wang Jun; Jiang Yadong [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: jsyu@uestc.edu.cn

    2009-01-07

    White organic light-emitting devices were fabricated using an ultrathin red fluorescent dye of 3-(dicyanomethylene)-5, 5-dimethyl-1-(4-dimethylamino-styryl)cyclohexene inserted in tris(8-quinolinolato) aluminium layer as a red and green emitting layer (EML) and a thin 4, 4'-bis(2, 2'-diphenylvinyl)-1, 1'-diphenyl (DPVBi) layer as blue EML. A maximum power efficiency of 2.4 lm W{sup -1} at 5.5 V and a maximum luminance of 16 690 cd m{sup -2} at 18.5 V were obtained. Pure white emission with a good colour rendering index of 80 was achieved as low as 5 V. The Commission Internationale de l'Eclairage (CIE) coordinates near (0.330, 0.300) show a slight variation of (-0.020, +0.002) in a wide range of voltages. The achievement of full colour white emission at low-operation voltages and high-colour stability is attributed to the confining emission zone function of the thin EML and direct carrier trapping in the ultrathin layer.

  7. Enhancement of efficiency and stability of phosphorescent OLEDs based on heterostructured light-emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Byung Doo, E-mail: bdchin@dankook.ac.kr [Department of Polymer Science and Engineering and Center for Photofunctional Energy Materials, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of)

    2011-03-23

    The light-emitting efficiency and stability of a phosphorescent organic light-emitting device (OLED), whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by heterostructured emissive layers, are studied. The variation of the material combination of the heterostructured emitter, both for mixed and double layer configuration, affects the charge injection behaviour, luminous efficiency and stability. Both double and mixed emitter configurations yield low-voltage and high-efficiency behaviour (51 lm W{sup -1} at 1000 cd m{sup -2}; 30 lm W{sup -1} at 10 000 cd m{sup -2}). Such an improvement in power efficiency at elevated brightness is sufficiently universal, while the enhancement of device half-lifetime is rather sensitive to the circumstantial layout of heterostructural emitters. With an optimal mixture of hole-transport type and electron-transport type, a half-lifetime of more than 2500 h at 4000 cd m{sup -2} is obtained, which is 8 times the half-lifetime of control devices with a single emitter structure. The origin and criterion for enhancement of efficiency and lifetime are discussed in terms of the carrier transport behaviour with a specific device architecture.

  8. 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.

  9. Efficient red phosphorescent organic light emitting diodes with double emission layers

    International Nuclear Information System (INIS)

    Ben Khalifa, M; Mazzeo, M; Maiorano, V; Mariano, F; Carallo, S; Melcarne, A; Cingolani, R; Gigli, G

    2008-01-01

    We demonstrate efficient red phosphorescent organic light emitting diodes with a bipolar emission structure (D-EML) formed by two different layers doped with a red phosphorescent dye. Due to its self-balancing character, the recombination zone is shifted far from the emission/carrier-blocking-layer interfaces. This prevents the accumulation of carriers at the interfaces and reduces the triplet-triplet annihilation, resulting in an improved efficiency of the D-EML device compared with the standard single-EML architecture. However, a current efficiency of 8.4 cd A -1 at 10 mA cm -2 is achieved in the D-EML device compared with 3.7 cd A -1 in the single-EML device

  10. Efficient red phosphorescent organic light emitting diodes with double emission layers

    Energy Technology Data Exchange (ETDEWEB)

    Ben Khalifa, M; Mazzeo, M; Maiorano, V; Mariano, F; Carallo, S; Melcarne, A; Cingolani, R; Gigli, G [NNL, National Nanotechnology Laboratory of CNR-INFM, Distretto tecnologico ISUFI, Universita del Salento, Italy, Via per Arnesano, Km.5, 73100 Lecce (Italy)], E-mail: mohamed.benkhalifa@unile.it

    2008-08-07

    We demonstrate efficient red phosphorescent organic light emitting diodes with a bipolar emission structure (D-EML) formed by two different layers doped with a red phosphorescent dye. Due to its self-balancing character, the recombination zone is shifted far from the emission/carrier-blocking-layer interfaces. This prevents the accumulation of carriers at the interfaces and reduces the triplet-triplet annihilation, resulting in an improved efficiency of the D-EML device compared with the standard single-EML architecture. However, a current efficiency of 8.4 cd A{sup -1} at 10 mA cm{sup -2} is achieved in the D-EML device compared with 3.7 cd A{sup -1} in the single-EML device.

  11. Fabrication of White Organic Light Emitting Diode Using Two Types of Zn-Complexes as an Emitting Layer.

    Science.gov (United States)

    Kim, Dong-Eun; Kwon, Young-Soo; Shin, Hoon-Kyu

    2015-01-01

    We have studied white OLED using two types of Zn-complexes as an emitting layer. We synthesized brand new two emissive materials, Zn(HPQ)2 as a yellow emitting material and Zn(HPB)2 as a blue emitting material. The Zn-complexes are low-molecular compounds and stable thermally. The fundamental structures of the fabricated OLED was ITO/NPB (40 nm)/Zn(HPB)2 (30 nm)/Zn(HPQ)2/LiF/Al. We varied the thickness of the Zn(HPQ)2 layer by 20, 30, and 40 nm. When the thickness of the Zn(HPQ)2 layer was 20 nm, the white emission was achieved. The maximum luminance was 12,000 cd/m2 at a current density of 800 mA/cm2. The CIE coordinates of the white emission were (0.319, 0.338) at an applied voltage of 10 V.

  12. Enhancement of efficiencies for tandem green phosphorescent organic light-emitting devices with a p-type charge generation layer

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Byung Soo; Jeon, Young Pyo; Lee, Dae Uk; Kim, Tae Whan, E-mail: twk@hanayng.ac.kr

    2014-10-15

    The operating voltage of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was improved by 3% over that of the organic light-emitting device with a molybdenum trioxide layer. The maximum brightness of the tandem green phosphorescent organic light-emitting device at 21.9 V was 26,540 cd/m{sup 2}. The dominant peak of the electroluminescence spectra for the devices was related to the fac-tris(2-phenylpyridine) iridium emission. - Highlights: • Tandem OLEDs with CGL were fabricated to enhance their efficiency. • The operating voltage of the tandem OLED with a HAT-CN layer was improved by 3%. • The efficiency and brightness of the tandem OLED were 13.9 cd/A and 26,540 cd/m{sup 2}. • Efficiency of the OLED with a HAT-CN layer was lower than that with a MoO{sub 3} layer. - Abstract: Tandem green phosphorescent organic light-emitting devices with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile or a molybdenum trioxide charge generation layer were fabricated to enhance their efficiency. Current density–voltage curves showed that the operating voltage of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was improved by 3% over that of the corresponding organic light-emitting device with a molybdenum trioxide layer. The efficiency and the brightness of the tandem green phosphorescent organic light-emitting device were 13.9 cd/A and 26,540 cd/m{sup 2}, respectively. The current efficiency of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was lower by 1.1 times compared to that of the corresponding organic light-emitting device with molybdenum trioxide layer due to the decreased charge generation and transport in the 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer resulting from triplet–triplet exciton annihilation.

  13. High-performance organic light-emitting diodes comprising ultrastable glass layers

    Science.gov (United States)

    Rodríguez-Viejo, Javier

    2018-01-01

    Organic light-emitting diodes (OLEDs) are one of the key solid-state light sources for various applications including small and large displays, automotive lighting, solid-state lighting, and signage. For any given commercial application, OLEDs need to perform at their best, which is judged by their device efficiency and operational stability. We present OLEDs that comprise functional layers fabricated as ultrastable glasses, which represent the thermodynamically most favorable and, thus, stable molecular conformation achievable nowadays in disordered solids. For both external quantum efficiencies and LT70 lifetimes, OLEDs with four different phosphorescent emitters show >15% enhancements over their respective reference devices. The only difference to the latter is the growth condition used for ultrastable glass layers that is optimal at about 85% of the materials’ glass transition temperature. These improvements are achieved through neither material refinements nor device architecture optimization, suggesting a general applicability of this concept to maximize the OLED performance, no matter which specific materials are used. PMID:29806029

  14. White organic light-emitting diodes based on doped and ultrathin Rubrene layer

    Science.gov (United States)

    Li, Yi; Jiang, Yadong; Wen, Wen; Yu, Junsheng

    2010-10-01

    Based on a yellow fluorescent dye of 5, 6, 11, 12-tetraphenylnaphthacene (Rubrene), WOLEDs were fabricated, with doping structure and ultrathin layer structure utilized in the devices. By doping Rubrene into blue-emitting N,N'-bis-(1- naphthyl)-N,N'-biphenyl-1,1'-biphenyl-4,4'-diamine (NPB), the device with a structure of indium-tin-oxide (ITO)/NPB (40 nm)/NPB:Rubrene (0.25 wt%, 7 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (30 nm)/Mg:Ag exhibited a warm white light with Commissions Internationale De L'Eclairage (CIE) coordinates of (0.38, 0.41) at 12 V. The electroluminescent spectrum of the OLED consisted of blue and yellow fluorescent emissions, the intensity of blue emission increased gradually relative to the orange emission with increasing voltage. This is mainly due to the recombination zone shifted towards the anode side as the transmission rate of electrons grows faster than that of holes under higher bias voltage. A maximum luminance of 7300 cd/m2 and a maximum power efficiency of 0.57 lm/W were achieved. Comparatively, by utilizing ultrathin dopant layer, the device with a structure of ITO/NPB (40 nm)/Rubrene (0.3 nm)/NPB (7 nm)/BCP (30 nm)/Mg:Ag achieved a low turn-on voltage of 3 V and a more stable white light. The peaks of EL spectra located at 430 and 560 nm corresponding to the CIE coordinates of (0.32, 0.32) under bias voltage ranging from 5 to 15 V. A maximum luminance of 5630 cd/m2 and a maximum power efficiency of 0.6 lm/W were achieved. The balanced spectra were attributed to the stable confining of charge carriers and exciton by the thin emitting layers. Hence, with simple device structure and fabricating process, the device with ultrathin layer achieved low turn-on voltage, stable white light emitting and higher power efficiency.

  15. Efficiency of solution-processed multilayer polymer light-emitting diodes using charge blocking layers

    Science.gov (United States)

    Kasparek, Christian; Rörich, Irina; Blom, Paul W. M.; Wetzelaer, Gert-Jan A. H.

    2018-01-01

    By blending semiconducting polymers with the cross-linkable matrix ethoxylated-(4)-bisphenol-a-dimethacrylate (SR540), an insoluble layer is acquired after UV-illumination. Following this approach, a trilayer polymer light-emitting diode (PLED) consisting of a blend of poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD) and SR540 as an electron-blocking layer, Super Yellow-Poly(p-phenylene vinylene) (SY-PPV) blended with SR540 as an emissive layer, and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as a hole-blocking layer is fabricated from solution. The trilayer PLED shows a 23% increase in efficiency at low voltage as compared to a single layer SY-PPV PLED. However, at higher voltage, the advantage in current efficiency gradually decreases. A combined experimental and modelling study shows that the increased efficiency is not only due to the elimination of exciton quenching at the electrodes but also due to suppressed nonradiative trap-assisted recombination due to carrier confinement. At high voltages, holes can overcome the hole-blocking barrier, which explains the efficiency roll-off.

  16. All-solution processed composite hole transport layer for quantum dot light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoli [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Synergetic Innovation Center of Chemical Science and Engineering, Tianjin (China); Dai, Haitao, E-mail: htdai@tju.edu.cn [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Zhao, Junliang; Wang, Shuguo [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, School of Science, Tianjin University, Tianjin 300072 (China); Sun, Xiaowei [Department of Electrical & Electronic Engineering, South University of Science and Technology of China, Tangchang Road 1088, Shenzhen, Guangdong 518055 (China)

    2016-03-31

    In the present work, poly-TPD and TCTA composite hole transport layer (HTL) was employed in solution processed CdSe/ZnS quantum dot light emitting diodes (QLEDs). As the doping level of TCTA can determine the carriers transport efficiency of HTL, the proper mixing ratio of TCTA and poly-TPD should be found to optimize the performance of composite HTL for QLEDs. The doping of poly-TPD by low TCTA content can make its HOMO level lower and then reduce the energy barrier height from HTL to quantum dots (QDs), whereas the doping of poly-TPD by the concentrated TCTA results in the degraded performance of QLEDs due to its decreased hole transport mobility. By using the optimized composition with poly-TPD:TCTA (3:1) as the hole transport layer, the luminescence of the device exhibits about double enhancement compared with that of poly-TPD based device. The improvement of luminescence is mainly attributed to the lower energy barrier of hole injection. The Förster resonant energy transfer (FRET) mechanism in the devices was investigated through theoretical and experimental analysis and the results indicate that the TCTA doping makes no difference on FRET. Therefore, the charge injection mechanism dominates the improved performance of the devices. - Highlights: • Quantum dot light emitting diodes (QLEDs) were fabricated by all solution method. • The performance of QLEDs was optimized by varying the composite hole transport layer. • The blend HTL could promote hole injection by optimizing HOMO levels. • The energy transfer mechanism was analyzed by studying Förster resonant energy transfer process.

  17. Role of the inversion layer on the charge injection in silicon nanocrystal multilayered light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Tondini, S. [Nanoscience Laboratory, Department of Physics, University of Trento, Via Sommarive 14, 38123 Trento (Italy); Dipartimento di Fisica, Informatica e Matematica, Università di Modena e Reggio Emilia, Via Campi 213/a, 41125 Modena (Italy); Pucker, G. [Advanced Photonics and Photovoltaics Group, Bruno Kessler Foundation, Via Sommarive 18, 38123 Trento (Italy); Pavesi, L. [Nanoscience Laboratory, Department of Physics, University of Trento, Via Sommarive 14, 38123 Trento (Italy)

    2016-09-07

    The role of the inversion layer on injection and recombination phenomena in light emitting diodes (LEDs) is here studied on a multilayer (ML) structure of silicon nanocrystals (Si-NCs) embedded in SiO{sub 2}. Two Si-NC LEDs, which are similar for the active material but different in the fabrication process, elucidate the role of the non-radiative recombination rates at the ML/substrate interface. By studying current- and capacitance-voltage characteristics as well as electroluminescence spectra and time-resolved electroluminescence under pulsed and alternating bias pumping scheme in both the devices, we are able to ascribe the different experimental results to an efficient or inefficient minority carrier (electron) supply by the p-type substrate in the metal oxide semiconductor LEDs.

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

    International Nuclear Information System (INIS)

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

    2007-01-01

    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(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-O 3 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. White light emission from organic-inorganic hererostructure devices by using CdSe quantum dots as emitting layer

    International Nuclear Information System (INIS)

    Tang Aiwei; Teng Feng; Gao Yinhao; Li Dan; Zhao Suling; Liang Chunjun; Wang Yongsheng

    2007-01-01

    In this paper, white light emission was obtained from organic-inorganic heterostructure devices by using CdSe quantum dots as emitting layer, in which CdSe quantum dots were synthesized via a colloidal chemical approach by using CdO and Se powder as precursors. Photoluminescence of CdSe quantum dots demonstrated a white emission with a full wavelength at half maximum (FWHM) of about 200 nm under ambient conditions, and the white emission could be observed in both multilayer device ITO/PEDOT:PSS/CdSe/BCP/Alq 3 /Al and single-layer device: ITO/PEDOT:PSS/CdSe/Al. The broad emission was attributed to the inhomogeneous broadening. The CIE coordinates of the multilayer device were x=0.35 and y=0.40. The white-light-emitting diodes with CdSe quantum dots as the emitting layer are potentially useful in lighting applications

  20. 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.

  1. 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.

  2. Enhancing Carrier Injection Using Graded Superlattice Electron Blocking Layer for UVB Light-Emitting Diodes

    KAUST Repository

    Janjua, Bilal

    2014-12-01

    We have studied enhanced carrier injection by having an electron blocking layer (EBL) based on a graded superlattice (SL) design. Here, we examine, using a selfconsistent 6 × 6 k.p method, the energy band alignment diagrams under equilibrium and forward bias conditions while also considering carrier distribution and recombination rates (Shockley-Read-Hall, Auger, and radiative recombination rates). The graded SL is based on AlxGa1-xN (larger bandgap) Al0:5Ga0:5N (smaller bandgap) SL, where x is changed from 0.8 to 0.56 in steps of 0.06. Graded SL was found to be effective in reducing electron leakage and enhancing hole injection into the active region. Due to our band engineering scheme for EBL, four orders-of-magnitude enhancement were observed in the direct recombination rate, as compared with the conventional bulk EBL consisting of Al0:8Ga0:2N. An increase in the spatial overlap of carrier wavefunction was obtained due to polarization-induced band bending in the active region. An efficient single quantum-well ultraviolet-B light-emitting diode was designed, which emits at 280 nm. This is the effective wavelength for water disinfection application, among others.

  3. [Multiplayer white organic light-emitting diodes with different order and thickness of emission layers].

    Science.gov (United States)

    Xu, Wei; Lu, Fu-Han; Cao, Jin; Zhu, Wen-Qing; Jiang, Xue-Yin; Zhang, Zhi-Lin; Xu, Shao-Hong

    2008-02-01

    In multilayer OLED devices, the order and thickness of the emission layers have great effect on their spectrum. Based on the three basic colours of red, blue and green, a series of white organic light-emitting diodes(WOLEDS)with the structure of ITO/CuPc(12 nm)/NPB(50 nm)/EML/LiF(1 nm)/Al(100 nm) and a variety of emission layer's orders and thicknesses were fabricated. The blue emission material: 2-t-butyl-9,10-di-(2-naphthyl)anthracene (TBADN) doped with p-bis(p-N, N-diphenyl-amono-styryl)benzene(DSA-Ph), the green emission material: tris-[8-hydroxyquinoline]aluminum(Alq3) doped with C545, and the red emission material: tris-[8-hydroxyquinoline]aluminum( Alq3) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) were used. By adjusting the order and thickness of each emission layer in the RBG structure, we got a white OLED with current efficiency of 5.60 cd x A(-1) and Commission Internationale De L'Eclairage (CIE) coordinates of (0. 34, 0.34) at 200 mA x cm(-2). Its maximum luminance reached 20 700 cd x m(-2) at current density of 400 mA x cm(-2). The results were analyzed on the basis of the theory of excitons' generation and diffusion. According to the theory, an equation was set up which relates EL spectra to the luminance efficiency, the thickness of each layer and the exciton diffusion length. In addition, in RBG structure with different thickness of red layer, the ratio of th e spectral intensity of red to that of blue was calculated. It was found that the experimental results are in agreement with the theoretical values.

  4. Influence of emissive layer thickness on electrical characteristics of polyfluorene copolymer based polymer light emitting diodes

    International Nuclear Information System (INIS)

    Das, D; Gopikrishna, P; Singh, A; Dey, A; Iyer, P K

    2016-01-01

    Polymer light emitting diodes (PLEDs) with a device configuration of ITO/PEDOT:PSS/PFONPN01 [Poly [2,7-(9,9’-dioctylfluorene)-co-N-phenyl-1,8-naphthalimide (99:01)]/LiF/Al have been fabricated by varying the emissive layer (EML) thickness (40/65/80/130 nm) and the influence of EML thickness on the electrical characteristics of PLED has been studied. PLED can be modelled as a simple combination of resistors and capacitors. The impedance spectroscopy analysis showed that the devices with different EML thickness had different values of parallel resistance (R P ) and the parallel capacitance (C P ). The impedance of the devices is found to increase with increasing EML thickness resulting in an increase in the driving voltage. The device with an emissive layer thickness of 80nm, spin coated from a solution of concentration 15 mg/mL is found to give the best device performance with a maximum brightness value of 5226 cd/m 2 . (paper)

  5. Investigation of organic light-emitting diodes with novel organic electron injection layers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sunae; Sethuraman, Kunjithapatham; An, Jongdeok; Im, Chan [Konkuk University, Seoul (Korea, Republic of); Hwang, Boseon [Jinwoong Industrial Co. Ltd., Seoul (Korea, Republic of)

    2012-03-15

    1-(diphenyl-phosphinoyl)-4-(2,2-diphenyl-vinyl)-benzene (DpDvB) and 4-(diphenyl-phosphinoyl)-4'-(2,2-diphenyl-vinyl)-biphenyl (DpDvBp) have been prepared and used as efficient electron injection layers (EILs) between aluminum cathode and tris (8-hydroxyquinoline) aluminum organic light emitting diodes (OLED). The performances of devices with different thicknesses of DpDvB and DpDvBp were investigated. Experimental results show that the turn-on voltage of the devices was decreased and the luminance of the devices was enhanced with increasing thickness of the EILs. Power efficiencies of 1.07 lm/W and 0.97 lm/W were obtained by inserting a 3-nm-thick EIL of DpDvB and a 5 nm thick EIL of DpDvBp, respectively. These efficiencies are comparable to that of the device using LiF as an EIL. The results prove that DpDvB and DpDvBp layers are also suitable for efficient EILs in OLEDs.

  6. Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

    International Nuclear Information System (INIS)

    Niu Qiaoli; Xu Yunhua; Jiang Jiaxing; Peng Junbiao; Cao Yong

    2007-01-01

    Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m 2 at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages

  7. Mobility balance in the light-emitting layer governs the polaron accumulation and operational stability of organic light-emitting diodes

    Science.gov (United States)

    Kim, Jae-Min; Lee, Chang-Heon; Kim, Jang-Joo

    2017-11-01

    Organic light-emitting diode (OLED) displays are lighter and more flexible, have a wider color gamut, and consume less power than conventional displays. Stable materials and the structural design of the device are important for OLED longevity. Control of charge transport and accumulation in the device is particularly important because the interaction of excitons and polarons results in material degradation. This research investigated the charge dynamics of OLEDs experimentally and by drift-diffusion modeling. Parallel capacitance-voltage measurements of devices provided knowledge of charge behavior at different driving voltages. A comparison of exciplex-forming co-host and single host structures established that the mobility balance in the emitting layers determined the amount of accumulated polarons in those layers. Consequently, an exciplex-forming co-host provides a superior structure in terms of device lifetime and efficiency because of its well-balanced mobility. Minimizing polaron accumulation is key to achieving long OLED device lifetimes. This is a crucial aspect of device physics that must be considered in the device design structure.

  8. Highly efficient red phosphorescent organic light-emitting diodes based on solution processed emissive layer

    International Nuclear Information System (INIS)

    Liu, Baiquan; Xu, Miao; Tao, Hong; Ying, Lei; Zou, Jianhua; Wu, Hongbin; Peng, Junbiao

    2013-01-01

    Highly efficient red phosphorescent organic polymer light-emitting diodes (PhOLEDs) were fabricated based on a solution-processed small-molecule host 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) by doping an iridium complex, tris(1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine)iridium (III) (Ir(MPCPPZ) 3 ). A hole blocking layer 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBI) with a function of electron transport was thermally deposited onto the top of CBP layer. The diode with the structure of ITO/PEDOT:PSS (50 nm)/CBP:Ir(MPCPPZ) 3 (55 nm)/TPBI (30 nm)/Ba (4 nm)/Al (120 nm) showed an external quantum efficiency (QE ext ) of 19.3% and luminous efficiency (LE) of 18.3 cd/A at a current density of 0.16 mA/cm 2 , and Commission International de I'Eclairage (CIE) coordinates of (0.607, 0.375). It was suggested that the diodes using TPBI layer exhibited nearly 100% internal quantum efficiency and one order magnitude enhanced LE or QE ext efficiencies. -- Highlights: • Efficient red PhOLEDs based on a solution-processed small-molecule host were fabricated. • By altering volume ratio of chloroform/chlorobenzene solvent, we got best film quality of CBP. • EQE of the diode was 19.3%, indicating nearly 100% internal quantum yield was achieved

  9. Improved contrast polymer light-emitting diode with optical interference layers

    International Nuclear Information System (INIS)

    Liu, H.Y.; Sun, R.G.; Yang, K.X.; Peng, J.B.; Cao, Y.; Joo, S.K.

    2007-01-01

    An improved contrast polymer light diode based on the destructive optical interference layers deposited between the glass substrate and ITO anode is fabricated. It is unnecessary to be considered that the additional optical interference structure will impede carrier injection from the electrode to the carrier-transporting layer. Due to the quarter-wavelength thickness of medial ITO layer, the reflected light from first Cr layer is inverted 180 o out of phase with the reflected light from second Cr layer, resulting in the destructive interference. It is evident that the contrast ratio of the device with the optical interference structure is about three times higher than that of the conventional device

  10. High-Brightness Blue Light-Emitting Diodes Enabled by a Directly Grown Graphene Buffer Layer.

    Science.gov (United States)

    Chen, Zhaolong; Zhang, Xiang; Dou, Zhipeng; Wei, Tongbo; Liu, Zhiqiang; Qi, Yue; Ci, Haina; Wang, Yunyu; Li, Yang; Chang, Hongliang; Yan, Jianchang; Yang, Shenyuan; Zhang, Yanfeng; Wang, Junxi; Gao, Peng; Li, Jinmin; Liu, Zhongfan

    2018-06-08

    Single-crystalline GaN-based light-emitting diodes (LEDs) with high efficiency and long lifetime are the most promising solid-state lighting source compared with conventional incandescent and fluorescent lamps. However, the lattice and thermal mismatch between GaN and sapphire substrate always induces high stress and high density of dislocations and thus degrades the performance of LEDs. Here, the growth of high-quality GaN with low stress and a low density of dislocations on graphene (Gr) buffered sapphire substrate is reported for high-brightness blue LEDs. Gr films are directly grown on sapphire substrate to avoid the tedious transfer process and GaN is grown by metal-organic chemical vapor deposition (MOCVD). The introduced Gr buffer layer greatly releases biaxial stress and reduces the density of dislocations in GaN film and In x Ga 1- x N/GaN multiple quantum well structures. The as-fabricated LED devices therefore deliver much higher light output power compared to that on a bare sapphire substrate, which even outperforms the mature process derived counterpart. The GaN growth on Gr buffered sapphire only requires one-step growth, which largely shortens the MOCVD growth time. This facile strategy may pave a new way for applications of Gr films and bring several disruptive technologies for epitaxial growth of GaN film and its applications in high-brightness LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. 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.

  12. Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

    Energy Technology Data Exchange (ETDEWEB)

    Qian, L., E-mail: qian_lei@126.com; Xu, Z.; Teng, F.; Duan, X.-X. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China); Jin, Z.-S.; Du, Z.-L. [Henan University, Key Laboratory on special functional materials (China); Li, F.-S.; Zheng, M.-J. [State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Department of Physics (China); Wang, Y.-S. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China)

    2007-06-15

    Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

  13. Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

    Science.gov (United States)

    Qian, L.; Xu, Z.; Teng, F.; Duan, X.-X.; Jin, Z.-S.; Du, Z.-L.; Li, F.-S.; Zheng, M.-J.; Wang, Y.-S.

    2007-06-01

    Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)- p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

  14. Effect of the thickness of Zn(BTZ)2 emitting layer on the electroluminescent spectra of white organic light-emitting diodes

    International Nuclear Information System (INIS)

    Zhu, F.J.; Hua, Y.L.; Yin, S.G.; Deng, J.C.; Wu, K.W.; Niu, X.; Wu, X.M.; Petty, M.C.

    2007-01-01

    White organic light-emitting diodes (OLEDs) are fabricated with a simple bilayer structure: ITO/TPD/ Zn(BTZ) 2 /Al. White emission is composed of two parts: one is 470 nm, which originates from exciton emission in Zn(BTZ) 2 emitting layer; the other is 580 nm, which originates from exciplexes formation at the interface of TPD and Zn(BTZ) 2 . Specially, the thickness of Zn(BTZ) 2 layer effects the relative intensity of two emissions. When the Zn(BTZ) 2 layer becomes thin (or thick), the 470 nm (or 580 nm) emission intensity turns into weak (or strong). Finally, We successfully fabricated pure white OLED when the thickness of Zn(BTZ) 2 layer was 65 nm

  15. Effect of the thickness of Zn(BTZ){sub 2} emitting layer on the electroluminescent spectra of white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, F.J. [Institute of Material Physics, Tianjin University of Technology, Tianjin 300191 (China); Hua, Y.L. [Institute of Material Physics, Tianjin University of Technology, Tianjin 300191 (China)]. E-mail: yulinhua@tjut.edu.cn; Yin, S.G. [Institute of Material Physics, Tianjin University of Technology, Tianjin 300191 (China); Deng, J.C. [Institute of Material Physics, Tianjin University of Technology, Tianjin 300191 (China); Wu, K.W. [Institute of Material Physics, Tianjin University of Technology, Tianjin 300191 (China); Niu, X. [Institute of Material Physics, Tianjin University of Technology, Tianjin 300191 (China); Wu, X.M. [Institute of Modern Optics, Nankai University, Tianjin 300191 (China); Petty, M.C. [Centre for Molecular and Nanoscale Electronics, University of Durham, Durham DH1 3LE (United Kingdom)

    2007-01-15

    White organic light-emitting diodes (OLEDs) are fabricated with a simple bilayer structure: ITO/TPD/ Zn(BTZ){sub 2}/Al. White emission is composed of two parts: one is 470 nm, which originates from exciton emission in Zn(BTZ){sub 2} emitting layer; the other is 580 nm, which originates from exciplexes formation at the interface of TPD and Zn(BTZ){sub 2}. Specially, the thickness of Zn(BTZ){sub 2} layer effects the relative intensity of two emissions. When the Zn(BTZ){sub 2} layer becomes thin (or thick), the 470 nm (or 580 nm) emission intensity turns into weak (or strong). Finally, We successfully fabricated pure white OLED when the thickness of Zn(BTZ){sub 2} layer was 65 nm.

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

    Science.gov (United States)

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

    2016-09-01

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

  17. Moisture exposure to different layers in organic light-emitting diodes and the effect on electroluminescence characteristics

    International Nuclear Information System (INIS)

    Liao, L. S.; Tang, C. W.

    2008-01-01

    Moisture effect on electroluminescence characteristics, including current density versus voltage, luminance versus voltage, luminous efficiency versus current density, dark spot formation, and operational stability of organic light-emitting diodes, has been systematically investigated by exposing each layer of the devices to moisture at room temperature. Moisture has a different effect on each of the interfaces or surfaces, and the influence increases as exposure time increases. There is a slight effect on the electroluminescence characteristics after the anode surface has been exposed to moisture. However, severe luminance decrease, dark spot formation, and operational stability degradation take place after the light-emitting layer or the electron-transporting layer is exposed to moisture. It is also demonstrated that the effect of moisture can be substantially reduced if the exposure to moisture is in a dark environment

  18. Electroluminescence enhancement for near-ultraviolet light emitting diodes with graphene/AZO-based current spreading layers

    DEFF Research Database (Denmark)

    Lin, Li; Ou, Yiyu; Zhu, Xiaolong

    LEDs) have attracted significant research interest due to their intensive applications in various areas where indium tin oxide (ITO) is one of the most widely employed transparent conductive materials for NUV LEDs. Compared to ITO, indium-free aluminum-doped zinc oxide (AZO) has similar electrical......Near-ultraviolet light emitting diodes with different aluminum-doped zinc oxide-based current spreading layers were fabricated and electroluminescence (EL) was compared. A 170% EL enhancement was achieved by using a graphene-based interlayer. GaN-based near-ultraviolet light emitting diodes (NUV...... with a new type of current spreading layer (CSL) which combines AZO and a single-layer graphene (SLG) as an effective transparent CSL [1]. In the present work, LEDs with solo AZO CSL in Fig.1(a) and SLG/Ni/AZO-based CSL in Fig.1(b) were both fabricated for EL comparison. Standard mesa fabrication including...

  19. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    OpenAIRE

    Chen, Lei; Lin, Chun-Che; Yeh, Chiao-Wen; Liu, Ru-Shi

    2010-01-01

    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 incand...

  20. The use of light-emitting diodes (LED in commercial layer production

    Directory of Open Access Journals (Sweden)

    R Borille

    2013-06-01

    Full Text Available Artificial lighting is one of the most powerful management tools available to commercial layer producers. Artificial light allows anticipating or delaying the beginning of lay, improving egg production, and optimizing feed efficiency. This study aimed at comparing the performance of commercial layers submitted to lighting using different LED colors or conventional incandescent lamps. The study was carried out in a layer house divided in isolated environments in order to prevent any influenced from the neighboring treatments. In total, 360 Isa Brown layers, with an initial age of 56 weeks, were used. The following light sources were used: blue LED, yellow LED, green LED, red LED, white LED, and 40W incandescent light. Birds in all treatment were submitted to a 17-h continuous lighting program, and were fed a corn and soybean meal-based diet. A completely randomized experimental design with subplots was applied, with 24 treatments (six light sources and four periods of three replicates. Egg production (% was significantly different (p0.05 by light source. It was concluded that the replacement of incandescent light bulbs by white and red LEDs does not cause any negative effect on the egg production of commercial layers.

  1. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    CERN Document Server

    Morgado, J; Charas, A; Matos, M; Alcacer, L; Cacialli, F

    2003-01-01

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide.

  2. Self-assembly surface modified indium-tin oxide anodes for single-layer light-emitting diodes

    International Nuclear Information System (INIS)

    Morgado, Jorge; Barbagallo, Nunzio; Charas, Ana; Matos, Manuel; Alcacer, Luis; Cacialli, Franco

    2003-01-01

    We study the effect of indium-tin oxide surface modification by self assembling of highly polar molecules on the performance of single-layer light-emitting diodes (LEDs) fabricated with polyfluorene blends and aluminium cathodes. We find that the efficiency and light-output of such LEDs is comparable to, and sometimes better than, the values obtained for LEDs incorporating a hole injection layer of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid. This effect is attributed to the dipole-induced work function modification of indium-tin oxide

  3. Improved performance of GaN based light emitting diodes with ex-situ sputtered AlN nucleation layers

    Directory of Open Access Journals (Sweden)

    Shuo-Wei Chen

    2016-04-01

    Full Text Available The crystal quality, electrical and optical properties of GaN based light emitting diodes (LEDs with ex-situ sputtered physical vapor deposition (PVD aluminum nitride (AlN nucleation layers were investigated. It was found that the crystal quality in terms of defect density and x-ray diffraction linewidth was greatly improved in comparison to LEDs with in-situ low temperature GaN nucleation layer. The light output power was 3.7% increased and the reverse bias voltage of leakage current was twice on LEDs with ex-situ PVD AlN nucleation layers. However, larger compressive strain was discovered in LEDs with ex-situ PVD AlN nucleation layers. The study shows the potential and constrain in applying ex-situ PVD AlN nucleation layers to fabricate high quality GaN crystals in various optoelectronics.

  4. Efficient single light-emitting layer pure blue phosphorescent organic light-emitting devices with wide gap host and matched interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yunlong; Zhou, Liang, E-mail: zhoul@ciac.ac.cn; Cui, Rongzhen; Li, Yanan; Zhao, Xuesen; Zhang, Hongjie, E-mail: hongjie@ciac.ac.cn

    2015-12-15

    In this work, we report the highly efficient pure blue electroluminescent (EL) device based on bis[(3,5-difluoro-4-cyanophenyl)pyridine]picolinate iridium(III) (FCNIrpic) doped 9-(4-tert-Butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi) film. The matched energy levels of FCNIrpic and CzSi are helpful in facilitating the trapping of carriers, while the high triplet energy of CzSi can well avoid the undesired reverse energy transfer. More importantly, the injection of holes was further accelerated by inserting 5 nm 4,4′,4″-Tri(9-carbazoyl)triphenylamine (TcTa) film between hole transport layer and lighting-emitting layer (EML) as interlayer. Consequently, EL performances were significantly enhanced attributed to wider recombination zone and better balance of holes and electrons. Interestingly, single-EML device displayed higher performances than those of double-EMLs device. Finally, pure blue EL device with the structure of ITO/MoO{sub 3} (3 nm)/TAPC (40 nm)/TcTa (5 nm)/FCNIrpic (20%): CzSi (30 nm)/TmPyPB (40 nm)/LiF (1 nm)/Al (100 nm) realized the maximum brightness, current efficiency, power efficiency and external quantum efficiency up to 12,505 cd/m{sup 2}, 36.20 cd/A, 28.42 lm/W and 16.9%, respectively. Even at the high brightness of 1000 cd/m{sup 2}, current efficiency and external quantum efficiency up to 17.40 cd/A and 8.1%, respectively, can be retained by the same device.

  5. Light-Emitting Pickles

    Science.gov (United States)

    Vollmer, M.; Mollmann, K-P.

    2015-01-01

    We present experiments giving new insights into the classical light-emitting pickle experiment. In particular, measurements of the spectra and temperatures, as well as high-speed recordings, reveal that light emission is connected to the polarity of the electrodes and the presence of hydrogen.

  6. Improved performances of organic light-emitting diodes with mixed layer and metal oxide as anode buffer

    Science.gov (United States)

    Xue, Qin; Liu, Shouyin; Zhang, Shiming; Chen, Ping; Zhao, Yi; Liu, Shiyong

    2013-01-01

    We fabricated organic light-emitting devices (OLEDs) employing 2-methyl-9,10-di(2-naphthyl)-anthracene (MADN) as hole-transport material (HTM) instead of commonly used N,N'-bis-(1-naphthyl)-N,N'-diphenyl,1,1'-biphenyl-4,4'-diamine (NPB). After inserting a 0.9 nm thick molybdenum oxide (MoOx) layer at the indium tin oxide (ITO)/MADN interface and a 5 nm thick mixed layer at the organic/organic heterojunction interface, the power conversion efficiency of the device can be increased by 4-fold.

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

    International Nuclear Information System (INIS)

    Zhu, Wenqing; Xiao, Teng; Qian, Bingjie; Sun, Liangliang

    2015-01-01

    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)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-09-15

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

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

    International Nuclear Information System (INIS)

    Pereira, D.; Pinto, A.; Califórnia, A.; Gomes, J.; Pereira, L.

    2016-01-01

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

  10. Influence of co-deposited active layers on carrier transport and luminescent properties in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Murata, Masaya; Yamamoto, Takayuki; Haishi, Motoki; Ohtani, Naoki [Department of Electronics, Doshisha University, Tatara-Miyakodani, Kyotanabe-shi, Kyoto (Japan); Ando, Taro [Central Research Laboratory, Hamamatsu Photonics, Hirakuchi, Hamakita-ku, Hamamatsu-shi, Shizuoka (Japan)

    2009-01-15

    We have investigated the influence of a co-deposited active layer in organic light-emitting diodes (OLEDs) on carrier transport and optical properties to improve radiative characteristics of OLEDs. The co-deposited layer consists of two organic materials; one is a hole transport material (TPD) and the other is an electron transport/emissive material (Alq3). We evaluated current-voltage characteristics and electroluminescence (EL) properties of various samples in which the thicknesses and compound ratios of the co-deposited layers are different. The results indicate that the devices consisting of TPD:Alq3 co-deposited layer sandwiched between TPD and Alq3 layers exhibit lower starting voltages for the light emission than the sample of simple TPD/Alq3 heterojunction structure. In addition, the starting voltage is independent of the thickness of TPD:Alq3 co-deposited layer. These samples have two interfaces at both surfaces of TPD:Alq3 co-deposited layer. Thus, we estimated the radiative recombination occurs at the interfaces. Nevertheless, we found that the radiative recombination occurs only at the interface of TPD:Alq3 co-deposited layer and Alq3 layer. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Organic light emitting diode with light extracting electrode

    Energy Technology Data Exchange (ETDEWEB)

    Bhandari, Abhinav; Buhay, Harry

    2017-04-18

    An organic light emitting diode (10) includes a substrate (20), a first electrode (12), an emissive active stack (14), and a second electrode (18). At least one of the first and second electrodes (12, 18) is a light extracting electrode (26) having a metallic layer (28). The metallic layer (28) includes light scattering features (29) on and/or in the metallic layer (28). The light extracting features (29) increase light extraction from the organic light emitting diode (10).

  12. Improving the color purity and efficiency of blue organic light-emitting diodes (BOLED) by adding hole-blocking layer

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.J., E-mail: chien@nuk.edu.t [Department of Applied Physics, National University of Kaohsiung, 700 Kaohsiung University Road, Nan-Tzu, Kaohsiung, Taiwan (China); Kang, C.C. [Department of Electro-Optical Engineering, Southern Taiwan University of Technology, 1 Nan-Tai St., Yung-Kang City, Tainan, Taiwan (China); Lee, T.C. [Department of Electrical Engineering, Southern Taiwan University of Technology, 1 Nan-Tai St., Yung-Kang City, Tainan, Taiwan (China); Chen, W.R.; Meen, T.H. [Department of Electronic Engineering, National Formosa University, 64 Wen-Hwa Road, Hu-Wei, Yunlin, Taiwan (China)

    2009-11-15

    This work demonstrates the fabrication of a bright blue organic light-emitting diode (BOLED) with good color purity using 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi) and bathocuproine (BCP) as the emitting layer (EML) and the hole-blocking layer (HBL), respectively. Devices were prepared by vacuum deposition on indium tin oxide (ITO)-glass substrates. The thickness of DPVBi used in the OLED has an important effect on color and efficiency. The blue luminescence is maximal at 7670 cd/m{sup 2} when 13 V is applied and the BCP thickness is 2 nm. The CIE coordinate at a luminance of 7670 cd/m{sup 2} is (0.165, 0.173). Furthermore, the current efficiency is maximum at 4.25 cd/A when 9 V is applied.

  13. Improving the color purity and efficiency of blue organic light-emitting diodes (BOLED) by adding hole-blocking layer

    International Nuclear Information System (INIS)

    Huang, C.J.; Kang, C.C.; Lee, T.C.; Chen, W.R.; Meen, T.H.

    2009-01-01

    This work demonstrates the fabrication of a bright blue organic light-emitting diode (BOLED) with good color purity using 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi) and bathocuproine (BCP) as the emitting layer (EML) and the hole-blocking layer (HBL), respectively. Devices were prepared by vacuum deposition on indium tin oxide (ITO)-glass substrates. The thickness of DPVBi used in the OLED has an important effect on color and efficiency. The blue luminescence is maximal at 7670 cd/m 2 when 13 V is applied and the BCP thickness is 2 nm. The CIE coordinate at a luminance of 7670 cd/m 2 is (0.165, 0.173). Furthermore, the current efficiency is maximum at 4.25 cd/A when 9 V is applied.

  14. Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

    International Nuclear Information System (INIS)

    Lu, Yu-Hsuan; Pilkuhn, Manfred H.; Fu, Yi-Keng; Chu, Mu-Tao; Huang, Shyh-Jer; Su, Yan-Kuin; Wang, Kang L.

    2014-01-01

    The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL

  15. Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yu-Hsuan; Pilkuhn, Manfred H. [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Fu, Yi-Keng; Chu, Mu-Tao [Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China); Huang, Shyh-Jer, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States); Su, Yan-Kuin, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electronic Engineering, Kun-Shan University, Tainan 71003, Taiwan (China); Wang, Kang L. [Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States)

    2014-03-21

    The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

  16. Improvement of carrier transport and luminous efficiency of organic light emitting diodes by introducing a co-deposited active layer

    Energy Technology Data Exchange (ETDEWEB)

    Ohtani, Naoki; Murata, Masaya; Kashiwabara, Keiichiro; Kurata, Kazunori, E-mail: ohtani@mail.doshisha.ac.j [Department of Electronics, Doshisha University, 3-1 Tatara-Miyakodani, Kyotanabe-shi, Kyoto 610-0321 (Japan)

    2009-11-15

    We evaluated carrier transport and luminous efficiency of organic light-emitting diodes (OLEDs) whose active regions consist of a single co-deposited layer. One organic material is a hole transport material N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), while the other is an electron transport/emissive material Tris(8-hydroxyquinolinato)-aluminum (Alq3). It was found that the luminous efficiency strongly depends on the thickness and the ratio of the TPD:Alq3 co-deposited layer. This indicates that the carrier balance in the active region can be improved by changing the co-deposited layers. In addition, we performed the dye-doping method to clarify the recombination region. As a result, we found that the radiative recombination is caused in the whole TPD:Alq3 co-deposited layer.

  17. Highly Efficient White Organic Light-Emitting Diodes with Ultrathin Emissive Layers and a Spacer-Free Structure

    Science.gov (United States)

    Wu, Shengfan; Li, Sihua; Sun, Qi; Huang, Chenchao; Fung, Man-Keung

    2016-05-01

    Ultrathin emissive layers (UEMLs) of phosphorescent materials with a layer thickness of less than 0.3 nm were introduced for high-efficiency organic light-emitting diodes (OLEDs). All the UEMLs for white OLEDs can be prepared without the use of interlayers or spacers. Compared with devices fabricated with interlayers inserted in-between the UEMLs, our spacer-free structure not only significantly improves device efficiency, but also simplifies the fabrication process, thus it has a great potential in lowering the cost of OLED panels. In addition, its spacer-free structure decreases the number of interfaces which often introduce unnecessary energy barriers in these devices. In the present work, UEMLs of red, green and blue-emitting phosphorescent materials and yellow and blue phosphorescent emitters are utilized for the demonstration of spacer-free white OLEDs. Upon optimization of the device structure, we demonstrated spacer-free and simple-structured white-emitting OLEDs with a good device performance. The current and power efficiencies of our white-emitting devices are as high as 56.0 cd/A and 55.5 lm/W, respectively. These efficiencies are the highest ever reported for OLEDs fabricated with the UEML approach.

  18. Polymer light emitting diodes

    International Nuclear Information System (INIS)

    Gautier-Thianche, Emmmanuelle

    1998-01-01

    We study sandwich type semiconducting polymer light emitting diodes; anode/polymer/cathode. ITO is selected as anode, this polymer is a blend of a commercially available polymer with a high hole transport ability: polyvinyl-carbazole and a laser dye: coumarin-515. Magnesium covered with silver is chosen for the anode. We study the influence of polymer thickness and coumarin doping ratio on electroluminescence spectrum, electric characteristics and quantum efficiency. An important drawback is that diodes lifetime remains low. In the second part of our study we determine degradations causes with X-Ray reflectivity experiments. It may be due to ITO very high roughness. We realize a new type of planar electroluminescent device: a channel type electroluminescent device in which polymer layer is inserted into an aluminium channel. Such a device is by far more stable than using classical sandwich structures with the same polymer composition: indeed, charges are generated by internal-field ionization and there is no injection from the electrode to the polymer. This avoids electrochemical reactions at electrodes, thus reducing degradations routes. (author) [fr

  19. Improved organic light-emitting device with tris-(8-hydroxyquinoline) aluminium inserted between hole-injection layer and hole-transporting layer

    Energy Technology Data Exchange (ETDEWEB)

    Divayana, Y [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore (Singapore); Sun, X W [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore (Singapore); Chen, B J [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore (Singapore); Sarma, K R [Aerospace Electronic Systems, Honeywell, 21111 N 19th Avenue, Phoenix, AZ 85027 (United States)

    2007-01-07

    A layer of tris-(8-hydroxyquinoline) aluminium (Alq{sub 3}), which is normally used as an electron-transporting and emissive layer, was incorporated between the hole-transporting layer and the hole-injection layer to balance the electron-hole injection. The Alq{sub 3} layer performed to block the hole current which is a majority carrier in a typical organic light-emitting device. An increase in current efficiency by almost 30%, from 3.1 to 4.0 cd A{sup -1}, with a minimum voltage shift was achieved with a 2 nm Alq{sub 3} layer as a hole-blocking layer. A reduction in HTL thickness was observed to reduce the efficiency due to electron leakage to the HIL, whereby an inefficient exciplex emission was observed.

  20. Enhancing the performance of blue GaN-based light emitting diodes with carrier concentration adjusting layer

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yao; Huang, Yang; Wang, Junxi; Wang, Guohong [R& D Center for Semiconductor Lighting, Chinese Academy of Sciences, Beijing 100083,P. R. China (China); Liu, Zhiqiang, E-mail: lzq@semi.ac.cn, E-mail: spring@semi.ac.cn; Yi, Xiaoyan, E-mail: lzq@semi.ac.cn, E-mail: spring@semi.ac.cn; Li, Jinmin [R& D Center for Semiconductor Lighting, Chinese Academy of Sciences, Beijing 100083,P. R. China (China); State Key Laboratory of Solid State Lighting, Beijing 100083 (China); Beijing Engineering Research Center for the 3rd Generation Semiconductor Materials and Application, Beijing 100083 (China)

    2016-03-15

    In this work, a novel carrier concentration adjusting insertion layer for InGaN/GaN multiple quantum wells light-emitting diodes was proposed to mitigate the efficiency droop and improve optical output properties at high current density. The band diagrams and carrier distributions were investigated numerically and experimentally. The results indicate that due to the newly formed electron barrier and the adjusted built-in field near the active region, the hole injection has been improved and a better radiative recombination can be achieved. Compared to the conventional LED, the light output power of our new structure with the carrier concentration adjusting layers is enhanced by 127% at 350 mA , while the efficiency only droops to be 88.2% of its peak efficiency.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-03-30

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

  2. Device characteristics of organic light-emitting diodes based on electronic structure of the Ba-doped Alq3 layer.

    Science.gov (United States)

    Lim, Jong Tae; Kim, Kyung Nam; Yeom, Geun Young

    2009-12-01

    Organic light-emitting diodes (OLEDs) with a Ba-doped tris(8-quinolinolato)aluminum(III) (Alq3) layer were fabricated to reduce the barrier height for electron injection and to improve the electron conductivity. In the OLED consisting of glass/ITO/4,4',4"-tris[2-naphthylphenyl-1-phenylamino]triphenylamine (2-TNATA, 30 nm)/4,4'-bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (NPB, 18 nm)/Alq3 (42 nm)/Ba-doped Alq3 (20 nm, x%: x = 0, 10, 25, and 50)/Al (100 nm), the device with the Alq3 layer doped with 10% Ba showed the highest light out-coupling characteristic. However, as the Ba dopant concentration was increased from 25% to 50%, this device characteristic was largely reduced. The characteristics of these devices were interpreted on the basis of the chemical reaction between Ba and Alq3 and the electron injection property by analyzing the electronic structure of the Ba-doped Alq3 layer. At a low Ba doping of 10%, mainly the Alq3 radical anion species was formed. In addition, the barrier height for electron injection in this layer was decreased to 0.6 eV, when compared to the pristine Alq3 layer. At a high Ba doping of 50%, the Alq3 molecules were severely decomposed. When the Ba dopant concentration was changed, the light-emitting characteristics of the devices were well coincided with the formation mechanism of Alq3 radical anion and Alq3 decomposition species.

  3. Organic light-emitting diodes with F16CuPC as an efficient hole-injection layer

    International Nuclear Information System (INIS)

    Lee, H. K.; Shin, Y. C.; Kwon, D. S.; Lee, C. H.

    2006-01-01

    We report a new hole-injection material, copper hexadecafluorophthalocyanine (F 16 CuPC) for organic light-emitting diodes (OLEDs) consisting of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) as a hole-transport layer and 8-tris-hydroxyquinoline aluminum (Alq 3 ) as a light-emitting and electron-transport layer. The insertion of the F 16 CuPC between indium-tin oxide (ITO) and α-NPD reduces the operating voltage significantly and thereby increases the luminous efficiency. By measuring the device characteristics for various F 16 CuPC thicknesses, we find that an optimum F 16 CuPC thickness is about 15 nm. At a luminance of 1000 cd/m 2 , the device with 15-nm-thick F 16 CuPC shows a luminous efficiency of 1.5 lm/W and a device operating voltage of 7.2 V while the device without the F 16 CuPC layer shows 1.1 lm/W and 10.4 V. The significant decrease in a driving voltage and increase in the luminous efficiency can be attributed to the high hole-injection efficiency when F 16 CuPC is inserted between ITO and α-NPD.

  4. 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.

  5. High efficiency rubrene based inverted top-emission organic light emitting devices with a mixed single layer

    International Nuclear Information System (INIS)

    Wang, Zhaokui; Lou, Yanhui; Naka, Shigeki; Okada, Hiroyuki

    2010-01-01

    Inverted top-emission organic light emitting devices (TEOLEDs) with a mixed single layer by mixing of electron transport materials (PyPySPyPy and Alq 3 ), hole transport material (α-NPD) and dope material (rubrene) were investigated. Maximum power efficiency of 3.5 lm/W and maximum luminance of 7000 cd/m 2 were obtained by optimizing the mixing ratio of PyPySPyPy:Alq 3 :α-NPD:rubrene=25:50:25:1. Luminance and power efficiency of mixed single layer device were two times improved compared to bi-layer heterojunction device and tri-layer heterojunction device. Lifetime test also shows that the mixed single layer device exhibits longer operational lifetimes of 343 h, which is three times longer than the 109 h for tri-layer device, and two times longer than the 158 h for bi-layer device. In addition, the maximum luminance and power efficiency were obtained at 20,000 cd/m 2 and 7.5 lm/W, respectively, when a TPD layer of 45 nm was capped onto the top metal electrode.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jonghee, E-mail: jonghee.lee@etri.re.kr [OLED Research Center, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01062 Dresden (Germany); Koh, Tae-Wook [Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea, Republic of); Cho, Hyunsu [OLED Research Center, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea, Republic of); Schwab, Tobias [Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01062 Dresden (Germany); Lee, Jae-Hyun [Department School of Global Convergence Studies, Hanbat National University, San 16-1, Duckmyoung-dong, Daejeon 305-719 (Korea, Republic of); Hofmann, Simone [Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01062 Dresden (Germany); Lee, Jeong-Ik [OLED Research Center, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Yoo, Seunghyup [Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea, Republic of); and others

    2015-06-15

    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{sup −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.

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

    International Nuclear Information System (INIS)

    Lee, Jonghee; Koh, Tae-Wook; Cho, Hyunsu; Schwab, Tobias; Lee, Jae-Hyun; Hofmann, Simone; Lee, Jeong-Ik; Yoo, Seunghyup

    2015-01-01

    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

  8. Bi-layer non-doped small-molecular white organic light-emitting diodes with high colour stability

    International Nuclear Information System (INIS)

    Chen Shuming; Kwok, Hoi-Sing; Zhao Zujin; Tang Benzhong; Wang Zhiming; Lu Ping; Gao Zhao; Ma Yuguang

    2011-01-01

    Bi-layer non-doped white organic light-emitting diodes (WOLEDs) with hole-transporting layer 4-(4-(1,2,2-triphenylvinyl)phenyl)-7-(5-(4-(1,2,2-triphenylvinyl)phenyl) thiophen-2yl)benzo[c][1,2,5]thiadiazole (BTPETTD) as a red emitter and electron-transporting layer 4,4'-bis(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)biphenyl (DDPi) as a blue emitter are demonstrated. The blue emission is due to direct recombination of excitons in DPPi, while the red emission originates not only from the direct recombination of excitons in BTPETTD but also from a colour down-conversion process by absorbing blue emission and re-emitting red photons. The combination of blue emission and red emission yields an efficient and extremely stable white colour, regardless of driving voltages. In our demonstration, a bi-layer WOLED with an efficiency of 4.2 cd A -1 at 1000 cd m -2 , 1931 Commision International de L'Eclairage coordinates of (0.31, 0.31) and a high colour rendering index of 92 over a wide range of driving voltages is obtained.

  9. Ordered conducting polymer multilayer films and its application for hole injection layers in organic light-emitting devices

    International Nuclear Information System (INIS)

    Xu Jianhua; Yang Yajie; Yu Junsheng; Jiang Yadong

    2009-01-01

    We reported a controlled architecture growth of layer-ordered multilayer film of poly(3,4-ethylene dioxythiophene) (PEDOT) via a modified Langmuir-Blodgett (LB) method. An in situ polymerization of 3,4-ethylene dioxythiophene (EDOT) monomer in multilayer LB film occurred for the formation of ordered conducting polymer embedded multilayer film. The well-distribution of conducting polymer particles was characterized by secondary-ion mass spectrometry (SIMS). The conducting film consisting of ordered PEDOT ultrathin layers was investigated as a hole injection layer for organic light-emitting diodes (OLEDs). The results showed that, compared to conventional spin-coating PEDOT film and electrostatic self-assembly (ESA) film, the improved performance of OLEDs was obtained after using ordered PEDOT LB film as hole injection layer. It also indicated that well-ordered structure of hole injection layer was attributed to the improvement of OLED performance, leading to the increase of charged carrier mobility in hole injection layer and the recombination rate of electrons and holes in the electroluminescent layer.

  10. Development of a Highly Efficient Hybrid White Organic-Light-Emitting Diode with a Single Emission Layer by Solution Processing.

    Science.gov (United States)

    Wu, Jun-Yi; Chen, Show-An

    2018-02-07

    We use a mixed host, 2,6-bis[3-(carbazol-9-yl)phenyl]pyridine blended with 20 wt % tris(4-carbazoyl-9-ylphenyl)amine, to lower the hole-injection barrier, along with the bipolar and high-photoluminescence-quantum-yield (Φ p = 84%), blue thermally activated delay fluorescence (TADF) material of 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine (DMAC-TRZ) as a blue dopant to compose the emission layer for the fabrication of a TADF blue organic-light-emitting diode (BOLED). The device is highly efficient with the following performance parameters: maximum brightness (B max ) = 57586 cd/m 2 , maximum current efficiency (CE max ) = 35.3 cd/A, maximum power efficiency (PE max ) = 21.4 lm/W, maximum external quantum efficiency (EQE max ) = 14.1%, and CIE coordinates (0.18, 0.42). This device has the best performance recorded among the reported solution-processed TADF BOLEDs and has a low efficiency roll-off: at brightness values of 1000 and 5000 cd/m 2 , its CEs are close, being 35.1 and 30.1 cd/A, respectively. Upon further doping of the red phosphor Ir(dpm)PQ 2 (emission peak λ max = 595 nm) into the blue emission layer, we obtained a TADF-phosphor hybrid white organic-light-emitting diode (T-P hybrid WOLED) with high performance: B max = 43594 cd/m 2 , CE max = 28.8 cd/A, PE max = 18.1 lm/W, and CIE coordinates (0.38, 0.44). This B max = 43594 cd/m 2 is better than that of the vacuum-deposited WOLED with a blue TADF emitter, 10000 cd/m 2 . This is also the first report on a T-P hybrid WOLED with a solution-processed emitting layer.

  11. High-efficiency green phosphorescent organic light-emitting diodes with double-emission layer and thick N-doped electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Nobuki, Shunichiro, E-mail: shunichiro.nobuki.nb@hitachi.com [Hitachi Research Laboratory, Hitachi Ltd., 7-1-1 Omika-cho, Hitachi-city, Ibaraki 319-1292 (Japan); Wakana, Hironori; Ishihara, Shingo [Hitachi Research Laboratory, Hitachi Ltd., 7-1-1 Omika-cho, Hitachi-city, Ibaraki 319-1292 (Japan); Mikami, Akiyoshi [Dept. of Electrical Engineering, Kanazawa Institute of Technology, 7-1 Ohgigaoka, Nonoichimachi, Ishikawa 921-8501 (Japan)

    2014-03-03

    We have developed green phosphorescent organic light-emitting diodes (OLEDs) with high external quantum efficiency of 59.7% and power efficiency of 243 lm/W at 2.73 V at 0.053 mA/cm{sup 2}. A double emission layer and a thick n-doped electron transport layer were adopted to improve the exciton recombination factor. A high refractive index hemispherical lens was attached to a high refractive index substrate for extracting light trapped inside the substrate and the multiple-layers of OLEDs to air. Additionally, we analyzed an energy loss mechanism to clarify room for the improvement of our OLEDs including the charge balance factor. - Highlights: • We developed high efficiency green phosphorescent organic light-emitting diode (OLED). • Our OLED had external quantum efficiency of 59.7% and power efficiency of 243 lm/W. • A double emission layer and thick n-doped electron transport layer were adopted. • High refractive index media (hemispherical lens and substrate) were also used. • We analyzed an energy loss mechanism to clarify the charge balance factor of our OLED.

  12. Efficient and color-saturated inverted bottom-emitting organic light-emitting devices with a semi-transparent metal-assisted electron injection layer

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Meng-Huan, E-mail: kinneas.ac94g@nctu.edu.t [Department of Applied Chemistry, National Chiao Tung University, 210 R, CPT Building, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China); Wu, Chang-Yen [Department of Photonics, National Chiao Tung University, Hsinchu 300, Taiwan (China); Chen, Teng-Ming [Department of Applied Chemistry, National Chiao Tung University, 210 R, CPT Building, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China); Chen, Chin H. [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2011-01-15

    We report the development of highly efficient and color-saturated green fluorescent 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H, 11H-benzo[l]pyrano-[6,7,8-ij]quinolizin-11-one dye-doped inverted bottom-emitting organic light-emitting diode (IBOLED). This was enabled by the insertion of a silver (Ag) based semi-transparent metal-assisted electron injection layer between the ITO cathode and n-doped electron transporting layer. This IBOLED with ITO/Ag bilayer cathode with its synergistic microcavity effect achieved luminous efficiencies of 20.7 cd/A and 12.4 lm/W and a saturated CIE{sub x,y} of (0.22, 0.72) at 20 mA/cm{sup 2}, which are twice better than those of the conventional OLED and have over 60% improvement on IBOLED without ITO/Ag bilayer cathode.

  13. Carbazole/triarylamine based polymers as a hole injection/transport layer in organic light emitting devices.

    Science.gov (United States)

    Wang, Hui; Ryu, Jeong-Tak; Kwon, Younghwan

    2012-05-01

    This study examined the influence of the charge injection barriers on the performance of organic light emitting diodes (OLEDs) using polymers with a stepwise tuned ionization potential (I(p) approximately -5.01 - -5.29 eV) between the indium tin oxide (ITO) (phi approximately -4.8 eV) anode and tris(8-hydroxyquinolinato) aluminium (Alq3) (I(p) approximately -5.7 eV) layer. The energy levels of the polymers were tuned by structural modification. Double layer devices were fabricated with a configuration of ITO/polymer/Alq3/LiF/Al, where the polymers, Alq3, and LiF/Al were used as the hole injection/transport layer, emissive electron transport layer, and electron injection/cathode, respectively. Using the current density-voltage (J-V), luminescence-voltage (L-V) and efficiencies in these double layer devices, the device performance was evaluated in terms of the energy level alignments at the interfaces, such as the hole injection barriers (phi(h)(iTO/polymer) and phi(h)(polymer/Alq3)) from ITO through the polymers into the Alq3 layer, and the electron injection barrier (phi(e)(polymer/Alq3) or electron/exciton blocking barrier) at the polymer/Alq3 interface.

  14. Efficient white organic light-emitting devices using a thin 4,4'-bis(2,2'-diphenylvinyl)-1,1'-diphenyl layer

    International Nuclear Information System (INIS)

    Wang Jun; Yu Junsheng; Li Lu; Tang Xiaoqing; Jiang Yadong

    2008-01-01

    White organic light-emitting devices (OLEDs) were fabricated using phosphorescent material bis[2-(4-tert-butylphenyl)benzothiazolato-N,C 2' ]iridium (acetylacetonate) [(t-bt) 2 Ir(acac)] doped in 4,4'-bis(carbazol-9-yl) biphenyl (CBP) matrix as a yellow light-emitting layer and a thin layer 4,4'-bis(2,2'-diphenylvinyl)-1,1'-diphenyl (DPVBi) as the blue light-emitting layer. The light colour of the OLEDs can be adjusted by changing doped concentration and the thickness of the DPVBi thin layer. The maximum luminance and power efficiency of 5% doped device reached 15 460 cd m -2 and 8.1 lm W -1 , respectively. The 3% doped device showed the CIE coordinates of (0.344, 0.322) at 8 V and a maximum power efficiency of 5.7 lm W -1 at 4.5 V

  15. Magneto-electroluminescence effects in the single-layer organic light-emitting devices with macrocyclic aromatic hydrocarbons

    Directory of Open Access Journals (Sweden)

    S.-T. Pham

    2018-02-01

    Full Text Available Magneto-electroluminescence (MEL effects are observed in single-layer organic light-emitting devices (OLEDs comprising only macrocyclic aromatic hydrocarbons (MAHs. The fluorescence devices were prepared using synthesized MAHs, namely, [n]cyclo-meta-phenylene ([n]CMP, n = 5, 6. The MEL ratio of the resulting OLED is 1%–2% in the spectral wavelength range of 400-500 nm, whereas it becomes negative (−1.5% to −2% in the range from 650 to 700 nm. The possible physical origins of the sign change in the MEL are discussed. This wavelength-dependent sign change in the MEL ratio could be a unique function for future single-layer OLEDs capable of magnetic-field-induced color changes.

  16. All-inorganic quantum-dot light-emitting-diodes with vertical nickel oxide nanosheets as hole transport layer

    Directory of Open Access Journals (Sweden)

    Jiahui Li

    2016-10-01

    Full Text Available All-inorganic quantum dot light emitting diodes (QLEDs have gained great attention as a result of their high stability under oxygen-rich, humid and high current working conditions. In this work, we have fabricated an all-inorganic QLED device (FTO/NiO/QDs/AZO/Ag with sandwich-structure, wherein the inorganic metal oxides thin films of NiO and AZO were employed as hole and electron transport layers, respectively. The porous NiO layer with vertical lamellar nanosheets interconnected microstructure have been directly synthesized on the substrate of conductive FTO glass and increased the wettability of CdSe@ZnS QDs, which result in an enhancement of current transport performance of the QLED.

  17. Magneto-electroluminescence effects in the single-layer organic light-emitting devices with macrocyclic aromatic hydrocarbons

    Science.gov (United States)

    Pham, S.-T.; Ikemoto, K.; Suzuki, K. Z.; Izumi, T.; Taka, H.; Kita, H.; Sato, S.; Isobe, H.; Mizukami, S.

    2018-02-01

    Magneto-electroluminescence (MEL) effects are observed in single-layer organic light-emitting devices (OLEDs) comprising only macrocyclic aromatic hydrocarbons (MAHs). The fluorescence devices were prepared using synthesized MAHs, namely, [n]cyclo-meta-phenylene ([n]CMP, n = 5, 6). The MEL ratio of the resulting OLED is 1%-2% in the spectral wavelength range of 400-500 nm, whereas it becomes negative (-1.5% to -2%) in the range from 650 to 700 nm. The possible physical origins of the sign change in the MEL are discussed. This wavelength-dependent sign change in the MEL ratio could be a unique function for future single-layer OLEDs capable of magnetic-field-induced color changes.

  18. Efficiency improvement of flexible fluorescent and phosphorescent organic light emitting diodes by inserting a spin-coating buffer layer

    International Nuclear Information System (INIS)

    Tsai, Yu-Sheng; Wang, Shun-Hsi; Chen, Shen-Yaur; Su, Shin-Yuan; Juang, Fuh-Shyang

    2009-01-01

    We dissolved hole transport materials α-NPD and NPB in THF solvent, and spin-coated the α-NPD + THF or NPB + THF solution onto ITO anode surface to improve the luminance efficiency and lifetime of flexible fluorescent and phosphorescent organic light emitting diodes. Then the BCP and TPBi were employed as hole blocking layer (HBL) of phosphorescent device and its thickness was optimized. From the experimental results, the maximum luminance efficiency is 4.4 cd/A at 9 V of fluorescent device and 24.4 cd/A of phosphorescent device, respectively. Such an improvement in the device performance was attributed to the smoother surface and good contact between the interface of spin-coated HTL/ITO, the hole were effectively injected from the anode into the organic layer. And the deposited HTL can block excitons from diffusing into the anode to quench, thus improving the luminance efficiency and lifetime greatly.

  19. 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.

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

    International Nuclear Information System (INIS)

    Yang, Dan; Duan, Yahui; Yang, Yongqiang; Hu, Nan; Wang, Xiao; Sun, Fengbo; Duan, Yu

    2015-01-01

    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 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

  1. White light emission from an exciplex interface with a single emitting layer (Conference Presentation)

    Science.gov (United States)

    Bernal, Wilson; Perez-Gutierrez, Enrique; Agular, Andres; Barbosa G, J. Oracio C.; Maldonado, Jose L.; Meneses-Nava, Marco Antonio; Rodriguez Rivera, Mario A.; Rodriguez, Braulio

    2017-02-01

    Efficient solid state lighting devices based in inorganic emissive materials are now available in the market meanwhile for organic emissive materials still a lot of research work is in its way. [1,2] In this work a new organic emissive material based on carbazole, N-(4-Ethynylphenyl) carba-zole-d4 (6-d4), is used as electron-acceptor and commercial PEDOT:PSS as the electron-donor to obtain white emission. Besides the HOMO-LUMO levels of materials the white emission showed dependence on the films thicknesses and applied voltages. In here it is reported that by diminishing the thickness of the PEDOT:PSS layer, from 60 to 35 nm, and by keeping the derivative carbazole layer constant at 100 nm the electro-luminescence (EL) changed from emissive exciton states to the mixture of emissive exciton and exciplex states. [3] For the former thicknesses no white light was obtained meanwhile for the later the EL spectra broadened due to the emission of exciplex states. Under this condition, the best-achieved CIE coordinate was (0.31,0.33) with a driving voltage of 8 V. To lower the driving voltage of the devices a thin film of LiF was added between the derivative of carbazol and cathode but the CIE coordinates changed. The best CIE coordinates for this case were (0.29, 0.34) and (0.32, 0.37) with driving voltage of about 6.5 V. Acknowledgments: CeMie-Sol/27 (Mexico) 207450 References [1] Timothy L Dawson, Society of Dyers and Colourists, Color. Technol., 126, 1-10 (2010), doi: 10.1111/j.1478-4408.2010.00220.x [2] G. M. Farinola, R. Ragni, Journal of Solid State Lighting, 2:9 (2015), doi: 10.1186/s40539-015-0028-7. [3] E. Angioni, et al, J. Mater. Chem. C, 2016, 4, 3851, doi: 10.1039/c6tc00750c.

  2. Efficiency enhancement in a single emission layer yellow organic light emitting device: Contribution of CIS/ZnS quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Demir, Nuriye; Oner, Ilker; Varlikli, Canan, E-mail: canan.varlikli@ege.edu.tr; Ozsoy, Cihan; Zafer, Ceylan

    2015-08-31

    Electroluminescence (EL) efficiency from a single emission layer solution processed yellow emitting polymer, i.e. poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,10,3}-thiadiazole)] end-capped with dimethylphenyl (ADS233YE), is firstly enhanced by the optimization of stock polymer concentrations and the coating rates, and then with the addition of copper indium disulfide/zinc sulfide (CIS/ZnS) core/shell quantum dots (QDs). Using these bare core/shell QDs as the active layer in the studied device gave no EL at all. However, yellow EL with the maximum brightness of 56834 cd/m{sup 2}, maximum current efficiency of 4.7 cd/A and maximum power efficiency of 2.3 lm/W is obtained from the device structure of indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/ADS233YE:0.4 wt.% CIS/ZnS QD/Ca/Al those of which correspond to approximately 4 and 2 folds of enhancements in the brightness and luminous and power efficiency values, respectively, compared to that of the device without CIS/ZnS. - Highlights: • Copper indium disulfide/zinc sulfide (CIS/ZnS) particles are synthesized. • Polymer light emitting diode performance of a yellow emitting polymer is enhanced. • The presence of CIS/ZnS in active layer enhanced the power efficiency two folds. • Optimum concentration of CIS/ZnS in polymer is 0.4 wt.%.

  3. Efficiency enhancement in a single emission layer yellow organic light emitting device: Contribution of CIS/ZnS quantum dot

    International Nuclear Information System (INIS)

    Demir, Nuriye; Oner, Ilker; Varlikli, Canan; Ozsoy, Cihan; Zafer, Ceylan

    2015-01-01

    Electroluminescence (EL) efficiency from a single emission layer solution processed yellow emitting polymer, i.e. poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,10,3}-thiadiazole)] end-capped with dimethylphenyl (ADS233YE), is firstly enhanced by the optimization of stock polymer concentrations and the coating rates, and then with the addition of copper indium disulfide/zinc sulfide (CIS/ZnS) core/shell quantum dots (QDs). Using these bare core/shell QDs as the active layer in the studied device gave no EL at all. However, yellow EL with the maximum brightness of 56834 cd/m 2 , maximum current efficiency of 4.7 cd/A and maximum power efficiency of 2.3 lm/W is obtained from the device structure of indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/ADS233YE:0.4 wt.% CIS/ZnS QD/Ca/Al those of which correspond to approximately 4 and 2 folds of enhancements in the brightness and luminous and power efficiency values, respectively, compared to that of the device without CIS/ZnS. - Highlights: • Copper indium disulfide/zinc sulfide (CIS/ZnS) particles are synthesized. • Polymer light emitting diode performance of a yellow emitting polymer is enhanced. • The presence of CIS/ZnS in active layer enhanced the power efficiency two folds. • Optimum concentration of CIS/ZnS in polymer is 0.4 wt.%

  4. The effect of a charge control layer on the electroluminescent characteristic of blue and white organic light-emitting diodes.

    Science.gov (United States)

    Lee, Dong Hyung; Lee, Seok Jae; Koo, Ja-Ryong; Lee, Ho Won; Shin, Hyun Su; Lee, Song Eun; Kim, Woo Young; Lee, Kum Hee; Yoon, Seung Soo; Kim, Young Kwan

    2014-08-01

    We investigated blue fluorescent organic light-emitting diode (OLED) with a charge control layer (CCL) to produce high efficiency and improve the half-decay lifetime. Three types of devices (device A, B, and C) were fabricated following the number of CCLs within the emitting layer (EML), maintaining the thickness of whole EML. The CCL and host material, 2-methyl-9,10-di(2-naphthyl)anthracene, which has a bipolar property, was able to control the carrier movement with ease inside the EML. Device B demonstrated a maximum luminous efficiency (LE) and external quantum efficiency (EQE) of 9.19 cd/A and 5.78%, respectively. It also showed that the enhancement of the half-decay lifetime, measured at an initial luminance of 1,000 cd/m2, was 1.5 times longer than that of the conventional structure. A hybrid white OLED (WOLED) was also fabricated using a phosphorescent red emitter, bis(2-phenylquinoline)-acetylacetonate iridium III doped in 4,4'-N,N'-dicarbazolyl-biphenyl. The property of the hybrid WOLED with CCL showed a maximum LE and an EQE of 13.46 cd/A and 8.32%, respectively. It also showed white emission with Commission International de L'Éclairage coordinates of (x = 0.41, y = 0.33) at 10 V.

  5. Efficient Color-Stable Inverted White Organic Light-Emitting Diodes with Outcoupling-Enhanced ZnO Layer.

    Science.gov (United States)

    Zhao, Xin-Dong; Li, Yan-Qing; Xiang, Heng-Yang; Zhang, Yi-Bo; Chen, Jing-De; Xu, Lu-Hai; Tang, Jian-Xin

    2017-01-25

    Inverted organic light-emitting diode (OLED) has attracted extensive attention due to the demand in active-matrix OLED display panels as its geometry enables the direct connection with n-channel transistor backplane on the substrate. One key challenge of high-performance inverted OLED is an efficient electron-injection layer with superior electrical and optical properties to match the indium tin oxide cathode on substrate. We here propose a synergistic electron-injection architecture using surface modification of ZnO layer to simultaneously promote electron injection into organic emitter and enhance out-coupling of waveguided light. An efficient inverted white OLED is realized by introducing the nanoimprinted aperiodic nanostructure of ZnO for broadband and angle-independent light out-coupling and inserting an n-type doped interlayer for energy level tuning and injection barrier lowering. As a result, the optimized inverted white OLEDs have an external quantum efficiency of 42.4% and a power efficiency of 85.4 lm W 1- , which are accompanied by the superiority of angular color stability over the visible wavelength range. Our results may inspire a promising approach to fabricate high-efficiency inverted OLEDs for large-scale display panels.

  6. Highly transparent and conductive double-layer oxide thin films as anodes for organic light-emitting diodes

    International Nuclear Information System (INIS)

    Yang Yu; Wang Lian; Yan He; Jin Shu; Marks, Tobin J.; Li Shuyou

    2006-01-01

    Double-layer transparent conducting oxide thin film structures containing In-doped CdO (CIO) and Sn-doped In 2 O 3 (ITO) layers were grown on glass by metal-organic chemical vapor deposition and ion-assisted deposition (IAD), respectively, and used as anodes for polymer light-emitting diodes (PLEDs). These films have a very low overall In content of 16 at. %. For 180-nm-thick CIO/ITO films, the sheet resistance is 5.6 Ω/□, and the average optical transmittance is 87.1% in the 400-700 nm region. The overall figure of merit (Φ=T 10 /R sheet ) of the double-layer CIO/ITO films is significantly greater than that of single-layer CIO, IAD-ITO, and commercial ITO films. CIO/ITO-based PLEDs exhibit comparable or superior device performance versus ITO-based control devices. CIO/ITO materials have a much lower sheet resistance than ITO, rendering them promising low In content electrode materials for large-area optoelectronic devices

  7. Tandem organic light-emitting diodes with buffer-modified C60/pentacene as charge generation layer

    Science.gov (United States)

    Wang, Zhen; Zheng, Xin; Liu, Fei; Wang, Pei; Gan, Lin; Wang, Jing-jing

    2017-09-01

    Buffer-modified C60/pentacene as charge generation layer (CGL) is investigated to achieve effective performance of charge generation. Undoped green electroluminescent tandem organic light-emitting diodes (OLEDs) with multiple identical emissive units and using buffer-modified C60/pentacene organic semiconductor heterojunction (OHJ) as CGL are demonstrated to exhibit better current density and brightness, compared with conventional single-unit devices. The current density and brightness both can be significantly improved with increasing the thickness of Al. However, excessive thickness of Al seriously decreases the transmittance of films and damages the interface. As a result, the maximum current efficiency of 1.43 cd·A-1 at 30 mA·cm-2 can be achieved for tandem OLEDs with optimal thickness of Al. These results clearly demonstrate that Cs2CO3/Al is an effective buffer for C60/pentacene-based tandem OLEDs.

  8. Electrically conductive polyaniline as hole-injection layer for MEH-PPV:BT based polymer light emitting diodes

    International Nuclear Information System (INIS)

    Mohsennia, M.; Bidgoli, M. Massah; Boroumand, F. Akbari; Nia, A. Mohsen

    2015-01-01

    Graphical abstract: The PANI prepared at 15 °C with higher electrical conductivity has been used as hole-injection layer (HIL) in polymer light emitting diodes (PLEDs) with structure of ITO/PANI/MEHPPV:BT/Al. - Highlights: • Polyaniline (PANI) was synthesized at different temperatures (5, 10, 15, 20 and 25 °C). • The PANI sample with higher electrical conductivity was used as HIL in the PLED devices. • The PANI injection layer yielded higher current and lower turn-on voltage. • The effect of MEH-PPV:BT weight ratio on the PLED performance has been also investigated. • The J–V characteristics of the devices have been explained by FN tunneling model. - Abstract: Polyaniline (PANI) was synthesized by oxidative polymerization of aniline at different temperatures (5, 10, 15, 20 and 25 °C). The influence of polymerization temperature on sheet resistance of PANI was investigated, and the one prepared at 15 °C which showed lowest resistivity was chosen for further analysis. PANI was subsequently used as hole-injection layer (HIL) in polymer light emitting diodes (PLEDs) with structure of poly(ethylene terephthalate) (PET)/indium tin oxide (ITO)/PANI/MEH-PPV:BT/aluminum (Al). The PLEDs with emission layer made from a blend of poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and an electron transporting material, benzothiadiazole (BT), were fabricated at room conditions without using glove boxes. Our results showed an improvement in performance of our PANI-based fabricated PLEDs (PET/ITO/PANI/MEH-PPV:BT/Al) compared to the conventional devices that use poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PET/ITO/PEDOT:PSS/MEH-PPV:BT/Al) as their HIL. The hole injection barrier height (φ) of the fabricated PLEDs were then estimated using the Fowler–Nordheim (FN) field-emission tunneling theory and revealed that the barrier height decreases by increasing the BT concentration in the MEH-PPV:BT blend layer

  9. Fabrication and characterization of organic light-emitting diodes using zinc complexes as hole-blocking layer.

    Science.gov (United States)

    Kim, Won Sam; You, Jung Min; Lee, Burm-Jong; Jang, Yoon-Ki; Kim, Dong-Eun; Kwon, Young-Soo

    2006-11-01

    2-(2-Hydroxyphenyl)benzoxazole (HPB) was employed as organic ligand and the corresponding zinc complexes (Zn(HPB)2 and Zn(HPB)q) were synthesized. And their EL properties were characterized. The structures of zinc complexes were determined with FT-NMR, FT-IR, UV-Vis, and XPS. The thermal stability showed up to about 300 degrees C under nitrogen flow, which was measured by TGA. The photoluminescence (PL) of zinc complexes were measured from the DMF solution. The PL emitted in blue and yellow region, respectively. The EL devices were fabricated by the vacuum deposition. Two kinds of OLEDs devices were fabricated; ITO/NPB (40 nm)/Zn complexes (60 nm)/LiF/Al and ITO/NPB (40 nm)/Alq3 (60 nm)/Zn complexes (5 nm)/LiF/Al. Both of the EL properties as the emitting and the hole-blocking layer were investigated. The EL emission of Zn(HPB)q exhibited green light centered at 532 nm. The device showed a turn-on voltage at 5 V and a luminance of 6073 cd/m2 at 10 V. Meanwhile, the maximum EL the emission of the Zn(HPB)2 device was found to be at 447 nm. And the device showed a luminance of 2813 cd/m2 at 10 V. The ITO/NPB (40 nm)/Alq3 (60 nm)/Zn(HPB)2 (5 nm)/LiF/Al device showed increased luminance of L=17000 cd/m2 compared to L=12000 cd/m2 for similar device fabricated without the hole-blocking layer. And the turn-on voltage was significantly affected by the existence of the hole-blocking layer.

  10. Electroluminescence of organic light-emitting diodes consisting of an undoped (pbi)2Ir(acac) phosphorescent layer

    Science.gov (United States)

    Lei, Xia; Yu, Junsheng; Zhao, Juan; Jiang, Yadong

    2011-11-01

    The electroluminescence (EL) characteristics of phosphorescent organic light-emitting diodes (OLEDs) with an undoped bis(1,2-dipheny1-1H-benzoimidazole) iridium (acetylacetonate) [(pbi)2Ir(acac)] emissive layer (EML) of various film thicknesses were studied. The results showed that the intensity of green light emission decreased rapidly with the increasing thickness of (pbi)2Ir(acac), which was relevant to the triplet excimer emission. It suggested that the concentration quenching of monomer emission in the undoped (pbi)2Ir(acac) film was mainly due to the formation of triplet excimer and partly due to the triplet-triplet annihilation (TTA) and triplet-polaron annihilation (TPA). A green OLED with a maximum luminance of 26,531 cd/m2, a current efficiency of 36.2 cd/A, and a power efficiency of 32.4 lm/W was obtained, when the triplet excimer emission was eliminated. Moreover, the white OLED with low efficiency roll-off was realized due to the broadened recombination zone and reduced quenching effects in the EML when no electron blocking layer was employed.

  11. Enhanced polymer light-emitting diode property using fluorescent conducting polymer-reduced graphene oxide nanocomposite as active emissive layer

    Science.gov (United States)

    Singh, Jyoti Prakash; Saha, Uttam; Jaiswal, Rimpa; Anand, Raghubir Singh; Srivastava, Anurag; Goswami, Thako Hari

    2014-11-01

    The present article reports the polymer light-emitting diode property of the nanocomposite comprising poly 9,9-dioctyl fluorene- alt-bithiophene and reduced graphene oxide used as an emissive layer. Two times repetition of Hummers oxidation and hydrazine hydrate reduction method produce reduced graphene oxide (term as rGO2) with more uniform distribution in size and thickness. In addition, this uniquely synthesized rGO2 induces favorable shift in balance of electron and hole recombination zone toward the center of emissive layer owing to increase in in-plane crystallite size and high localize aromatic confinement. Five times increase in maximum device efficiency (Cd/A) and three times increase in maximum brightness (Cd/m2) are achieved with the LED device using nanocomposite as emissive layer compared to neat polymer. Also, the fabricated device requires relatively low turn-on voltage (4 V) because of low energy barrier between PEDOT work function (-5.0 eV) and HOMO levels of bi-thiophene copolymer -5.67 eV) and nanocomposite (-5.66 eV).

  12. Study of Sequential Dexter Energy Transfer in High Efficient Phosphorescent White Organic Light-Emitting Diodes with Single Emissive Layer

    Science.gov (United States)

    Kim, Jin Wook; You, Seung Il; Kim, Nam Ho; Yoon, Ju-An; Cheah, Kok Wai; Zhu, Fu Rong; Kim, Woo Young

    2014-11-01

    In this study, we report our effort to realize high performance single emissive layer three color white phosphorescent organic light emitting diodes (PHOLEDs) through sequential Dexter energy transfer of blue, green and red dopants. The PHOLEDs had a structure of; ITO(1500 Å)/NPB(700 Å)/mCP:Firpic-x%:Ir(ppy)3-0.5%:Ir(piq)3-y%(300 Å)/TPBi(300 Å)/Liq(20 Å)/Al(1200 Å). The dopant concentrations of FIrpic, Ir(ppy)3 and Ir(piq)3 were adjusted and optimized to facilitate the preferred energy transfer processes attaining both the best luminous efficiency and CIE color coordinates. The presence of a deep trapping center for charge carriers in the emissive layer was confirmed by the observed red shift in electroluminescent spectra. White PHOLEDs, with phosphorescent dopant concentrations of FIrpic-8.0%:Ir(ppy)3-0.5%:Ir(piq)3-0.5% in the mCP host of the single emissive layer, had a maximum luminescence of 37,810 cd/m2 at 11 V and a luminous efficiency of 48.10 cd/A at 5 V with CIE color coordinates of (0.35, 0.41).

  13. Monochromatic light-emitting diode (LED source in layers hens during the second production cycle

    Directory of Open Access Journals (Sweden)

    Rodrigo Borille

    2015-09-01

    Full Text Available ABSTRACTLight is an important environmental factor for birds, allowing not only their vision, but also influencing their physiological responses, such as behavioral and reproductive activity. The objective of this experiment was to evaluate the impact of different colors of monochromatic light (LED sources in laying hens production during the second laying cycle. The study was conducted in an experimental laying house during 70 days. A total of 300 laying hens Isa Brown® genetic strain, aged 95 weeks, in the second laying cycle were used in the study. The artificial light sources used were blue, yellow, green, red and white. The light regimen was continuous illumination of 17 h per day (12 h natural and 5 h artificial in a daily light regimen of 17L:5D (light: dark. The Latin Square design was adopted with five treatments (five colors divided into five periods, and five boxes, with six replicates of ten birds in each box. The production and egg quality were evaluated. The different colors of light source did not affect production parameters or egg quality (p > 0.05. The monochromatic light source may be considered as an alternative to artificial lighting in laying hens during the second production cycle.

  14. Efficiency enhancement of tandem organic light-emitting devices by a combined charge generation layer and organic n-type bis(ethylenedithio)-tetrathiafulvalene-doped electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jin Taek; Kim, Dae Hun; Koh, Eun Im; Kim, Tae Whan

    2014-11-03

    While the operating voltage of the tandem organic light-emitting devices (OLEDs) with both an organic p-type 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile charge generation layer and a bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF)-doped 1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene (TPBi) electron transport layer (ETL) was 1.3 V lower than that of the tandem OLEDs with a BEDT-TTF-undoped TPBi ETL. Luminance efficiency of the tandem OLEDs with a BEDT-TTF-doped TPBi ETL was 3.6 cd/A higher than that of the typical OLEDs. The increase in the luminance efficiency and the decrease in the operating voltage of the tandem OLEDs were attributed to improved electron injection due to the insertion of the BEDT-TTF-doped TPBi ETL. - Highlights: • Tandem organic light-emitting diodes (OLED) were fabricated. • OLED fabricated with an n-type bis(ethylenedithio)-tetrathiafulvalene. • Operating voltage of the tandem OLED was decreased from 19.8 to 18.5 V. • Luminance efficiency of the tandem OLED was increased from 31.8 to 35.4 cd/A. • Enhancement of the luminance efficiency in the tandem OLED was achieved.

  15. Efficiency enhancement of tandem organic light-emitting devices by a combined charge generation layer and organic n-type bis(ethylenedithio)-tetrathiafulvalene-doped electron transport layer

    International Nuclear Information System (INIS)

    Cho, Jin Taek; Kim, Dae Hun; Koh, Eun Im; Kim, Tae Whan

    2014-01-01

    While the operating voltage of the tandem organic light-emitting devices (OLEDs) with both an organic p-type 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile charge generation layer and a bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF)-doped 1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene (TPBi) electron transport layer (ETL) was 1.3 V lower than that of the tandem OLEDs with a BEDT-TTF-undoped TPBi ETL. Luminance efficiency of the tandem OLEDs with a BEDT-TTF-doped TPBi ETL was 3.6 cd/A higher than that of the typical OLEDs. The increase in the luminance efficiency and the decrease in the operating voltage of the tandem OLEDs were attributed to improved electron injection due to the insertion of the BEDT-TTF-doped TPBi ETL. - Highlights: • Tandem organic light-emitting diodes (OLED) were fabricated. • OLED fabricated with an n-type bis(ethylenedithio)-tetrathiafulvalene. • Operating voltage of the tandem OLED was decreased from 19.8 to 18.5 V. • Luminance efficiency of the tandem OLED was increased from 31.8 to 35.4 cd/A. • Enhancement of the luminance efficiency in the tandem OLED was achieved

  16. Light-emitting Si nanostructures formed by swift heavy ions in stoichiometric SiO2 layers

    Science.gov (United States)

    Kachurin, G. A.; Cherkova, S. G.; Marin, D. V.; Kesler, V. G.; Volodin, V. A.; Skuratov, V. A.

    2012-07-01

    Three hundred and twenty nanometer-thick SiO2 layers were thermally grown on the Si substrates. The layers were irradiated with 167 MeV Xe ions to the fluences ranging between 1012 cm-2 and 1014 cm-2, or with 700 MeV Bi ions in the fluence range of 3 × 1012-1 × 1013 cm-2. After irradiation the yellow-orange photoluminescence (PL) band appeared and grew with the ion fluences. In parallel optical absorption in the region of 950-1150 cm-1, Raman scattering and X-ray photoelectron spectroscopy evidenced a decrease in the number of Si-O bonds and an increase in the number of Si-coordinated atoms. The results obtained are interpreted as the formation of the light-emitting Si-enriched nanostructures inside the tracks of swift heavy ions through the disproportionation of SiO2. Ionization losses of the ions are regarded as responsible for the processes observed. Difference between the dependences of the PL intensity on the fluences of Xe and Bi ions are ascribed to their different stopping energy, therewith the diameters of the tracks of Xe and Bi ions were assessed as <3 nm and ˜10 nm, respectively. The observed shift of the PL bands, induced by Xe and Bi ions, agrees with the predictions of the quantum confinement theory.

  17. Light-emitting Si nanostructures formed by swift heavy ions in stoichiometric SiO{sub 2} layers

    Energy Technology Data Exchange (ETDEWEB)

    Kachurin, G.A., E-mail: kachurin@isp.nsc.ru [A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Cherkova, S.G. [A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Marin, D.V. [A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Kesler, V.G. [A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Volodin, V.A. [A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Skuratov, V.A. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)

    2012-07-01

    Three hundred and twenty nanometer-thick SiO{sub 2} layers were thermally grown on the Si substrates. The layers were irradiated with 167 MeV Xe ions to the fluences ranging between 10{sup 12} cm{sup -2} and 10{sup 14} cm{sup -2}, or with 700 MeV Bi ions in the fluence range of 3 Multiplication-Sign 10{sup 12}-1 Multiplication-Sign 10{sup 13} cm{sup -2}. After irradiation the yellow-orange photoluminescence (PL) band appeared and grew with the ion fluences. In parallel optical absorption in the region of 950-1150 cm{sup -1}, Raman scattering and X-ray photoelectron spectroscopy evidenced a decrease in the number of Si-O bonds and an increase in the number of Si-coordinated atoms. The results obtained are interpreted as the formation of the light-emitting Si-enriched nanostructures inside the tracks of swift heavy ions through the disproportionation of SiO{sub 2}. Ionization losses of the ions are regarded as responsible for the processes observed. Difference between the dependences of the PL intensity on the fluences of Xe and Bi ions are ascribed to their different stopping energy, therewith the diameters of the tracks of Xe and Bi ions were assessed as <3 nm and {approx}10 nm, respectively. The observed shift of the PL bands, induced by Xe and Bi ions, agrees with the predictions of the quantum confinement theory.

  18. Light-emitting Si nanostructures formed by swift heavy ions in stoichiometric SiO2 layers

    International Nuclear Information System (INIS)

    Kachurin, G.A.; Cherkova, S.G.; Marin, D.V.; Kesler, V.G.; Volodin, V.A.; Skuratov, V.A.

    2012-01-01

    Three hundred and twenty nanometer-thick SiO 2 layers were thermally grown on the Si substrates. The layers were irradiated with 167 MeV Xe ions to the fluences ranging between 10 12 cm −2 and 10 14 cm −2 , or with 700 MeV Bi ions in the fluence range of 3 × 10 12 –1 × 10 13 cm −2 . After irradiation the yellow–orange photoluminescence (PL) band appeared and grew with the ion fluences. In parallel optical absorption in the region of 950–1150 cm −1 , Raman scattering and X-ray photoelectron spectroscopy evidenced a decrease in the number of Si–O bonds and an increase in the number of Si-coordinated atoms. The results obtained are interpreted as the formation of the light-emitting Si-enriched nanostructures inside the tracks of swift heavy ions through the disproportionation of SiO 2 . Ionization losses of the ions are regarded as responsible for the processes observed. Difference between the dependences of the PL intensity on the fluences of Xe and Bi ions are ascribed to their different stopping energy, therewith the diameters of the tracks of Xe and Bi ions were assessed as <3 nm and ∼10 nm, respectively. The observed shift of the PL bands, induced by Xe and Bi ions, agrees with the predictions of the quantum confinement theory.

  19. Improved hole-injection and power efficiency of organic light-emitting diodes using an ultrathin cerium fluoride buffer layer

    Science.gov (United States)

    Lu, Hsin-Wei; Kao, Po-Ching; Chu, Sheng-Yuan

    2016-09-01

    In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF3 film as an ultra-thin buffer layer between the ITO and NPB hole transport layer, with the structure configuration ITO/CeF3 (1 nm)/NPB (40 nm)/Alq3 (60 nm)/LiF (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The work function increased from 4.8 eV (standard ITO electrode) to 5.2 eV (1-nm-thick UV-ozone treated CeF3 film deposited on the ITO electrode). The turn-on voltage decreased from 4.2 V to 4.0 V at 1 mA/cm2, the luminance increased from 7588 cd/m2 to 10820 cd/m2, and the current efficiency increased from 3.2 cd/A to 3.5 cd/A when the 1-nm-thick UV-ozone treated CeF3 film was inserted into the OLEDs.

  20. Color-tunable and stable-efficiency white organic light-emitting diode fabricated with fluorescent-phosphorescent emission layers

    International Nuclear Information System (INIS)

    Yang, Su-Hua; Shih, Po-Jen; Wu, Wen-Jie; Huang, Yi-Hua

    2013-01-01

    White organic light emitting diodes (OLEDs) were fabricated for color-tunable lighting applications. Fluorescent and phosphorescent hybrid emission layers (EMLs) were used to enhance the luminance and stability of the devices, which have blue-EML/CBP interlayer/green-EML/phosphorescent-sensitized-EML/red-EML structures. The influence of the composition and structure of the EMLs on the electroluminescence properties of the devices were investigated from the viewpoint of their emission spectra. The possible exciton harvesting, diffusion, transport, and annihilation processes occurring in the EMLs were also evaluated. A maximum luminance intensity of 7400 cd/m 2 and a highly stable current efficiency of 3.2 cd/A were obtained. Good color tunability was achieved for the white OLEDs; the chromatic coordinates linearly shifted from pure white (0.300, 0.398) to cold white (0.261, 0.367) when the applied voltage was varied from 10 to 14 V. -- Highlights: • Exciton harvesting, diffusion, transport, and annihilation processes were evaluated. • The electroluminescence properties were investigated from the viewpoint of the emission spectra. • Good color tunability and stable-efficiency were achieved for the white OLEDs

  1. Influence of PEDOT:PSS on the effectiveness of barrier layers prepared by atomic layer deposition in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wegler, Barbara, E-mail: barbara.wegler@siemens.com [Siemens AG, Corporate Technology, Guenther-Scharowsky-Strasse 1, 91058 Erlangen, Germany and Center for Medical Physics and Engineering, University of Erlangen-Nuremberg, Henkestrasse 91, 91052 Erlangen (Germany); Schmidt, Oliver [Siemens AG, Corporate Technology, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany); Hensel, Bernhard [Center for Medical Physics and Engineering, University of Erlangen-Nuremberg, Henkestrasse 91, 91052 Erlangen (Germany)

    2015-01-15

    Organic light emitting diodes (OLEDs) are well suited for energy saving lighting applications, especially when thinking about highly flexible and large area devices. In order to avoid the degradation of the organic components by water and oxygen, OLEDs need to be encapsulated, e.g., by a thin sheet of glass. As the device is then no longer flexible, alternative coatings are required. Atomic layer deposition (ALD) is a very promising approach in this respect. The authors studied OLEDs that were encapsulated by 100 nm Al{sub 2}O{sub 3} deposited by ALD. The authors show that this coating effectively protects the active surface area of the OLEDs from humidity. However, secondary degradation processes still occur at sharp edges of the OLED stack where the extremely thin encapsulation layer does not provide perfect coverage. Particularly, the swelling of poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate), which is a popular choice for the planarization of the bottom electrode and at the same time acts as a hole injection layer, affects the effectiveness of the encapsulation layer.

  2. Al/WO{sub 3}/Au as the interconnecting layer for efficient tandem white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hongmei; Dai Yanfeng; Ma Dongge [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Changchun 130022 (China)], E-mail: mdg1014@ciac.jl.cn

    2008-05-21

    White light emission from tandem organic light-emitting diodes consisting of blue and red light units separated by a transparent interconnecting layer of Al/WO{sub 3}/Au has been realized. The devices have a structure of indium-tin-oxide (ITO)/molybdenum oxide (MoO{sub 3}) (8 nm)/N, N'-di(naphthalene-1-yl)-N, N'-diphenyl-benzidine (NPB)(100 nm)/p-bis(p-N,N-diphenyl-aminostyryl)benzene) (DSA-ph):2-methyl-9,10-di(2-naphthyl) anthracene (MADN)(40 nm)/tris(8-hydroxylquinoline) aluminium (Alq{sub 3}) (10 nm)/LiF(1 nm)/Al(2 nm)/WO{sub 3}(3 nm)/Au(16 nm)/MoO{sub 3}(5 nm)/NPB(60 nm)/Alq{sub 3}: 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)(30 nm)/Alq{sub 3}(30 nm)/LiF(1 nm)/Al(150 nm). It can be seen that a stable white light emission, including 461 and 491 nm peaks from DSA-ph and 620 nm peak from DCJTB, with Commission International De L'Eclairage chromaticity coordinates from (0.35, 0.33) at 8 V to (0.37, 0.30) at 12 V was obtained. The current efficiency and brightness of the white devices are basically equal to the sum of the blue unit and red unit devices. The maximum brightness reached 20 700 cd m{sup -2} at a bias of 23 V, and the maximum current efficiency was 9.1 cd A{sup -1} at a current density of 0.41 mA cm{sup -2}. (fast track communication)

  3. Analysis of the Electrical Properties of an Electron Injection Layer in Alq3-Based Organic Light Emitting Diodes.

    Science.gov (United States)

    Kim, Soonkon; Choi, Pyungho; Kim, Sangsub; Park, Hyoungsun; Baek, Dohyun; Kim, Sangsoo; Choi, Byoungdeog

    2016-05-01

    We investigated the carrier transfer and luminescence characteristics of organic light emitting diodes (OLEDs) with structure ITO/HAT-CN/NPB/Alq3/Al, ITO/HAT-CN/NPB/Alq3/Liq/Al, and ITO/HAT-CN/NPB/Alq3/LiF/A. The performance of the OLED device is improved by inserting an electron injection layer (EIL), which induces lowering of the electron injection barrier. We also investigated the electrical transport behaviors of p-Si/Alq3/Al, p-Si/Alq3/Liq/Al, and p-Si/Alq3/LiF/Al Schottky diodes, by using current-voltage (L-V) and capacitance-voltage (C-V) characterization methods. The parameters of diode quality factor n and barrier height φ(b) were dependent on the interlayer materials between Alq3 and Al. The barrier heights φ(b) were 0.59, 0.49, and 0.45 eV, respectively, and the diode quality factors n were 1.34, 1.31, and 1.30, respectively, obtained from the I-V characteristics. The built in potentials V(bi) were 0.41, 0.42, and 0.42 eV, respectively, obtained from the C-V characteristics. In this experiment, Liq and LiF thin film layers improved the carrier transport behaviors by increasing electron injection from Al to Alq3, and the LiF schottky diode showed better I-V performance than the Liq schottky diode. We confirmed that a Liq or LiF thin film inter-layer governs electron and hole transport at the Al/Alq3 interface, and has an important role in determining the electrical properties of OLED devices.

  4. Comparison of light out-coupling enhancements in single-layer blue-phosphorescent organic light emitting diodes using small-molecule or polymer hosts

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yung-Ting [Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, Taiwan (China); Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 10617, Taiwan (China); Liu, Shun-Wei [Department of Electronic Engineering, Mingchi University of Technology, New Taipei, Taiwan 24301, Taiwan (China); Yuan, Chih-Hsien; Lee, Chih-Chien [Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10607, Taiwan (China); Ho, Yu-Hsuan; Wei, Pei-Kuen [Research Center for Applied Science Academia Sinica, Taipei, Taiwan 11527, Taiwan (China); Chen, Kuan-Yu [Chilin Technology Co., LTD, Tainan City, Taiwan 71758, Taiwan (China); Lee, Yi-Ting; Wu, Min-Fei; Chen, Chin-Ti, E-mail: cchen@chem.sinica.edu.tw, E-mail: chihiwu@cc.ee.ntu.edu.tw [Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, Taiwan (China); Wu, Chih-I, E-mail: cchen@chem.sinica.edu.tw, E-mail: chihiwu@cc.ee.ntu.edu.tw [Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 10617, Taiwan (China)

    2013-11-07

    Single-layer blue phosphorescence organic light emitting diodes (OLEDs) with either small-molecule or polymer hosts are fabricated using solution process and the performances of devices with different hosts are investigated. The small-molecule device exhibits luminous efficiency of 14.7 cd/A and maximum power efficiency of 8.39 lm/W, which is the highest among blue phosphorescence OLEDs with single-layer solution process and small molecular hosts. Using the same solution process for all devices, comparison of light out-coupling enhancement, with brightness enhancement film (BEF), between small-molecule and polymer based OLEDs is realized. Due to different dipole orientation and anisotropic refractive index, polymer-based OLEDs would trap less light than small molecule-based OLEDs internally, about 37% better based simulation results. In spite of better electrical and spectroscopic characteristics, including ambipolar characteristics, higher carrier mobility, higher photoluminescence quantum yield, and larger triplet state energy, the overall light out-coupling efficiency of small molecule-based devices is worse than that of polymer-based devices without BEF. However, with BEF for light out-coupling enhancement, the improved ratio in luminous flux and luminous efficiency for small molecule based device is 1.64 and 1.57, respectively, which are significantly better than those of PVK (poly-9-vinylcarbazole) devices. In addition to the theoretical optical simulation, the experimental data also confirm the origins of differential light-outcoupling enhancement. The maximum luminous efficiency and power efficiency are enhanced from 14.7 cd/A and 8.39 lm/W to 23 cd/A and 13.2 lm/W, respectively, with laminated BEF, which are both the highest so far for single-layer solution-process blue phosphorescence OLEDs with small molecule hosts.

  5. Comparison of light out-coupling enhancements in single-layer blue-phosphorescent organic light emitting diodes using small-molecule or polymer hosts

    International Nuclear Information System (INIS)

    Chang, Yung-Ting; Liu, Shun-Wei; Yuan, Chih-Hsien; Lee, Chih-Chien; Ho, Yu-Hsuan; Wei, Pei-Kuen; Chen, Kuan-Yu; Lee, Yi-Ting; Wu, Min-Fei; Chen, Chin-Ti; Wu, Chih-I

    2013-01-01

    Single-layer blue phosphorescence organic light emitting diodes (OLEDs) with either small-molecule or polymer hosts are fabricated using solution process and the performances of devices with different hosts are investigated. The small-molecule device exhibits luminous efficiency of 14.7 cd/A and maximum power efficiency of 8.39 lm/W, which is the highest among blue phosphorescence OLEDs with single-layer solution process and small molecular hosts. Using the same solution process for all devices, comparison of light out-coupling enhancement, with brightness enhancement film (BEF), between small-molecule and polymer based OLEDs is realized. Due to different dipole orientation and anisotropic refractive index, polymer-based OLEDs would trap less light than small molecule-based OLEDs internally, about 37% better based simulation results. In spite of better electrical and spectroscopic characteristics, including ambipolar characteristics, higher carrier mobility, higher photoluminescence quantum yield, and larger triplet state energy, the overall light out-coupling efficiency of small molecule-based devices is worse than that of polymer-based devices without BEF. However, with BEF for light out-coupling enhancement, the improved ratio in luminous flux and luminous efficiency for small molecule based device is 1.64 and 1.57, respectively, which are significantly better than those of PVK (poly-9-vinylcarbazole) devices. In addition to the theoretical optical simulation, the experimental data also confirm the origins of differential light-outcoupling enhancement. The maximum luminous efficiency and power efficiency are enhanced from 14.7 cd/A and 8.39 lm/W to 23 cd/A and 13.2 lm/W, respectively, with laminated BEF, which are both the highest so far for single-layer solution-process blue phosphorescence OLEDs with small molecule hosts

  6. Development of White-Light Emitting Active Layers in Nitride Based Heterostructures for Phosphorless Solid State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Jan Talbot; Kailash Mishra

    2007-12-31

    This report provides a summary of research activities carried out at the University of California, San Diego and Central Research of OSRAM SYLVANIA in Beverly, MA partially supported by a research contract from US Department of Energy, DE-FC26-04NT422274. The main objective of this project was to develop III-V nitrides activated by rare earth ions, RE{sup 3+}, which could eliminate the need for phosphors in nitride-based solid state light sources. The main idea was to convert electron-hole pairs injected into the active layer in a LED die to white light directly through transitions within the energy levels of the 4f{sup n}-manifold of RE{sup 3+}. We focused on the following materials: Eu{sup 3+}(red), Tb{sup 3+}(green), Er{sup 3+}(green), Dy{sup 3+}(yellow) and Tm{sup 3+}(blue) in AlN, GaN and alloys of AlN and GaN. Our strategy was to explore candidate materials in powder form first, and then study their behavior in thin films. Thin films of these materials were to be deposited on sapphire substrates using pulsed laser deposition (PLD) and metal organic vapor phase epitaxy (MOVPE). The photo- and cathode-luminescence measurements of these materials were used to investigate their suitability for white light generation. The project proceeded along this route with minor modifications needed to produce better materials and to expedite our progress towards the final goal. The project made the following accomplishments: (1) red emission from Eu{sup 3+}, green from Tb{sup 3+}, yellow from Dy{sup 3+} and blue from Tm{sup 3+} in AlN powders; (2) red emission from Eu{sup 3+} and green emission from Tb{sup 3+} in GaN powder; (3) red emission from Eu{sup 3+} in alloys of GaN and AlN; (4) green emission from Tb{sup 3+} in GaN thin films by PLD; (5) red emission from Eu{sup 3+} and Tb{sup 3+} in GaN thin films deposited by MOVPE; (6) energy transfer from host to RE{sup 3+}; (7) energy transfer from Tb{sup 3+} to Eu{sup 3+} in AlN powders; (8) emission from AlN powder samples

  7. Multilayered phosphorescent polymer light-emitting diodes using a solution-processed n-doped electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yuehua; Zhang, Mengke [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Zhang, Xinwen, E-mail: iamxwzhang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Lei, Zhenfeng; Zhang, Xiaolin; Hao, Lin; Fan, Quli [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Lai, Wenyong, E-mail: iamwylai@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Huang, Wei [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing 211816 (China)

    2017-06-15

    Efficient multilayered green phosphorescent polymer light-emitting devices (PhPLEDs) were successfully fabricated using a solution-processed n-doped small molecular electron transporting layer (ETL) composed of 1,3,5-tris(N-phenyl-benzimidazol-2-yl)-benzene (TPBi) and CsF. We found that the electroluminescence properties of the devices with n-doped ETLs are significantly improved. The maximum luminance efficiency of the device with 7.5 wt% CsF doped TPBi ETL reached 26.9 cd/A, which is 1.5 times as large as that of the undoped device. The impedance spectra of the devices and electron transport properties of the CsF doped ETLs demonstrate that doping dramatically decreases the impedance and enhances the electrical conductivity. Similarly, enhanced performance of PhPLED is also observed by use of CsF-doped 4,7-diphenyl-1,10 -phenanthroline (BPhen) ETL. These results demonstrate that CsF can be used as an effective n-dopant in solution-processed devices.

  8. Multilayered phosphorescent polymer light-emitting diodes using a solution-processed n-doped electron transport layer

    International Nuclear Information System (INIS)

    Chen, Yuehua; Zhang, Mengke; Zhang, Xinwen; Lei, Zhenfeng; Zhang, Xiaolin; Hao, Lin; Fan, Quli; Lai, Wenyong; Huang, Wei

    2017-01-01

    Efficient multilayered green phosphorescent polymer light-emitting devices (PhPLEDs) were successfully fabricated using a solution-processed n-doped small molecular electron transporting layer (ETL) composed of 1,3,5-tris(N-phenyl-benzimidazol-2-yl)-benzene (TPBi) and CsF. We found that the electroluminescence properties of the devices with n-doped ETLs are significantly improved. The maximum luminance efficiency of the device with 7.5 wt% CsF doped TPBi ETL reached 26.9 cd/A, which is 1.5 times as large as that of the undoped device. The impedance spectra of the devices and electron transport properties of the CsF doped ETLs demonstrate that doping dramatically decreases the impedance and enhances the electrical conductivity. Similarly, enhanced performance of PhPLED is also observed by use of CsF-doped 4,7-diphenyl-1,10 -phenanthroline (BPhen) ETL. These results demonstrate that CsF can be used as an effective n-dopant in solution-processed devices.

  9. Optical characterization of magnesium incorporation in p-GaN layers for core–shell nanorod light-emitting diodes

    Science.gov (United States)

    Gîrgel, I.; Šatka, A.; Priesol, J.; Coulon, P.-M.; Le Boulbar, E. D.; Batten, T.; Allsopp, D. W. E.; Shields, P. A.

    2018-04-01

    III-nitride nanostructures are of interest for a new generation of light-emitting diodes (LEDs). However, the characterization of doping incorporation in nanorod (NR) structures, which is essential for creating the p-n junction diodes, is extremely challenging. This is because the established electrical measurement techniques (such as capacitance–voltage or Hall-effect methods) require a simple sample geometry and reliable ohmic contacts, both of which are difficult to achieve in nanoscale devices. The need for homogenous, conformal n-type or p-type layers in core–shell nanostructures magnifies these challenges. Consequently, we demonstrate how a combination of non-contact methods (micro-photoluminescence, micro-Raman and cathodoluminescence), as well as electron-beam-induced-current, can be used to analyze the uniformity of magnesium incorporation in core–shell NRs and make a first estimate of doping levels by the evolution of band transitions, strain and current mapping. These techniques have been used to optimize the growth of core–shell nanostructures for electrical carrier injection, a significant milestone for their use in LEDs.

  10. Continuous blade coating for multi-layer large-area organic light-emitting diode and solar cell

    Science.gov (United States)

    Chen, Chun-Yu; Chang, Hao-Wen; Chang, Yu-Fan; Chang, Bo-Jie; Lin, Yuan-Sheng; Jian, Pei-Siou; Yeh, Han-Cheng; Chien, Hung-Ta; Chen, En-Chen; Chao, Yu-Chiang; Meng, Hsin-Fei; Zan, Hsiao-Wen; Lin, Hao-Wu; Horng, Sheng-Fu; Cheng, Yen-Ju; Yen, Feng-Wen; Lin, I.-Feng; Yang, Hsiu-Yuan; Huang, Kuo-Jui; Tseng, Mei-Rurng

    2011-11-01

    A continuous roll-to-roll compatible blade-coating method for multi-layers of general organic semiconductors is developed. Dissolution of the underlying film during coating is prevented by simultaneously applying heating from the bottom and gentle hot wind from the top. The solvent is immediately expelled and reflow inhibited. This method succeeds for polymers and small molecules. Uniformity is within 10% for 5 cm by 5 cm area with a mean value of tens of nanometers for both organic light-emitting diode (OLED) and solar cell structure with little material waste. For phosphorescent OLED 25 cd/A is achieved for green, 15 cd/A for orange, and 8 cd/A for blue. For fluorescent OLED 4.3 cd/A is achieved for blue, 9 cd/A for orange, and 6.9 cd/A for white. For OLED with 2 cm by 3 cm active area, the luminance variation is within 10%. Power conversion efficiency of 4.1% is achieved for polymer solar cell, similar to spin coating using the same materials. Very-low-cost and high-throughput fabrication of efficient organic devices is realized by the continuous blade-only method.

  11. Performance Improvement of GaN-Based Flip-Chip White Light-Emitting Diodes with Diffused Nanorod Reflector and with ZnO Nanorod Antireflection Layer

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The GaN-based flip-chip white light-emitting diodes (FCWLEDs with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. The light output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layer were improved from 21.15 mW to 23.90 mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively.

  12. Effects of the thickness of NiO hole transport layer on the performance of all-inorganic quantum dot light emitting diode

    International Nuclear Information System (INIS)

    Zhang, Xiao Li; Dai, Hai Tao; Zhao, Jun Liang; Li, Chen; Wang, Shu Guo; Sun, Xiao Wei

    2014-01-01

    All-inorganic quantum dot light emitting diodes (QLEDs) have recently gained great attention owing to their high stability under oxygenic, humid environment and higher operating currents. In this work, we fabricated all-inorganic CdSe/ZnS core-shell QLEDs composed of ITO/NiO/QDs/ZnO/Al, in which NiO and ZnO thin film deposited via all-solution method were employed as hole and electron transport layer, respectively. To achieve high light emitting efficiency, the balance transport between electrons and holes play a key role. In this work, the effects of the thickness of NiO film on the performance of QLEDs were explored experimentally in details. NiO layers with various thicknesses were prepared with different rotation speeds. Experimental results showed that thinner NiO layer deposited at higher rotation speed had higher transmittance and larger band gap. Four typical NiO thickness based QLEDs were fabricated to optimize the hole transport layer. Thinner NiO layer based device performs bright emission with high current injection, which is ascribed to the reduced barrier height between hole transport layer and quantum dot. - Highlights: • All-inorganic quantum dot light emitting diodes (QLEDs) were fabricated. • Thinner NiO film can effectively enhance on–off properties of devices. • Improved performance of QLEDs is mainly attributed to energy barrier reduction

  13. Enhanced optical output power of InGaN/GaN light-emitting diodes grown on a silicon (111) substrate with a nanoporous GaN layer.

    Science.gov (United States)

    Lee, Kwang Jae; Chun, Jaeyi; Kim, Sang-Jo; Oh, Semi; Ha, Chang-Soo; Park, Jung-Won; Lee, Seung-Jae; Song, Jae-Chul; Baek, Jong Hyeob; Park, Seong-Ju

    2016-03-07

    We report the growth of InGaN/GaN multiple quantum wells blue light-emitting diodes (LEDs) on a silicon (111) substrate with an embedded nanoporous (NP) GaN layer. The NP GaN layer is fabricated by electrochemical etching of n-type GaN on the silicon substrate. The crystalline quality of crack-free GaN grown on the NP GaN layer is remarkably improved and the residual tensile stress is also decreased. The optical output power is increased by 120% at an injection current of 20 mA compared with that of conventional LEDs without a NP GaN layer. The large enhancement of optical output power is attributed to the reduction of threading dislocation, effective scattering of light in the LED, and the suppression of light propagation into the silicon substrate by the NP GaN layer.

  14. Growth of light-emitting SiGe heterostructures on strained silicon-on-insulator substrates with a thin oxide layer

    Energy Technology Data Exchange (ETDEWEB)

    Baidakova, N. A., E-mail: banatale@ipmras.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Bobrov, A. I. [University of Nizhny Novgorod (Russian Federation); Drozdov, M. N.; Novikov, A. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Pavlov, D. A. [University of Nizhny Novgorod (Russian Federation); Shaleev, M. V.; Yunin, P. A.; Yurasov, D. V.; Krasilnik, Z. F. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2015-08-15

    The possibility of using substrates based on “strained silicon on insulator” structures with a thin (25 nm) buried oxide layer for the growth of light-emitting SiGe structures is studied. It is shown that, in contrast to “strained silicon on insulator” substrates with a thick (hundreds of nanometers) oxide layer, the temperature stability of substrates with a thin oxide is much lower. Methods for the chemical and thermal cleaning of the surface of such substrates, which make it possible to both retain the elastic stresses in the thin Si layer on the oxide and provide cleaning of the surface from contaminating impurities, are perfecte. It is demonstrated that it is possible to use the method of molecular-beam epitaxy to grow light-emitting SiGe structures of high crystalline quality on such substrates.

  15. 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.

  16. Nano-particle based scattering layers for optical efficiency enhancement of organic light-emitting diodes and organic solar cells

    Science.gov (United States)

    Chang, Hong-Wei; Lee, Jonghee; Hofmann, Simone; Hyun Kim, Yong; Müller-Meskamp, Lars; Lüssem, Björn; Wu, Chung-Chih; Leo, Karl; Gather, Malte C.

    2013-05-01

    The performance of both organic light-emitting diodes (OLEDs) and organic solar cells (OSC) depends on efficient coupling between optical far field modes and the emitting/absorbing region of the device. Current approaches towards OLEDs with efficient light-extraction often are limited to single-color emission or require expensive, non-standard substrates or top-down structuring, which reduces compatibility with large-area light sources. Here, we report on integrating solution-processed nano-particle based light-scattering films close to the active region of organic semiconductor devices. In OLEDs, these films efficiently extract light that would otherwise remain trapped in the device. Without additional external outcoupling structures, translucent white OLEDs containing these scattering films achieve luminous efficacies of 46 lm W-1 and external quantum efficiencies of 33% (both at 1000 cd m-2). These are by far the highest numbers ever reported for translucent white OLEDs and the best values in the open literature for any white device on a conventional substrate. By applying additional light-extraction structures, 62 lm W-1 and 46% EQE are reached. Besides universally enhancing light-extraction in various OLED configurations, including flexible, translucent, single-color, and white OLEDs, the nano-particle scattering film boosts the short-circuit current density in translucent organic solar cells by up to 70%.

  17. Organic Light-Emitting Diodes with Magnesium Doped CuPc as an Efficient Electron Injection Layer

    International Nuclear Information System (INIS)

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

    2008-01-01

    Bright organic electroluminescent devices are developed using a metal-doped organic layer intervening between the cathode and the emitting layer. The typical device structure is a glass substrate/indium-tin oxide (ITO)/copper phthalocyanine(CuPc)/N,N-bis-(1-naphthl)-diphenyl-1, 1'-biphenyl-4,4'-diamine (NPB)/Tris(8-quinolinolato) alu-minum(Alq 3 )/Mg-doped CuPc/Ag. At a driving voltage of 11 V, the device with a layer of Mg-doped CuPc (1:2 in weight) shows a brightness of 4312 cd/m 2 and a current efficiency of 2.52 cd/A, while the reference device exhibits 514 cd/m 2 and 1.25 cd/A

  18. Tandem organic light-emitting diodes with KBH4 doped 9,10-bis(3-(pyridin-3-yl)phenyl) anthracene connected to the charge generation layer.

    Science.gov (United States)

    Duan, Lian; Tsuboi, Taiju; Qiu, Yong; Li, Yanrui; Zhang, Guohui

    2012-06-18

    Tandem organic light emitting diodes (OLEDs) are ideal for lighting applications due to their low working current density at high brightness. In this work, we have studied an efficient electron transporting layer of KBH(4) doped 9,10-bis(3-(pyridin-3-yl)phenyl)anthracene (DPyPA) which is located adjacent to charge generation layer of MoO(3)/NPB. The excellent transporting property of the DPyPA:KBH(4) layer helps the tandem OLED to achieve a lower voltage than the tandem device with the widely used tris-(8-hydroxyquinoline)aluminum:Li. For the tandem white OLED with a fluorescent blue unit and a phosphorescent yellow unit, we've achieved a high current efficiency of 75 cd/A, which can be further improved to 120 cd/A by attaching a diffuser layer.

  19. Determination of an optimized Alq3 layer thickness in organic light-emitting diodes by using microcavity effects

    International Nuclear Information System (INIS)

    Jung, Boo-Young; Hwangbo, Chang-Kwon

    2006-01-01

    In this paper, an optical model of an organic light-emitting diode (OLED) based on the optical thin film theory is derived to calculate the output intensity of a small-molecule OLED. Two types of Alq 3 -based OLEDs are designed using the optical model and deposited to compare with the designed OLEDs. The optical model shows that the radiance of the OLED can be affected by the Fabry-Perot multiple beam interference effect, the two-beam interference effect, and the spontaneous emission spectrum of the emitting material. The measured spectral characteristics for the two types of OLEDs are found to be in good agreement with the simulation. The result suggests that the proposed optical model can be used for optimizing the architecture of small-molecule OLEDs.

  20. Effect of inserting of thin Rubrene layer on performance of Organic Light-Emitting Diodes based on Zn(BTz)2

    Science.gov (United States)

    Tomova, R. L.; Petrova, P. K.; Stoycheva-Topalova, R. T.

    2010-11-01

    Organic light-emitting diodes (OLEDs) with improved performances are fabricated using a thin (1 nm) yellow-emitting layer of 5,6,11,12-tetraphenylnaphthacene (Rubrene) inserted at different position in green emitting electroluminescent (EL) layer of bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTz)2) in configuration: ITO/PVK:TPD/ Zn(BTz)2 (x nm)/ Rubrene (1 nm)/ Zn(BTz)2 (75-x nm)/Al, where PVK:TPD is a hole transporting layer of N, N'-bis(3-methylphenyl)-N, N'-diphenylbenzidine (TPD) incorporated in poly(N-vinylcarbazole) (PVK) matrix and Al is a cathode. EL spectra predominantly influenced by Rubrene emission when the doping layer is close to (PVK:TPD)/ Zn(BTz)2 (x→ 0-15 nm) and to Zn(BTz)2/Al (x→ 70-75 nm) interfaces and shift toward emission of Zn(BTz)2 increasing the distance of Rubrene from both interfaces (x→35 nm). The same dependence of the EL efficiency on the position of the doping Rubrene layer in the OLED structure was found.

  1. Effect of inserting of thin Rubrene layer on performance of Organic Light-Emitting Diodes based on Zn(BTz){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Tomova, R L; Petrova, P K; Stoycheva-Topalova, R T, E-mail: reni@clf.bas.b [Institute of optical materials and technologies ' Acad. J. Malinowski' , Bulgarian Academy of Sciences, ' Acad. G. Bonchev' str. bl. 109, 1113 Sofia (Bulgaria)

    2010-11-01

    Organic light-emitting diodes (OLEDs) with improved performances are fabricated using a thin (1 nm) yellow-emitting layer of 5,6,11,12-tetraphenylnaphthacene (Rubrene) inserted at different position in green emitting electroluminescent (EL) layer of bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTz){sub 2}) in configuration: ITO/PVK:TPD/ Zn(BTz){sub 2} (x nm)/ Rubrene (1 nm)/ Zn(BTz){sub 2} (75-x nm)/Al, where PVK:TPD is a hole transporting layer of N, N'-bis(3-methylphenyl)-N, N'-diphenylbenzidine (TPD) incorporated in poly(N-vinylcarbazole) (PVK) matrix and Al is a cathode. EL spectra predominantly influenced by Rubrene emission when the doping layer is close to (PVK:TPD)/ Zn(BTz){sub 2} (x{yields} 0-15 nm) and to Zn(BTz){sub 2}/Al (x{yields} 70-75 nm) interfaces and shift toward emission of Zn(BTz){sub 2} increasing the distance of Rubrene from both interfaces (x{yields}35 nm). The same dependence of the EL efficiency on the position of the doping Rubrene layer in the OLED structure was found.

  2. Synthesis Alq3and effect of concentration iton optical and electrical performance of Organic Light Emitting Diodes withtwo single-layer mixture and multilayer structures

    Directory of Open Access Journals (Sweden)

    Mohammadreza Jafari

    2017-05-01

    Full Text Available In this article, organic light emitting diode with the two structures of ITO / PEDOT: PSS /PVK/Alq3/PBD/Al and ITO/PEDOT: PSS/PVK: Alq3: PBD/Alwith different concentrations were fabricated. The effects of concentration of Alq3 complex on the characteristics of diodes, which were made, were studied. Layers with the same weight percentages PVK, PBD and different wt. %Alq3 by spin coating on PEDOT: PSS layer was deposited. Current - voltage characteristic curve - and luminescence (El were studied. Experimental results showed that by increasing the concentration of the Alq3complexin both structure, luminescence increased and the operating voltage is reduced.

  3. Enhanced brightness of organic light-emitting diodes based on Mg:Ag cathode using alkali metal chlorides as an electron injection layer

    International Nuclear Information System (INIS)

    Zou Ye; Deng Zhenbo; Xu Denghui; Lü Zhaoyue; Yin Yuehong; Du Hailiang; Chen Zheng; Wang Yongsheng

    2012-01-01

    Different thicknesses of cesium chloride (CsCl) and various alkali metal chlorides were inserted into organic light-emitting diodes (OLEDs) as electron injection layers (EILs). The basic structure of OLED is indium tin oxide (ITO)/N,N′-diphenyl-N,N′-bis(1-napthyl-phenyl)-1.1′-biphenyl-4.4′-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (Alq 3 )/Mg:Ag/Ag. The electroluminescent (EL) performance curves show that both the brightness and efficiency of the OLEDs can be obviously enhanced by using a thin alkali metal chloride layer as an EIL. The electron injection barrier height between the Alq 3 layer and Mg:Ag cathode is reduced by inserting a thin alkali metal chloride as an EIL, which results in enhanced electron injection and electron current. Therefore, a better balance of hole and electron currents at the emissive interface is achieved and consequently the brightness and efficiency of OLEDs are improved. - Highlights: ► Alkaline metal chlorides were used as electron injection layers in organic light-emitting diodes based on Mg:Ag cathode. ► Brightness and efficiency of OLEDs with alkaline metal chlorides as electron injection layers were all greatly enhanced. ► The Improved OLED performance was attributed to the possible interfacial chemical reaction. ► Electron-only devices are fabricated to demonstrate the electron injection enhancement.

  4. Luminescence mechanisms of organic/inorganic hybrid organic light-emitting devices fabricated utilizing a Zn2SiO4:Mn color-conversion layer

    International Nuclear Information System (INIS)

    Choo, D.C.; Ahn, S.D.; Jung, H.S.; Kim, T.W.; Lee, J.Y.; Park, J.H.; Kwon, M.S.

    2010-01-01

    Zn 2 SiO 4 :Mn phosphor layers used in this study were synthesized by using the sol-gel method and printed on the glass substrates by using a vehicle solution and a heating process. Organic/inorganic hybrid organic light-emitting devices (OLEDs) utilizing a Zn 2 SiO 4 :Mn color-conversion layer were fabricated. X-ray diffraction data for the synthesized Zn 2 SiO 4 :Mn phosphor films showed that the Zn ions in the phosphor were substituted into Mn ions. The electroluminescence (EL) spectrum of the deep blue OLEDs showed that a dominant peak at 461 nm appeared. The photoluminescence spectrum for the Zn 2 SiO 4 :Mn phosphor layer by using a 470 nm excitation source showed that a dominant peak at 527 nm appeared, which originated from the 4 T 1 - 6 A 1 transitions of Mn ions. The appearance of the peak around 527 nm of the EL spectra for the OLEDs fabricated utilizing a Zn 2 SiO 4 :Mn phosphor layer demonstrated that the emitted blue color from the deep blue OLEDs was converted into a green color due to the existence of the color-conversion layer. The luminescence mechanisms of organic/inorganic hybrid OLEDs fabricated utilizing a Zn 2 SiO 4 :Mn color-conversion layer are described on the basis of the EL and PL spectra.

  5. Improve the surface of silver nanowire transparent electrode using a double-layer structure for the quantum-dot light-emitting diodes

    Science.gov (United States)

    Cho, Seok Hyeon; Been Heo, Su; Kang, Seong Jun

    2018-03-01

    We developed a double-layer structured transparent electrode for use in flexible quantum-dot light-emitting diodes (QLEDs). Silver nanowires (AgNWs) and highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were coated on a transparent substrate to obtain a highly conductive and flexible transparent electrode. The highly conductive PEDOT:PSS improved the surface roughness of the AgNWs transparent electrode film as well as the surface coverage area of the film. The double-layer structured transparent electrode showed superior mechanical properties than conventional indium-tin oxide (ITO) and AgNWs transparent electrodes. QLEDs with the double-layer structured transparent electrode also showed good reliability under cyclic bending conditions. These results indicate that the double-layer structured AgNWs/PEDOT:PSS transparent electrode described here is a feasible alternative to ITO transparent electrodes for flexible QLEDs.

  6. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chiao-Wen Yeh

    2010-03-01

    Full Text Available White light-emitting diodes (WLEDs have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV LEDs and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED or polymer light-emitting diode (PLED, have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm and nUV (380-400 nm LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+ is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

  7. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Science.gov (United States)

    Chen, Lei; Lin, Chun-Che; Yeh, Chiao-Wen; Liu, Ru-Shi

    2010-01-01

    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.

  8. White organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Rosenow, Thomas Conrad

    2011-03-22

    Three approaches were taken in order to achieve reproducible and highly efficient white OLEDs with excellent colour quality. The first approach is based on the triplet harvesting concept. Otherwise unused triplet excitons are transferred from a fluorescent to a phosphorescent emitter with a smaller triplet energy. Because a blue emitter allowing for triplet transfer to a phosphorescent green emitter was not available, a model system for a three-colour white OLED was developed and investigated. This model device consists of the fluorescent blue emitter 4P-NPD and the phosphorescent emitters Ir(dhfpy){sub 2}acac and Ir(MDQ){sub 2}acac emitting in the yellow and red region, respectively. Here, it was shown that both phosphorescent emitters are excited by triplet diffusion and not by direct charge carrier recombination. The second approach is based on a hybrid white OLED with a single emission layer. This layer is a combination of a fluorescent blue and two phosphorescent emitters in a common matrix material. Because of the above mentioned lack of a blue emitter, which allows for triplet transfer to a green phosphorescent emitter, the concentrations of all emitters were chosen in a way that exciton transfer between the emitters was suppressed. The result is a non-radiative recombination of triplet excitons on the fluorescent blue emitter and an accordingly low quantum efficiency. However, a remarkable colour stability against varying brightness was achieved with this OLED. The most successful approach is based on a stacked OLED. Here, the concept of triplet harvesting is limited to triplet transfer between a fluorescent blue and a phosphorescent red emitter. The resulting spectral gap is filled by a full phosphorescent unit comprising the emission of a green and a yellow emitter, which is stacked on top of the triplet harvesting OLED. By individually optimising both units, it was possible to reach lighting relevant luminous efficacies up to {eta}{sub {nu}}=33 lm/W at

  9. Colour tuneable light-emitting transistor

    Energy Technology Data Exchange (ETDEWEB)

    Feldmeier, Eva J.; Melzer, Christian; Seggern, Heinz von [Electronic Materials Department, Institute of Materials Science, Technische Universitaet Darmstadt (Germany)

    2010-07-01

    In recent years the interest in ambipolar organic light-emitting field-effect transistors has increased steadily as the devices combine switching behaviour of transistors with light emission. Usually, small molecules and polymers with a band gap in the visible spectral range serve as semiconducting materials. Mandatory remain balanced injection and transport properties for both charge carrier types to provide full control of the spatial position of the recombination zone of electrons and holes in the transistor channel via the applied voltages. As will be presented here, the spatial control of the recombination zone opens new possibilities towards light-emitting devices with colour tuneable emission. In our contribution an organic light-emitting field-effect transistors is presented whose emission colour can be changed by the applied voltages. The organic top-contact field-effect transistor is based on a parallel layer stack of acenes serving as organic transport and emission layers. The transistor displays ambipolar characteristics with a narrow recombination zone within the transistor channel. During operation the recombination zone can be moved by a proper change in the drain and gate bias from one organic semiconductor layer to another one inducing a change in the emission colour. In the presented example the emission maxima can be switched from 530 nm to 580 nm.

  10. Improvement of optical and electrical properties of indium tin oxide layer of GaN-based light-emitting diode by surface plasmon in silver nanoparticles

    International Nuclear Information System (INIS)

    Cho, Chu-Young; Hong, Sang-Hyun; Park, Seong-Ju

    2015-01-01

    We report on the effect of silver (Ag) nanoparticles on the optical transmittance and electrical conductivity of indium tin oxide (ITO) transparent conducting layer deposited on p-GaN layer of light-emitting diodes (LEDs). The sheet resistance of ITO and the series resistance of LEDs were decreased due to the increased electrical conductivity of ITO by Ag nanoparticles, compared with those of the LEDs with a bare ITO only. The ITO transmittance was also improved by localized surface plasmon resonance between the incident light and the randomly distributed Ag nanoparticles on ITO. The optical output power of LEDs with Ag nanoparticles on ITO was increased by 16% at 20 mA of injection current. - Highlights: • We studied the effect of Ag nanoparticles deposited on ITO on the properties of LED. • The optical power of LED and transmittance of ITO were improved by Ag surface plasmon. • The electrical conductivity of ITO was increased by Ag nanoparticles

  11. Ultraviolet electroluminescence from nitrogen-doped ZnO-based heterojuntion light-emitting diodes prepared by remote plasma in situ atomic layer-doping technique.

    Science.gov (United States)

    Chien, Jui-Fen; Liao, Hua-Yang; Yu, Sheng-Fu; Lin, Ray-Ming; Shiojiri, Makoto; Shyue, Jing-Jong; Chen, Miin-Jang

    2013-01-23

    Remote plasma in situ atomic layer doping technique was applied to prepare an n-type nitrogen-doped ZnO (n-ZnO:N) layer upon p-type magnesium-doped GaN (p-GaN:Mg) to fabricate the n-ZnO:N/p-GaN:Mg heterojuntion light-emitting diodes. The room-temperature electroluminescence exhibits a dominant ultraviolet peak at λ ≈ 370 nm from ZnO band-edge emission and suppressed luminescence from GaN, as a result of the decrease in electron concentration in ZnO and reduced electron injection from n-ZnO:N to p-GaN:Mg because of the nitrogen incorporation. The result indicates that the in situ atomic layer doping technique is an effective approach to tailoring the electrical properties of materials in device applications.

  12. Thermal Characteristics of InGaN/GaN Flip-Chip Light Emitting Diodes with Diamond-Like Carbon Heat-Spreading Layers

    Directory of Open Access Journals (Sweden)

    Pai-Yang Tsai

    2014-01-01

    Full Text Available The temperature-dependent optical, electrical, and thermal properties of flip-chip light emitting diodes (FCLEDs with diamond-like carbon (DLC heat-spreading layers were investigated. On the basis of the measured results in the 20°C to 100°C temperature range, a significant performance improvement can be achieved for FCLEDs with DLC heat-spreading layers (DLC-FCLED compared with FCLEDs without DLC heat-spreading layers (non-DLC-FCLED. The external quantum efficiency (EQE of the DLC-FCLED improves by 9% at an injection current of 1000 mA and a temperature of 100°C. The forward voltage and spectra variations are smaller than those of non-DLC-FCLEDs. The DLC-FCLED provides high efficiency and high stability performance for high-power and high-temperature applications.

  13. Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

    Science.gov (United States)

    Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo; Peng, Yingquan

    2013-12-01

    Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs.

  14. Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo [Institute of Microelectronics, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Peng, Yingquan, E-mail: yqpeng@lzu.edu.cn [Institute of Microelectronics, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2013-12-28

    Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs.

  15. Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

    International Nuclear Information System (INIS)

    Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo; Peng, Yingquan

    2013-01-01

    Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs

  16. Hybrid light emitting transistors (Presentation Recording)

    Science.gov (United States)

    Muhieddine, Khalid; Ullah, Mujeeb; Namdas, Ebinazar B.; Burn, Paul L.

    2015-10-01

    Organic light-emitting diodes (OLEDs) are well studied and established in current display applications. Light-emitting transistors (LETs) have been developed to further simplify the necessary circuitry for these applications, combining the switching capabilities of a transistor with the light emitting capabilities of an OLED. Such devices have been studied using mono- and bilayer geometries and a variety of polymers [1], small organic molecules [2] and single crystals [3] within the active layers. Current devices can often suffer from low carrier mobilities and most operate in p-type mode due to a lack of suitable n-type organic charge carrier materials. Hybrid light-emitting transistors (HLETs) are a logical step to improve device performance by harnessing the charge carrier capabilities of inorganic semiconductors [4]. We present state of the art, all solution processed hybrid light-emitting transistors using a non-planar contact geometry [1, 5]. We will discuss HLETs comprised of an inorganic electron transport layer prepared from a sol-gel of zinc tin oxide and several organic emissive materials. The mobility of the devices is found between 1-5 cm2/Vs and they had on/off ratios of ~105. Combined with optical brightness and efficiencies of the order of 103 cd/m2 and 10-3-10-1 %, respectively, these devices are moving towards the performance required for application in displays. [1] M. Ullah, K. Tandy, S. D. Yambem, M. Aljada, P. L. Burn, P. Meredith, E. B. Namdas., Adv. Mater. 2013, 25, 53, 6213 [2] R. Capelli, S. Toffanin, G. Generali, H. Usta, A. Facchetti, M. Muccini, Nature Materials 2010, 9, 496 [3] T. Takenobu, S. Z. Bisri, T. Takahashi, M. Yahiro, C. Adachi, Y. Iwasa, Phys. Rev. Lett. 2008, 100, 066601 [4] H. Nakanotani, M. Yahiro, C. Adachi, K. Yano, Appl. Phys. Lett. 2007, 90, 262104 [5] K. Muhieddine, M. Ullah, B. N. Pal, P. Burn E. B. Namdas, Adv. Mater. 2014, 26,37, 6410

  17. Enhanced light extraction of GaN-based light-emitting diodes with periodic textured SiO2 on Al-doped ZnO transparent conductive layer

    Science.gov (United States)

    Yu, Zhao; Bingfeng, Fan; Yiting, Chen; Yi, Zhuo; Zhoujun, Pang; Zhen, Liu; Gang, Wang

    2016-07-01

    We report an effective enhancement in light extraction of GaN-based light-emitting diodes (LEDs) with an Al-doped ZnO (AZO) transparent conductive layer by incorporating a top regular textured SiO2 layer. The 2 inch transparent through-pore anodic aluminum oxide (AAO) membrane was fabricated and used as the etching mask. The periodic pore with a pitch of about 410 nm was successfully transferred to the surface of the SiO2 layer without any etching damages to the AZO layer and the electrodes. The light output power was enhanced by 19% at 20 mA and 56% at 100 mA compared to that of the planar LEDs without a patterned surface. This approach offers a technique to fabricate a low-cost and large-area regular pattern on the LED chip for achieving enhanced light extraction without an obvious increase of the forward voltage. ).

  18. Enhanced light extraction of GaN-based light-emitting diodes with periodic textured SiO2 on Al-doped ZnO transparent conductive layer

    International Nuclear Information System (INIS)

    Zhao Yu; Fan Bingfeng; Chen Yiting; Zhuo Yi; Wang Gang; Pang Zhoujun; Liu Zhen

    2016-01-01

    We report an effective enhancement in light extraction of GaN-based light-emitting diodes (LEDs) with an Al-doped ZnO (AZO) transparent conductive layer by incorporating a top regular textured SiO 2 layer. The 2 inch transparent through-pore anodic aluminum oxide (AAO) membrane was fabricated and used as the etching mask. The periodic pore with a pitch of about 410 nm was successfully transferred to the surface of the SiO 2 layer without any etching damages to the AZO layer and the electrodes. The light output power was enhanced by 19% at 20 mA and 56% at 100 mA compared to that of the planar LEDs without a patterned surface. This approach offers a technique to fabricate a low-cost and large-area regular pattern on the LED chip for achieving enhanced light extraction without an obvious increase of the forward voltage. (paper)

  19. Effect of 3C-SiC intermediate layer in GaN—based light emitting diodes grown on Si(111) substrate

    Science.gov (United States)

    Zhu, Youhua; Wang, Meiyu; Li, Yi; Tan, Shuxin; Deng, Honghai; Guo, Xinglong; Yin, Haihong; Egawa, Takashi

    2017-03-01

    GaN-based light emitting diodes (LEDs) have been grown by metalorganic chemical vapor deposition on Si(111) substrate with and without 3C-SiC intermediate layer (IL). Structural property has been characterized by means of atomic force microscope, X-ray diffraction, and transmission electron microscope measurements. It has been revealed that a significant improvement in crystalline quality of GaN and superlattice epitaxial layers can be achieved by using 3C-SiC as IL. Regarding of electrical and optical characteristics, it is clearly observed that the LEDs with its IL have a smaller leakage current and higher light output power comparing with the LEDs without IL. The better performance of LEDs using 3C-SiC IL can be contributed to both of the improvements in epitaxial layers quality and light extraction efficiency. As a consequence, in terms of optical property, a double enhancement of the light output power and external quantum efficiency has been realized.

  20. Enhancement of hole-injection and power efficiency of organic light emitting devices using an ultra-thin ZnO buffer layer

    International Nuclear Information System (INIS)

    Huang, H.-H.; Chu, S.-Y.; Kao, P.-C.; Chen, Y.-C.; Yang, M.-R.; Tseng, Z.-L.

    2009-01-01

    The advantages of using an anode buffer layer of ZnO on the electro-optical properties of organic light emitting devices (OLEDs) are reported. ZnO powders were thermal-evaporated and then treated with ultra-violet (UV) ozone exposure to make the ZnO layers. The turn-on voltage of OLEDs decreased from 4 V (4.2 cd/m 2 ) to 3 V (3.4 cd/m 2 ) and the power efficiency increased from 2.7 lm/W to 4.7 lm/W when a 1-nm-thick ZnO layer was inserted between indium tin oxide (ITO) anodes and α-naphthylphenylbiphenyl diamine (NPB) hole-transporting layers. X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS) results revealed the formation of the ZnO layer and showed that the work function increased by 0.59 eV when the ZnO/ITO layer was treated by UV-ozone for 20 min. The surface of the ZnO/ITO film became smoother than that of bare ITO film after the UV-ozone treatment. Thus, the hole-injection energy barrier was lowered by inserting an ZnO buffer layer, resulting in a decrease of the turn-on voltage and an increase of the power efficiency of OLEDs.

  1. Top-emitting organic light-emitting diodes.

    Science.gov (United States)

    Hofmann, Simone; Thomschke, Michael; Lüssem, Björn; Leo, Karl

    2011-11-07

    We review top-emitting organic light-emitting diodes (OLEDs), which are beneficial for lighting and display applications, where non-transparent substrates are used. The optical effects of the microcavity structure as well as the loss mechanisms are discussed. Outcoupling techniques and the work on white top-emitting OLEDs are summarized. We discuss the power dissipation spectra for a monochrome and a white top-emitting OLED and give quantitative reports on the loss channels. Furthermore, the development of inverted top-emitting OLEDs is described.

  2. Copper (I) Selenocyanate (CuSeCN) as a Novel Hole-Transport Layer for Transistors, Organic Solar Cells, and Light-Emitting Diodes

    KAUST Repository

    Wijeyasinghe, Nilushi; Tsetseris, Leonidas; Regoutz, Anna; Sit, Wai-Yu; Fei, Zhuping; Du, Tian; Wang, Xuhua; McLachlan, Martyn A.; Vourlias, George; Patsalas, Panos A.; Payne, David J.; Heeney, Martin; Anthopoulos, Thomas D.

    2018-01-01

    The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution-processable hole-transport layer (HTL) material in transistors, organic light-emitting diodes, and solar cells are reported. Density-functional theory calculations combined with X-ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution-processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at −5.1 eV. Hole-transport analysis performed using field-effect measurements confirms the p-type character of CuSeCN yielding a hole mobility of 0.002 cm2 V−1 s−1. When CuSeCN is incorporated as the HTL material in organic light-emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.

  3. Copper (I) Selenocyanate (CuSeCN) as a Novel Hole-Transport Layer for Transistors, Organic Solar Cells, and Light-Emitting Diodes

    KAUST Repository

    Wijeyasinghe, Nilushi

    2018-02-01

    The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution-processable hole-transport layer (HTL) material in transistors, organic light-emitting diodes, and solar cells are reported. Density-functional theory calculations combined with X-ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution-processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at −5.1 eV. Hole-transport analysis performed using field-effect measurements confirms the p-type character of CuSeCN yielding a hole mobility of 0.002 cm2 V−1 s−1. When CuSeCN is incorporated as the HTL material in organic light-emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.

  4. Efficient bright white organic light-emitting diode based on non-doped ultrathin 5,6,11,12-tetraphenylnaphthacene layer

    International Nuclear Information System (INIS)

    Li Lu; Yu Junsheng; Tang Xiaoqing; Wang Tao; Li Wei; Jiang Yadong

    2008-01-01

    High-performance undoped white organic light-emitting diode (OLED) has been fabricated using an ultrathin yellow-emitting layer of 5,6,11,12-tetraphenylnaphthacene (rubrene) inserted at two sides of interface between two N,N'-bis-(1-naphthyl)-N,N'- biphenyl-1,1'-biphenyl-4,4'- diamine (NPB) layers as a hole transporting and blue emissive layer, respectively. The results showed that a maximum luminance of the device reached to as high as 21,500 cd/m 2 at 15 V. The power efficiencies of 2.5 and 1.6 lm/W at a luminance of 1000 and 10000 cd/m 2 , respectively, were obtained. The peaks of electroluminescent (EL) spectra locate at 429 and 560 nm corresponding to the Commissions Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.33), which is independent of bias voltage. The performance enhancement of the device may result from direct charge carrier trapping in rubrene. Energy transfer mechanism was also found in the EL process

  5. Efficient bright white organic light-emitting diode based on non-doped ultrathin 5,6,11,12-tetraphenylnaphthacene layer

    Energy Technology Data Exchange (ETDEWEB)

    Li Lu [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 [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: jsyu@uestc.edu.cn; Tang Xiaoqing; Wang Tao; Li Wei; Jiang Yadong [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)

    2008-11-15

    High-performance undoped white organic light-emitting diode (OLED) has been fabricated using an ultrathin yellow-emitting layer of 5,6,11,12-tetraphenylnaphthacene (rubrene) inserted at two sides of interface between two N,N'-bis-(1-naphthyl)-N,N'- biphenyl-1,1'-biphenyl-4,4'- diamine (NPB) layers as a hole transporting and blue emissive layer, respectively. The results showed that a maximum luminance of the device reached to as high as 21,500 cd/m{sup 2} at 15 V. The power efficiencies of 2.5 and 1.6 lm/W at a luminance of 1000 and 10000 cd/m{sup 2}, respectively, were obtained. The peaks of electroluminescent (EL) spectra locate at 429 and 560 nm corresponding to the Commissions Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.33), which is independent of bias voltage. The performance enhancement of the device may result from direct charge carrier trapping in rubrene. Energy transfer mechanism was also found in the EL process.

  6. Influence of the thickness of electrochemically deposited polyaniline used as hole transporting layer on the behaviour of polymer light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, J.L. [Dpto. de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Av. de la Universidad s/n, Ed. Torrepinet, 03202, Elche, Alicante (Spain)], E-mail: j.l.alonso@umh.es; Ferrer, J.C. [Dpto. de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Av. de la Universidad s/n, Ed. Torrepinet, 03202, Elche, Alicante (Spain); Cotarelo, M.A.; Montilla, F. [Dpto. de Quimica Fisica e Instituto Universitario de Materiales de Alicante, Apdo. de Correos 99, E-03080, Alicante (Spain); Fernandez de Avila, S. [Dpto. de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Av. de la Universidad s/n, Ed. Torrepinet, 03202, Elche, Alicante (Spain)

    2009-02-27

    An experimental study about the influence of the thickness of electrochemically deposited polyaniline (PANI), used as hole-transporting layer, on the behaviour of polymer light emitting diodes is presented. Two sets of devices with a different conjugated polymer used as active layer were prepared. Poly(9-vinylcarbazole) was used for the first type of devices, whereas Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] was used for the second type. Each set consists of five polymeric diodes in which the hole-transporting layer has been varied. In one case of each set no layer was deposited, in other one a Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) layer was deposited, and in the rest of the diodes a different thickness of electrochemically deposited PANI was employed. The optic and electronic characterization of the devices show that controlling the thickness of the PANI hole transporting layer, both the maximum emission peak of the electroluminescence curves and the driving voltage could be tuned. Furthermore, an exponential behaviour has been demonstrated for the maximum intensity of the electroluminescence curves as a function of the applied excitation voltage between anode and cathode.

  7. Influence of the thickness of electrochemically deposited polyaniline used as hole transporting layer on the behaviour of polymer light-emitting diodes

    International Nuclear Information System (INIS)

    Alonso, J.L.; Ferrer, J.C.; Cotarelo, M.A.; Montilla, F.; Fernandez de Avila, S.

    2009-01-01

    An experimental study about the influence of the thickness of electrochemically deposited polyaniline (PANI), used as hole-transporting layer, on the behaviour of polymer light emitting diodes is presented. Two sets of devices with a different conjugated polymer used as active layer were prepared. Poly(9-vinylcarbazole) was used for the first type of devices, whereas Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] was used for the second type. Each set consists of five polymeric diodes in which the hole-transporting layer has been varied. In one case of each set no layer was deposited, in other one a Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) layer was deposited, and in the rest of the diodes a different thickness of electrochemically deposited PANI was employed. The optic and electronic characterization of the devices show that controlling the thickness of the PANI hole transporting layer, both the maximum emission peak of the electroluminescence curves and the driving voltage could be tuned. Furthermore, an exponential behaviour has been demonstrated for the maximum intensity of the electroluminescence curves as a function of the applied excitation voltage between anode and cathode

  8. Effects of plasma polymerized para-xylene intermediate layers on characteristics of flexible organic light emitting diodes fabricated on polyethylene terephthalate substrates

    International Nuclear Information System (INIS)

    Sohn, Sunyoung; Kim, Kyuhyung; Kho, Samil; Jung, Donggeun; Boo, Jin-hyo

    2008-01-01

    Characteristics of flexible organic light emitting diodes (FOLEDs) with the plasma polymerized para-xylene (PPpX) intermediate layer were investigated. For the purpose of reducing moisture permeation through plastic substrates, a PPpX intermediate layer was inserted between FOLEDs and the plastic substrates. As the concentration of C-H bonding in the PPpX film deposited at 25 deg. C was increased, PPpX films showed increased transmittance. Surface morphologies of polyethylene terephthalate (PET) covered with the PPpX intermediate layer were improved compared to PET without PPpX on it. Due to the highly cross-linked network structure in the plasma polymer film, water vapor permeability of PET substrates with the PPpX intermediate layer of 75 nm was decreased compared to PET substrates without PPpX on it. FOLEDs with the PPpX intermediate layer showed improved optical and electrical characteristics as well as lifetimes than FOLEDs without the PPpX intermediate layer

  9. Interfacial engineering with ultrathin poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) layer for high efficient perovskite light-emitting diodes

    Science.gov (United States)

    Lin, Chunyan; Chen, Ping; Xiong, ZiYang; Liu, Debei; Wang, Gang; Meng, Yan; Song, Qunliang

    2018-02-01

    Organic-inorganic hybrid perovskites have attracted great attention in the field of lighting and display due to their very high color purity and low-cost solution-process. Researchers have done a lot of work in realizing high performance electroluminescent devices. However, the current efficiency (CE) of methyl-ammonium lead halide perovskite light-emitting diodes (PeLEDs) still needs to be improved. Herein, we demonstrate the enhanced performance of PeLEDs through introducing an ultrathin poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) buffer layer between poly(3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and CH3NH3PbBr3 perovskite. Compared to the reference device without PFO, the optimal device luminous intensity, the maximum CE, and the maximum external quantum efficiency increases from 8139 cd m-2 to 30 150 cd m-2, from 7.20 cd A-1 (at 6.8 V) to 10.05 cd A-1 (at 6.6 V), and from 1.73% to 2.44%, respectively. The ultrathin PFO layer not only reduces the exciton quenching at the interface between the hole-transport layer and emission layer, but also passivates the shallow-trap ensure increasing hole injection, as well as increases the coverage of perovskite film.

  10. Single-Layer Halide Perovskite Light-Emitting Diodes with Sub-Band Gap Turn-On Voltage and High Brightness.

    Science.gov (United States)

    Li, Junqiang; Shan, Xin; Bade, Sri Ganesh R; Geske, Thomas; Jiang, Qinglong; Yang, Xin; Yu, Zhibin

    2016-10-03

    Charge-carrier injection into an emissive semiconductor thin film can result in electroluminescence and is generally achieved by using a multilayer device structure, which requires an electron-injection layer (EIL) between the cathode and the emissive layer and a hole-injection layer (HIL) between the anode and the emissive layer. The recent advancement of halide perovskite semiconductors opens up a new path to electroluminescent devices with a greatly simplified device structure. We report cesium lead tribromide light-emitting diodes (LEDs) without the aid of an EIL or HIL. These so-called single-layer LEDs have exhibited a sub-band gap turn-on voltage. The devices obtained a brightness of 591 197 cd m -2 at 4.8 V, with an external quantum efficiency of 5.7% and a power efficiency of 14.1 lm W -1 . Such an advancement demonstrates that very high efficiency of electron and hole injection can be obtained in perovskite LEDs even without using an EIL or HIL.

  11. Electron injection mechanisms of green organic light-emitting devices fabricated utilizing a double electron injection layer consisting of cesium carbonate and fullerene

    International Nuclear Information System (INIS)

    Yang, J.S.; Choo, D.C.; Kim, T.W.; Jin, Y.Y.; Seo, J.H.; Kim, Y.K.

    2010-01-01

    Electron injection mechanisms of the luminance efficiency of green organic light-emitting devices (OLEDs) fabricated utilizing a cesium carbonate (Cs 2 CO 3 )/fullerene (C 60 ) heterostructure acting as an electron injection layer (EIL) were investigated. Current density-voltage and luminance-voltage measurements showed that the current densities and the luminances of the OLEDs with a Cs 2 CO 3 or Cs 2 CO 3 /C 60 EIL were higher than that of the OLEDs with a Liq EIL. The luminance efficiency of the OLEDs with a Cs 2 CO 3 EIL was almost three times higher than that of the OLEDs with a Liq EIL. Because the electron injection efficiency of the Cs 2 CO 3 layer in OLEDs was different from that of the C 60 layer, the luminance efficiency of the OLEDs with a double EIL consisting of a Cs 2 CO 3 layer and a C 60 layer was smaller than that of the OLEDs with a Cs 2 CO 3 EIL. The electron injection mechanisms of OLEDs with a Cs 2 CO 3 and C 60 double EIL are described on the basis of the experimental results.

  12. All-Quantum-Dot Infrared Light-Emitting Diodes

    KAUST Repository

    Yang, Zhenyu; Voznyy, Oleksandr; Liu, Mengxia; Yuan, Mingjian; Ip, Alexander H.; Ahmed, Osman S.; Levina, Larissa; Kinge, Sachin; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    © 2015 American Chemical Society. Colloidal quantum dots (CQDs) are promising candidates for infrared electroluminescent devices. To date, CQD-based light-emitting diodes (LEDs) have employed a CQD emission layer sandwiched between carrier transport

  13. Role of the polymeric hole injection layer on the efficiency and stability of organic light emitting diodes with small molecular emitters

    International Nuclear Information System (INIS)

    Chin, Byung Doo

    2008-01-01

    In this paper, an improvement in the properties of the small molecular organic light emitting diode (OLED) upon application of a polymeric hole injection layer (HIL) was reported. The luminous efficiency, operating voltage and lifetime of devices with dye-doped small molecule emitters (fluorescent and phosphorescent) were found to be sensitive to the HIL/hole transport layer (HTL) combination used, where the improved injection and brightness was shown at the hole cascading structure and the longer lifetime behaviour was obtained at the hole-trapping structure. Use of a polymeric HIL significantly increased the luminous current efficiency and lifetime for both fluorescent blue and phosphorescent green/red light emitters. The polymeric HIL was effective in terms of the driving characteristics of phosphorescent OLED, since it provides higher brightness behaviour at lower current density. The apparent shade of the pixel image at light emission, which will probably induce degradation at the pixel wall interface, will be suppressed by the use of polymeric HIL. In spite of the ambiguity in the formation of such shaded pixels and their influence at the decay of OLED, intrinsic stability of polymeric HIL/anode would be advantageous for stable storage and operation of devices.

  14. Light-emitting diodes based on solution-processed nontoxic quantum dots: oxides as carrier-transport layers and introducing molybdenum oxide nanoparticles as a hole-inject layer.

    Science.gov (United States)

    Bhaumik, Saikat; Pal, Amlan J

    2014-07-23

    We report fabrication and characterization of solution-processed quantum dot light-emitting diodes (QDLEDs) based on a layer of nontoxic and Earth-abundant zinc-diffused silver indium disulfide (AIZS) nanoparticles as an emitting material. In the QDLEDs fabricated on indium tin oxide (ITO)-coated glass substrates, we use layers of oxides, such as graphene oxide (GO) and zinc oxide (ZnO) nanoparticles as a hole- and electron-transport layer, respectively. In addition, we introduce a layer of MoO3 nanoparticles as a hole-inject one. We report a comparison of the characteristics of different device architectures. We show that an inverted device architecture, ITO/ZnO/AIZS/GO/MoO3/Al, yields a higher electroluminescence (EL) emission, compared to direct ones, for three reasons: (1) the GO/MoO3 layers introduce barriers for electrons to reach the Al electrode, and, similarly, the ZnO layers acts as a barrier for holes to travel to the ITO electrode; (2) the introduction of a layer of MoO3 nanoparticles as a hole-inject layer reduces the barrier height for holes and thereby balances charge injection in the inverted structure; and (3) the wide-bandgap zinc oxide next to the ITO electrode does not absorb the EL emission during its exit from the device. In the QDLEDs with oxides as carrier inject and transport layers, the EL spectrum resembles the photoluminescence emission of the emitting material (AIZS), implying that excitons are formed in the quaternary nanocrystals and decay radiatively.

  15. Significant performance enhancement of inverted organic light-emitting diodes by using ZnIx as a hole-blocking layer

    Science.gov (United States)

    Cheng, Chuan-Hui; Zhang, Bi-Long; Sun, Chao; Li, Ruo-Xuan; Wang, Yuan; Tian, Wen-Ming; Zhao, Chun-Yi; Jin, Sheng-Ye; Liu, Wei-Feng; Luo, Ying-Min; Du, Guo-Tong; Cong, Shu-Lin

    2017-06-01

    A highly efficient inverted organic light emitting diode using 1.0 nm-thick ZnIx as a hole-blocking layer is developed. We fabricate devices with the configuration ITO/ZnIx (1.0 nm)/Alq3 (50 nm)/NPB (50 nm)/MoO3 (6.0 nm)/Al (100 nm). The deposition of a ZnIx layer increases the maximum luminance by two orders of magnitude from 13.4 to 3566.1 cd/m2. In addition, the maximum current efficiency and power efficiency are increased by three orders of magnitude, and the turn-on voltage to reach 1 cd/m2 decreases from 13 to 8 V. The results suggest that the electron injection efficiency is not improved by introducing a ZnIx layer. Instead, the improved device performance originates from the strong hole-blocking ability of ZnIx. This work indicates that layered materials may lead to novel applications in optoelectronic devices.

  16. Characteristics of the epitaxy of InGaN-based light-emitting diodes grown by nanoscale epitaxial lateral overgrowth using a nitrided titanium buffer layer

    International Nuclear Information System (INIS)

    Shieh, Chen-Yu; Li, Zhen-Yu; Chang, Jenq-Yang; Chi, Gou-Chung

    2015-01-01

    In this work, a buffer layer of nitrided titanium (Ti) achieved through the nitridation of a Ti metal layer on a sapphire substrate was used for the epitaxial growth of InGaN-based light-emitting diodes (LEDs) achieved by low pressure metal-organic chemical vapor deposition. The effect of in-situ Ti metal nitridation on the performance of these InGaN-based LEDs was then investigated. It was very clear that the use of the nitrided Ti buffer layer (NTBL) induced the formation of a nanoscale epitaxial lateral overgrowth layer during the epitaxial growth. When evaluated by Raman spectroscopy, this epi-layer exhibited large in-plane compressive stress releasing with a Raman shift value of 567.9 cm -1 . Cathodoluminescence spectroscopy and transmission electron microscopy results indicated that the InGaN-based LEDs with an NTBL have improved crystal quality, with a low threading dislocations density being yielded via the strain relaxation in the InGaN-based LEDs. Based on the results mentioned above, the electroluminescence results indicate that the light performance of InGaN-based LEDs with an NTBL can be enhanced by 45% and 42% at 20 mA and 100 mA, respectively. These results suggest that the strain relaxation and quality improvement in the GaN epilayer could be responsible for the enhancement of emission power. - Highlights: • The crystal-quality of InGaN-based LEDs with NTBL by NELOG was improved. • The InGaN-based LEDs with NTBL have strain releases by NELOG. • The optical properties of InGaN-based LEDs were shown by CL and EL measurements

  17. Improved efficiency in organic light-emitting devices with tris-(8-hydroxyquinoline) aluminium doped 9,10-di(2-naphthyl) anthracene emission layer

    Energy Technology Data Exchange (ETDEWEB)

    Yuan Yongbo; Lian Jiarong; Li Shuang; Zhou Xiang [State Key Lab of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou, 510275 (China)], E-mail: stszx@mail.sysu.edu.cn

    2008-11-21

    Organic light-emitting devices with tris-(8-hydroxyquinoline) aluminium (Alq{sub 3}) doped 9,10-di(2-naphthyl) anthracene (ADN) as the emission layer (EML) have been fabricated. These devices exhibit efficient electroluminescence (EL) originated from the Alq{sub 3} as the mass ratio of Alq{sub 3} to ADN was varied from 1 to 50%. The devices with an optimal Alq{sub 3} mass ratio of 10 wt% showed a peak EL efficiency and an external quantum efficiency of 9.1 cd A{sup -1} and 2.7% at a luminance of 1371 cd m{sup -2}, which is improved by a factor of 2.2 compared with 4.1 cd A{sup -1} and 1.2% at a luminance of 3267 cd m{sup -2} for conventional devices with the neat Alq{sub 3} as the EML.

  18. Effect of Hydrogen Post-Annealing on Transparent Conductive ITO/Ga2O3 Bi-Layer Films for Deep Ultraviolet Light-Emitting Diodes.

    Science.gov (United States)

    Kim, Kyeong Heon; Kim, Su Jin; Park, Sang Young; Kim, Tae Geun

    2015-10-01

    The effect of hydrogen post-annealing on the electrical and optical properties of ITO/Ga2O bi-layer films, deposited by RF magnetron sputtering, is investigated for potential applications to transparent conductive electrodes of ultraviolet (UV) light-emitting diodes. Three samples--an as-deposited sample and two samples post-annealed in N2 gas and N2-H2 gas mixture--were prepared and annealed at different temperatures ranging from 100 °C to 500 °C for comparison. Among these samples, the sample annealed at 300 °C in a mixture of N2 and H2 gases shows the lowest sheet resistance of 301.3 Ω/square and a high UV transmittance of 87.1% at 300 nm.

  19. Enhanced performance of organic light-emitting devices by using electropolymerized poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film as the anode modification layer

    Energy Technology Data Exchange (ETDEWEB)

    Liu Xiaona [Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Yan Jun [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Meng Lingchuan [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Sun Chenghua; Hu Xiujie; Chen Ping [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Zhou Shuyun, E-mail: zhou_shuyun@mail.ipc.ac.cn [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Teng Feng [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)

    2012-01-31

    Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films were prepared by electropolymerization on patterned indium tin oxide substrates in isopropanol solution. The thickness and doping level of the PEDOT:PSS films were controlled by adjusting the electropolymerization time and the concentration of poly(styrene sulfonate) acid, respectively. Organic light-emitting diodes were fabricated using the electropolymerized PEDOT:PSS film as the anode modification layer. The dependence of the performance on thickness of PEDOT:PSS films was investigated. It is shown that the performance of the device can be further enhanced when the thickness of PEDOT:PSS films reached an optimum condition. This method facilitates manufacturing procedures of conducting polymers films and may offer an economical route for producing organic electroluminescent devices.

  20. High efficient white organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Stefan; Krause, Ralf [Department of Materials Science VI, University of Erlangen-Nuremberg (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Kozlowski, Fryderyk; Schmid, Guenter; Hunze, Arvid [Siemens AG, CT MM 1, Erlangen (Germany); Winnacker, Albrecht [Department of Materials Science VI, University of Erlangen-Nuremberg (Germany)

    2007-07-01

    Due to the rapid progress in the last years the performance of organic light emitting diodes (OLEDs) has reached a level where general lighting presents a most interesting application target. We demonstrate, how the color coordinates of the emission spectrum can be adjusted using a combinatorial evaporation tool to lie on the desired black body curve representing cold and warm white, respectively. The evaluation includes phosphorescent and fluorescent dye approaches to optimize lifetime and efficiency, simultaneously. Detailed results are presented with respect to variation of layer thicknesses and dopant concentrations of each layer within the OLED stack. The most promising approach contains phosphorescent red and green dyes combined with a fluorescent blue one as blue phosphorescent dopants are not yet stable enough to achieve long lifetimes.

  1. Zigzag and Helical AlN Layer Prepared by Glancing Angle Deposition and Its Application as a Buffer Layer in a GaN-Based Light-Emitting Diode

    Directory of Open Access Journals (Sweden)

    Lung-Chien Chen

    2012-01-01

    Full Text Available This study investigates an aluminum nitride (AlN nanorod structure sputtered by glancing angle deposition (GLAD and its application as a buffer layer for GaN-based light-emitting diodes (LEDs that are fabricated on sapphire substrates. The ray tracing method is adopted with a three-dimensional model in TracePro software. Simulation results indicate that the zigzag AlN nanorod structure is an optimal buffer layer in a GaN-based LED. Furthermore, the light output power of a GaN-based LED with a zigzag AlN nanorod structure improves to as much as 28.6% at a forward current of 20 mA over that of the GaN-based LED with a normal AlN buffer layer.

  2. 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.

  3. Effect of Nonionic Surfactant Additive in PEDOT:PSS on PFO Emission Layer in Organic-Inorganic Hybrid Light-Emitting Diode.

    Science.gov (United States)

    Cho, Seong Rae; Porte, Yoann; Kim, Yun Cheol; Myoung, Jae-Min

    2018-03-21

    Poly(9,9-dioctylfluorene) (PFO) has attracted significant interests owing to its versatility in electronic devices. However, changes in its optical properties caused by its various phases and the formation of oxidation defects limit the application of PFO in light-emitting diodes (LEDs). We investigated the effects of the addition of Triton X-100 (hereinafter shortened as TX) in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to induce interlayer diffusion between PEDOT:PSS and PFO to enhance the stability of the PFO phase and suppress its oxidation. Photoluminescence (PL) measurement on PFO/TX-mixed PEDOT:PSS layers revealed that, upon increasing the concentration of TX in the PEDOT:PSS layer, the β phase of PFO could be suppressed in favor of the glassy phase and the wide PL emission centered at 535 nm caused by ketone defects formed by oxidation was decreased considerably. LEDs were then fabricated using PFO as an emission layer, TX-mixed PEDOT:PSS as hole-transport layer, and zinc oxide (ZnO) nanorods as electron-transport layer. As the TX concentration reached 3 wt %, the devices exhibited dramatic increases in current densities, which were attributed to the enhanced hole injection due to TX addition, along with a shift in the dominant emission wavelength from a green electroluminescence (EL) emission centered at 518 nm to a blue EL emission centered at 448 nm. The addition of TX in PEDOT:PSS induced a better hole injection in the PFO layer, and through interlayer diffusion, stabilized the glassy phase of PFO and limited the formation of oxidation defects.

  4. Influence of the substrate platform on the opto-electronic properties of multi-layer organic light-emitting field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Generali, Gianluca; Capelli, Raffaella; Toffanin, Stefano; Muccini, Michele [Consiglio Nazionale delle Ricerche (CNR), Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), via P. Gobetti 101, I-40129 Bologna (Italy); Dinelli, Franco, E-mail: g.generali@bo.ismn.cnr.it, E-mail: m.muccini@bo.ismn.cnr.it [Consiglio Nazionale delle Ricerche (CNR), INO U.O.S. ' A. Gozzini' Area della Ricerca di Pisa - S. Cataldo, via Moruzzi 1, I-56124 Pisa (Italy)

    2011-06-08

    In this paper, we present a study of the effects of the influence of the substrate platform on the properties of a three-layer vertical hetero-junction made of thin films of {alpha}, {omega}-diperfluorohexyl-4T (DHF4T), a blend of tris(8-hydroxyquinoline)aluminium (Alq3) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) and {alpha}, {omega}-dihexyl-quaterthiophene (DH4T). The hetero-junction represents the active component of an organic light-emitting transistor (OLET). The substrate platforms investigated in this study are glass/indium-tin-oxide/poly(methyl-methacrylate) (PMMA) and Si{sup ++}/silicon oxide (SiO{sub 2})/PMMA. The first platform is almost completely transparent to light and therefore is very promising for use in OLET applications. The second one has been chosen for comparison as it employs standard microelectronic materials, i.e. Si{sup ++}/SiO{sub 2}. We show how different gate materials and structure can affect the relevant field-effect electrical characteristics, such as the charge mobility and threshold voltage. By means of an atomic force microscopy analysis, a systematic study has been made in order to correlate the morphology of the active layers with the electrical properties of the devices.

  5. Electron-transporting layer doped with cesium azide for high-performance phosphorescent and tandem white organic light-emitting devices

    Science.gov (United States)

    Yu, Yaoyao; Chen, Xingming; Jin, Yu; Wu, Zhijun; Yu, Ye; Lin, Wenyan; Yang, Huishan

    2017-07-01

    Cesium azide was employed as an effective n-dopant in the electron-transporting layer (ETL) of organic light-emitting devices (OLEDs) owing to its low deposition temperature and high ambient stability. By doping cesium azide onto 4,7-diphenyl-1,10-phenanthroline, a green phosphorescent OLED having best efficiencies of 66.25 cd A-1, 81.22 lm W-1 and 18.82% was realized. Moreover, the efficiency roll-off from 1000 cd m-2 to 10 000 cd m-2 is only 12.9%, which is comparable with or even lower than that of devices utilizing the co-host system. Physical mechanisms for the improvement of device performance were studied in depth by analyzing the current density-voltage (J-V) characteristics of the electron-only devices. In particular, by comparing the J-V characteristics of the electron-only devices instead of applying the complicated ultraviolet photoelectron spectrometer measurements, we deduced the decrease in barrier height for electron injection at the ETL/cathode contact. Finally, an efficient tandem white OLED utilizing the n-doped layer in the charge generation unit (CGU) was constructed. As far as we know, this is the first report on the application of this CGU for fabricating tandem white OLEDs. The emissions of the tandem device are all in the warm white region from 1213 cd m-2 to 10870 cd m-2, as is beneficial to the lighting application.

  6. Effects of GaN/AlGaN/Sputtered AlN nucleation layers on performance of GaN-based ultraviolet light-emitting diodes

    Science.gov (United States)

    Hu, Hongpo; Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Gui, Chengqun; Liu, Sheng

    2017-03-01

    We report on the demonstration of GaN-based ultraviolet light-emitting diodes (UV LEDs) emitting at 375 nm grown on patterned sapphire substrate (PSS) with in-situ low temperature GaN/AlGaN nucleation layers (NLs) and ex-situ sputtered AlN NL. The threading dislocation (TD) densities in GaN-based UV LEDs with GaN/AlGaN/sputtered AlN NLs were determined by high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM), which revealed that the TD density in UV LED with AlGaN NL was the highest, whereas that in UV LED with sputtered AlN NL was the lowest. The light output power (LOP) of UV LED with AlGaN NL was 18.2% higher than that of UV LED with GaN NL owing to a decrease in the absorption of 375 nm UV light in the AlGaN NL with a larger bandgap. Using a sputtered AlN NL instead of the AlGaN NL, the LOP of UV LED was further enhanced by 11.3%, which is attributed to reduced TD density in InGaN/AlInGaN active region. In the sputtered AlN thickness range of 10-25 nm, the LOP of UV LED with 15-nm-thick sputtered AlN NL was the highest, revealing that optimum thickness of the sputtered AlN NL is around 15 nm.

  7. Using an ultra-thin non-doped orange emission layer to realize high efficiency white organic light-emitting diodes with low efficiency roll-off

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Liping; Chen, Jiangshan; Ma, Dongge, E-mail: mdg1014@ciac.ac.cn [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate University of the Chinese Academy of Sciences, Changchun 130022 (China); Zhao, Yongbiao [Luminous Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, Singapore 639798 (Singapore); Zhang, Hongmei [Department of Materials Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China)

    2014-06-28

    By adopting an ultra-thin non-doped orange emission layer sandwiched between two blue emission layers, high efficiency white organic light-emitting diodes (WOLEDs) with reduced efficiency roll-off were fabricated. The optimized devices show a balanced white emission with Internationale de L'Eclairage of (0.41, 0.44) at the luminance of 1000 cd/m{sup 2}, and the maximum power efficiency, current efficiency (CE), and external quantum efficiency reach 63.2 lm/W, 59.3 cd/A, and 23.1%, which slightly shift to 53.4 lm/W, 57.1 cd/A, and 22.2% at 1000 cd/m{sup 2}, respectively, showing low efficiency roll-off. Detailed investigations on the recombination zone and the transient electroluminescence (EL) clearly reveal the EL processes of the ultra-thin non-doped orange emission layer in WOLEDs.

  8. Highly efficient inverted organic light emitting diodes by inserting a zinc oxide/polyethyleneimine (ZnO:PEI) nano-composite interfacial layer

    Science.gov (United States)

    Kaçar, Rifat; Pıravadılı Mucur, Selin; Yıldız, Fikret; Dabak, Salih; Tekin, Emine

    2017-06-01

    The electrode/organic interface is one of the key factors in attaining superior device performance in organic electronics, and inserting a tailor-made layer can dramatically modify its properties. The use of nano-composite (NC) materials leads to many advantages by combining materials with the objective of obtaining a desirable combination of properties. In this context, zinc oxide/polyethyleneimine (ZnO:PEI) NC film was incorporated as an interfacial layer into inverted bottom-emission organic light emitting diodes (IBOLEDs) and fully optimized. For orange-red emissive MEH-PPV based IBOLEDs, a high power efficiency of 6.1 lm W-1 at a luminance of 1000 cd m-2 has been achieved. Notably, the external quantum efficiency (EQE) increased from 0.1 to 4.8% and the current efficiency (CE) increased from 0.2 to 8.7 cd A-1 with rise in luminance (L) from 1000 to above 10 000 cd m-2 levels when compared to that of pristine ZnO-based devices. An identical device architecture containing a ZnO:PEI NC layer has also been used to successfully fabricate green and blue emissive IBOLEDs. The significant enhancement in the inverted device performance, in terms of luminance and efficiency, is attributed to a good energy-level alignment between the cathode/organic interface which leads to effective carrier balance, resulting in efficient radiative-recombination.

  9. I. Hole-transporting dendrimers and their use in organic light-emitting devices (OLEDs) and II. Novel layered catalysts containing bipyridinium and zero-valent metal species

    Science.gov (United States)

    Koene, Shannon Carol

    A series of polyaromatic ether/ester dendrimers containing a hole transporting naphthylphenylbenzyl amine at the periphery and a variety of fluorescent dyes at the core has been studied in an effort to observe energy transfer in these species. The dyes incorporated in these dendrimers include 1,4-dihydroxyanthraquinone (quinizarin), Coumarin 343, and a benzopentathiophene. These dendrimers have been incorporated into both single layer and heterostructure organic light emitting devices (OLEDs). In the case of first generation dendrimer OLEDs, excimer/exciplex formation was predominant. In third generation dendrimers, complete energy transfer from the periphery to the dye at the core was observed both in photoluminescence spectra and electroluminescence in OLEDs. Dendrimers containing different dye cores can be combined to achieve color mixing/tuning. In addition, layered catalysts were prepared via both covalent and electrostatic means to achieve the catalytic production of hydrogen peroxide from hydrogen and oxygen. Covalent catalysts were prepared by first growing layers of zirconium and a bipyridinium containing bisphosphonate onto silica particles. Palladium and/or platinum was ion-exchanged into the structure and reduced to the zero valent metal by hydrogen gas. A second set of catalysts was prepared by electrostatically depositing polycations/polyanions onto carboxylate or amine functionalized polystyrene microspheres. Anionic colloidal particles were adsorbed to the polycationic surface. An octacationic viologen oligomer was used in an attempt to increase the affinity of adsorption of the Pd particles to the surface of the microspheres. Catalytic studies of both types of catalysts are herein reported.

  10. Numerical study of the influence of applied voltage on the current balance factor of single layer organic light-emitting diodes

    International Nuclear Information System (INIS)

    Lu, Fei-ping; Liu, Xiao-bin; Xing, Yong-zhong

    2014-01-01

    Current balance factor (CBF) value, the ratio of the recombination current density and the total current density of a device, has an important function in fluorescence-based organic light-emitting diodes (OLEDs), as well as in the performance of the organic electrophosphorescent devices. This paper investigates the influence of the applied voltage of a device on the CBF value of single layer OLED based on the numerical model of a bipolar single layer OLED with organic layer trap free and without doping. Results show that the largest CBF value can be achieved when the electron injection barrier (ϕ n ) is equal to the hole injection barrier (ϕ p ) in the lower voltage region at any instance. The largest CBF in the higher voltage region can be achieved in the case of ϕ n  > ϕ p under the condition of electron mobility (μ 0n ) > hole mobility (μ 0p ), whereas the result for the case of μ 0n   0p , is opposite. The largest CBF when μ 0n  = μ 0p can be achieved in the case of ϕ n  = ϕ p in the entire region of the applied voltage. In addition, the CBF value of the device increases with increasing applied voltage. The results obtained in this paper can present an in-depth understanding of the OLED working mechanism and help in the future fabrication of high efficiency OLEDs

  11. Low-driving-voltage and colour-stable white organic light-emitting diodes with a cross-patterned multi-emissive layer

    International Nuclear Information System (INIS)

    Hyun, Woo Jin; Park, O Ok; Park, Jae Kyun; Chin, Byung Doo

    2012-01-01

    We have applied a simple cross-patterning technique for the fabrication of phosphorescent white organic light-emitting diodes (WOLEDs) with red, green and blue (RGB) emitters; the resulting device has relatively low driving voltage and high colour stability. The selectively cross-patterned multicolour emitting layer (EML) was easily prepared using a metal mask without an alignment process. Not only was the characteristic of low driving voltage obtained but also of improved colour stability, which can be ascribed to the simplified stack of the EML and the corresponding suppression of the biased shift in the recombination zone. The spatial distribution and variation of the stacked EML structure could explain the origin of the robust white emission. Compared with the conventional WOLED with a RGB simple stack, the cross-patterned multi-EML device showed a slight change in colour coordinates in the luminance range 100-8000 cd m -2 , with a decrease in the driving voltage of 0.5-2.0 V, while the luminous efficiency was maintained. (paper)

  12. High Intensity Organic Light-emitting Diodes

    Science.gov (United States)

    Qi, Xiangfei

    This thesis is dedicated to the fabrication, modeling, and characterization to achieve high efficiency organic light-emitting diodes (OLEDs) for illumination applications. Compared to conventional lighting sources, OLEDs enabled the direct conversion of electrical energy into light emission and have intrigued the world's lighting designers with the long-lasting, highly efficient illumination. We begin with a brief overview of organic technology, from basic organic semiconductor physics, to its application in optoelectronics, i.e. light-emitting diodes, photovoltaics, photodetectors and thin-film transistors. Due to the importance of phosphorescent materials, we will focus on the photophysics of metal complexes that is central to high efficiency OLED technology, followed by a transient study to examine the radiative decay dynamics in a series of phosphorescent platinum binuclear complexes. The major theme of this thesis is the design and optimization of a novel architecture where individual red, green and blue phosphorescent OLEDs are vertically stacked and electrically interconnected by the compound charge generation layers. We modeled carrier generation from the metal-oxide/doped organic interface based on a thermally assisted tunneling mechanism. The model provides insights to the optimization of a stacked OLED from both electrical and optical point of view. To realize the high intensity white lighting source, the efficient removal of heat is of a particular concern, especially in large-area devices. A fundamental transfer matrix analysis is introduced to predict the thermal properties in the devices. The analysis employs Laplace transforms to determine the response of the system to the combined effects of conduction, convection, and radiation. This perspective of constructing transmission matrices greatly facilitates the calculation of transient coupled heat transfer in a general multi-layer composite. It converts differential equations to algebraic forms, and

  13. Light emitting device having peripheral emissive region

    Science.gov (United States)

    Forrest, Stephen R

    2013-05-28

    Light emitting devices are provided that include one or more OLEDs disposed only on a peripheral region of the substrate. An OLED may be disposed only on a peripheral region of a substantially transparent substrate and configured to emit light into the substrate. Another surface of the substrate may be roughened or include other features to outcouple light from the substrate. The edges of the substrate may be beveled and/or reflective. The area of the OLED(s) may be relatively small compared to the substrate surface area through which light is emitted from the device. One or more OLEDs also or alternatively may be disposed on an edge of the substrate about perpendicular to the surface of the substrate through which light is emitted, such that they emit light into the substrate. A mode expanding region may be included between each such OLED and the substrate.

  14. Study of shifting of recombination zone in multi-emissive layer organic light emitting devices and its effect on color stability

    International Nuclear Information System (INIS)

    Tyagi, Priyanka; Srivastava, Ritu; Kumar, Arunandan; Tuli, Suneet; Kamalasanan, M.N.

    2013-01-01

    Color stability in multi-emissive layer organic light emitting devices (Me-OLEDs) has been investigated. Me-OLEDs were based on multiple emitters with a common host CBP doped with three dopants, BCzVBi, Ir(ppy) 3 and Ir(btp) 2 acac for blue, green and red emission. A major variation in CIE coordinates were found from (0.312, 0.294) to (0.236, 0.267) with increase in voltage from 6 to 9 V. This coordinate shift in Me-OLEDs has been attributed to the shifting of recombination zone with increase in voltage. In order to support our experimental observation, the EL spectrum of Me-OLEDs has been expressed as a linear combination of EL intensities of OLEDs with its individual constituting layers as emitters. In this way, the contribution of each layer in the EL spectrum of Me-OLEDs has been evaluated at each voltage. It has been observed from these calculations that the contribution of red emitter decreases from 47% to 33.33% and blue emitter increases from 38% to 51.67% with the increase in voltage from 6 to 9 V. This supports our hypothesis of shifting of recombination zone with the change in voltage. This shifting has been attributed to the field dependency of electron mobility in CBP. Me-OLED with CBP layers between the emitters was fabricated to improve the color stability. Significant improvement in color stability was achieved without changes in current efficiency in Me-OLED with interlayers. Highlights: ► Me-OLEDs have been fabricated by using three primary colors (RGB). ► CIE coordinates of these Me-OLEDs were voltage dependent. ► Analytical fitting has been performed to study the shifting of recombination zone. ► CBP interlayers have been introduced to improve the color stability. ► Color stability has been improved without any change in current efficiency

  15. Enhancing the Performance of Quantum Dot Light-Emitting Diodes Using Room-Temperature-Processed Ga-Doped ZnO Nanoparticles as the Electron Transport Layer

    KAUST Repository

    Cao, Sheng

    2017-04-19

    Colloidal ZnO nanoparticle (NP) films are recognized as efficient electron transport layers (ETLs) for quantum dot light-emitting diodes (QD-LEDs) with good stability and high efficiency. However, because of the inherently high work function of such films, spontaneous charge transfer occurs at the QD/ZnO interface in such a QD-LED, thus leading to reduced performance. Here, to improve the QD-LED performance, we prepared Ga-doped ZnO NPs with low work functions and tailored band structures via a room-temperature (RT) solution process without the use of bulky organic ligands. We found that the charge transfer at the interface between the CdSe/ZnS QDs and the doped ZnO NPs was significantly weakened because of the incorporated Ga dopants. Remarkably, the as-assembled QD-LEDs, with Ga-doped ZnO NPs as the ETLs, exhibited superior luminances of up to 44 000 cd/m2 and efficiencies of up to 15 cd/A, placing them among the most efficient red-light QD-LEDs ever reported. This discovery provides a new strategy for fabricating high-performance QD-LEDs by using RT-processed Ga-doped ZnO NPs as the ETLs, which could be generalized to improve the efficiency of other optoelectronic devices.

  16. High-performance flexible inverted organic light-emitting diodes by exploiting MoS2 nanopillar arrays as electron-injecting and light-coupling layers.

    Science.gov (United States)

    Guo, Kunping; Si, Changfeng; Han, Ceng; Pan, Saihu; Chen, Guo; Zheng, Yanqiong; Zhu, Wenqing; Zhang, Jianhua; Sun, Chang; Wei, Bin

    2017-10-05

    Inverted organic light-emitting diodes (IOLEDs) on plastic substrates have great potential application in flexible active-matrix displays. High energy consumption, instability and poor electron injection are key issues limiting the commercialization of flexible IOLEDs. Here, we have systematically investigated the electrooptical properties of molybdenum disulfide (MoS 2 ) and applied it in developing highly efficient and stable blue fluorescent IOLEDs. We have demonstrated that MoS 2 -based IOLEDs can significantly improve electron-injecting capacity. For the MoS 2 -based device on plastic substrates, we have achieved a very high external quantum efficiency of 7.3% at the luminance of 9141 cd m -2 , which is the highest among the flexible blue fluorescent IOLEDs reported. Also, an approximately 1.8-fold improvement in power efficiency was obtained compared to glass-based IOLEDs. We attributed the enhanced performance of flexible IOLEDs to MoS 2 nanopillar arrays due to their light extraction effect. The van der Waals force played an important role in the formation of MoS 2 nanopillar arrays by thermal evaporation. Notably, MoS 2 -based flexible IOLEDs exhibit an intriguing efficiency roll-up, that is, the current efficiency increases slightly from 14.0 to 14.6 cd A -1 with the luminance increasing from 100 to 5000 cd m -2 . In addition, we observed that the initial brightness of 500 cd m -2 can be maintained at 97% after bending for 500 cycles, demonstrating the excellent mechanical stability of flexible IOLEDs. Furthermore, we have successfully fabricated a transparent, flexible IOLED with low efficiency roll-off at high current density.

  17. Effect of a thin layer of tris (8-hydroxyquinoline) aluminum doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) on the chromaticity of white organic light-emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Gang; Zhao Yi; Li Feng; Xie Wenfa; Liu Shiyong

    2004-11-22

    Efficient white organic light-emitting devices (OLEDs) are demonstrated by inserting a thin layer of tris (8-hydroxyquinoline) aluminum (Alq) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) (DCJTB) into N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) layer. Alq without doping is used as an electron-transporting layer and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine or BCP) as an exciton-blocking layer. NPB layers are separated by the doped Alq layer, the layer that sandwiched between BCP and doped Alq layers acts as a blue-emitting layer, and the other as a hole-transporting layer. The doped Alq layer acts as a red and green-emitting as well as chromaticity-tuning layer, whose thickness and position as well as the concentration of DCJTB in Alq permit the tuning of the device spectrum to achieve a balanced white emission with Commission Internationale De L'Eclairage (CIE) coordinates of (0.33, 0.33). The device has a maximum luminance of 6745 cd/m{sup 2}, a maximum external efficiency of 1.36 %, corresponding to 2.56 cd/A.

  18. Effect of a thin layer of tris (8-hydroxyquinoline) aluminum doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) on the chromaticity of white organic light-emitting devices

    International Nuclear Information System (INIS)

    Cheng Gang; Zhao Yi; Li Feng; Xie Wenfa; Liu Shiyong

    2004-01-01

    Efficient white organic light-emitting devices (OLEDs) are demonstrated by inserting a thin layer of tris (8-hydroxyquinoline) aluminum (Alq) doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) (DCJTB) into N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) layer. Alq without doping is used as an electron-transporting layer and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine or BCP) as an exciton-blocking layer. NPB layers are separated by the doped Alq layer, the layer that sandwiched between BCP and doped Alq layers acts as a blue-emitting layer, and the other as a hole-transporting layer. The doped Alq layer acts as a red and green-emitting as well as chromaticity-tuning layer, whose thickness and position as well as the concentration of DCJTB in Alq permit the tuning of the device spectrum to achieve a balanced white emission with Commission Internationale De L'Eclairage (CIE) coordinates of (0.33, 0.33). The device has a maximum luminance of 6745 cd/m 2 , a maximum external efficiency of 1.36 %, corresponding to 2.56 cd/A

  19. Recent developments in white light emitting diodes

    Science.gov (United States)

    Lohe, P. P.; Nandanwar, D. V.; Belsare, P. D.; Moharil, S. V.

    2018-05-01

    In the recent years solid state lighting based on LEDs has revolutionized lighting technology. LEDs have many advantages over the conventional lighting based on fluorescent and incandescent lamps such as mercury free, high conversion efficiency of electrical energy into light, long lifetime reliability and ability to use with many types of devices. LEDs have emerged as a new potentially revolutionary technology that could save up to half of energy used for lighting applications. White LEDs would be the most important light source in the future, so much so that this aspect had been highlighted by the Nobel committee during the award of 2014 Nobel Prize for Physics. Recent advancement in the fabrication of GaN chip capable of emitting in blue and near UV region paved way for fabrication of white LED lamps. Mainly there are two approaches used for preparing white emitting solid state lamp. In the first approach blue light (λ=450 nm) emitted from the InGaN LED chip is partially absorbed by the YAG:Ce3+ phosphor coated on it and re-emitted as yellow fluorescence. A white light can be generated by the combination of blue + yellow emission bands. These lamps are already available. But they are suffering from major drawback that their Colour Rendering Index (CRI) is low. In the second approach, white LEDs are made by coating near ultraviolet emitting (360 to 410nm) LED with a mixture of high efficiency red, green and blue emitting phosphors, analogous to the fluorescent lamp. This method yields lamps with better color rendition. Addition of a yellow emitting phosphor improves CRI further. However conversion efficiency is compromised to some extent. Further the cost of near UV emitting chip is very high compared to blue emitting chips. Thus cost and light output wise, near UV chips are much inferior to blue chips. Recently some rare earth activated oxynitrides, silicates, fluorides have emerged as an important family of luminescent materials for white LED application

  20. Electron-transporting layer doped with cesium azide for high-performance phosphorescent and tandem white organic light-emitting devices

    International Nuclear Information System (INIS)

    Yu, Yaoyao; Chen, Xingming; Jin, Yu; Wu, Zhijun; Yu, Ye; Lin, Wenyan; Yang, Huishan

    2017-01-01

    Cesium azide was employed as an effective n-dopant in the electron-transporting layer (ETL) of organic light-emitting devices (OLEDs) owing to its low deposition temperature and high ambient stability. By doping cesium azide onto 4,7-diphenyl-1,10-phenanthroline, a green phosphorescent OLED having best efficiencies of 66.25 cd A −1 , 81.22 lm W −1 and 18.82% was realized. Moreover, the efficiency roll-off from 1000 cd m −2 to 10 000 cd m −2 is only 12.9%, which is comparable with or even lower than that of devices utilizing the co-host system. Physical mechanisms for the improvement of device performance were studied in depth by analyzing the current density–voltage ( J – V ) characteristics of the electron-only devices. In particular, by comparing the J – V characteristics of the electron-only devices instead of applying the complicated ultraviolet photoelectron spectrometer measurements, we deduced the decrease in barrier height for electron injection at the ETL/cathode contact. Finally, an efficient tandem white OLED utilizing the n-doped layer in the charge generation unit (CGU) was constructed. As far as we know, this is the first report on the application of this CGU for fabricating tandem white OLEDs. The emissions of the tandem device are all in the warm white region from 1213 cd m −2 to 10870 cd m −2 , as is beneficial to the lighting application. (paper)

  1. Numerical study of the influence of applied voltage on the current balance factor of single layer organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Fei-ping, E-mail: lufp-sysu@163.com; Liu, Xiao-bin; Xing, Yong-zhong [College of Physics and Information Science, Tianshui Normal University, Tianshui 741001 (China)

    2014-04-28

    Current balance factor (CBF) value, the ratio of the recombination current density and the total current density of a device, has an important function in fluorescence-based organic light-emitting diodes (OLEDs), as well as in the performance of the organic electrophosphorescent devices. This paper investigates the influence of the applied voltage of a device on the CBF value of single layer OLED based on the numerical model of a bipolar single layer OLED with organic layer trap free and without doping. Results show that the largest CBF value can be achieved when the electron injection barrier (ϕ{sub n}) is equal to the hole injection barrier (ϕ{sub p}) in the lower voltage region at any instance. The largest CBF in the higher voltage region can be achieved in the case of ϕ{sub n} > ϕ{sub p} under the condition of electron mobility (μ{sub 0n}) > hole mobility (μ{sub 0p}), whereas the result for the case of μ{sub 0n} < μ{sub 0p}, is opposite. The largest CBF when μ{sub 0n} = μ{sub 0p} can be achieved in the case of ϕ{sub n} = ϕ{sub p} in the entire region of the applied voltage. In addition, the CBF value of the device increases with increasing applied voltage. The results obtained in this paper can present an in-depth understanding of the OLED working mechanism and help in the future fabrication of high efficiency OLEDs.

  2. Formation of light-emitting nanostructures in layers of stoichiometric SiO{sub 2} irradiated with swift heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Kachurin, G. A., E-mail: kachurin@isp.nsc.ru; Cherkova, S. G. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics (Russian Federation); Skuratov, V. A. [Joint Institute for Nuclear Research (Russian Federation); Marin, D. V.; Kesler, V. G.; Volodin, V. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics (Russian Federation)

    2011-10-15

    Thermally grown SiO{sub 2} layers have been irradiated with 700-MeV Bi ions with doses of (3-10) Multiplication-Sign 10{sup 12} cm{sup -2}. It is found that, even after a dose of 3 Multiplication-Sign 10{sup 12} cm{sup -2}, a photoluminescence band in the region of 600 nm appears. Its intensity levels off at a dose of {approx}5 Multiplication-Sign 10{sup 12} cm{sup -2}. The nature of the emission centers is studied by the methods of infrared transmission, Raman scattering, X-ray photoelectron spectroscopy, ellipsometry, and the reaction to passivating low-temperature anneals. It is established that irradiation brings about a decrease in the number of Si-O bonds with a relevant increase in the Si-Si bonds. It is assumed that the photoluminescence is caused by nanostructures containing an excess Si and/or having a deficit of O. The reaction of reduction of SiO{sub 2} proceeds in ion tracks due to high levels of ionization and heating within these tracks. The dose dependence is used to estimate the diameter of a track at 8-9 nm.

  3. Formation of light-emitting nanostructures in layers of stoichiometric SiO2 irradiated with swift heavy ions

    International Nuclear Information System (INIS)

    Kachurin, G. A.; Cherkova, S. G.; Skuratov, V. A.; Marin, D. V.; Kesler, V. G.; Volodin, V. A.

    2011-01-01

    Thermally grown SiO 2 layers have been irradiated with 700-MeV Bi ions with doses of (3–10) × 10 12 cm −2 . It is found that, even after a dose of 3 × 10 12 cm −2 , a photoluminescence band in the region of 600 nm appears. Its intensity levels off at a dose of ∼5 × 10 12 cm −2 . The nature of the emission centers is studied by the methods of infrared transmission, Raman scattering, X-ray photoelectron spectroscopy, ellipsometry, and the reaction to passivating low-temperature anneals. It is established that irradiation brings about a decrease in the number of Si-O bonds with a relevant increase in the Si-Si bonds. It is assumed that the photoluminescence is caused by nanostructures containing an excess Si and/or having a deficit of O. The reaction of reduction of SiO 2 proceeds in ion tracks due to high levels of ionization and heating within these tracks. The dose dependence is used to estimate the diameter of a track at 8–9 nm.

  4. Evaluation of light-emitting diode beacon light fixtures.

    Science.gov (United States)

    2009-12-01

    Rotating beacons containing filament light sources have long been used on highway maintenance trucks : to indicate the presence of the truck to other drivers. Because of advances in light-emitting diode (LED) : technologies, flashing lights containin...

  5. Perovskite Materials for Light-Emitting Diodes and Lasers.

    Science.gov (United States)

    Veldhuis, Sjoerd A; Boix, Pablo P; Yantara, Natalia; Li, Mingjie; Sum, Tze Chien; Mathews, Nripan; Mhaisalkar, Subodh G

    2016-08-01

    Organic-inorganic hybrid perovskites have cemented their position as an exceptional class of optoelectronic materials thanks to record photovoltaic efficiencies of 22.1%, as well as promising demonstrations of light-emitting diodes, lasers, and light-emitting transistors. Perovskite materials with photoluminescence quantum yields close to 100% and perovskite light-emitting diodes with external quantum efficiencies of 8% and current efficiencies of 43 cd A(-1) have been achieved. Although perovskite light-emitting devices are yet to become industrially relevant, in merely two years these devices have achieved the brightness and efficiencies that organic light-emitting diodes accomplished in two decades. Further advances will rely decisively on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional perovskites, nanostructures, charge-transport materials, and device processing with architectural innovations. Here, the rapid advancements in perovskite light-emitting devices and lasers are reviewed. The key challenges in materials development, device fabrication, operational stability are addressed, and an outlook is presented that will address market viability of perovskite light-emitting devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The effect of composition on the formation of light-emitting Si nanostructures in SiOx layers on irradiation with swift heavy ions

    International Nuclear Information System (INIS)

    Kachurin, G. A.; Cherkova, S. G.; Marin, D. V.; Kesler, V. G.; Skuratov, V. A.; Cherkov, A. G.

    2011-01-01

    The SiO x layers different in composition (0 14 cm −2 to stimulate the formation of light-emitting Si nanostructures. The irradiation gives rise to a photoluminescence band with the parameters dependent on x. As the Si content is increased, the photoluminescence is first enhanced, with the peak remaining arranged near the wavelength λ ≈ 600 nm, and then the peak shifts to λ ≈ 800 nm. It is concluded that the emission sources are quantum-confined nanoprecipitates formed by disproportionation of SiO x in ion tracks due to profound ionization losses. Changes in the photoluminescence spectrum with increasing x are attributed firstly to the increase in the probability of formation of nanoprecipitates and then to the increase in their dimensions; the latter effect is accompanied with a shift of the emission band to longer wavelengths. The subsequent quenching of photoluminescence is interpreted as a result of the removal of quantum confinement in nanoprecipitates and their coagulation.

  7. The effect of composition on the formation of light-emitting Si nanostructures in SiO{sub x} layers on irradiation with swift heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Kachurin, G. A., E-mail: kachurin@isp.nsc.ru; Cherkova, S. G.; Marin, D. V.; Kesler, V. G. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Skuratov, V. A. [Joint Institute for Nuclear Research (Russian Federation); Cherkov, A. G. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2011-03-15

    The SiO{sub x} layers different in composition (0 < x < 2) are irradiated with Xe ions with the energy 167 MeV and the dose 10{sup 14} cm{sup -2} to stimulate the formation of light-emitting Si nanostructures. The irradiation gives rise to a photoluminescence band with the parameters dependent on x. As the Si content is increased, the photoluminescence is first enhanced, with the peak remaining arranged near the wavelength {lambda} Almost-Equal-To 600 nm, and then the peak shifts to {lambda} Almost-Equal-To 800 nm. It is concluded that the emission sources are quantum-confined nanoprecipitates formed by disproportionation of SiO{sub x} in ion tracks due to profound ionization losses. Changes in the photoluminescence spectrum with increasing x are attributed firstly to the increase in the probability of formation of nanoprecipitates and then to the increase in their dimensions; the latter effect is accompanied with a shift of the emission band to longer wavelengths. The subsequent quenching of photoluminescence is interpreted as a result of the removal of quantum confinement in nanoprecipitates and their coagulation.

  8. The feasibility of using solution-processed aqueous La2O3 as effective hole injection layer in organic light-emitting diode

    Science.gov (United States)

    Zhang, Yan; Li, Wanshu; Zhang, Ting; Yang, Bo; Zheng, Qinghong; Xu, Jiwen; Wang, Hua; Wang, Lihui; Zhang, Xiaowen; Wei, Bin

    2018-01-01

    Low-cost and scalable manufacturing boosts organic electronic devices with all solution process. La2O3 powders and corresponding aqueous solutions are facilely synthesized. Atomic force microscopy and scanning electron microscopy measurements show that solution-processed La2O3 behaves superior film morphology. X-ray diffraction and X-ray photoelectron spectroscopy measurements verify crystal phase and typical La signals. In comparison with the most widely-used hole injection layers (HILs) of MoOx and poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), enhanced luminous efficiency is observed in organic light-emitting diode (OLED) using solution-processed La2O3 HIL. Current-voltage, impedance-voltage and phase angle-voltage transition curves clarify that solution-processed La2O3 behaves nearly comparable hole injection capacity to MoOx and PEDOT:PSS, and favorably tailors carrier balance. Moreover, the hole injection mechanism of solution-processed La2O3 is proven to be predominantly controlled by Fowler-Nordheim tunneling process and the hole injection barrier height between ITO and NPB via La2O3 interlayer is estimated to be 0.098 eV. Our experiments provide a feasible application of La2O3 in organic electronic devices with solution process.

  9. Hybrid active layers from a conjugated polymer and inorganic nanoparticles for organic light emitting devices with emission colour tuned by electric field

    Energy Technology Data Exchange (ETDEWEB)

    Aleshin, Andrey N; Alexandrova, Elena L; Shcherbakov, Igor P [Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26, Polytechnicheskaya Str., St Petersburg 194021 (Russian Federation)], E-mail: aleshin@transport.ioffe.ru

    2009-05-21

    We report on the investigation of the electrical and optical properties of hybrid active layers for organic devices consisting of a conjugated polymer MEH-PPV mixed with ZnO and Si nanoparticles. The effect of an electric field on the photoluminescence (PL) from a MEH-PPV : ZnO composite film is studied. We have found that in the absence of an electric field PL emission from the MEH-PPV : ZnO composites have two main maxima in the blue-red regions. Three additional minor PL maxima attributed to the exciplex states were found at {approx}420-480 nm. Application of a voltage bias to planar electrodes significantly suppresses the blue emission. Generation of excited states in the MEH-PPV : ZnO structures implies the presence of several radiative recombination mechanisms with the formation of polymer-nanoparticle complexes including exciplex states and charge transfer between the polymer and nanoparticles that can be controlled by an electric field. This effect provides the possibility to tune by an electric field the emission colour of organic light emitting diodes by combining an efficient emission from both organic/inorganic materials involved.

  10. Hybrid active layers from a conjugated polymer and inorganic nanoparticles for organic light emitting devices with emission colour tuned by electric field

    International Nuclear Information System (INIS)

    Aleshin, Andrey N; Alexandrova, Elena L; Shcherbakov, Igor P

    2009-01-01

    We report on the investigation of the electrical and optical properties of hybrid active layers for organic devices consisting of a conjugated polymer MEH-PPV mixed with ZnO and Si nanoparticles. The effect of an electric field on the photoluminescence (PL) from a MEH-PPV : ZnO composite film is studied. We have found that in the absence of an electric field PL emission from the MEH-PPV : ZnO composites have two main maxima in the blue-red regions. Three additional minor PL maxima attributed to the exciplex states were found at ∼420-480 nm. Application of a voltage bias to planar electrodes significantly suppresses the blue emission. Generation of excited states in the MEH-PPV : ZnO structures implies the presence of several radiative recombination mechanisms with the formation of polymer-nanoparticle complexes including exciplex states and charge transfer between the polymer and nanoparticles that can be controlled by an electric field. This effect provides the possibility to tune by an electric field the emission colour of organic light emitting diodes by combining an efficient emission from both organic/inorganic materials involved.

  11. High-performance tandem organic light-emitting diodes based on a buffer-modified p/n-type planar organic heterojunction as charge generation layer

    Science.gov (United States)

    Wu, Yukun; Sun, Ying; Qin, Houyun; Hu, Shoucheng; Wu, Qingyang; Zhao, Yi

    2017-04-01

    High-performance tandem organic light-emitting diodes (TOLEDs) were realized using a buffer-modified p/n-type planar organic heterojunction (OHJ) as charge generation layer (CGL) consisting of common organic materials, and the configuration of this p/n-type CGL was "LiF/N,N'-diphenyl-N,N'-bis(1-napthyl)-1,1'-biphenyl-4,4'-diamine (NPB)/4,7-diphenyl-1,10-phenanthroline (Bphen)/molybdenum oxide (MoOx)". The optimized TOLED exhibited a maximum current efficiency of 77.6 cd/A without any out-coupling techniques, and the efficiency roll-off was greatly improved compared to the single-unit OLED. The working mechanism of the p/n-type CGL was discussed in detail. It is found that the NPB/Bphen heterojunction generated enough charges under a forward applied voltage and the carrier extraction was a tunneling process. These results could provide a new method to fabricate high-performance TOLEDs.

  12. Improving the performance of AlGaN-based deep-ultraviolet light-emitting diodes using electron blocking layer with a heart-shaped graded Al composition

    Science.gov (United States)

    Kwon, M. R.; Park, T. H.; Lee, T. H.; Lee, B. R.; Kim, T. G.

    2018-04-01

    We propose a design for highly efficient AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) using a heart-shaped graded Al composition electron-blocking layer (EBL). This novel structure reduced downward band bending at the interface between the last quantum barrier and the EBL and flattened the electrostatic field in the interlayer between the barriers of the multi-quantum barrier EBL. Consequently, electron leakage was significantly suppressed and hole injection efficiency was found to have improved. The parameter values of simulation were extracted from the experimental data of the reference DUV LEDs. Using the SimuLED, we compared the electrical and optical properties of three structures with different Al compositions in the active region and the EBL. The internal quantum efficiency of the proposed structure was shown to exceed those of the reference DUV LEDs by a factor of 1.9. Additionally, the output power at 20 mA was found to increase by a factor of 2.1.

  13. Nanoengineering of organic light-emitting diodes

    International Nuclear Information System (INIS)

    Lupton, J.M.

    2000-11-01

    This thesis reports nanoengineerging of the emission and transport properties of organic light-emitting diodes (LEDs). This is achieved by a control of the electronic material properties and the photonic device properties. A novel class of conjugated materials for electroluminescence (EL) applications is presented, based on successively branching, or dendritic, materials comprising an emissive core and a shielding dendritic architecture. Exciton localisation at the centre of these dendrimers is observed in both luminescence and absorption. A detailed quantum chemical investigation using an exciton model supports these findings and accurately describes the energies and oscillator strengths of transitions in the core and branches. The dendrimer generation describes the degree of branching and gives a direct measure of the separation and interaction between chromophores. Increasing generation is found to lead to a reduction in red tail emission. This correlates with an increase in operating field and LED efficiency. Dendrimer blends with triplet harvesting dendritic phosphors are also investigated and found to exhibit unique emission properties. A numerical device model is presented, which is used to describe the temperature dependence of single layer polymer LEDs by fitting the field-dependent mobility and the barrier to hole injection. The device model is also used to obtain mobility values for the dendrimer materials, which are in excellent agreement with results obtained from time-of-flight measurements. The dendrimer generation is shown to provide a direct control of hopping mobility, which decreases by two orders of magnitude as the dendrimer generation increases from 0 to 3. The photonic properties and spontaneous emission of an LED are modified by incorporating a periodic wavelength scale microstructure into the emitting film. This is found to double the amount of light emitted with no effect on the device current. An investigation of the angular dependence

  14. Hybrid white organic light-emitting diodes combining blue-fluorescent polymer and red phosphorescent Pt(II) complexes as active layer

    Energy Technology Data Exchange (ETDEWEB)

    Germino, Jose Carlos; Faleiros, Marcelo Meira; Moraes, Emmanuel Santos; Atvars, Teresa Dib Zambon, E-mail: kakagermino@hotmail.com [Universidade Estadual de Campinas (UNICAMP), SP (Brazil); Domingues, Raquel Aparecida [Universidade Federal de Sao Paulo (UNIFESP), SP (Brazil); Quites, Fernando Junior [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil); Freitas, Jilian Nei de [Centro de Tecnologia da Informacao Renato Archer, Campinas, SP (Brazil)

    2016-07-01

    Full text: In this work we proposed a PFO composite with two salicylidene based Pt(II) coordination compounds, the [Pt(salophen)] and [Pt(sal-3,4-ben)] (red emitters), as emissive layer (EML) for Organic Light-emitting Diodes (OLEDs), combining a blue-fluorescent polymer (PFO) with red-phosphorescent Pt(II) coordination complexes in order to obtain an efficient white electroluminescent EML for WOLEDs application. Firstly, [Pt(salophen)] and [Pt(sal-3,4-ben)] were synthesized, purified and characterized by single crystal X-ray diffraction, yielding their respective expected molecular structures. The photoluminescence properties of the devices were evaluated by steady-state (electronic absorption and emission spectroscopies) and transient (fluorescence decays and TRES) measurements. It was observed the presence of non-radiative energy transfer processes between the PFO derivative and Pt(II) complexes. Posteriorly, the Pt(II) complexes were blended with PVK at 1% mol:mol ratio and OLEDs were made, leading to red-emitting devices with high color purity for the two coordination compounds. However, the two devices present low current efficiency values. In order to improve the electroluminescence properties of Pt(II) complexes PhOLEDs, PVK host was substituted by PFO at 0.5, 1.0 and 2.5% mol:mol ratios of complex and it was observed a great improvement of their optical-electronic properties in terms of luminance, voltage, current density and current efficiency in comparison to PVK composites or pure PFO devices. At 2.5% concentration, predominant bands of Pt(II) complexes were observed at low and high voltages. For the other concentrations, a different behavior was observed: the emission bands and device color were function of applied electrical field, exhibiting a red color at lower voltages (5 to 9V) and the PFO characteristic emission between 9 and 13V, leading to a white light emission at 13V. The best results were obtained for [Pt(sal-3,4-ben)] coordination compound

  15. Pyridine Based Polymer Light-Emitting Devices

    National Research Council Canada - National Science Library

    Wang, Y

    1997-01-01

    ...) as a hole transporting/electron blocking layer. This improves the device efficiency and brightness significantly due to the charge confinement and exciplex emission at the PVK/emitting polymer interface...

  16. The effects of ultra-thin cerium fluoride film as the anode buffer layer on the electrical characteristics of organic light emitting diodes

    Science.gov (United States)

    Lu, Hsin-Wei; Tsai, Cheng-Che; Hong, Cheng-Shong; Kao, Po-Ching; Juang, Yung-Der; Chu, Sheng-Yuan

    2016-11-01

    In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF3film as an ultra-thin buffer layer between the indium tin oxide (ITO) electrode and α-naphthylphenylbiphenyldiamine (NPB) hole transport layer, with the structure configuration ITO/CeF3 (0.5, 1, and 1.5 nm)/α-naphthylphenylbiphenyl diamine (NPB) (40 nm)/tris(8-hydroxyquinoline) aluminum (Alq3) (60 nm)/lithium fluoride (LiF) (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone treated CeF3 film. The work function increased from 4.8 eV (standard ITO electrode) to 5.22 eV (0.5-nm-thick UV-ozone treated CeF3 film deposited on the ITO electrode). The surface roughness of the UV-ozone treated CeF3 film was smoother than that of the standard ITO electrode. Further, the UV-ozone treated CeF3 film increased both the surface energy and polarity, as determined from contact angle measurements. In addition, admittance spectroscopy measurements showed an increased capacitance and conductance of the OLEDs. Accordingly, the turn-on voltage decreased from 4.2 V to 3.6 V at 1 mA/cm2, the luminance increased from 7588 cd/m2 to 24760 cd/m2, and the current efficiency increased from 3.2 cd/A to 3.8 cd/A when the 0.5-nm-thick UV-ozone treated CeF3 film was inserted into the OLEDs.

  17. Highly efficient silicon light emitting diode

    NARCIS (Netherlands)

    Le Minh, P.; Holleman, J.; Wallinga, Hans

    2002-01-01

    In this paper, we describe the fabrication, using standard silicon processing techniques, of silicon light-emitting diodes (LED) that efficiently emit photons with energy around the silicon bandgap. The improved efficiency had been explained by the spatial confinement of charge carriers due to a

  18. Highly efficient white top-emitting organic light-emitting diodes with forward directed light emission

    Energy Technology Data Exchange (ETDEWEB)

    Freitag, Patricia; Reineke, Sebastian; Furno, Mauro; Luessem, Bjoern; Leo, Karl [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

    2010-07-01

    The demand for highly efficient and energy saving illumination has increased considerably during the last decades. Organic light emitting diodes (OLEDs) are promising candidates for future lighting technologies. They offer high efficiency along with excellent color quality, allowing substantially lower power consumption than traditional illuminants. Recently, especially top-emitting devices have attracted high interest due to their compatibility with opaque substrates like metal sheets. In this contribution, we demonstrate top-emitting OLEDs with white emission spectra employing a multilayer hybrid cavity structure with two highly efficient phosphorescent emitter materials for orange-red (Ir(MDQ)2(acac)) and green (Ir(ppy)3) emission as well as the stable fluorescent blue emitter TBPe. To improve the OLED performance and modify the color quality, two different electron blocking layers and anode material combinations are tested. Compared to Lambertian emission, our devices show considerably enhanced forward emission, which is preferred for most lighting applications. Besides broadband emission and angle independent emission maxima, power efficiencies of 13.3 lm/W at 3 V and external quantum efficiencies of 5.3% are achieved. The emission shows excellent CIE coordinates of (0.420,0.407) at approx. 1000 cd/m{sup 2} and color rendering indices up to 77.

  19. Electrically driven surface plasmon light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of GaN light-emitting diodes (LEDs) with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  20. Light emitting fabric technologies for photodynamic therapy.

    Science.gov (United States)

    Mordon, Serge; Cochrane, Cédric; Tylcz, Jean Baptiste; Betrouni, Nacim; Mortier, Laurent; Koncar, Vladan

    2015-03-01

    Photodynamic therapy (PDT) is considered to be a promising method for treating various types of cancer. A homogeneous and reproducible illumination during clinical PDT plays a determinant role in preventing under- or over-treatment. The development of flexible light sources would considerably improve the homogeneity of light delivery. The integration of optical fiber into flexible structures could offer an interesting alternative. This paper aims to describe different methods proposed to develop Side Emitting Optical Fibers (SEOF), and how these SEOF can be integrated in a flexible structure to improve light illumination of the skin during PDT. Four main techniques can be described: (i) light blanket integrating side-glowing optical fibers, (ii) light emitting panel composed of SEOF obtained by micro-perforations of the cladding, (iii) embroidery-based light emitting fabric, and (iv) woven-based light emitting fabric. Woven-based light emitting fabrics give the best performances: higher fluence rate, best homogeneity of light delivery, good flexibility. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Single component Mn-doped perovskite-related CsPb2ClxBr5-x nanoplatelets with a record white light quantum yield of 49%: a new single layer color conversion material for light-emitting diodes.

    Science.gov (United States)

    Wu, Hao; Xu, Shuhong; Shao, Haibao; Li, Lang; Cui, Yiping; Wang, Chunlei

    2017-11-09

    Single component nanocrystals (NCs) with white fluorescence are promising single layer color conversion media for white light-emitting diodes (LED) because the undesirable changes of chromaticity coordinates for the mixture of blue, green and red emitting NCs can be avoided. However, their practical applications have been hindered by the relative low photoluminescence (PL) quantum yield (QY) for traditional semiconductor NCs. Though Mn-doped perovskite nanocube is a potential candidate, it has been unable to realize a white-light emission to date. In this work, the synthesis of Mn-doped 2D perovskite-related CsPb 2 Cl x Br 5-x nanoplatelets with a pure white emission from a single component is reported. Unlike Mn-doped perovskite nanocubes with insufficient energy transfer efficiency, the current reported Mn-doped 2D perovskite-related CsPb 2 Cl x Br 5-x nanoplatelets show a 10 times higher energy transfer efficiency from perovskite to Mn impurities at the required emission wavelengths (about 450 nm for perovskite emission and 580 nm for Mn emission). As a result, the Mn/perovskite dual emission intensity ratio surprisingly elevates from less than 0.25 in case of Mn-doped nanocubes to 0.99 in the current Mn-doped CsPb 2 Cl x Br 5-x nanoplatelets, giving rise to a pure white light emission with Commission Internationale de l'Eclairage (CIE) color coordinates of (0.35, 0.32). More importantly, the highest PL QY for Mn-doped perovskite-related CsPb 2 Cl x Br 5-x nanoplatelets is up to 49%, which is a new record for white-emitting nanocrystals with single component. These highly luminescent nanoplatelets can be blended with polystyrene (PS) without changing the white light emission but dramatically improving perovskite stability. The perovskite-PS composites are available not only as a good solution processable coating material for assembling LED, but also as a superior conversion material for achieving white light LED with a single conversion layer.

  2. Laterally injected light-emitting diode and laser diode

    Science.gov (United States)

    Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

    2015-06-16

    A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

  3. All-Quantum-Dot Infrared Light-Emitting Diodes

    KAUST Repository

    Yang, Zhenyu

    2015-12-22

    © 2015 American Chemical Society. Colloidal quantum dots (CQDs) are promising candidates for infrared electroluminescent devices. To date, CQD-based light-emitting diodes (LEDs) have employed a CQD emission layer sandwiched between carrier transport layers built using organic materials and inorganic oxides. Herein, we report the infrared LEDs that use quantum-tuned materials for each of the hole-transporting, the electron-transporting, and the light-emitting layers. We successfully tailor the bandgap and band position of each CQD-based component to produce electroluminescent devices that exhibit emission that we tune from 1220 to 1622 nm. Devices emitting at 1350 nm achieve peak external quantum efficiency up to 1.6% with a low turn-on voltage of 1.2 V, surpassing previously reported all-inorganic CQD LEDs.

  4. Light emitting diodes with InAs/GaAsSb self-assembled quantum dot layer embedded in GaAs

    Czech Academy of Sciences Publication Activity Database

    Hazdra, P.; Oswald, Jiří; Hospodková, Alice; Hulicius, Eduard; Pangrác, Jiří

    2013-01-01

    Roč. 543, Sept (2013), 83-87 ISSN 0040-6090 R&D Projects: GA ČR GAP102/10/1201; GA ČR GA202/09/0676 Institutional research plan: CEZ:AV0Z10100521 Keywords : quantum dots * electroluminescence * metalorganic vapor phase epitaxy * InAs * GaAsSb * light emitting diodes Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.867, year: 2013

  5. Remanagement of Singlet and Triplet Excitons in Single-Emissive-Layer Hybrid White Organic Light-Emitting Devices Using Thermally Activated Delayed Fluorescent Blue Exciplex.

    Science.gov (United States)

    Liu, Xiao-Ke; Chen, Zhan; Qing, Jian; Zhang, Wen-Jun; Wu, Bo; Tam, Hoi Lam; Zhu, Furong; Zhang, Xiao-Hong; Lee, Chun-Sing

    2015-11-25

    A high-performance hybrid white organic light-emitting device (WOLED) is demonstrated based on an efficient novel thermally activated delayed fluorescence (TADF) blue exciplex system. This device shows a low turn-on voltage of 2.5 V and maximum forward-viewing external quantum efficiency of 25.5%, which opens a new avenue for achieving high-performance hybrid WOLEDs with simple structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Lighting emitting microstructures in porous silicon

    International Nuclear Information System (INIS)

    Squire, E.

    1999-01-01

    Experimental and theoretical techniques are used to examine microstructuring effects on the optical properties of single layer, multilayer, single and multiple microcavity structures fabricated from porous silicon. Two important issues regarding the effects of the periodic structuring of this material are discussed. Firstly, the precise role played by this microstructuring, given that the luminescence is distributed throughout the entire structure and the low porosity layers are highly absorbing at short wavelengths. The second issue examined concerns the observed effects on the optical spectra of the samples owing to the emission bandwidth of the material being greater than the optical stopband of the structure. Measurements of the reflectivity and photoluminescence spectra of different porous silicon microstructures are presented and discussed. The results are modelled using a transfer matrix technique. The matrix method has been modified to calculate the optical spectra of porous silicon specifically by accounting for the effects of dispersion, absorption and emission within the material. Layer thickness and porosity gradients have also been included in the model. The dielectric function of the two component layers (i.e. silicon and air) is calculated using the Looyenga formula. This approach can be adapted to suit other porous semiconductors if required. Examination of the experimental results have shown that the emitted light is strongly controlled by the optical modes of the structures. Furthermore, the data display an interplay of a wide variety of effects dependent upon the structural composition. Comparisons made between the experimental and calculated reflectivity and photoluminescence spectra of many different porous silicon microstructures show very good agreement. (author)

  7. High-efficiency/CRI/color stability warm white organic light-emitting diodes by incorporating ultrathin phosphorescence layers in a blue fluorescence layer

    Directory of Open Access Journals (Sweden)

    Miao Yanqin

    2018-01-01

    Full Text Available By incorporating ultrathin (80, low correlated color temperature of <3600 K, and high color stability at a wide voltage range of 5 V–9 V. These hybrid WOLEDs also reveal high forward-viewing external quantum efficiencies (EQE of 17.82%–19.34%, which are close to the theoretical value of 20%, indicating an almost complete exciton harvesting. In addition, the electroluminescence spectra of the hybrid WOLEDs can be easily improved by only changing the incorporating sequence of the ultrathin phosphorescence layers without device efficiency loss. For example, the hybrid WOLED with an incorporation sequence of ultrathin red/yellow/green phosphorescence layers exhibits an ultra-high CRI of 96 and a high EQE of 19.34%. To the best of our knowledge, this is the first WOLED with good tradeoff among device efficiency, CRI, and color stability. The introduction of ultrathin (<0.1 nm phosphorescence layers can also greatly reduce the consumption of phosphorescent emitters as well as simplify device structures and fabrication process, thus leading to low cost. Such a finding is very meaningful for the potential commercialization of hybrid WOLEDs.

  8. Assessing the potential of group 13 and 14 metal/metalloid phthalocyanines as hole transport layers in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Plint, Trevor; Lessard, Benoît H. [Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5 (Canada); Bender, Timothy P. [Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5 (Canada); Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario M5S 3E4 (Canada); Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada)

    2016-04-14

    In this study, we have assessed the potential application of group 13 and 14 metal and metalloid phthalocyanines ((X){sub n}-MPcs) and their axially substituted derivatives as hole-transporting layers in organic light emitting diodes (OLEDs). OLEDs studied herein have the generic structure of glass/ITO/(N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) or (X){sub n}-MPc)(50 nm)/Alq{sub 3} (60 nm)/LiF (1 nm)/Al (80 nm), where X is an axial substituent group. OLEDs using chloro aluminum phthalocyanine (Cl-AlPc) showed good peak luminance values of 2620 ± 113 cd/m{sup 2} at 11 V. To our knowledge, Cl-AlPc has not previously been shown to work as a hole transport material (HTL) in OLEDs. Conversely, the di-chlorides of silicon, germanium, and tin phthalocyanine (Cl{sub 2}-SiPc, Cl{sub 2}-GePc, and Cl{sub 2}-SnPc, respectively) showed poor performance compared to Cl-AlPc, having peak luminances of only 38 ± 4 cd/m{sup 2} (12 V), 23 ± 1 cd/m{sup 2} (8.5 V), and 59 ± 5 cd/m{sup 2} (13.5 V), respectively. However, by performing a simple axial substitution of the chloride groups of Cl{sub 2}-SiPc with pentafluorophenoxy groups, the resulting bis(pentafluorophenoxy) silicon phthalocyanine (F{sub 10}-SiPc) containing OLED had a peak luminance of 5141 ± 941 cd/m{sup 2} (10 V), a two order of magnitude increase over its chlorinated precursor. This material showed OLED characteristics approaching those of a baseline OLED based on the well-studied triarylamine NPB. Attempts to attach the pentafluorophenoxy axial group to both SnPc and GePc were hindered by synthetic difficulties and low thermal stability, respectively. In light of the performance improvements observed by simple axial substitution of SiPc in OLEDs, the use of axially substituted MPcs in organic electronic devices remains of continuing interest to us and potentially the field in general.

  9. Assessing the potential of group 13 and 14 metal/metalloid phthalocyanines as hole transport layers in organic light emitting diodes

    Science.gov (United States)

    Plint, Trevor; Lessard, Benoît H.; Bender, Timothy P.

    2016-04-01

    In this study, we have assessed the potential application of group 13 and 14 metal and metalloid phthalocyanines ((X)n-MPcs) and their axially substituted derivatives as hole-transporting layers in organic light emitting diodes (OLEDs). OLEDs studied herein have the generic structure of glass/ITO/(N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) or (X)n-MPc)(50 nm)/Alq3 (60 nm)/LiF (1 nm)/Al (80 nm), where X is an axial substituent group. OLEDs using chloro aluminum phthalocyanine (Cl-AlPc) showed good peak luminance values of 2620 ± 113 cd/m2 at 11 V. To our knowledge, Cl-AlPc has not previously been shown to work as a hole transport material (HTL) in OLEDs. Conversely, the di-chlorides of silicon, germanium, and tin phthalocyanine (Cl2-SiPc, Cl2-GePc, and Cl2-SnPc, respectively) showed poor performance compared to Cl-AlPc, having peak luminances of only 38 ± 4 cd/m2 (12 V), 23 ± 1 cd/m2 (8.5 V), and 59 ± 5 cd/m2 (13.5 V), respectively. However, by performing a simple axial substitution of the chloride groups of Cl2-SiPc with pentafluorophenoxy groups, the resulting bis(pentafluorophenoxy) silicon phthalocyanine (F10-SiPc) containing OLED had a peak luminance of 5141 ± 941 cd/m2 (10 V), a two order of magnitude increase over its chlorinated precursor. This material showed OLED characteristics approaching those of a baseline OLED based on the well-studied triarylamine NPB. Attempts to attach the pentafluorophenoxy axial group to both SnPc and GePc were hindered by synthetic difficulties and low thermal stability, respectively. In light of the performance improvements observed by simple axial substitution of SiPc in OLEDs, the use of axially substituted MPcs in organic electronic devices remains of continuing interest to us and potentially the field in general.

  10. Photon extraction from nitride ultraviolet light-emitting devices

    Science.gov (United States)

    Schowalter, Leo J; Chen, Jianfeng; Grandusky, James R

    2015-02-24

    In various embodiments, a rigid lens is attached to a light-emitting semiconductor die via a layer of encapsulant having a thickness insufficient to prevent propagation of thermal expansion mismatch-induced strain between the rigid lens and the semiconductor die.

  11. Light emitting structures porous silicon-silicon substrate

    International Nuclear Information System (INIS)

    Monastyrskii, L.S.; Olenych, I.B.; Panasjuk, M.R.; Savchyn, V.P.

    1999-01-01

    The research of spectroscopic properties of porous silicon has been done. Complex of photoluminescence, electroluminescence, cathodoluminescence, thermostimulated depolarisation current analyte methods have been applied to study of geterostructures and free layers of porous silicon. Light emitting processes had tendency to decrease. The character of decay for all kinds of luminescence were different

  12. White-light-emitting supramolecular gels.

    Science.gov (United States)

    Praveen, Vakayil K; Ranjith, Choorikkat; Armaroli, Nicola

    2014-01-07

    Let there be light, let it be white: Recent developments in the use of chromophore-based gels as scaffolds for the assembly of white-light-emitting soft materials have been significant. The main advantage of this approach lies in the facile accommodation of selected luminescent components within the gel. Excitation-energy-transfer processes between these components ultimately generate the desired light output. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Color-stable and efficient tandem white organic light-emitting devices using a LiF n-doping layer and a MoO{sub x} p-doping layer as charge generating unit

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu; Wu, Qingyang; Zhang, Zhensong; Yue, Shouzhen; Guo, Runda; Wang, Peng; Wu, Mingzhu; Gou, Changhua; Zhao, Yi, E-mail: yizhao@jlu.edu.cn; Liu, Shiyong

    2013-10-31

    We have demonstrated color-stable and efficient tandem organic light-emitting devices (OLEDs) using 4,7-diphenyl-1,10-phenanthroline (Bphen):LiF/4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA):molybdenum oxide (MoO{sub x}) as charge generating unit (CGU), which has the advantages of air stability and ease of fabrication; the working mechanism of Bphen:LiF/m-MTDATA:MoO{sub x} is also discussed through analysis of the electrical and spectral emission properties of tandem devices with different CGUs. The performance of tandem white OLED, comprising blue and yellow phosphorescent EL units, can be improved by optimizing the thickness of Bphen:LiF layer. The device comprised of 30 nm Bphen:LiF layer has a maximum current efficiency of 38.7 cd/A and it can still maintain 24.6 cd/A at the luminance of 10,370 cd/m{sup 2}. Moreover, the Commission Internationale de L'Eclairage (CIE) coordinates of the device are rather stable and the variation is only (± 0.003, ± 0.007) over a wide range of luminance (100–13,000 cd/m{sup 2}). - Highlights: • LiF n-doping layer and MoO{sub x} p-doping layer were used as charge generating units. • The device performance was improved by optimizing the thickness of n-doping layer. • High luminance and efficiency were both achieved at a very low current density. • The device showed rather stable spectra over a wide range of luminance.

  14. [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.

  15. Principles of phosphorescent organic light emitting devices.

    Science.gov (United States)

    Minaev, Boris; Baryshnikov, Gleb; Agren, Hans

    2014-02-07

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

  16. Fluorescence lifetime imaging using light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, Gordon T; Munro, Ian; Poher, Vincent; French, Paul M W; Neil, Mark A A [Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Elson, Daniel S [Institute of Biomedical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Hares, Jonathan D [Kentech Instruments Ltd, Unit 9, Hall Farm Workshops, South Moreton, Didcot, Oxfordshire, OX11 9AG (United Kingdom)], E-mail: gordon.kennedy@imperial.ac.uk

    2008-05-07

    We demonstrate flexible use of low cost, high-power light emitting diodes as illumination sources for fluorescence lifetime imaging (FLIM). Both time-domain and frequency-domain techniques have been implemented at wavelengths spanning the range 450-640 nm. Additionally, we demonstrate optically sectioned fluorescence lifetime imaging by combining structured illumination with frequency-domain FLIM.

  17. Light-emitting device test systems

    Science.gov (United States)

    McCord, Mark; Brodie, Alan; George, James; Guan, Yu; Nyffenegger, Ralph

    2018-01-23

    Light-emitting devices, such as LEDs, are tested using a photometric unit. The photometric unit, which may be an integrating sphere, can measure flux, color, or other properties of the devices. The photometric unit may have a single port or both an inlet and outlet. Light loss through the port, inlet, or outlet can be reduced or calibrated for. These testing systems can provide increased reliability, improved throughput, and/or improved measurement accuracy.

  18. Enhanced quantum efficiency in blue-emitting polymer/dielectric nanolayer nanocomposite light-emitting devices

    International Nuclear Information System (INIS)

    Park, Jong Hyeok; Lim, Yong Taik; Park, O Ok; Yu, Jae-Woong; Kim, Jai Kyeong; Kim, Young Chul

    2004-01-01

    Light-emitting devices based on environmentally stable, blue-emitting polymer/dielectric nanolayer nanocomposites were fabricated by blending poly(di-octylfluorene) (PDOF) with organo-clay. By reducing the excimer formation that leads to long wavelength tails, the photoluminescence (PL) and electroluminescence (EL) color purity of the device was enhanced. When a conjugated polymer/dielectric nanolayer nanocomposite is applied to an EL device, we expect an electronic structure similar to the well-known quantum well in small nanodomains. The ratio of PDOF/organo-clay was regulated from 2:1 to 0.5:1 (w/w). The light-emitting device of 0.5:1 (w/w) blend demonstrated the highest quantum efficiency (QE), 0.72% (ph/el), which is ∼500 times higher value compared with that of the pure PDOF layer device. However, the driving voltage of the nanocomposite devices tended to increase with increasing organo-clay content

  19. Hybrid Light-Emitting Diode Enhanced With Emissive Nanocrystals

    DEFF Research Database (Denmark)

    Kopylov, Oleksii

    This thesis investigates a new type of white light emitting hybrid diode, composed of a light emitting GaN/InGaN LED and a layer of semiconductor nanocrystals for color conversion. Unlike standard white LEDs, the device is configured to achieve high color conversion efficiency via non-radiative e......This thesis investigates a new type of white light emitting hybrid diode, composed of a light emitting GaN/InGaN LED and a layer of semiconductor nanocrystals for color conversion. Unlike standard white LEDs, the device is configured to achieve high color conversion efficiency via non...... of the hybrid diode fabrication including process techniques for GaN LED and incorporation of the nanocrystals are presented with the emphasis on the differences with standard LED processing. Results and analysis of optical and electrical characterization including photoluminescence (PL), micro-PL, time......-resolved PL and electroluminescence (EL) together with current-voltage characteristics are presented to evaluate the device performance. A clear evidence of non-radiative energy transfer was seen in the carrier dynamics of both the LED and the nanocrystals when the quantum well – nanocrystals separation...

  20. GREEN LIGHT EMITTING TRICOMPONENT LUMINOPHORS OF 2-NAPHTHOL FOR CONSTRUCTION OF ORGANIC LIGHT EMITTING DEVICES

    OpenAIRE

    K. G. MANE , P. B. NAGORE , DR. S. R. PUJARI

    2018-01-01

    This article presents a previous study and incredible progress in basic theoretical modeling, and working for organic light-emitting devices (OLEDs) including preparation and characteristic studies of Organo- Luminescent Materials by conventional solid state reaction technique.

  1. Solution processed, white emitting tandem organic light-emitting diodes with inverted device architecture.

    Science.gov (United States)

    Höfle, Stefan; Schienle, Alexander; Bernhard, Christoph; Bruns, Michael; Lemmer, Uli; Colsmann, Alexander

    2014-08-13

    Fully solution processed monochromatic and white-light emitting tandem or multi-photon polymer OLEDs with an inverted device architecture have been realized by employing WO3 /PEDOT:PSS/ZnO/PEI charge carrier generation layers. The luminance of the sub-OLEDs adds up in the stacked device indicating multi-photon emission. The white OLEDs exhibit a CRI of 75. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Improvement in light-extraction efficiency of light emitting diode ...

    Indian Academy of Sciences (India)

    The effect of various microlens parameters such as diameter and area fraction on light-extraction efficiency was systematically studied. Improvement of 4% in extraction efficiency was obtained by employing it on white light emitting diode. The area fraction of microlenses was increased up to 0.34 by reducing the spin speed.

  3. The Light-Emitting Diode as a Light Detector

    Science.gov (United States)

    Baird, William H.; Hack, W. Nathan; Tran, Kiet; Vira, Zeeshan; Pickett, Matthew

    2011-01-01

    A light-emitting diode (LED) and operational amplifier can be used as an affordable method to provide a digital output indicating detection of an intense light source such as a laser beam or high-output LED. When coupled with a microcontroller, the combination can be used as a multiple photogate and timer for under $50. A similar circuit is used…

  4. Weak-microcavity organic light-emitting diodes with improved light out-coupling.

    Science.gov (United States)

    Cho, Sang-Hwan; Song, Young-Woo; Lee, Joon-gu; Kim, Yoon-Chang; Lee, Jong Hyuk; Ha, Jaeheung; Oh, Jong-Suk; Lee, So Young; Lee, Sun Young; Hwang, Kyu Hwan; Zang, Dong-Sik; Lee, Yong-Hee

    2008-08-18

    We propose and demonstrate weak-microcavity organic light-emitting diode (OLED) displays with improved light-extraction and 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 are enhanced by 56%, 107%, and 26%, respectively, with improved color purity. Moreover, full-color passive-matrix bottom-emitting OLED displays are fabricated by employing low-index layers of two thicknesses. As a display, the EL efficiency of white color was 27% higher than that of a conventional OLED display.

  5. Safety of light emitting diodes in toys.

    Science.gov (United States)

    Higlett, M P; O'Hagan, J B; Khazova, M

    2012-03-01

    Light emitting diodes (LEDs) are increasingly being used in toys. An assessment methodology is described for determining the accessible emission limits for the optical radiation from the toys, which takes account of expected use and reasonably foreseeable misuse of toys. Where data are available, it may be possible to assess the toy from the data sheet alone. If this information is not available, a simple measurement protocol is proposed.

  6. Safety of light emitting diodes in toys

    International Nuclear Information System (INIS)

    Higlett, M P; O'Hagan, J B; Khazova, M

    2012-01-01

    Light emitting diodes (LEDs) are increasingly being used in toys. An assessment methodology is described for determining the accessible emission limits for the optical radiation from the toys, which takes account of expected use and reasonably foreseeable misuse of toys. Where data are available, it may be possible to assess the toy from the data sheet alone. If this information is not available, a simple measurement protocol is proposed.

  7. A white organic light emitting diode with improved stability

    International Nuclear Information System (INIS)

    Zhang Zhilin; Jiang Xueyin; Zhu Wenqing; Zhang Buxin; Xu Shaohong

    2001-01-01

    A white organic light emitting diode (OLED) has been constructed by employing a new blue material and a red dye directly doped in the blue emitting layer. For comparison, another white cell with a blocking layer has also been made. The configurations of the devices are ITO/CuPc/NPB/JBEM(P):DCJT/Alq/MgAg (device 1) and ITO/CuPc/NPB/TPBi:DCJT/Alq/MgAg (device 2) where copper phthalocyanine (CuPc) is the buffer layer, N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1.1'bipheny1-4-4'-diamine (NPB) is the hole transporting layer, 9,10-bis(3'5'-diaryl)phenyl anthracene doped with perylene (JBEM(P)) is the new blue emitting material, N,arylbenzimidazoles (TPBi) is the hole blocking layer, tris(8-quinolinolato)aluminium complex (Alq) is the electron transporting layer, and DCJT is a red dye. A stable and current independent white OLED has been obtained in device 1, which has a maximum luminance of 14 850 cd m -2 , an efficiency of 2.88 Lm W -1 , Commission Internationale de l'Eclairage coordinates of x=0.32, y=0.38 between 4-200 mA cm -2 , and a half lifetime of 2860 h at the starting luminance of 100 cd m -2 . Device 1 has a stability more than 50 times better than that of device 2. (author)

  8. Does antimatter emit a new light?

    International Nuclear Information System (INIS)

    Santilli, Ruggero Maria

    1997-01-01

    Contemporary theories of antimatter have a number of insufficiencies which stimulated the recent construction of the new isodual theory based on a certain anti-isomorphic map of all (classical and quantum) formulations of matter called isoduality. In this note we show that the isodual theory predicts that antimatter emits a new light, called isodual light, which can be distinguished from the ordinary light emitted by matter via gravitational interactions (only). In particular, the isodual theory predicts that all stable antiparticles such as the isodual photon, the positron and the antiproton experience antigravity in the field of matter (defined as the reversal of the sign of the curvature tensor). The antihydrogen atom is therefore predicted to: experience antigravity in the field of Earth; emit the isodual photon; and have the same spectroscopy of the hydrogen atom, although subjected to an anti-isomorphic isodual map. In this note we also show that the isodual theory predicts that bound states of elementary particles and antiparticles (such as the positronium) experience ordinary gravitation in both fields of matter and antimatter, thus bypassing known objections against antigravity. A number of intriguing and fundamental, open theoretical and experimental problems of 'the new physics of antimatter' are pointed out

  9. Does antimatter emit a new light?

    Energy Technology Data Exchange (ETDEWEB)

    Santilli, Ruggero Maria [Instituto per la Ricerca di Base (Italy)

    1997-08-15

    Contemporary theories of antimatter have a number of insufficiencies which stimulated the recent construction of the new isodual theory based on a certain anti-isomorphic map of all (classical and quantum) formulations of matter called isoduality. In this note we show that the isodual theory predicts that antimatter emits a new light, called isodual light, which can be distinguished from the ordinary light emitted by matter via gravitational interactions (only). In particular, the isodual theory predicts that all stable antiparticles such as the isodual photon, the positron and the antiproton experience antigravity in the field of matter (defined as the reversal of the sign of the curvature tensor). The antihydrogen atom is therefore predicted to: experience antigravity in the field of Earth; emit the isodual photon; and have the same spectroscopy of the hydrogen atom, although subjected to an anti-isomorphic isodual map. In this note we also show that the isodual theory predicts that bound states of elementary particles and antiparticles (such as the positronium) experience ordinary gravitation in both fields of matter and antimatter, thus bypassing known objections against antigravity. A number of intriguing and fundamental, open theoretical and experimental problems of 'the new physics of antimatter' are pointed out.

  10. Does antimatter emit a new light?

    International Nuclear Information System (INIS)

    Santilli, R.M.

    1996-01-01

    Contemporary theories of antimatter have a number of insufficiencies which stimulated the recent construction of the new isodual theory based on a certain anti-isomorphic map of all (classical and quantum) formulations of matter called isoduality. In this note we show that the isodual theory predicts that antimatter emits a new light, called isodual light, which can be distinguished from the ordinary light emitted by matter via gravitational interactions (only). In particular, the isodual theory predicts that all stable antiparticles such as the isodual photon, the positron and the antiproton experience antigravity in the field of matter (defined as the reversal of the sign of the curvature tensor). The antihydrogen atom is therefore predicted to: experience antigravity in the field of Earth; emit the isodual photon; and have the same spectroscopy of the hydrogen atom, although subjected to an anti-isomorphic isodual map. In this note we also show that the isodual theory predicts that bound states of elementary particle sand antiparticles (such as the positronium) experience ordinary gravitation in both fields of matter and antimatter, thus by passing known objections against antigravity. A number of intriguing and fundamental, open theoretical and experimental problems of 'the new physics of antimatter' are pointed out. 16 refs

  11. 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

  12. Study of photophysical processes in organic light-emitting diodes based on light-emission profile reconstruction

    NARCIS (Netherlands)

    Carvelli, M.

    2012-01-01

    Organic light-emitting diodes (OLEDs) are emerging as a promising option for energy-efficient, flexible light sources. A key factor that needs to be measured and controlled is the shape of the emission profile, i.e. the spatial distribution of the emitting excitons across the active layer thickness.

  13. Opto-electronic properties and light-emitting device application of widegap layered oxychalcogenides: LaCuOCh (Ch=chalcogen) and La2CdO2Se2

    International Nuclear Information System (INIS)

    Hiramatsu, Hidenori; Hirano, Masahiro; Kamioka, Hayato; Ueda, Kazushige; Ohta, Hiromichi; Kamiya, Toshio; Hosono, Hideo

    2006-01-01

    Electronic and optical properties of widegap oxychalcogenides, LaCuOCh (Ch chalcogen) and La 2 CdO 2 Se 2 , are reviewed with a focus on those relevant to their layered crystal structures, including high hole mobility, degenerate p-type conduction, room temperature exciton, and large third order optical nonlinearity. In particular, the widegap p-type metallic conduction was realized in Mg-doped LaCuOSe: the first demonstration among any class of widegap materials including GaN:Mg. Furthermore, we demonstrate the room temperature operation of a blue light-emitting diode using a pn hetero-junction composed of a LaCuOSe epilayer and an n-type amorphous InGaZn 5 O 8 . Those results strongly suggest that a series of the layered oxychalcogenides are applicable to the light-emitting layers in opto-electronic devices that operate in the ultraviolet-blue region as well as to transparent p-type conductors. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  14. Nearly Efficiency-Droop-Free AlGaN-Based Ultraviolet Light-Emitting Diodes with a Specifically Designed Superlattice p-Type Electron Blocking Layer for High Mg Doping Efficiency

    Science.gov (United States)

    Zhang, Zi-Hui; Huang Chen, Sung-Wen; Chu, Chunshuang; Tian, Kangkai; Fang, Mengqian; Zhang, Yonghui; Bi, Wengang; Kuo, Hao-Chung

    2018-04-01

    This work reports a nearly efficiency-droop-free AlGaN-based deep ultraviolet light-emitting diode (DUV LED) emitting in the peak wavelength of 270 nm. The DUV LED utilizes a specifically designed superlattice p-type electron blocking layer (p-EBL). The superlattice p-EBL enables a high hole concentration in the p-EBL which correspondingly increases the hole injection efficiency into the multiple quantum wells (MQWs). The enhanced hole concentration within the MQW region can more efficiently recombine with electrons in the way of favoring the radiative recombination, leading to a reduced electron leakage current level. As a result, the external quantum efficiency for the proposed DUV LED structure is increased by 100% and the nearly efficiency-droop-free DUV LED structure is obtained experimentally.

  15. Efficiency enhancement of blue light emitting diodes by eliminating V-defects from InGaN/GaN multiple quantum well structures through GaN capping layer control

    Science.gov (United States)

    Tsai, Sheng-Chieh; Li, Ming-Jui; Fang, Hsin-Chiao; Tu, Chia-Hao; Liu, Chuan-Pu

    2018-05-01

    A facile method for fabricating blue light-emitting diodes (B-LEDs) with small embedded quantum dots (QDs) and enhanced light emission is demonstrated by tuning the temperature of the growing GaN capping layer to eliminate V-defects. As the growth temperature increases from 770 °C to 840 °C, not only does the density of the V-defects reduce from 4.12 ∗ 108 #/cm2 nm to zero on a smooth surface, but the QDs also get smaller. Therefore, the growth mechanism of smaller QDs assisted by elimination of V-defects is discussed. Photoluminescence and electroluminescence results show that smaller embedded QDs can improve recombination efficiency, and thus achieve higher peak intensity with smaller peak broadening. Accordingly, the external quantum efficiency of the B-LEDs with smaller QDs is enhanced, leading to a 6.8% increase in light output power in lamp-form package LEDs.

  16. Improved emission spectrum from quantum dot superluminescent light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Li, L.H.; Rossetti, M.; Fiore, A. [Institute of Photonics and Quantum Electronics, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Occhi, L.; Velez, C. [EXALOS AG, Technoparkstrasse 1, 8005 Zuerich (Switzerland)

    2006-12-15

    The size dispersion of InAs quantum dots (QD) was optimized to broaden the photoluminescence (PL) spectrum. A broad PL spectral width up to 96 nm is achieved from a single QD layer with InAs thickness smaller than 2.4 monolayers at a growth temperature of 510 C. QD Superluminescent light emitting diodes with an ultrawide (115 nm), smooth output spectrum are obtained by incorporating this QD layer into chirped stacked structures. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Improvement in light-extraction efficiency of light emitting diode ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... emitting diode (OLED) can be enhanced by using light- extraction ... to grow, ω should posses a positive value, which is possible only when ∂φ/∂h < 0, .... To detect small changes, first, the source LED was sta- bilized by ...

  18. Printing method for organic light emitting device lighting

    Science.gov (United States)

    Ki, Hyun Chul; Kim, Seon Hoon; Kim, Doo-Gun; Kim, Tae-Un; Kim, Snag-Gi; Hong, Kyung-Jin; So, Soon-Yeol

    2013-03-01

    Organic Light Emitting Device (OLED) has a characteristic to change the electric energy into the light when the electric field is applied to the organic material. OLED is currently employed as a light source for the lighting tools because research has extensively progressed in the improvement of luminance, efficiency, and life time. OLED is widely used in the plate display device because of a simple manufacture process and high emitting efficiency. But most of OLED lighting projects were used the vacuum evaporator (thermal evaporator) with low molecular. Although printing method has lower efficiency and life time of OLED than vacuum evaporator method, projects of printing OLED actively are progressed because was possible to combine with flexible substrate and printing technology. Printing technology is ink-jet, screen printing and slot coating. This printing method allows for low cost and mass production techniques and large substrates. In this research, we have proposed inkjet printing for organic light-emitting devices has the dominant method of thick film deposition because of its low cost and simple processing. In this research, the fabrication of the passive matrix OLED is achieved by inkjet printing, using a polymer phosphorescent ink. We are measured optical and electrical characteristics of OLED.

  19. Light emitting diodes as a plant lighting source

    Energy Technology Data Exchange (ETDEWEB)

    Bula, R.J.; Tennessen, D.J.; Morrow, R.C. [Wisconsin Center for Space Automation and Robotics, Madison, WI (United States); Tibbitts, T.W. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-31

    Electroluminescence in solid materials is defined as the generation of light by the passage of an electric current through a body of solid material under an applied electric field. A specific type of electroluminescence, first noted by Lossew in 1923, involves the generation of photons when electrons are passed through a p-n junction of certain solid materials (junction of a n-type semiconductor, an electron donor, and a p-type semiconductor, an electron acceptor). Development efforts to translate these observations into visible light emitting devices, however, was not undertaken until the 1950s. The term, light emitting diode (LEDs), was first used in a report by Wolfe, et al., in 1955. The development of this light emitting semiconductor technology dates back less than 30 years. During this period of time, the LED has evolved from a rare and expensive light generating device to one of the most widely used electronic components. The most popular applications of the LED are as indicators or as optoelectronic switches. However, several recent advances in LED technology have made possible the utilization of LEDs for applications that require a high photon flux, such as for plant lighting in controlled environments. The new generation of LEDs based on a gallium aluminum arsenide (GaAlAS) semiconductor material fabricated as a double heterostructure on a transparent substrate has opened up many new applications for these LEDs.

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

    Science.gov (United States)

    Zhang, Congcong; Chen, Penglei; Hu, Wenping

    2016-03-09

    Organic light-emitting transistors (OLETs) represent an emerging class of organic optoelectronic devices, wherein the electrical switching capability of organic field-effect transistors (OFETs) and the light-generation capability of organic light-emitting diodes (OLEDs) are inherently incorporated in a single device. In contrast to conventional OFETs and OLEDs, the planar device geometry and the versatile multifunctional nature of OLETs not only endow them with numerous technological opportunities in the frontier fields of highly integrated organic electronics, but also render them ideal scientific scaffolds to address the fundamental physical events of organic semiconductors and devices. This review article summarizes the recent advancements on OLETs in light of materials, device configurations, operation conditions, etc. Diverse state-of-the-art protocols, including bulk heterojunction, layered heterojunction and laterally arranged heterojunction structures, as well as asymmetric source-drain electrodes, and innovative dielectric layers, which have been developed for the construction of qualified OLETs and for shedding new and deep light on the working principles of OLETs, are highlighted by addressing representative paradigms. This review intends to provide readers with a deeper understanding of the design of future OLETs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Si light-emitting device in integrated photonic CMOS ICs

    Science.gov (United States)

    Xu, Kaikai; Snyman, Lukas W.; Aharoni, Herzl

    2017-07-01

    The motivation for integrated Si optoelectronics is the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive biochemical sensors in the environmental control or medicine leads to the development of integrated high resolution sensors. Here CMOS-compatible Si light-emitting device structures are presented for investigating the effect of various depletion layer profiles and defect engineering on the photonic transition in the 1.4-2.8 eV. A novel Si device is proposed to realize both a two-terminal Si-diode light-emitting device and a three-terminal Si gate-controlled diode light-emitting device in the same device structure. In addition to the spectral analysis, differences between two-terminal and three-terminal devices are discussed, showing the light emission efficiency change. The proposed Si optical source may find potential applications in micro-photonic systems and micro-optoelectro-mechanical systems (MOEMS) in CMOS integrated circuitry.

  2. Light emission mechanism of mixed host organic light-emitting diodes

    Science.gov (United States)

    Song, Wook; Lee, Jun Yeob

    2015-03-01

    Light emission mechanism of organic light-emitting diodes with a mixed host emitting layer was studied using an exciplex type mixed host and an exciplex free mixed host. Monitoring of the current density and luminance of the two type mixed host devices revealed that the light emission process of the exciplex type mixed host was dominated by energy transfer, while the light emission of the exciplex free mixed host was controlled by charge trapping. Mixed host composition was also critical to the light emission mechanism, and the contribution of the energy transfer process was maximized at 50:50 mixed host composition. Therefore, it was possible to manage the light emission process of the mixed host devices by managing the mixed host composition.

  3. Analytic formalism for current crowding in light emitting diodes

    International Nuclear Information System (INIS)

    Lee, Kyu-Seok

    2012-01-01

    This paper presents an analytic approach to simulating current crowding (CC) in light-emitting diodes with parallel p- and n-contacts. The electrical potential difference across the p-i-n layers is derived from the Laplace equation, whereas the current density through the p-i-n layers is obtained from the current density - voltage relation of a single-diode model. Since these two properties influence each other, they are calculated iteratively. It is found that CC depends on the applied voltage (or the average current density), the sheet resistances of the p- and the n-contact layers, the width of the active region, and the specific series resistance and ideality factor of the p-i-n layers. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. 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.

  5. III-nitride based light emitting diodes and applications

    CERN Document Server

    Han, Jung; Amano, Hiroshi; Morkoç, Hadis

    2013-01-01

    Light emitting diodes (LEDs) are already used in traffic signals, signage lighting, and automotive applications. However, its ultimate goal is to replace traditional illumination through LED lamps since LED lighting significantly reduces energy consumption and cuts down on carbon-dioxide emission. Despite dramatic advances in LED technologies (e.g., growth, doping and processing technologies), however, there remain critical issues for further improvements yet to be achieved for the realization of solid-state lighting. This book aims to provide the readers with some contemporary LED issues, which have not been comprehensively discussed in the published books and, on which the performance of LEDs is seriously dependent. For example, most importantly, there must be a breakthrough in the growth of high-quality nitride semiconductor epitaxial layers with a low density of dislocations, in particular, in the growth of Al-rich and and In-rich GaN-based semiconductors. The materials quality is directly dependent on th...

  6. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal

    2016-10-06

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  7. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal; Dursun, Ibrahim; Priante, Davide; Saidaminov, Makhsud I.; Ng, Tien Khee; Bakr, Osman; Ooi, Boon S.

    2016-01-01

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  8. Colloidal quantum dot light-emitting devices

    Directory of Open Access Journals (Sweden)

    Vanessa Wood

    2010-07-01

    Full Text Available Colloidal quantum dot light-emitting devices (QD-LEDs have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with a high color rendering index (CRI. We review the key advantages of using quantum dots (QDs in display and lighting applications, including their color purity, solution processability, and stability. After highlighting the main developments in QD-LED technology in the past 15 years, we describe the three mechanisms for exciting QDs – optical excitation, Förster energy transfer, and direct charge injection – that have been leveraged to create QD-LEDs. We outline the challenges facing QD-LED development, such as QD charging and QD luminescence quenching in QD thin films. We describe how optical downconversion schemes have enabled researchers to overcome these challenges and develop commercial lighting products that incorporate QDs to achieve desirable color temperature and a high CRI while maintaining efficiencies comparable to inorganic white LEDs (>65 lumens per Watt. We conclude by discussing some current directions in QD research that focus on achieving higher efficiency and air-stable QD-LEDs using electrical excitation of the luminescent QDs.

  9. Salt-Doped Polymer Light-Emitting Devices

    Science.gov (United States)

    Gautier, Bathilde

    Polymer Light-Emitting Electrochemical Cells (PLECs) are solid state devices based on the in situ electrochemical doping of the luminescent polymer and the formation of a p-n junction where light is emitted upon the application of a bias current or voltage. PLECs answer the drawbacks of polymer light-emitting diodes as they do not require an ultra-thin active layer nor are they reliant on low work function cathode materials that are air unstable. However, because of the dynamic nature of the doping, they suffer from slow response times and poor stability over time. Frozen-junction PLECs offer a solution to these drawbacks, yet they are impractical due to their sub-ambient operation temperature requirement. Our work presented henceforth aims to achieve room temperature frozen-junction PLECS. In order to do that we removed the ion solvating/transporting polymer from the active layer, resulting in a luminescent polymer combined solely with a salt sandwiched between an ITO electrode and an aluminum electrode. The resulting device was not expected to operate like a PLEC due to the absence of an ion-solvating and ion-transporting medium. However, we discovered that the polymer/salt devices could be activated by applying a large voltage bias, resulting in much higher current and luminance. More important, the activated state is quasi static. Devices based on the well-known orange-emitting polymer MEH-PPV displayed a luminance storage half-life of 150 hours when activated by forward bias (ITO biased positively with respect to the aluminum) and 200 hours when activated by reverse bias. More remarkable yet, devices based on a green co-polymer displayed no notable decay in current density or luminance even after being stored for 1200 hours at room temperature! PL imaging under UV excitation demonstrates the presence of doping. These devices are described herein along with an explanation of their operating mechanisms.

  10. Near-infrared light emitting device using semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Supran, Geoffrey J.S.; Song, Katherine W.; Hwang, Gyuweon; Correa, Raoul Emile; Shirasaki, Yasuhiro; Bawendi, Moungi G.; Bulovic, Vladimir; Scherer, Jennifer

    2018-04-03

    A near-infrared light emitting device can include semiconductor nanocrystals that emit at wavelengths beyond 1 .mu.m. The semiconductor nanocrystals can include a core and an overcoating on a surface of the core.

  11. Controlled light emission from white organic light-emitting devices with a single blue-emitting host and multiple fluorescent dopants

    International Nuclear Information System (INIS)

    Chin, Byung Doo; Kim, Jai Kyeong; Park, O Ok

    2007-01-01

    In this work, we fabricated white organic light-emitting devices (WOLEDs) containing a layered light-emitting region composed of a single blue-emitting host and different fluorescent dopant materials. The effects of varying the dye-doping ratio and emitting layer thickness on the efficiency, lifetime, spectral voltage-dependence and white balance were investigated for devices with a blue/orange stacked layer structure. Addition of a blue host layer doped with a green-emitting dopant, to give a blue/green/orange emitter, resulted in a broadband white spectrum without the need for a charge-blocking interlayer. The composition of blue, green and orange dopants in the host and the thickness of each emitting layer were optimized, resulting in a device efficiency of 9-11 cd A -1 even at a high brightness of 10 000 cd m -2 (achieved at a bias voltage of less than 9 V) with an emission spectrum suitable for lighting applications

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

    Science.gov (United States)

    D'Andrade, Brian [Westampton, NJ; Esler, James [Levittown, PA

    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.

  13. Optimization of emission color and efficiency of organic light emitting diodes for lighting applications

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Stefan; Krause, Ralf [Department of Materials Science VI, University of Erlangen-Nuernberg (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Kozlowski, Fryderyk; Schmid, Guenter; Hunze, Arvid [Siemens AG, CT MM 1, Erlangen (Germany); Winnacker, Albrecht [Department of Materials Science VI, University of Erlangen-Nuernberg (Germany)

    2008-07-01

    In recent years the performance of organic light emitting diodes (OLEDs) has reached a level where OLED lighting presents an interesting application target. Research activities therefore focus amongst other things on the development of high efficient and stable white light emitting devices. We demonstrate how the color coordinates can be adjusted to achieve a warm white emission spectrum, whereas the OLED stack contains phosphorescent red and green dyes combined with a fluorescent blue one. Detailed results are presented with respect to a variation of layer thicknesses and dopant concentrations of the emission layers. Furthermore the influence of various dye molecules and hence different energy level alignments between host and dopants on color and efficiency will be discussed.

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

    International Nuclear Information System (INIS)

    Liu Xiang; Wei Fuxiang; Liu Hui

    2009-01-01

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

  15. Highly efficient exciplex organic light-emitting diodes incorporating a heptazine derivative as an electron acceptor.

    Science.gov (United States)

    Li, Jie; Nomura, Hiroko; Miyazaki, Hiroshi; Adachi, Chihaya

    2014-06-11

    Highly efficient exciplex systems incorporating a heptazine derivative () as an electron acceptor and 1,3-di(9H-carbazol-9-yl)benzene () as an electron donor are developed. An organic light-emitting diode containing 8 wt% : as an emitting layer exhibits a maximum external quantum efficiency of 11.3%.

  16. Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Alnoor, Hatim, E-mail: hatim.alnoor@liu.se; Iandolo, Donata; Willander, Magnus; Nur, Omer [Department of Science and Technology (ITN), Linköping University, SE-601 74 Norrköping (Sweden); Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-583 81 Linköping (Sweden)

    2016-04-28

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (∼575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.

  17. Effects of a highly Si-doped GaN current spreading layer at the n+-GaN/multi-quantum-well interface on InGaN/GaN blue-light-emitting diodes

    International Nuclear Information System (INIS)

    Kim, C. S.; Cho, H. K.; Choi, R. J.; Hahn, Y. B.; Lee, H. J.; Hong, C. H.

    2004-01-01

    Highly Si-doped GaN thin current spreading layer (CSL) with various carrier concentrations were inserted before the n + -GaN/multi-quantum-well (MQW) interface controlled by the growth rate and the modulated Si-doping in InGaN/GaN blue light-emitting diodes (LEDs), and their effects were investigated by using capacitance-voltage (C-V), current-voltage (I-V), and output power measurements. The LEDs with a highly Si-doped CSL show enhanced I-V characteristics and increased output power with increasing carrier concentration up to some critical point in the CSL. This means that proper high Si-doping in some limited area before the interface may enhance the device performance through the current spreading effect.

  18. Liquid-phase exfoliation of chemical vapor deposition-grown single layer graphene and its application in solution-processed transparent electrodes for flexible organic light-emitting devices

    International Nuclear Information System (INIS)

    Wu, Chaoxing; Li, Fushan; Wu, Wei; Chen, Wei; Guo, Tailiang

    2014-01-01

    Efficient and low-cost methods for obtaining high performance flexible transparent electrodes based on chemical vapor deposition (CVD)-grown graphene are highly desirable. In this work, the graphene grown on copper foil was exfoliated into micron-size sheets through controllable ultrasonication. We developed a clean technique by blending the exfoliated single layer graphene sheets with conducting polymer to form graphene-based composite solution, which can be spin-coated on flexible substrate, forming flexible transparent conducting film with high conductivity (∼8 Ω/□), high transmittance (∼81% at 550 nm), and excellent mechanical robustness. In addition, CVD-grown-graphene-based polymer light emitting diodes with excellent bendable performances were demonstrated

  19. Luminance mechanisms in green organic light-emitting devices fabricated utilizing tris(8-hydroxyquinoline)aluminum/4,7-diphenyl-1, 10-phenanthroline multiple heterostructures acting as an electron transport layer.

    Science.gov (United States)

    Choo, Dong Chul; Seo, Su Yul; Kim, Tae Whan; Jin, You Young; Seo, Ji Hyun; Kim, Young Kwan

    2010-05-01

    The electrical and the optical properties in green organic light-emitting devices (OLEDs) fabricated utilizing tris(8-hydroxyquinoline)aluminum (Alq3)/4,7-diphenyl-1,10-phenanthroline (BPhen) multiple heterostructures acting as an electron transport layer (ETL) were investigated. The operating voltage of the OLEDs with a multiple heterostructure ETL increased with increasing the number of the Alq3/BPhen heterostructures because more electrons were accumulated at the Alq3/BPhen heterointerfaces. The number of the leakage holes existing in the multiple heterostructure ETL of the OLEDs at a low voltage range slightly increased due to an increase of the internal electric field generated from the accumulated electrons at the Alq3/BPhen heterointerface. The luminance efficiency of the OLEDs with a multiple heterostructure ETL at a high voltage range became stabilized because the increase of the number of the heterointerface decreased the quantity of electrons accumulated at each heterointerface.

  20. Numerical study of the light output intensity of the bilayer organic light-emitting diodes

    Science.gov (United States)

    Lu, Feiping

    2017-02-01

    The structure of organic light-emitting diodes (OLEDs) is one of most important issues that influence the light output intensity (LOI) of OLEDs. In this paper, based on a simple but accurate optical model, the influences of hole and electron transport layer thickness on the LOI of bilayer OLEDs, which with N,N0- bis(naphthalen-1-yl)-N,N0- bis(phenyl)- benzidine (NPB) or N,N'- diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4-diamine (TPD) as hole transport layer, with tris(8-hydroxyquinoline) aluminum (Alq3) as electron transport and light emitting layers, were investigated. The laws of LOI for OLEDs under different organic layer thickness values were obtained. The results show that the LOI of devices varies in accordance with damped cosine or sine function as the increasing of organic layer thickness, and the results show that the bilayer OLEDs with the structure of Glass/ITO/NPB (55 nm)/Alq3 (75 nm)/Al and Glass/ITO/TPB (60 nm)/Alq3 (75 nm)/Al have most largest LOI. When the thickness of Alq3 is less than 105 nm, the OLEDs with TPD as hole transport layer have larger LOI than that with NPB as hole transport layer. The results obtained in this paper can present an in-depth understanding of the working mechanism of OLEDs and help ones fabricate high efficiency OLEDs.

  1. White organic light-emitting diodes with fluorescent tube efficiency.

    Science.gov (United States)

    Reineke, Sebastian; Lindner, Frank; Schwartz, Gregor; Seidler, Nico; Walzer, Karsten; Lüssem, Björn; Leo, Karl

    2009-05-14

    The development of white organic light-emitting diodes (OLEDs) holds great promise for the production of highly efficient large-area light sources. High internal quantum efficiencies for the conversion of electrical energy to light have been realized. Nevertheless, the overall device power efficiencies are still considerably below the 60-70 lumens per watt of fluorescent tubes, which is the current benchmark for novel light sources. Although some reports about highly power-efficient white OLEDs exist, details about structure and the measurement conditions of these structures have not been fully disclosed: the highest power efficiency reported in the scientific literature is 44 lm W(-1) (ref. 7). Here we report an improved OLED structure which reaches fluorescent tube efficiency. By combining a carefully chosen emitter layer with high-refractive-index substrates, and using a periodic outcoupling structure, we achieve a device power efficiency of 90 lm W(-1) at 1,000 candelas per square metre. This efficiency has the potential to be raised to 124 lm W(-1) if the light outcoupling can be further improved. Besides approaching internal quantum efficiency values of one, we have also focused on reducing energetic and ohmic losses that occur during electron-photon conversion. We anticipate that our results will be a starting point for further research, leading to white OLEDs having efficiencies beyond 100 lm W(-1). This could make white-light OLEDs, with their soft area light and high colour-rendering qualities, the light sources of choice for the future.

  2. Degradation in organic light emitting devices

    Science.gov (United States)

    Dinh, Vincent Vinh

    This thesis is about the fundamental causes of degradation in tris(8-Hydroxyquinoline) Aluminum (Alq3)-based organic light emitting diodes (OLEDs). Degradation typically occurs when a current is forced through an insulating material. Since the insulator does not support conduction waves (in its ground state), chemical restructuring must occur to accommodate the current. OLEDs have many technical advantages over the well known semiconductor-based light emitting diodes (LEDs). OLEDs have quantum efficiencies ˜1% (˜10 times higher than the LEDs), and operational power thresholds ˜.05mW (˜100 lower than the LEDs). OLEDs are preferred in power limited and portable devices; devices such as laptops and displays consume ˜1/4 of the supplied power---any power saving is significant. Other advantages, like better compliance to curved surfaces and ease of fabrication, give the OLEDs an even greater edge over the LEDs. OLEDs must have at least comparable or better lifetimes to remain attractive. Typical OLEDs last several 100hrs compared to the several 1000hrs for the LEDs. For reliable OLED application, it is necessary to understand the above breakdown mechanism. In this thesis, we attempt to understand the breakdown by looking at how OLEDs are made, how they work, and when they don't. In the opening sections, we give an overview of OLEDs and LEDs, especially how sustained luminescence is achieved through current circulation. Then in Chapter 2, we look at the basic components in the OLEDs. In Chapter 3 we look at how a hole material (like poly-vinyl carbazole or PVK) establishes an excitonic environment for the sustained luminescence in Alq3. We then approximate how potential is distributed when a simple luminescence system is in operation. In Chapter 4, we look at ways of measuring this distribution via the OLED impedance. Finally in Chapter 5, we look at the OLED stability under light emission conditions via PVK and Alq3 photoemission and photoabsorption spectra

  3. Power saving regulated light emitting diode circuit

    International Nuclear Information System (INIS)

    Haville, G. D.

    1985-01-01

    A power saving regulated light source circuit, comprising a light emitting diode (LED), a direct current source and a switching transistor connected in series with the LED, a control voltage producing resistor connected in series with the LED to produce a control voltage corresponding to the current through the LED, a storage capacitor connected in parallel with the series combination of the LED and the resistor, a comparator having its output connected to the input of the transistor, the comparator having a reference input and a control input, a stabilized biasing source for supplying a stabilized reference voltage to the reference input, the control input of the comparator being connected to the control voltage producing resistor, the comparator having a high output state when the reference voltage exceeds the control voltage while having a low output state when the control voltage exceeds the reference voltage, the transistor being conductive in response to the high state while being nonconductive in response to the low state, the transistor when conductive being effective to charge the capacitor and to increase the control voltage, whereby the comparator is cycled between the high and low output states while the transistor is cycled between conductive and nonconductive states

  4. Aggregation in organic light emitting diodes

    Science.gov (United States)

    Meyer, Abigail

    Organic light emitting diode (OLED) technology has great potential for becoming a solid state lighting source. However, there are inefficiencies in OLED devices that need to be understood. Since these inefficiencies occur on a nanometer scale there is a need for structural data on this length scale in three dimensions which has been unattainable until now. Local Electron Atom Probe (LEAP), a specific implementation of Atom Probe Tomography (APT), is used in this work to acquire morphology data in three dimensions on a nanometer scale with much better chemical resolution than is previously seen. Before analyzing LEAP data, simulations were used to investigate how detector efficiency, sample size and cluster size affect data analysis which is done using radial distribution functions (RDFs). Data is reconstructed using the LEAP software which provides mass and position data. Two samples were then analyzed, 3% DCM2 in C60 and 2% DCM2 in Alq3. Analysis of both samples indicated little to no clustering was present in this system.

  5. Coherence characteristics of light-emitting diodes

    International Nuclear Information System (INIS)

    Mehta, Dalip Singh; Saxena, Kanchan; Dubey, Satish Kumar; Shakher, Chandra

    2010-01-01

    We report the measurement of coherence characteristics of light-emitting diodes (LEDs). Experiments were performed using red and green color LEDs directly illuminating the Young's double slit kept in the far-zone. Fourier transform fringe analysis technique was used for the measurement of the visibility of interference fringes from which the modulus of degree of spectral coherence was determined. Low degree of spectral coherence, typically 0.4 for red and 0.2 for green LED with double-slit separation of 400 μm was observed. A variable slit was then kept in front of the LEDs and the double slit was illuminated with the light coming out of the slit. Experiments were performed with various slit sizes and the visibility of the interference fringes was observed. It was found that visibility of the interference fringes changes drastically in presence of variable slit kept in front of LEDs and a high degree of spectral coherence, typically 0.85 for red and 0.8 for green LED with double-slit separation of 400 μm and rectangular slit opening of 500 μm was observed. The experimental results are compared with the theoretical counterparts. Coherence lengths of both the LEDs were also determined and it was obtained 5.8±2 and 24±4 μm for green and red LEDs, respectively.

  6. Efficient small molecular organic light emitting diode with graphene cathode covered by a Sm layer with nano-hollows and n-doped by Bphen:Cs2CO3 in the hollows

    Science.gov (United States)

    Yao, Li; Li, Lei; Qin, Laixiang; Ma, Yaoguang; Wang, Wei; Meng, Hu; Jin, Weifeng; Wang, Yilun; Xu, Wanjin; Ran, Guangzhao; You, Liping; Qin, Guogang

    2017-03-01

    Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ˜4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs2CO3 to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs2CO3 is still too high to be ˜1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs2CO3, are deposited. The Bphen:Cs2CO3 can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O--Sm+ dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs2CO3/Alq3:C545T/NPB/MoO3/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

  7. Recent Advances in Conjugated Polymers for Light Emitting Devices

    Science.gov (United States)

    AlSalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  8. Impact of Plasma Electron Flux on Plasma Damage-Free Sputtering of Ultrathin Tin-Doped Indium Oxide Contact Layer on p-GaN for InGaN/GaN Light-Emitting Diodes.

    Science.gov (United States)

    Son, Kwang Jeong; Kim, Tae Kyoung; Cha, Yu-Jung; Oh, Seung Kyu; You, Shin-Jae; Ryou, Jae-Hyun; Kwak, Joon Seop

    2018-02-01

    The origin of plasma-induced damage on a p -type wide-bandgap layer during the sputtering of tin-doped indium oxide (ITO) contact layers by using radiofrequency-superimposed direct current (DC) sputtering and its effects on the forward voltage and light output power (LOP) of light-emitting diodes (LEDs) with sputtered ITO transparent conductive electrodes (TCE) is systematically studied. Changing the DC power voltage from negative to positive bias reduces the forward voltages and enhances the LOP of the LEDs. The positive DC power drastically decreases the electron flux in the plasma obtained by plasma diagnostics using a cutoff probe and a Langmuir probe, suggesting that the repulsion of plasma electrons from the p -GaN surface can reduce plasma-induced damage to the p -GaN. Furthermore, electron-beam irradiation on p -GaN prior to ITO deposition significantly increases the forward voltages, showing that the plasma electrons play an important role in plasma-induced damage to the p -GaN. The plasma electrons can increase the effective barrier height at the ITO/deep-level defect (DLD) band of p -GaN by compensating DLDs, resulting in the deterioration of the forward voltage and LOP. Finally, the plasma damage-free sputtered-ITO TCE enhances the LOP of the LEDs by 20% with a low forward voltage of 2.9 V at 20 mA compared to LEDs with conventional e-beam-evaporated ITO TCE.

  9. Behavior of Layers under Different Light Sources

    Directory of Open Access Journals (Sweden)

    BO Tavares

    2015-12-01

    Full Text Available ABSTRACT Light is an important factor in the management of laying poultry. The ideal lamp spectrum that provides the best welfare conditions still needs to be determined. Wavelength and light intensity influence poultry behavior and their welfare. This study evaluated the influence of four lamps types with different light spectra on the behavior of seventy 52-week laying hens. Incandescent, fluorescent, and sodium and mercury vapor lamps were set in a different poultry house each and supplied similar light intensities. Layer behavior was video-recorded three times weekly using video cameras installed on the ceiling. The effects of different wavelengths emitted by the light sources on layer behavior were evaluated by the Kruskal-Wallis median test. Results indicated that incandescent and sodium vapor lamps increased the occurrence of nesting, and of active behaviors, such as floor-scratching and pecking.

  10. Light collection optics for measuring flux and spectrum from light-emitting devices

    Science.gov (United States)

    McCord, Mark A.; DiRegolo, Joseph A.; Gluszczak, Michael R.

    2016-05-24

    Systems and methods for accurately measuring the luminous flux and color (spectra) from light-emitting devices are disclosed. An integrating sphere may be utilized to directly receive a first portion of light emitted by a light-emitting device through an opening defined on the integrating sphere. A light collector may be utilized to collect a second portion of light emitted by the light-emitting device and direct the second portion of light into the integrating sphere through the opening defined on the integrating sphere. A spectrometer may be utilized to measure at least one property of the first portion and the second portion of light received by the integrating sphere.

  11. Low driving voltage blue, green, yellow, red and white organic light-emitting diodes with a simply double light-emitting structure.

    Science.gov (United States)

    Zhang, Zhensong; Yue, Shouzhen; Wu, Yukun; Yan, Pingrui; Wu, Qingyang; Qu, Dalong; Liu, Shiyong; Zhao, Yi

    2014-01-27

    Low driving voltage blue, green, yellow, red and white phosphorescent organic light-emitting diodes (OLEDs) with a common simply double emitting layer (D-EML) structure are investigated. Our OLEDs without any out-coupling schemes as well as n-doping strategies show low driving voltage, e.g. white OLED, respectively. This work demonstrates that the low driving voltages and high efficiencies can be simultaneously realized with a common simply D-EML structure.

  12. Codoped emission layers for the application in white, organic light-emitting diodes; Kodotierte Emissionsschichten zur Anwendung in weissen, organischen Leuchtdioden

    Energy Technology Data Exchange (ETDEWEB)

    Steinbacher, Frank

    2012-07-01

    In this dissertation, the first step towards an application of mixed emission layers in highly efficient white OLEDs is an investigation of the underlying exciton transfer process. Simple, solution processable samples of dispersed phosphorescent dye molecules in a PMMA matrix are investigated by (time-resolved) photoluminescence. An optimized yellow OLED acts as a starting point for the use of a mixed emission layer in highly efficient white OLEDS. Although some adaptation of existing layouts is needed, it is possible to introduce mixed emission layers into regular as well as stacked white diode concepts. An evaporation technique which uses a combination of two dyes in one crucible is tested for its applicability. Although rate detection can be simplified in that way, different evaporation properties of the materials lead to a continuously changing composition in the mixed crucible. In summary, the fundamental exciton transfer process in mixed emission layers was investigated and explained in simple setups as well as complete OLEDs. (orig.)

  13. High mobility solution-processed hybrid light emitting transistors

    International Nuclear Information System (INIS)

    Walker, Bright; Kim, Jin Young; Ullah, Mujeeb; Burn, Paul L.; Namdas, Ebinazar B.; Chae, Gil Jo; Cho, Shinuk; Seo, Jung Hwa

    2014-01-01

    We report the design, fabrication, and characterization of high-performance, solution-processed hybrid (inorganic-organic) light emitting transistors (HLETs). The devices employ a high-mobility, solution-processed cadmium sulfide layer as the switching and transport layer, with a conjugated polymer Super Yellow as an emissive material in non-planar source/drain transistor geometry. We demonstrate HLETs with electron mobilities of up to 19.5 cm 2 /V s, current on/off ratios of >10 7 , and external quantum efficiency of 10 −2 % at 2100 cd/m 2 . These combined optical and electrical performance exceed those reported to date for HLETs. Furthermore, we provide full analysis of charge injection, charge transport, and recombination mechanism of the HLETs. The high brightness coupled with a high on/off ratio and low-cost solution processing makes this type of hybrid device attractive from a manufacturing perspective

  14. Blue-light emitting triazolopyridinium and triazoloquinolinium salts

    KAUST Repository

    Carboni, Valentina; Su, Xin; Qian, Hai; Aprahamian, Ivan; Credi, Alberto

    2017-01-01

    Compounds that emit blue light are of interest for applications that include optoelectronic devices and chemo/biosensing and imaging. The design and synthesis of small organic molecules that can act as high-efficiency deep-blue-light emitters

  15. Improved outcoupling of light in organic light emitting devices, utilizing a holographic DFB-structure

    Energy Technology Data Exchange (ETDEWEB)

    Reinke, Nils [Organische Funktionsmaterialien, University of Duisburg-Essen (Germany)]. E-mail: nils.reinke@physik.uni-augsburg.de; Fuhrmann, Thomas [Macromolecular Chemistry and Molecular Materials, University of Kassel (Germany); Perschke, Alexandra [Organische Funktionsmaterialien, University of Duisburg-Essen (Germany); Franke, Hilmar [Organische Funktionsmaterialien, University of Duisburg-Essen (Germany)

    2004-12-10

    In this work organic light emitting devices (OLEDs) were fabricated implementing gratings, in order to extract waveguided electroluminescence (EL). The gratings were recorded by exposing thin films of the molecular azo glass N, N'-bis (4-phenyl)-N, N'-bis [(4-phenylazo)-phenyl] benzidine (AZOPD) to holographic light patterns. The photopatterned AZOPD serves as hole transport material for devices with aluminum-tris(8-hydroxyquinoline) doped with 1% of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (Alq{sub 3}:DCM) as emissive/electron transport layer. The corrugated devices showed enhanced emission in the forward direction. The emitted light is polarized preferably parallel to the grating lines. In addition, we have found a doubling in the total luminance with respect to the unstructured device.

  16. 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.

  17. 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...

  18. 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.

  19. Optical properties of white organic light-emitting devices fabricated utilizing a mixed CaAl12O19:Mn4+ and Y3Al5O12:Ce3+ color conversion layer.

    Science.gov (United States)

    Jeong, H S; Kim, S H; Lee, K S; Jeong, J M; Yoo, T W; Kwon, M S; Yoo, K H; Kim, T W

    2013-06-01

    White organic light-emitting devices (OLEDs) were fabricated by combining a blue OLED with a color conversion layer made of mixed Y3Al5O12:Ce3+ green and Ca2AlO19:Mn4+ red phosphors. The X-ray diffraction patterns showed that Ce3+ ions in the Y3Al5O12:Ce3+ phosphors completely substituted for the Y3+ ions and the Mn4+ ions in the CaAl12O19:Mn4+ phosphors completely substituted for the Ca2+ ions. Electroluminescence spectra at 11 V for the OLEDs fabricated utilizing a color conversion layer showed that the Commission Internationale de l'Eclairage coordinates for the Y3Al5O12:Ce3+ and CaAl12O19:Mn4+ phosphors mixed at the ratio of 1:5 and 1:10 were (0.31, 0.34) and (0.32, 0.37), respectively, indicative of a good white color.

  20. Device model investigation of bilayer organic light emitting diodes

    International Nuclear Information System (INIS)

    Crone, B. K.; Davids, P. S.; Campbell, I. H.; Smith, D. L.

    2000-01-01

    Organic materials that have desirable luminescence properties, such as a favorable emission spectrum and high luminescence efficiency, are not necessarily suitable for single layer organic light-emitting diodes (LEDs) because the material may have unequal carrier mobilities or contact limited injection properties. As a result, single layer LEDs made from such organic materials are inefficient. In this article, we present device model calculations of single layer and bilayer organic LED characteristics that demonstrate the improvements in device performance that can occur in bilayer devices. We first consider an organic material where the mobilities of the electrons and holes are significantly different. The role of the bilayer structure in this case is to move the recombination away from the electrode that injects the low mobility carrier. We then consider an organic material with equal electron and hole mobilities but where it is not possible to make a good contact for one carrier type, say electrons. The role of a bilayer structure in this case is to prevent the holes from traversing the device without recombining. In both cases, single layer device limitations can be overcome by employing a two organic layer structure. The results are discussed using the calculated spatial variation of the carrier densities, electric field, and recombination rate density in the structures. (c) 2000 American Institute of Physics

  1. Structural effects of a light emitting copolymer having perylene moieties in the side chain on the electroluminescent characteristics

    International Nuclear Information System (INIS)

    Lee, Chang Ho; Ryu, Seung Hoon; Jang, Hee Dong; Oh, Se Young

    2004-01-01

    We have synthesized a novel side chain light emitting copolymer. The side chain light emitting copolymer has a perylene moiety as an emitting unit and methylmethacrylate (MMA) as a spacer to decrease the concentration quenching of light emitting site in the polymer intrachain. These polymers are very soluble in most organic solvents such as monochlorobenzene, tetrahydrofuran, chloroform and benzene. The single-layered electroluminescent (EL) device consisting of ITO/carrier transporting copolymer and light emitting copolymer/Al was manufactured. The carrier transporting copolymer has triphenylamine moiety as a hole transporting unit and triazine moiety as an electron transporting unit in the polymer side chain. This device exhibits maximum external quantum efficiency when the MMA contents of light emitting copolymer is 30 wt.%. In particular, the device emits more blue light as MMA contents increase

  2. Transparent conductive graphene electrode in GaN-based ultra-violet light emitting diodes.

    Science.gov (United States)

    Kim, Byung-Jae; Mastro, Michael A; Hite, Jennifer; Eddy, Charles R; Kim, Jihyun

    2010-10-25

    We report a graphene-based transparent conductive electrode for use in ultraviolet (UV) GaN light emitting diodes (LEDs). A few-layer graphene (FLG) layer was mechanically deposited. UV light at a peak wavelength of 368 nm was successfully emitted by the FLG layer as transparent contact to p-GaN. The emission of UV light through the thin graphene layer was brighter than through the thick graphene layer. The thickness of the graphene layer was characterized by micro-Raman spectroscopy. Our results indicate that this novel graphene-based transparent conductive electrode holds great promise for use in UV optoelectronics for which conventional ITO is less transparent than graphene.

  3. Ultra-bright and highly efficient inorganic based perovskite light-emitting diodes

    Science.gov (United States)

    Zhang, Liuqi; Yang, Xiaolei; Jiang, Qi; Wang, Pengyang; Yin, Zhigang; Zhang, Xingwang; Tan, Hairen; Yang, Yang (Michael); Wei, Mingyang; Sutherland, Brandon R.; Sargent, Edward H.; You, Jingbi

    2017-06-01

    Inorganic perovskites such as CsPbX3 (X=Cl, Br, I) have attracted attention due to their excellent thermal stability and high photoluminescence quantum efficiency. However, the electroluminescence quantum efficiency of their light-emitting diodes was CsPbBr3 lattice and by depositing a hydrophilic and insulating polyvinyl pyrrolidine polymer atop the ZnO electron-injection layer to overcome these issues. As a result, we obtained light-emitting diodes exhibiting a high brightness of 91,000 cd m-2 and a high external quantum efficiency of 10.4% using a mixed-cation perovskite Cs0.87MA0.13PbBr3 as the emitting layer. To the best of our knowledge, this is the brightest and most-efficient green perovskite light-emitting diodes reported to date.

  4. 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.

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

    International Nuclear Information System (INIS)

    Guan Yunxia; Niu Lianbin

    2009-01-01

    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 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.

  6. Wireless Power Transmission to Organic Light Emitting Diode Lighting Panel with Magnetically Coupled Resonator

    Science.gov (United States)

    Kim, Yong-Hae; Han, Jun-Han; Kang, Seung-Youl; Cheon, Sanghoon; Lee, Myung-Lae; Ahn, Seong-Deok; Zyung, Taehyoung; Lee, Jeong-Ik; Moon, Jaehyun; Chu, Hye Yong

    2012-09-01

    We are successful to lit the organic light emitting diode (OLED) lighting panel through the magnetically coupled wireless power transmission technology. For the wireless power transmission, we used the operation frequency 932 kHz, specially designed double spiral type transmitter, small and thin receiver on the four layered printed circuit board, and schottky diodes for the full bridge rectifier. Our white OLED is a hybrid type, in which phosphorescent and fluorescent organics are used together to generate stable white color. The total efficiency of power transmission is around 72%.

  7. Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties

    Directory of Open Access Journals (Sweden)

    Guang Zhang

    2016-10-01

    Full Text Available Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer (D1 manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one (D2 displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1, in a three-layer organic light emitting diode (OLED by solution processing gave a pure blue emission with Commission Internationale de l’Éclairage 1931 CIE xy = (0.16, 0.12, a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m2. This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

  8. Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties.

    Science.gov (United States)

    Zhang, Guang; Auer-Berger, Manuel; Gehrig, Dominik W; Blom, Paul W M; Baumgarten, Martin; Schollmeyer, Dieter; List-Kratochvil, E J W; Müllen, Klaus

    2016-10-20

    Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer ( D1 ) manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT) in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one ( D2 ) displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1 , in a three-layer organic light emitting diode (OLED) by solution processing gave a pure blue emission with Commission Internationale de l'Éclairage 1931 CIE xy = (0.16, 0.12), a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m². This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

  9. 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.

  10. Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

    Science.gov (United States)

    Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

    2018-05-01

    Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ultraviolet light-absorbing and emitting diodes consisting of a p-type transparent-semiconducting NiO film deposited on an n-type GaN homoepitaxial layer

    Science.gov (United States)

    Nakai, Hiroshi; Sugiyama, Mutsumi; Chichibu, Shigefusa F.

    2017-05-01

    Gallium nitride (GaN) and related (Al,Ga,In)N alloys provide practical benefits in the production of light-emitting diodes (LEDs) and laser diodes operating in ultraviolet (UV) to green wavelength regions. However, obtaining low resistivity p-type AlN or AlGaN of large bandgap energies (Eg) is a critical issue in fabricating UV and deep UV-LEDs. NiO is a promising candidate for useful p-type transparent-semiconducting films because its Eg is 4.0 eV and it can be doped into p-type conductivity of sufficiently low resistivity. By using these technologies, heterogeneous junction diodes consisting of a p-type transparent-semiconducting polycrystalline NiO film on an n-type single crystalline GaN epilayer on a low threading-dislocation density, free-standing GaN substrate were fabricated. The NiO film was deposited by using the conventional RF-sputtering method, and the GaN homoepitaxial layer was grown by metalorganic vapor phase epitaxy. They exhibited a significant photovoltaic effect under UV light and also exhibited an electroluminescence peak at 3.26 eV under forward-biased conditions. From the conduction and valence band (EV) discontinuities, the NiO/GaN heterointerface is assigned to form a staggered-type (TYPE-II) band alignment with the EV of NiO higher by 2.0 eV than that of GaN. A rectifying property that is consistent with the proposed band diagram was observed in the current-voltage characteristics. These results indicate that polycrystalline NiO functions as a hole-extracting and injecting layer of UV optoelectronic devices.

  12. Hybrid Structure White Organic Light Emitting Diode for Enhanced Efficiency by Varied Doping Rate.

    Science.gov (United States)

    Kim, Dong-Eun; Kang, Min-Jae; Park, Gwang-Ryeol; Kim, Nam-Kyu; Lee, Burm-Jong; Kwon, Young-Soo; Shin, Hoon-Kyu

    2016-03-01

    Novel materials based on Zn(HPB)2 and Ir-complexes were synthesized as blue or red emitters, respectively. White organic light emitting diodes were fabricated using the Zn(HPB)2 as a blue emitting layer, Ir-complexes as a red emitting layer and Alq3 as a green emitting layer. The obtained experimental results, were based on white OLEDs fabricated using double emission layers of Zn(HPB)2 and Alq3:Ir-complexes. The doping rate of the Ir-complexes was varied at 0.4%, 0.6%, 0.8% and 1.0%. When the doping rate of the Alq3:Ir-complexes was 0.6%, a white emission was achieved. The Commission Internationale de l'Eclairage coordinates of the device's white emission were (0.316, 0.331) at an applied voltage of 10.75 V.

  13. Three-peak standard white organic light-emitting devices for solid-state lighting

    Science.gov (United States)

    Guo, Kunping; Wei, Bin

    2014-12-01

    Standard white organic light-emitting device (OLED) lighting provides a warm and comfortable atmosphere and shows mild effect on melatonin suppression. A high-efficiency red OLED employing phosphorescent dopant has been investigated. The device generates saturated red emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.66, 0.34), characterized by a low driving voltage of 3.5 V and high external quantum efficiency of 20.1% at 130 cd m-2. In addition, we have demonstrated a two-peak cold white OLED by combining with a pure blue emitter with the electroluminescent emission of 464 nm, 6, 12-bis{[N-(3,4-dimethylpheyl)-N-(2,4,5-trimethylphenyl)]} chrysene (BmPAC). It was found that the man-made lighting device capable of yielding a relatively stable color emission within the luminance range of 1000-5000 cd m-2. And the chromaticity coordinates, varying from (0.25, 0.21) to (0.23, 0.21). Furthermore, an ultrathin layer of green-light-emitting tris (2-phenylpyridinato)iridium(Ⅲ) Ir(ppy)3 in the host material was introduced to the emissive region for compensating light. By appropriately controlling the layer thickness, the white light OLED achieved good performance of 1280 cd m-2 at 5.0 V and 5150 cd m-2 at 7.0 V, respectively. The CIE coordinates of the emitted light are quite stable at current densities from 759 cd m-2 to 5150 cd m-2, ranging from (0.34, 0.37) to (0.33, 0.33).

  14. 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.

  15. Manufacturing polymer light emitting diode with high luminance efficiency by solution process

    Science.gov (United States)

    Kim, Miyoung; Jo, SongJin; Yang, Ho Chang; Yoon, Dang Mo; Kwon, Jae-Taek; Lee, Seung-Hyun; Choi, Ju Hwan; Lee, Bum-Joo; Shin, Jin-Koog

    2012-06-01

    While investigating polymer light emitting diodes (polymer-LEDs) fabricated by solution process, surface roughness influences electro-optical (E-O) characteristics. We expect that E-O characteristics such as luminance and power efficiency related to surface roughness and layer thickness of emitting layer with poly-9-Vinylcarbazole. In this study, we fabricated polymer organic light emitting diodes by solution process which guarantees easy, eco-friendly and low cost manufacturing for flexible display applications. In order to obtain high luminescence efficiency, E-O characteristics of these devices by varying parameters for printing process have been investigated. Therefore, we optimized process condition for polymer-LEDs by adjusting annealing temperatures of emission, thickness of emission layer showing efficiency (10.8 cd/A) at 10 mA/cm2. We also checked wavelength dependent electroluminescence spectrum in order to find the correlation between the variation of efficiency and the thickness of the layer.

  16. Exciplex emission and decay of co-deposited 4,4',4″-tris[3-methylphenyl(phenyl)amino]triphenylamine:tris-[3-(3-pyridyl)mesityl]borane organic light-emitting devices with different electron transporting layer thicknesses

    Science.gov (United States)

    Huang, Qingyu; Zhao, Suling; Xu, Zheng; Fan, Xing; Shen, Chongyu; Yang, Qianqian

    2014-04-01

    Highly efficient fluorescence organic light-emitting diodes (OLEDs) based on the mixed 4,4',4″-tris[3-methylphenyl(phenyl)amino]triphenylamine:tris-[3-(3-pyridyl)mesityl]borane (1:1) system are reported. The electroluminescence due to the exciplex emission is red shifted when the thickness of the electron-transporting layer increases. The prepared OLEDs achieve a low turn-on voltage of 2.1 V, a high current efficiency of 36.79 cd/A, and a very high luminescence of 17 100 cd/m2, as well as a low efficiency roll-off. The current efficiency of the optimized OLED is maintained at more than 28.33 cd/A up to 10 000 cd m-2. The detailed recombination mechanism of the prepared OLEDs is investigated by the transient electroluminescence method. It is concluded that there are no contributions from trapped charges and annihilations of triplet-triplet excitons to the detected electroluminescence.

  17. Investigations of thin p-GaN light-emitting diodes with surface plasmon compatible metallization

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    2016-01-01

    We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  18. Investigations of thin p-GaN light-emitting diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed; Ou, Yiyu; Iida, Daisuke

    2016-01-01

    We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement.......We investigate device performance of InGaN light-emitting diodes with a 30-nm p-GaN layer. The metallization used to separate the p-contact from plasmonic metals, reveals limitations on current spreading which reduces surface plasmonic enhancement....

  19. Green Fluorescent Organic Light Emitting Device with High Luminance

    Directory of Open Access Journals (Sweden)

    Ning YANG

    2014-06-01

    Full Text Available In this work, we fabricated the small molecule green fluorescent bottom-emission organic light emitting device (OLED with the configuration of glass substrate/indium tin oxide (ITO/Copper Phthalocyanine (CuPc 25 nm/ N,N’-di(naphthalen-1-yl-N,N’-diphenyl-benzidine (NPB 45 nm/ tris(8-hydroxyquinoline aluminium (Alq3 60 nm/ Lithium fluoride (LiF 1 nm/Aluminum (Al 100 nm where CuPc and NPB are the hole injection layer and the hole transport layer, respectively. CuPc is introduced in this device to improve carrier injection and efficiency. The experimental results indicated that the turn-on voltage is 2.8 V with a maximum luminance of 23510 cd/m2 at 12 V. The maximum current efficiency and power efficiency are 4.8 cd/A at 100 cd/m2 and 4.2 lm/W at 3 V, respectively. The peak of electroluminance (EL spectrum locates at 530 nm which is typical emission peak of green light. In contrast, the maximum current efficiency and power efficiency of the device without CuPc are only 4.0 cd/A at 100 mA/cm2 and 4.2 lm/W at 3.6 V, respectively.

  20. High efficiency electrophosphorescence from bilayer organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Li Minghang; Lin, Ming-Te; Shepherd, Nigel D [Department of Material Science and Engineering, University of North Texas, Denton, TX (United States); Chen, Wei-Hsuan; Oswald, Iain; Omary, Mohammad [Department of Chemeistry, University of North Texas, Denton, TX (United States)

    2011-09-14

    An electron mobility of 2.7 x 10{sup -5} cm{sup 2} V{sup -1} s{sup -1} was measured for the phosphorescent emitter bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II)(Pt(ptp)2), which prompted its evaluation as both the emissive layer and electron transport layer in organic light emitting diodes with a simple bilayer structure. Power and external quantum efficiencies of 54.0 {+-} 0.2 lm W{sup -1} and 15.9% were obtained, which as far as we could ascertain are amongst the highest reported values for bilayer devices. We ascribe the high device efficiency to the combination of the high electron mobility, short excited-state lifetime (117 ns) and high luminescence quantum yield (60%) of the bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II). The colour temperature of the devices was 2855 K at 5 V, which places the emission in the 'warm' light spectral region.

  1. Can a tachyon emit light radiation in all directions

    Energy Technology Data Exchange (ETDEWEB)

    Ramanujam, G A [NGM Coll., Tamil Nadu (India). Dept. of Physics

    1976-03-01

    It is shown here that a critical analysis of the approaches employed by various authors to accommodate tachyons into special relativity leads one to the conclusion that a tachyon can emit light radiation only along its line of motion.

  2. Fabrication of organic light emitting diode using Molybdenum ...

    Indian Academy of Sciences (India)

    65

    out by measuring sheet resistance, optical transmittance and surface ... role in the organic light-emitting diode (OLED) performance because it determines the .... coated glass by thermal vacuum deposition method and optimize it by using ...

  3. Vacuum Deposited Organic Light Emitting Devices on Flexible Substrates

    National Research Council Canada - National Science Library

    Forrest, Stephen

    2002-01-01

    The objective of this eight year program was to demonstrate both passive and active matrix, flexible, small scale displays based on small molecular weight organic light emitting device (OLED) technology...

  4. 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.

  5. Multilayer polymer light-emitting diodes by blade coating method

    Science.gov (United States)

    Tseng, Shin-Rong; Meng, Hsin-Fei; Lee, Kuan-Chen; Horng, Sheng-Fu

    2008-10-01

    Multilayer polymer light-emitting diodes fabricated by blade coating are presented. Multilayer of polymers can be easily deposited by blade coating on a hot plate. The multilayer structure is confirmed by the total thickness and the cross section view in the scanning electron microscope. The film thickness variation is only 3.3% in 10cm scale and the film roughness is about 0.3nm in the micron scale. The efficiency of single layer poly(para-phenylene vinylene) copolymer Super Yellow and poly(9,9-dioctylfluorene) (PFO, deep blue) devices are 9 and 1.7cd/A, respectively, by blade coating. The efficiency of the PFO device is raised to 2.9cd/A with a 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) hole-blocking layer and to 2.3cd/A with a poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] elec-tron-blocking layer added by blade coating.

  6. White organic light-emitting devices incorporating nanoparticles of II-VI semiconductors

    International Nuclear Information System (INIS)

    Ahn, Jin H; Bertoni, Cristina; Dunn, Steve; Wang, Changsheng; Talapin, Dmitri V; Gaponik, Nikolai; Eychmueller, Alexander; Hua Yulin; Bryce, Martin R; Petty, Michael C

    2007-01-01

    A blue-green fluorescent organic dye and red-emitting nanoparticles, based on II-VI semiconductors, have been used together in the fabrication of white organic light-emitting devices. In this work, the materials were combined in two different ways: in the form of a blend, and as separate layers deposited on the opposite sides of the substrate. The blended-layer structure provided purer white emission. However, this device also exhibited a number of disadvantages, namely a high drive voltage, a low efficiency and some colour instability. These problems could be avoided by using a device structure that was fabricated using separate dye and nanoparticle layers

  7. Origin of colour stability in blue/orange/blue stacked phosphorescent white organic light-emitting diodes

    International Nuclear Information System (INIS)

    Kim, Sung Hyun; Jang, Jyongsik; Yook, Kyoung Soo; Lee, Jun Yeob

    2009-01-01

    The origin of colour stability in phosphorescent white organic light-emitting diodes (PHWOLEDs) with a blue/orange/blue stacked emitting structure was studied by monitoring the change in a recombination zone. A balanced recombination zone shift between the blue and the orange light-emitting layers was found to be responsible for the colour stability in the blue/orange/blue stacked PHWOLEDs.

  8. Micro-light-emitting-diode array with dual functions of visible light communication and illumination

    International Nuclear Information System (INIS)

    Huang Yong; Guo Zhi-You; Sun Hui-Qing; Huang Hong-Yong

    2017-01-01

    We demonstrate high-speed blue 4 × 4 micro-light-emitting-diode (LED) arrays with 14 light-emitting units (two light-emitting units are used as the positive and negative electrodes for power supply, respectively) comprising multiple quantum wells formed of GaN epitaxial layers grown on a sapphire substrate, and experimentally test their applicability for being used as VLC transmitters and illuminations. The micro-LED arrays provide a maximum −3-dB frequency response of 60.5 MHz with a smooth frequency curve from 1 MHz to 500 MHz for an optical output power of 165 mW at an injection current of 30 mA, which, to our knowledge, is the highest response frequency ever reported for blue GaN-based LEDs operating at that level of optical output power. The relationship between the frequency and size of the device single pixel diameter reveals the relationship between the response frequency and diffusion capacitance of the device. (paper)

  9. Phosphorescent Organic Light Emitting Diodes Implementing Platinum Complexes

    Science.gov (United States)

    Ecton, Jeremy Exton

    Organic light emitting diodes (OLEDs) are a promising approach for display and solid state lighting applications. However, further work is needed in establishing the availability of efficient and stable materials for OLEDs with high external quantum efficiency's (EQE) and high operational lifetimes. Recently, significant improvements in the internal quantum efficiency or ratio of generated photons to injected electrons have been achieved with the advent of phosphorescent complexes with the ability to harvest both singlet and triplet excitons. Since then, a variety of phosphorescent complexes containing heavy metal centers including Os, Ni, Ir, Pd, and Pt have been developed. Thus far, the majority of the work in the field has focused on iridium based complexes. Platinum based complexes, however, have received considerably less attention despite demonstrating efficiency's equal to or better than their iridium analogs. In this study, a series of OLEDs implementing newly developed platinum based complexes were demonstrated with efficiency's or operational lifetimes equal to or better than their iridium analogs for select cases. In addition to demonstrating excellent device performance in OLEDs, platinum based complexes exhibit unique photophysical properties including the ability to form excimer emission capable of generating broad white light emission from a single emitter and the ability to form narrow band emission from a rigid, tetradentate molecular structure for select cases. These unique photophysical properties were exploited and their optical and electrical properties in a device setting were elucidated. Utilizing the unique properties of a tridentate Pt complex, Pt-16, a highly efficient white device employing a single emissive layer exhibited a peak EQE of over 20% and high color quality with a CRI of 80 and color coordinates CIE(x=0.33, y=0.33). Furthermore, by employing a rigid, tetradentate platinum complex, PtN1N, with a narrow band emission into a

  10. Evaluation of light-emitting diode beacon light fixtures : final report.

    Science.gov (United States)

    2009-12-01

    Rotating beacons containing filament light sources have long been used on highway maintenance trucks : to indicate the presence of the truck to other drivers. Because of advances in light-emitting diode (LED) : technologies, flashing lights containin...

  11. 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

    2013-05-06

    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.

  12. White top-emitting OLEDs using organic colour-conversion layers for improved colour-stability

    Energy Technology Data Exchange (ETDEWEB)

    Schwab, Tobias; Hofmann, Simone; Thomschke, Michael; Luessem, Bjoern; Leo, Karl [Institut fuer Angewandte Photophysik, Technische Universitaet Dresden (Germany)

    2011-07-01

    In contrast to white organic light-emitting diodes (OLEDs) using several vertical stacked emitters, the principle of down-conversion gives the chance to achieve white light with a simplified layer structure and enhanced colour stability by preventing a colour shift over lifetime due to differential aging of dyes. We investigate an approach where the conversion material is integrated into a top-emitting OLED structure in a way, that only electrons can pass this layer. This assures optical excitation and avoids unwanted electrical recombination inside the conversion layer. The emission spectra, CIE-coordinates, efficiencies, and IV-characteristics depending on the conversion layer thickness have been determined and were compared to the non-emitting host-material with similar optical properties. Lifetime measurements show that these OLEDs have almost no colour change over an investigated period up to 2200 hours. It is shown that the external quantum efficiency of the OLED does not necessarily decrease with an increased conversion layer thickness, even if the photoluminescence quantum yield of these materials is below unity. This indicates that the efficiency is improved by out-coupling of isotropic re-emitted wave-guided modes.

  13. Light emitting diodes for today's energy conscious world

    Energy Technology Data Exchange (ETDEWEB)

    Papanier, J

    2000-10-01

    The role played by light emitting diodes in back lighting, decorative illumination, emergency lighting, and automated signage are described as indicators of the many benefits and advantages of LED technology. The basic principles underlying the functioning of LEDs are explained, including the reasons behind their high efficiency in applications requiring colour. The difference between wattage and lumens is clarified; wattage refers to power consumption, whereas lumens measure brightness or light output, the measure most significant in the case of LEDs.

  14. The effect of Ag layer thickness on the properties of WO{sub 3}/Ag/MoO{sub 3} multilayer films as anode in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zadsar, Mehdi, E-mail: mehdi_zadsar@yahoo.com [Physics Department, University of Isfahan, Isfahan (Iran, Islamic Republic of); Fallah, Hamid Reza; Mahmoodzadeh, Morteza Haji [Physics Department, University of Isfahan, Isfahan (Iran, Islamic Republic of); Quantum Optics Research Group, University of Isfahan, Isfahan (Iran, Islamic Republic of); Tabatabaei, Seyed Vahid [Physics Department, University of Isfahan, Isfahan (Iran, Islamic Republic of)

    2012-04-15

    Transparent conductive WO{sub 3}/Ag/MoO{sub 3} (WAM) multilayer electrodes were fabricated by thermal evaporation and the effects of Ag layer thickness on the optoelectronic and structural properties of multilayer electrode as anode in organic light emitting diodes (OLEDs) were investigated using different analytical methods. For Ag layers with thickness varying between 5 and 20 nm, the best WAM performances, high optical transmittance (81.7%, at around 550 nm), and low electrical sheet resistance (9.75 {Omega}/cm{sup 2}) were obtained for 15 nm thickness. Also, the WAM structure with 15 nm of Ag layer thickness has a very smooth surface with an RMS roughness of 0.37 nm, which is suitable for use as transparent conductive anode in OLEDs. The current density-voltage-luminance (J-V-L) characteristics measurement shows that the current density of WAM/PEDOT:PSS/TPD/Alq{sub 3}/LiF/Al organic diode increases with the increase in thickness of Ag and WO{sub 3}/Ag (15 nm)/MoO{sub 3} device exhibits a higher luminance intensity at lower voltage than ITO/PEDOT:PSS/TPD/Alq{sub 3}/LiF/Al control device. Furthermore, this device shows the highest power efficiency (0.31 lm/W) and current efficiency (1.2 cd/A) at the current density of 20 mA/cm{sup 2}, which is improved 58% and 41% compared with those of the ITO-based device, respectively. The lifetime of the WO{sub 3}/Ag (15 nm)/MoO{sub 3} device was measured to be 50 h at an initial luminance of 50 cd/m{sup 2}, which is five times longer than 10 h for ITO-based device. - Highlights: Black-Right-Pointing-Pointer Investigation of Ag thickness effect on the properties of WO{sub 3}/Ag/MoO{sub 3} films. Black-Right-Pointing-Pointer Electrical conductivity of multilayer films increases with increasing Ag thickness. Black-Right-Pointing-Pointer Optical transmittance increases by Ag thickness and at 15 nm, reaches 81.7%. Black-Right-Pointing-Pointer Power efficiency of WO{sub 3}/Ag (15 nm)/MoO{sub 3} based devices is higher than that of

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-06-09

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

  16. Organic light emitting diodes on ITO-free polymer anodes

    Energy Technology Data Exchange (ETDEWEB)

    Fehse, Karsten; Schwartz, Gregor; Walzer, Karsten; Leo, Karl [Institut fuer Angewandte Photophysik, TU Dresden, D-01062 Dresden (Germany)

    2007-07-01

    The high material cost of indium, being the main component of the commonly used indium-tin-oxide anodes (ITO) in organic light emitting diodes (OLEDs), is an obstacle for the production of efficient low-cost OLEDs. Therefore, new anode materials are needed for large scale OLED production. Recently, we demonstrated that the polymer PEDOT:PSS can substitute ITO as anode. Another highly conductive polymer is polyaniline (PANI) that provides 200 S/cm with a work function of 4.8 eV. In this study, we use PANI as anode for OLEDs (without ITO layer underneath the polymer) with electrically doped hole- and electron transport layers and intrinsic materials in between. Fluorescent blue (Spiro-DPVBi) as well as phosphorescent green (Ir(ppy){sub 3}) and red emitters (Ir(MDQ){sub 2}(acac)) were used for single colour and white OLEDs. Green single and double emission OLEDs achieve device efficiencies of 34 lm/W and 40.7 lm/W, respectively. The white OLED shows a power efficiency of 8.9 lm/W at 1000 cd/m{sup 2} with CIE coordinates of (0.42/0.39).

  17. Tuning the colour of white polymer light emitting diodes

    NARCIS (Netherlands)

    Kok, M.M. de; Sarfert, W.; Paetzold, R.

    2010-01-01

    Colour tuning of white polymer light emitting diode (LED) light sources can be attained by various methods at various stages in the production process of the lamps and/or by the design of the active material incorporated in the LEDs. In this contribution we will describe the methods and discuss the

  18. Oxycarbonitride phosphors and light emitting devices using the same

    Science.gov (United States)

    Li, Yuanqiang; Romanelli, Michael Dennis; Tian, Yongchi

    2013-10-08

    Disclosed herein is a novel family of oxycarbidonitride phosphor compositions and light emitting devices incorporating the same. Within the sextant system of M--Al--Si--O--N--C--Ln and quintuplet system of M--Si--O--N--C--Ln (M=alkaline earth element, Ln=rare earth element), the phosphors are composed of either one single crystalline phase or two crystalline phases with high chemical and thermal stability. In certain embodiments, the disclosed phosphor of silicon oxycarbidonitrides emits green light at wavelength between 530-550 nm. In further embodiments, the disclosed phosphor compositions emit blue-green to yellow light in a wavelength range of 450-650 nm under near-UV and blue light excitation.

  19. Fast spatial atomic layer deposition of Al{sub 2}O{sub 3} at low temperature (<100 °C) as a gas permeation barrier for flexible organic light-emitting diode displays

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hagyoung; Shin, Seokyoon; Jeon, Hyeongtag, E-mail: hjeon@hanyang.ac.kr [Department of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Choi, Yeongtae; Kim, Junghun; Kim, Sanghun; Chung, Seog Chul; Oh, Kiyoung [LIG INVENIA Co., Ltd., Seongnam, Gyeonggi 462-807 (Korea, Republic of)

    2016-01-15

    The authors developed a high throughput (70 Å/min) and scalable space-divided atomic layer deposition (ALD) system for thin film encapsulation (TFE) of flexible organic light-emitting diode (OLED) displays at low temperatures (<100 °C). In this paper, the authors report the excellent moisture barrier properties of Al{sub 2}O{sub 3} films deposited on 2G glass substrates of an industrially relevant size (370 × 470 mm{sup 2}) using the newly developed ALD system. This new ALD system reduced the ALD cycle time to less than 1 s. A growth rate of 0.9 Å/cycle was achieved using trimethylaluminum as an Al source and O{sub 3} as an O reactant. The morphological features and step coverage of the Al{sub 2}O{sub 3} films were investigated using field emission scanning electron microscopy. The chemical composition was analyzed using Auger electron spectroscopy. These deposited Al{sub 2}O{sub 3} films demonstrated a good optical transmittance higher than 95% in the visible region based on the ultraviolet visible spectrometer measurements. Water vapor transmission rate lower than the detection limit of the MOCON test (less than 3.0 × 10{sup −3} g/m{sup 2} day) were obtained for the flexible substrates. Based on these results, Al{sub 2}O{sub 3} deposited using our new high-throughput and scalable spatial ALD is considered a good candidate for preparation of TFE films of flexible OLEDs.

  20. Achieving Extreme Utilization of Excitons by an Efficient Sandwich-Type Emissive Layer Architecture for Reduced Efficiency Roll-Off and Improved Operational Stability in Organic Light-Emitting Diodes.

    Science.gov (United States)

    Wu, Zhongbin; Sun, Ning; Zhu, Liping; Sun, Hengda; Wang, Jiaxiu; Yang, Dezhi; Qiao, Xianfeng; Chen, Jiangshan; Alshehri, Saad M; Ahamad, Tansir; Ma, Dongge

    2016-02-10

    It has been demonstrated that the efficiency roll-off is generally caused by the accumulation of excitons or charge carriers, which is intimately related to the emissive layer (EML) architecture in organic light-emitting diodes (OLEDs). In this article, an efficient sandwich-type EML structure with a mixed-host EML sandwiched between two single-host EMLs was designed to eliminate this accumulation, thus simultaneously achieving high efficiency, low efficiency roll-off and good operational stability in the resulting OLEDs. The devices show excellent electroluminescence performances, realizing a maximum external quantum efficiency (EQE) of 24.6% with a maximum power efficiency of 105.6 lm W(-1) and a maximum current efficiency of 93.5 cd A(-1). At the high brightness of 5,000 cd m(-2), they still remain as high as 23.3%, 71.1 lm W(-1), and 88.3 cd A(-1), respectively. And, the device lifetime is up to 2000 h at initial luminance of 1000 cd m(-2), which is significantly higher than that of compared devices with conventional EML structures. The improvement mechanism is systematically studied by the dependence of the exciton distribution in EML and the exciton quenching processes. It can be seen that the utilization of the efficient sandwich-type EML broadens the recombination zone width, thus greatly reducing the exciton quenching and increasing the probability of the exciton recombination. It is believed that the design concept provides a new avenue for us to achieve high-performance OLEDs.

  1. 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

  2. A triphenylamine substituted quinacridone derivative for solution processed organic light emitting diodes

    NARCIS (Netherlands)

    Pilz da Cunha, M.; Do, T.T.; Yambem, S.D.; Pham, H.D.; Chang, S.; Manzhos, S.; Katoh, R.; Sonar, P.

    2018-01-01

    We report on a novel quinacridone derivative design, namely, 2,9-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-5,12-bis(2-ethylhexyl)-5,12-dihydroquinolino[2,3-b]acridine-7,14-dione (TPA-QA-TPA) for possible use as a solution processable emissive layer in organic light emitting diodes (OLEDs). TPA-QA-TPA

  3. Polymer Light-Emitting Diode Prepared by Floating-Off Film-Transfer Technique

    KAUST Repository

    Park, Jihoon; Kim, Eugene

    2015-01-01

    © 2015 Copyright Taylor & Francis Group, LLC. Floating-off film-transfer technique was used for the formation of semiconducting polymer multi-layers and the effect on the performance of polymer light-emitting diode (PLED) was studied. This method

  4. 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 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.

  5. Direct transparent electrode patterning on layered GaN substrate by screen printing of indium tin oxide nanoparticle ink for Eu-doped GaN red light-emitting diode

    International Nuclear Information System (INIS)

    Kashiwagi, Y.; Yamamoto, M.; Saitoh, M.; Takahashi, M.; Ohno, T.; Nakamoto, M.; Koizumi, A.; Fujiwara, Y.; Takemura, Y.; Murahashi, K.; Ohtsuka, K.; Furuta, S.

    2014-01-01

    Transparent electrodes were formed on Eu-doped GaN-based red-light-emitting diode (GaN:Eu LED) substrates by the screen printing of indium tin oxide nanoparticle (ITO np) inks as a wet process. The ITO nps with a mean diameter of 25 nm were synthesized by the controlled thermolysis of a mixture of indium complexes and tin complexes. After the direct screen printing of ITO np inks on GaN:Eu LED substrates and sintering at 850 °C for 10 min under atmospheric conditions, the resistivity of the ITO film was 5.2 mΩ cm. The fabricated LED up to 3 mm square surface emitted red light when the on-voltage was exceeded

  6. Direct transparent electrode patterning on layered GaN substrate by screen printing of indium tin oxide nanoparticle ink for Eu-doped GaN red light-emitting diode

    Science.gov (United States)

    Kashiwagi, Y.; Koizumi, A.; Takemura, Y.; Furuta, S.; Yamamoto, M.; Saitoh, M.; Takahashi, M.; Ohno, T.; Fujiwara, Y.; Murahashi, K.; Ohtsuka, K.; Nakamoto, M.

    2014-12-01

    Transparent electrodes were formed on Eu-doped GaN-based red-light-emitting diode (GaN:Eu LED) substrates by the screen printing of indium tin oxide nanoparticle (ITO np) inks as a wet process. The ITO nps with a mean diameter of 25 nm were synthesized by the controlled thermolysis of a mixture of indium complexes and tin complexes. After the direct screen printing of ITO np inks on GaN:Eu LED substrates and sintering at 850 °C for 10 min under atmospheric conditions, the resistivity of the ITO film was 5.2 mΩ cm. The fabricated LED up to 3 mm square surface emitted red light when the on-voltage was exceeded.

  7. Direct transparent electrode patterning on layered GaN substrate by screen printing of indium tin oxide nanoparticle ink for Eu-doped GaN red light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Kashiwagi, Y., E-mail: kasiwagi@omtri.or.jp; Yamamoto, M.; Saitoh, M.; Takahashi, M.; Ohno, T.; Nakamoto, M. [Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553 (Japan); Koizumi, A.; Fujiwara, Y. [Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Takemura, Y.; Murahashi, K.; Ohtsuka, K. [Okuno Chemical Industries Co., Ltd., 2-1-25 Hanaten-nishi, Joto-ku, Osaka 536-0011 (Japan); Furuta, S. [Tomoe Works Co., Ltd., 7-13 Tsurumachi, Amagasaki 660-0092 (Japan)

    2014-12-01

    Transparent electrodes were formed on Eu-doped GaN-based red-light-emitting diode (GaN:Eu LED) substrates by the screen printing of indium tin oxide nanoparticle (ITO np) inks as a wet process. The ITO nps with a mean diameter of 25 nm were synthesized by the controlled thermolysis of a mixture of indium complexes and tin complexes. After the direct screen printing of ITO np inks on GaN:Eu LED substrates and sintering at 850 °C for 10 min under atmospheric conditions, the resistivity of the ITO film was 5.2 mΩ cm. The fabricated LED up to 3 mm square surface emitted red light when the on-voltage was exceeded.

  8. Theoretical analysis of enhanced light output from a GaN light emitting diode with an embedded photonic crystal

    International Nuclear Information System (INIS)

    Wen Feng; Liu Deming; Huang Lirong

    2010-01-01

    The enhancement of the light output of an embedded photonic crystal light emitting diode is investigated based on the finite-difference time-domain modeling. The embedded photonic crystal (PC) lattice type, multi-layer embedded PC, distance between the multiple quantum well and the embedded PC are studied. It is found that the embedded one dimensional PC can act as well as embedded two dimensional PCs. The emitted light flux in the up direction can be increased by a new kind of multi-layer embedded PC. Also, we show that the light output in the up direction for the LED with both surfaces and embedded PC could be as high as five times that of a conventional LED. (semiconductor devices)

  9. Theoretical analysis of enhanced light output from a GaN light emitting diode with an embedded photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Wen Feng; Liu Deming; Huang Lirong, E-mail: hlr5649@163.co [Wuhan National Laboratory for Optoelectronics, College of Opto-Electronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2010-10-15

    The enhancement of the light output of an embedded photonic crystal light emitting diode is investigated based on the finite-difference time-domain modeling. The embedded photonic crystal (PC) lattice type, multi-layer embedded PC, distance between the multiple quantum well and the embedded PC are studied. It is found that the embedded one dimensional PC can act as well as embedded two dimensional PCs. The emitted light flux in the up direction can be increased by a new kind of multi-layer embedded PC. Also, we show that the light output in the up direction for the LED with both surfaces and embedded PC could be as high as five times that of a conventional LED. (semiconductor devices)

  10. Influence of intensive light exposure on the complex impedance of polymer light-emitting diodes

    Directory of Open Access Journals (Sweden)

    Fábio Rogério Cury

    2008-06-01

    Full Text Available In this work we investigated the effect of visible radiation on the electrical properties of poly[(2-methoxy-5-hexyloxy-p-phenylenevinylene]- MH-PPV films and light emitting diodes. Complex impedance measurements of (Au or ITO/MH-PPV/(Au or Al samples were carried out at room temperature and exposed to white light. Over the frequency range from 100 mHz to 2 MHz, the electrical results of Au/MH-PPV/Au was dominated by the Cole-Cole approach, where the electrode influence is negligible. However, some additional influence of the interface was observed to occur when Al was used as electrode. These effects were observed under both dark and visible-light illumination conditions. A simple model based on resistor-capacitor parallel circuits was developed to represent the complex impedance of the samples, thereby separating bulk and interface contributions. We observed that the polymer electrical resistivity decreased while the dielectric constant of the polymer and the thickness of the Al/MH-PPV layer were almost constant with increasing light intensity. The decrease of the polymer layer resistance comes from a better charge injection due to a light induced dissociation of positive charge carriers at the electrode.

  11. Light-emitting waveguide-plasmon polaritions

    NARCIS (Netherlands)

    Rodriguez, S.R.K.; Murai, S.; Verschuuren, M.A.; Gómez Rivas, J.

    2012-01-01

    We demonstrate the generation of light in an optical waveguide strongly coupled to a periodic array of metallic nanoantennas. This coupling gives rise to hybrid waveguide-plasmon polaritons (WPPs), which undergo a transmutation from plasmon to waveguide mode and vice versa as the eigenfrequency

  12. Light-emitting diodes - Their potential in biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Naichia Gary; Wu, Chia-Hao [College of Applied Sciences, MingDao University, 369 Wen-Hua Road, Peetou, Changhua 52345 (China); Cheng, Ta Chih [Department of Tropical Agriculture and International Cooperation, National Pingtung University of Science and Technology, 1 Hseuh-Fu Rd., Nei-Pu Hsiang, Pingtung 91201 (China)

    2010-10-15

    The rapid development of high brightness light-emitting diodes (LEDs) makes feasible the use of LEDs, among other light sources (such as laser, intense pulse light and other incoherent light systems), for medical treatment and light therapy. This paper provides a general review on red, green, blue, ultraviolet LED applications in photo rejuvenation and medical treatments of a variety of physical abnormalities, as well as the relief of stress, circadian rhythm disorders, and seasonal affective disorder. The review, concentrated in the papers published after 1990, intends to show that LEDs are well qualified to succeed its more energy demanding counterparts in the named areas and beyond. (author)

  13. Determination of illuminants representing typical white light emitting diodes sources

    DEFF Research Database (Denmark)

    Jost, S.; Ngo, M.; Ferrero, A.

    2017-01-01

    is to develop LED-based illuminants that describe typical white LED products based on their Spectral Power Distributions (SPDs). Some of these new illuminants will be recommended in the update of the CIE publication 15 on colorimetry with the other typical illuminants, and among them, some could be used......Solid-state lighting (SSL) products are already in use by consumers and are rapidly gaining the lighting market. Especially, white Light Emitting Diode (LED) sources are replacing banned incandescent lamps and other lighting technologies in most general lighting applications. The aim of this work...... to complement the CIE standard illuminant A for calibration use in photometry....

  14. Irradiation Pattern Analysis for Designing Light Sources-Based on Light Emitting Diodes

    International Nuclear Information System (INIS)

    Rojas, E.; Stolik, S.; La Rosa, J. de; Valor, A.

    2016-01-01

    Nowadays it is possible to design light sources with a specific irradiation pattern for many applications. Light Emitting Diodes present features like high luminous efficiency, durability, reliability, flexibility, among others as the result of its rapid development. In this paper the analysis of the irradiation pattern of the light emitting diodes is presented. The approximation of these irradiation patterns to both, a Lambertian, as well as a Gaussian functions for the design of light sources is proposed. Finally, the obtained results and the functionality of bringing the irradiation pattern of the light emitting diodes to these functions are discussed. (Author)

  15. Light extraction efficiency enhancement for fluorescent SiC based white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    Fluorescent SiC based white light-emitting diodes(LEDs) light source, as an innovative energy-efficient light source, would even have longer lifetime, better light quality and eliminated blue-tone effect, compared to the current phosphor based white LED light source. In this paper, the yellow...

  16. Degradation of light emitting diodes: a proposed methodology

    International Nuclear Information System (INIS)

    Koh, Sau; Vam Driel, Willem; Zhang, G.Q.

    2011-01-01

    Due to their long lifetime and high efficacy, light emitting diodes have the potential to revolutionize the illumination industry. However, self heat and high environmental temperature which will lead to increased junction temperature and degradation due to electrical overstress can shorten the life of the light emitting diode. In this research, a methodology to investigate the degradation of the LED emitter has been proposed. The epoxy lens of the emitter can be modelled using simplified Eyring methods whereas an equation has been proposed for describing the degradation of the LED emitters. (semiconductor devices)

  17. Investigation of organic light emitting diodes for interferometric purposes

    Science.gov (United States)

    Pakula, Anna; Zimak, Marzena; Sałbut, Leszek

    2011-05-01

    Recently the new type of light source has been introduced to the market. Organic light emitting diode (OLED) is not only interesting because of the low applying voltage, wide light emitting areas and emission efficiency. It gives the possibility to create a light source of a various shape, various color and in the near future very likely even the one that will change shape and spectrum in time in controlled way. Those opportunities have not been in our reach until now. In the paper authors try to give an answer to the question if the new light source -OLED - is suitable for interferometric purposes. Tests cover the short and long term spectrum stability, spectrum changes due to the emission area selection. In the paper the results of two OLEDs (red and white) are shown together with the result of an attempt to use them in an interferometric setup.

  18. Is it viable to improve light output efficiency by nano-light-emitting diodes?

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chao-Hung; Huang, Yu-Wen [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Wu, Shang-En [Genesis Photonics Incorporation, Tainan 70101, Taiwan (China); Liu, Chuan-Pu, E-mail: cpliu@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2013-12-02

    Nanopillar arrays with InGaN/GaN multiple-quantum-disks (MQDs) are fabricated by focused-ion-beam milling with surface damage layer removed by KOH wet etching. Nano-light-emitting diodes (Nano-LEDs) made of the InGaN/GaN MQD nanopillars are found to have 19.49% less output power than that of a conventional LED. The reasons are analyzed in detail and considering their current-voltage and electroluminescence characteristics, internal quantum efficiency, external quantum efficiency, light extraction, and wall-plug efficiency. Our results suggest that nanopillar-LED can outperform if the density can be increased to 2.81 × 10{sup 9} cm{sup −2} with the size unchanged or the size can be increased to 854.4 nm with the density unchanged.

  19. Visible-light electroluminescence in Mn-doped GaAs light-emitting diodes

    International Nuclear Information System (INIS)

    Nam Hai, Pham; Maruo, Daiki; Tanaka, Masaaki

    2014-01-01

    We observed visible-light electroluminescence (EL) due to d-d transitions in light-emitting diodes with Mn-doped GaAs layers (here, referred to as GaAs:Mn). Besides the band-gap emission of GaAs, the EL spectra show two peaks at 1.89 eV and 2.16 eV, which are exactly the same as 4 A 2 ( 4 F) → 4 T 1 ( 4 G) and 4 T 1 ( 4 G) → 6 A 1 ( 6 S) transitions of Mn atoms doped in ZnS. The temperature dependence and the current-density dependence are consistent with the characteristics of d-d transitions. We explain the observed EL spectra by the p-d hybridized orbitals of the Mn d electrons in GaAs

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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)/Alq 3 (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 (ΔCIE x, 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. (paper)

  1. 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.

  2. Light extraction in planar light-emitting diode with nonuniform current injection: model and simulation.

    Science.gov (United States)

    Khmyrova, Irina; Watanabe, Norikazu; Kholopova, Julia; Kovalchuk, Anatoly; Shapoval, Sergei

    2014-07-20

    We develop an analytical and numerical model for performing simulation of light extraction through the planar output interface of the light-emitting diodes (LEDs) with nonuniform current injection. Spatial nonuniformity of injected current is a peculiar feature of the LEDs in which top metal electrode is patterned as a mesh in order to enhance the output power of light extracted through the top surface. Basic features of the model are the bi-plane computation domain, related to other areas of numerical grid (NG) cells in these two planes, representation of light-generating layer by an ensemble of point light sources, numerical "collection" of light photons from the area limited by acceptance circle and adjustment of NG-cell areas in the computation procedure by the angle-tuned aperture function. The developed model and procedure are used to simulate spatial distributions of the output optical power as well as the total output power at different mesh pitches. The proposed model and simulation strategy can be very efficient in evaluation of the output optical performance of LEDs with periodical or symmetrical configuration of the electrodes.

  3. Infrared Organic Light-Emitting Diodes with Carbon Nanotube Emitters.

    Science.gov (United States)

    Graf, Arko; Murawski, Caroline; Zakharko, Yuriy; Zaumseil, Jana; Gather, Malte C

    2018-03-01

    While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum are widespread, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter is demonstrated. By using a multilayer stacked architecture with matching charge blocking and charge-transport layers, narrow-band electroluminescence at wavelengths between 1000 and 1200 nm is achieved, with spectral features characteristic of excitonic and trionic emission of the employed (6,5) SWCNTs. Here, the OLED performance is investigated in detail and it is found that local conduction hot-spots lead to pronounced trion emission. Analysis of the emissive dipole orientation shows a strong horizontal alignment of the SWCNTs with an average inclination angle of 12.9° with respect to the plane, leading to an exceptionally high outcoupling efficiency of 49%. The SWCNT-based OLEDs represent a highly attractive platform for emission across the entire nIR. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Time-dependent simulation of organic light-emitting diodes

    International Nuclear Information System (INIS)

    Sharifi, M J

    2009-01-01

    Several methods to simulate the behavior of organic light-emitting diodes (OLEDs) have been proposed in the past. In this paper, we develop a previous method, based on the master equation, in order to allow the simulation of time-dependent behavior and transient states. The calculation algorithm of the program that we have written is described. The time-dependent behaviors of two simple monolayer devices and of a more complicated three-layer device were simulated by means of this program, and the results are discussed. The results show that the turn-off speed of an OLED might be very slow, especially in the case of a multilayer device. This behavior is related to the low mobility of the organic material in weak electric fields. An interesting feature of the time behavior is pointed out, whereby the recombination rate may become considerably larger after the falling edge of an applied voltage pulse. Moreover, the validity of the transient electro-luminescent method for measuring carrier mobility in organic material has been examined by means of simulation. The results show that there is some inconsistency especially in high electric fields

  5. Dr. Harry Whelan With the Light Emitting Diode Probe

    Science.gov (United States)

    1999-01-01

    The red light from the Light Emitting Diode (LED) probe shines through the fingers of Dr. Harry Whelan, a pediatric neurologist at the Children's Hospital of Wisconsin in Milwaukee. Dr. Whelan uses the long waves of light from the LED surgical probe to activate special drugs that kill brain tumors. Laser light previously has been used for this type of surgery, but the LED light illuminates through all nearby tissues, reaching parts of tumors that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. Also, it can be used for hours at a time while still remaining cool to the touch. The probe was developed for photodynamic cancer therapy under a NASA Small Business Innovative Research Program grant. The program is part of NASA's Technology Transfer Department at the Marshall Space Flight Center.

  6. Magnetoelectroluminescence in organic light-emitting diodes

    Science.gov (United States)

    Lawrence, Joseph E.; Lewis, Alan M.; Manolopoulos, David E.; Hore, P. J.

    2016-06-01

    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 experimental data for both normal (H-) and deuterated (D-) DOO-PPV over a wide range of magnetic field strengths once singlet-triplet dephasing is taken into account. Without this effect, which has not been included in any previous simulation of magnetoelectroluminescence, it is not possible to reproduce the experimental data for both isotopologues in a consistent fashion. Our results also indicate that the magnetoconductance of DOO-PPV cannot be solely due to the effect of the magnetic field on the dissociation of polaron pairs.

  7. Magnetoelectroluminescence in organic light-emitting diodes

    International Nuclear Information System (INIS)

    Lawrence, Joseph E.; Lewis, Alan M.; 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 experimental data for both normal (H-) and deuterated (D-) DOO-PPV over a wide range of magnetic field strengths once singlet-triplet dephasing is taken into account. Without this effect, which has not been included in any previous simulation of magnetoelectroluminescence, it is not possible to reproduce the experimental data for both isotopologues in a consistent fashion. Our results also indicate that the magnetoconductance of DOO-PPV cannot be solely due to the effect of the magnetic field on the dissociation of polaron pairs.

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

    International Nuclear Information System (INIS)

    Zhu, Peifen

    2016-01-01

    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 TiO 2 sphere in 0.30 μm PS layer with optimized in-coupling efficiency, out-coupling efficiency and cavity effect. (paper)

  9. Longitudinally mounted light emitting plasma in a dielectric resonator

    Energy Technology Data Exchange (ETDEWEB)

    Gilliard, Richard; DeVincentis, Marc; Hafidi, Abdeslam; O' Hare, Daniel; Hollingsworth, Gregg [LUXIM Corporation, 1171 Borregas Avenue, Sunnyvale, CA 94089 (United States)

    2011-06-08

    Methods for coupling power from a dielectric resonator to a light-emitting plasma have been previously described (Gilliard et al IEEE Trans. Plasma Sci. at press). Inevitably, regardless of the efficiency of power transfer, much of the emitted light is absorbed in the resonator itself which physically surrounds much if not all of the radiating material. An investigation into a method is presented here for efficiently coupling power to a longitudinally mounted plasma vessel which is mounted on the surface of the dielectric material of the resonator, thereby eliminating significant absorption of light within the resonator structure. The topology of the resonator and its physical properties as well as those of the metal halide plasma are presented. Results of basic models of the field configuration and plasma are shown as well as a configuration suitable as a practical light source.

  10. Optimization of light quality from color mixing light-emitting diode systems for general lighting

    Science.gov (United States)

    Thorseth, Anders

    2012-03-01

    Given the problem of metamerisms inherent in color mixing in light-emitting diode (LED) systems with more than three distinct colors, a method for optimizing the spectral output of multicolor LED system with regards to standardized light quality parameters has been developed. The composite spectral power distribution from the LEDs are simulated using spectral radiometric measurements of single commercially available LEDs for varying input power, to account for the efficiency droop and other non-linear effects in electrical power vs. light output. The method uses electrical input powers as input parameters in a randomized steepest decent optimization. The resulting spectral power distributions are evaluated with regard to the light quality using the standard characteristics: CIE color rendering index, correlated color temperature and chromaticity distance. The results indicate Pareto optimal boundaries for each system, mapping the capabilities of the simulated lighting systems with regard to the light quality characteristics.

  11. [White organic light emitting device with dyestuff DCJTB blended in polymer].

    Science.gov (United States)

    Zhang, Yan-Fei; Xu, Zheng; Zhang, Fu-Jun; Wang, Yong; Zhao, Su-Ling

    2008-04-01

    The Alq3 and DCJTB were blended with poly (N-vinylcarbazole) (PVK) in different weight ratios and spin coated into films. Multilayer devices with the light emitting layer PVK : Alq3 : DCJTB were fabricated, and their structure was ITO/ PVK : Alq3 : DCJTB/ BCP/Alq3/LiF/Al in which BCP and Alq3 were employed as the hole-blocking and electron-transporting layers respectively, PVK is the blue light-emitting as well as hole-transporting layer. The mass proportion of PVK relative to Alq3 was tuned while the quality ratio of PVK to DCJTB remained (100 : 1). Finally, fairly pure and stabile white emission was achieved when PVK : Alq3 : DCJTB was 100 : 5 : 1. The CIE coordinate was (0.33, 0.36) at 14 V, which is very stable at various biases (10-14 V).

  12. GaN light-emitting device based on ionic liquid electrolyte

    Science.gov (United States)

    Hirai, Tomoaki; Sakanoue, Tomo; Takenobu, Taishi

    2018-06-01

    Ionic liquids (ILs) are attractive materials for fabricating unique hybrid devices based on electronics and electrochemistry; thus, IL-gated transistors and organic light-emitting devices of light-emitting electrochemical cells (LECs) are investigated for future low-voltage and high-performance devices. In LECs, voltage application induces the formation of electrochemically doped p–n homojunctions owing to ion rearrangements in composites of semiconductors and electrolytes, and achieves electron–hole recombination for light emission at the homojunctions. In this work, we applied this concept of IL-induced electrochemical doping to the fabrication of GaN-based light-emitting devices. We found that voltage application to the layered IL/GaN structure accumulated electrons on the GaN surface owing to ion rearrangements and improved the conductivity of GaN. The ion rearrangement also enabled holes to be injected by the strong electric field of electric double layers on hole injection contacts. This simultaneous injection of holes and electrons into GaN mediated by ions achieves light emission at a low voltage of around 3.4 V. The light emission from the simple IL/GaN structure indicates the usefulness of an electrochemical technique in generating light emission with great ease of fabrication.

  13. 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

  14. High-efficient and brightness white organic light-emitting diodes operated at low bias voltage

    Science.gov (United States)

    Zhang, Lei; Yu, Junsheng; Yuan, Kai; Jian, Yadong

    2010-10-01

    White organic light-emitting diodes (OLEDs) used for display application and lighting need to possess high efficiency, high brightness, and low driving voltage. In this work, white OLEDs consisted of ambipolar 9,10-bis 2-naphthyl anthracene (ADN) as a host of blue light-emitting layer (EML) doped with tetrabutyleperlene (TBPe) and a thin codoped layer consisted of N, N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB) as a host of yellow light-emitting layer doped with 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) were investigated. With appropriate tuning in the film thickness, position, and dopant concentration of the co-doped layer, a white OLED with a luminance yield of 10.02 cd/A with the CIE coordinates of (0.29, 0.33) has been achieved at a bias voltage of 9 V and a luminance level of over 10,000 cd/m2. By introducing the PIN structure with both HIL and bis(10- hydroxybenzo-quinolinato)-beryllium (BeBq2) ETL, the power efficiency of white OLED was improved.

  15. Organic light emitting diodes with spin polarized electrodes

    NARCIS (Netherlands)

    Arisi, E.; Bergenti, I.; Dediu, V.; Loi, M.A.; Muccini, M.; Murgia, M.; Ruani, G.; Taliani, C.; Zamboni, R.

    2003-01-01

    Electrical and optical properties of Alq3 based organic light emitting diodes with normal and spin polarized electrodes are presented. Epitaxial semitransparent highly spin polarized La0.7Sr0.3MnO3 were used as hole injector, substituting the traditional indium tin oxide electrode. A comparison of

  16. Liquid metals as electrodes in polymer light emitting diodes

    NARCIS (Netherlands)

    Andersson, G.G.; Gommans, H.H.P.; Denier van der Gon, A.W.; Brongersma, H.H.

    2003-01-01

    We demonstrate that liquid metals can be used as cathodes in light emitting diodes (pLEDs). The main difference between the use of liquid cathodes and evaporated cathodes is the sharpness of the metal–polymer interface. Liquid metal cathodes result in significantly sharper metal–organic interfaces

  17. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    Science.gov (United States)

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  18. An assessment of ultraviolet radiation components of light emitted ...

    African Journals Online (AJOL)

    An assessment of ultraviolet radiation components of light emitted from electric arc and their possible exposure risks. ... The study of Ultraviolet Radiation has of recent become interesting because of the health hazards it poses to human. Apart from its intensity reaching the earth from the sun, other man-made sources have ...

  19. Atom probe tomography of a commercial light emitting diode

    International Nuclear Information System (INIS)

    Larson, D J; Prosa, T J; Olson, D; Lawrence, D; Clifton, P H; Kelly, T F; Lefebvre, W

    2013-01-01

    The atomic-scale analysis of a commercial light emitting diode device purchased at retail is demonstrated using a local electrode atom probe. Some of the features are correlated with transmission electron microscopy imaging. Subtle details of the structure that are revealed have potential significance for the design and performance of this device

  20. Performance of injection-limited polymer light-emitting diodes

    NARCIS (Netherlands)

    Blom, P.W.M.; Woudenberg, T.V.; Huiberts, H.; Jabbour, GE; Carter, SA; Kido, J; Lee, ST; Sariciftci, NS

    2002-01-01

    The electro-optical characteristics of a polymer light emitting diode (PLED) with a strongly reduced hole injection have been investigated. The device consists of a poly-p-phenylene vinylene semiconductor with a Ag hole injecting contact, which has an injection barrier of about 1 eV. It is observed

  1. A white organic light emitting diode based on anthracene-triphenylamine derivatives

    Science.gov (United States)

    Jiang, Quan; Qu, Jianjun; Yu, Junsheng; Tao, Silu; Gan, Yuanyuan; Jiang, Yadong

    2010-10-01

    White organic lighting-diode (WOLED) can be used as flat light sources, backlights for liquid crystal displays and full color displays. Recently, a research mainstream of white OLED is to develop the novel materials and optimize the structure of devices. In this work a WOLED with a structure of ITO/NPB/PAA/Alq3: x% rubrene/Alq3/Mg: Ag, was fabricated. The device has two light-emitting layers. NPB is used as a hole transport layer, PAA as a blue emitting layer, Alq3: rubrene host-guest system as a yellow emitting layer, and Alq3 close to the cathode as an electron transport layer. In the experiment, the doping concentration of rubrene was optimized. WOLED 1 with 4% rubrene achieved a maximum luminous efficiency of 1.80 lm/W, a maximum luminance of 3926 cd/m2 and CIE coordinates of (0.374, 0.341) .WOLED 2 with 2% rubrene achieved a maximum luminous efficiency of 0.65 lm/W, a maximum luminance of 7495cd/m2 and CIE coordinates of (0.365,0.365).

  2. AlGaInN-based ultraviolet light-emitting diodes grown on Si(111)

    International Nuclear Information System (INIS)

    Kipshidze, G.; Kuryatkov, V.; Borisov, B.; Holtz, M.; Nikishin, S.; Temkin, H.

    2002-01-01

    Ultraviolet light-emitting diodes grown on Si(111) by gas-source molecular-beam epitaxy with ammonia are described. The layers are composed of superlattices of AlGaN/GaN and AlN/AlGaInN. The layers are doped n and p type with Si and Mg, respectively. Hole concentration of 4x10 17 cm -3 , with a mobility of 8 cm2/Vs, is measured in Al 0.4 Ga 0.6 N/GaN. We demonstrate effective n- and p-type doping of structures based on AlN/AlGaInN. Light-emitting diodes based on these structures show light emission between 290 and 334 nm

  3. Simulations of charge transport in organic light emitting diodes

    International Nuclear Information System (INIS)

    Martin, Simon James

    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 the observed temperature and electric field dependence of carrier mobilities in disordered organic semiconductors. A hopping transport model has been developed which accounts explicitly for the structure in highly ordered films of rigid rod liquid-crystalline conjugated polymers. Chapter 2 discusses the formation of metal-semiconductor contacts, and current injection processes in OLEDs. If the barrier to carrier injection at a metal-semiconductor contact is small, or the contact is Ohmic, then the current may be space charge limited; this second limiting regime of current flow for OLEDs is also described. The remainder of Chapter 2 describes the drift-diffusion model used in this work in some detail. Chapter 3 contains results obtained from modelling the J-V characteristics of single-layer OLEDs, which are compared to experimental data in order to validate the drift-diffusion model. Chapter 4 contains results of simulating bi-layer OLEDs; rather than examining J

  4. Broadband mid-infrared superlattice light-emitting diodes

    Science.gov (United States)

    Ricker, R. J.; Provence, S. R.; Norton, D. T.; Boggess, T. F.; Prineas, J. P.

    2017-05-01

    InAs/GaSb type-II superlattice light-emitting diodes were fabricated to form a device that provides emission over the entire 3-5 μm mid-infrared transmission window. Variable bandgap emission regions were coupled together using tunnel junctions to emit at peak wavelengths of 3.3 μm, 3.5 μm, 3.7 μm, 3.9 μm, 4.1 μm, 4.4 μm, 4.7 μm, and 5.0 μm. Cascading the structure recycles the electrons in each emission region to emit several wavelengths simultaneously. At high current densities, the light-emitting diode spectra broadened into a continuous, broadband spectrum that covered the entire mid-infrared band. When cooled to 77 K, radiances of over 1 W/cm2 sr were achieved, demonstrating apparent temperatures above 1000 K over the 3-5 μm band. InAs/GaSb type-II superlattices are capable of emitting from 3 μm to 30 μm, and the device design can be expanded to include longer emission wavelengths.

  5. Double surface plasmon enhanced organic light-emitting diodes by gold nanoparticles and silver nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Chia-Yuan; Chen, Ying-Chung [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); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2015-12-30

    Graphical abstract: - Highlights: • The buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated. • The silver nanoclusters will generate surface plasmon resonance effect, resulting that the localized electric field around the silver nanoclusters is enhanced. • When the recombination region of the excitons is too close to the nanoparticles of the hole-transport layer, the nonradiative quenching of excitons is generated. - Abstract: The influence of gold nanoparticles (GNPs) and silver nanoclusters (SNCs) on the performance of organic light-emitting diodes is investigated in this study. The GNPs are doped into (poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate)) (PEDOT: PSS) and the SNCs are introduced between the electron-injection layer and cathode alumina. The power efficiency of the device, at the maximum luminance, with double surface plasmon resonance and buffer layer is about 2.15 times higher than that of the device without GNPs and SNCs because the absorption peaks of GNPs and SNCs are as good as the photoluminescence peak of the emission layer, resulting in strong surface plasmon resonance effect in the device. In addition, the buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated.

  6. Multi-solution processes of small molecule for flexible white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Yu-Sheng, E-mail: ystsai@nfu.edu.tw [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Chittawanij, Apisit; Hong, Lin-Ann; Guo, Siou-Wei [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Wang, Ching-Chiun [Department of Solid State Lighting Technology, Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan, ROC (China); Juang, Fuh-Shyang [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China); Lai, Shih-Hsiang [Department of Solid State Lighting Technology, Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan, ROC (China); Lin, Yang-Ching [Institute of Electro-optical and Materials Science, National Formosa University, Yunlin 63201, Taiwan, ROC (China)

    2016-04-01

    Most small molecule organic light emitting diode (SM-OLED) device structures are made in one layer using solution-based processing because the solution is usually a high dissolvent material that easily attacks the layer below it. We demonstrate a simple and reliable stamping technique for fabricating multi-solution process flexible white SM-OLEDs. The structure is anode/spin-hole injection layer/spin-emitting layer/stamping-electron transport layer/cathode. Poly(di-methyl silane) (PDMS) stamp is used for transferring electron transport layer. An intermediate ultraviolet-ozone surface treatment is introduced to temporarily modify the PDMS stamp surface. Then, the solution-based electron transport layer film can therefore be uniformly formed on top of the PDMS surface. After that the electron transport layer film on the PDMS stamp is transfer-printed onto the emitting layer with suitable heating and pressing. A solution-based processing is successfully established to efficiently fabricate flexible white SM-OLEDs. The SM-OLEDs were obtained at the current density of 20 mA/cm{sup 2}, luminance of 1062 cd/m{sup 2}, current efficiency of 5.57 cd/A, and Commission internationale de l'éclairage coordinate of (0.32, 0.35). - Highlights: • All solution-processed small molecule materials (emitting layer, electron transport layer). • Poly(di-methylsilane) (PDMS) stamp is subsequently used for stamping transfer. • The flexible white SM-OLEDs are based on solution-processes with a low-cost method.

  7. Multi-solution processes of small molecule for flexible white organic light-emitting diodes

    International Nuclear Information System (INIS)

    Tsai, Yu-Sheng; Chittawanij, Apisit; Hong, Lin-Ann; Guo, Siou-Wei; Wang, Ching-Chiun; Juang, Fuh-Shyang; Lai, Shih-Hsiang; Lin, Yang-Ching

    2016-01-01

    Most small molecule organic light emitting diode (SM-OLED) device structures are made in one layer using solution-based processing because the solution is usually a high dissolvent material that easily attacks the layer below it. We demonstrate a simple and reliable stamping technique for fabricating multi-solution process flexible white SM-OLEDs. The structure is anode/spin-hole injection layer/spin-emitting layer/stamping-electron transport layer/cathode. Poly(di-methyl silane) (PDMS) stamp is used for transferring electron transport layer. An intermediate ultraviolet-ozone surface treatment is introduced to temporarily modify the PDMS stamp surface. Then, the solution-based electron transport layer film can therefore be uniformly formed on top of the PDMS surface. After that the electron transport layer film on the PDMS stamp is transfer-printed onto the emitting layer with suitable heating and pressing. A solution-based processing is successfully established to efficiently fabricate flexible white SM-OLEDs. The SM-OLEDs were obtained at the current density of 20 mA/cm"2, luminance of 1062 cd/m"2, current efficiency of 5.57 cd/A, and Commission internationale de l'éclairage coordinate of (0.32, 0.35). - Highlights: • All solution-processed small molecule materials (emitting layer, electron transport layer). • Poly(di-methylsilane) (PDMS) stamp is subsequently used for stamping transfer. • The flexible white SM-OLEDs are based on solution-processes with a low-cost method.

  8. A Solution Processed Flexible Nanocomposite Electrode with Efficient Light Extraction for Organic Light Emitting Diodes

    Science.gov (United States)

    Li, Lu; Liang, Jiajie; Chou, Shu-Yu; Zhu, Xiaodan; Niu, Xiaofan; Zhibinyu; Pei, Qibing

    2014-03-01

    Highly efficient organic light emitting diodes (OLEDs) based on multiple layers of vapor evaporated small molecules, indium tin oxide transparent electrode, and glass substrate have been extensively investigated and are being commercialized. The light extraction from the exciton radiative decay is limited to less than 30% due to plasmonic quenching on the metallic cathode and the waveguide in the multi-layer sandwich structure. Here we report a flexible nanocomposite electrode comprising single-walled carbon nanotubes and silver nanowires stacked and embedded in the surface of a polymer substrate. Nanoparticles of barium strontium titanate are dispersed within the substrate to enhance light extraction efficiency. Green polymer OLED (PLEDs) fabricated on the nanocomposite electrode exhibit a maximum current efficiency of 118 cd/A at 10,000 cd/m2 with the calculated external quantum efficiency being 38.9%. The efficiencies of white PLEDs are 46.7 cd/A and 30.5%, respectively. The devices can be bent to 3 mm radius repeatedly without significant loss of electroluminescent performance. The nanocomposite electrode could pave the way to high-efficiency flexible OLEDs with simplified device structure and low fabrication cost.

  9. Luminescence and squeezing of a superconducting light-emitting diode

    Science.gov (United States)

    Hlobil, Patrik; Orth, Peter P.

    2015-05-01

    We investigate a semiconductor p -n junction in contact with superconducting leads that is operated under forward bias as a light-emitting diode. The presence of superconductivity results in a significant increase of the electroluminescence in a sharp frequency window. We demonstrate that the tunneling of Cooper pairs induces an additional luminescence peak on resonance. There is a transfer of superconducting to photonic coherence that results in the emission of entangled photon pairs and squeezing of the fluctuations in the quadrature amplitudes of the emitted light. We show that the squeezing angle can be electrically manipulated by changing the relative phase of the order parameters in the superconductors. We finally derive the conditions for lasing in the system and show that the laser threshold is reduced due to superconductivity. This reveals how the macroscopic coherence of a superconductor can be used to control the properties of light.

  10. Non-doped-type white organic light-emitting diodes for lighting purpose

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Jianzhuo [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Li Wenlian, E-mail: wllioel@yahoo.com.c [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Chu Bei, E-mail: beichu@163.co [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Yan Fei; Yang Dongfang; Liu Huihui; Wang Junbo [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China)

    2010-05-15

    We demonstrate a non-doped white organic light-emitting diode (WOLED) in which the blue-, green- and red-emissions are generated from 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl, tris(8-hydroxyquinoline)aluminum (Alq) and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyl-julolidyl 9-enyl)-4H-pyran (DCJTB), which is used as an ultrathin layer. The DCJTB ultrathin layer plays the chromaticity tuning role in optimizing the white spectral band by modulating the location of the DCJTB ultrathin layer in the green emissive Alq layer. The optimized WOLED gives the Commission Internationale de l'Eclairage-1931 xy coordinates of (0.319, 0.335), a color rendering index of 91.2 at 10 V, a maximum brightness of 21010 cd/m{sup 2} at 12 V and a maximum current efficiency of 5.17 cd/A at 6.6 V. The electroluminescence mechanism of the white device is also discussed.

  11. Optimization of freeform lightpipes for light-emitting-diode projectors.

    Science.gov (United States)

    Fournier, Florian; Rolland, Jannick

    2008-03-01

    Standard nonimaging components used to collect and integrate light in light-emitting-diode-based projector light engines such as tapered rods and compound parabolic concentrators are compared to optimized freeform shapes in terms of transmission efficiency and spatial uniformity. We show that the simultaneous optimization of the output surface and the profile shape yields transmission efficiency within the étendue limit up to 90% and spatial uniformity higher than 95%, even for compact sizes. The optimization process involves a manual study of the trends for different shapes and the use of an optimization algorithm to further improve the performance of the freeform lightpipe.

  12. 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.

  13. Printing Smart Designs of Light Emitting Devices with Maintained Textile Properties

    Directory of Open Access Journals (Sweden)

    Inge Verboven

    2018-02-01

    Full Text Available To maintain typical textile properties, smart designs of light emitting devices are printed directly onto textile substrates. A first approach shows improved designs for alternating current powder electroluminescence (ACPEL devices. A configuration with the following build-up, starting from the textile substrate, was applied using the screen printing technique: silver (10 µm/barium titanate (10 µm/zinc-oxide (10 µm and poly(3,4-ethylenedioxythiophenepoly(styrenesulfonate (10 µm. Textile properties such as flexibility, drapability and air permeability are preserved by implementing a pixel-like design of the printed layers. Another route is the application of organic light emitting devices (OLEDs fabricated out of following layers, also starting from the textile substrate: polyurethane or acrylate (10–20 µm as smoothing layer/silver (200 nm/poly(3,4-ethylenedioxythiophenepoly(styrenesulfonate (35 nm/super yellow (80 nm/calcium/aluminum (12/17 nm. Their very thin nm-range layer thickness, preserving the flexibility and drapability of the substrate, and their low working voltage, makes these devices the possible future in light-emitting wearables.

  14. Printing Smart Designs of Light Emitting Devices with Maintained Textile Properties †

    Science.gov (United States)

    Verboven, Inge; Stryckers, Jeroen; Mecnika, Viktorija; Vandevenne, Glen; Jose, Manoj

    2018-01-01

    To maintain typical textile properties, smart designs of light emitting devices are printed directly onto textile substrates. A first approach shows improved designs for alternating current powder electroluminescence (ACPEL) devices. A configuration with the following build-up, starting from the textile substrate, was applied using the screen printing technique: silver (10 µm)/barium titanate (10 µm)/zinc-oxide (10 µm) and poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (10 µm). Textile properties such as flexibility, drapability and air permeability are preserved by implementing a pixel-like design of the printed layers. Another route is the application of organic light emitting devices (OLEDs) fabricated out of following layers, also starting from the textile substrate: polyurethane or acrylate (10–20 µm) as smoothing layer/silver (200 nm)/poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (35 nm)/super yellow (80 nm)/calcium/aluminum (12/17 nm). Their very thin nm-range layer thickness, preserving the flexibility and drapability of the substrate, and their low working voltage, makes these devices the possible future in light-emitting wearables. PMID:29438276

  15. Optimization of light quality from color mixing light-emitting diode systems for general lighting

    DEFF Research Database (Denmark)

    Thorseth, Anders

    2012-01-01

    are simulated using radiometrically measured single LED spectra. The method uses electrical input powers as input parameters and optimizes the resulting spectral power distribution with regard to color rendering index, correlated color temperature and chromaticity distance. The results indicate Pareto optimal......To address the problem of spectral light quality from color mixing light-emitting diode systems, a method for optimizing the spectral output of multicolor LED system with regards to standardized quality parameters has been developed. The composite spectral power distribution from the LEDs...

  16. Adoption of Light-Emitting Diodes in Common Lighting Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Mary [Navigant Consulting, Suwanee, GA (United States); Chwastyk, Dan [Navigant Consulting, Suwanee, GA (United States)

    2013-05-01

    Report estimating LED energy savings in nine applications where LEDs compete with traditional lighting sources such as incandescent, halogen, high-pressure sodium, and certain types of fluorescent. The analysis includes indoor lamp, indoor luminaire, and outdoor luminaire applications.

  17. Adoption of Light-Emitting Diodes in Common Lighting Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Mary [Navigant, Chicago, IL (United States); Stober, Kelsey [Navigant, Chicago, IL (United States)

    2015-07-01

    Report estimating LED energy savings between 2012 and 2014 in 10 applications where LEDs competed with traditional lighting sources such as incandescent, halogen, high-pressure sodium, and fluorescent. The analysis includes indoor lamp, indoor luminaire, and outdoor luminaire applications.

  18. Doping of nano structures for light emitting diode applications

    International Nuclear Information System (INIS)

    Han, S. W.; Yoo, H. J.; Jeong, E. S.; Park, S. H.

    2006-04-01

    Lighting Emitting Diodes (LED) have been widely studied and developed for practical applications and the LED market in the world have been dramatically expended. GaN-based LEDs are mostly used. However, for diverse application, we should first solved several problems in the GaN-based LEDs, thermal heating effects and low light emitting efficiency. The thermal heating effects reduce the life time of LEDs and the low light emitting efficiency are disadvantageous in competition with electric lights. In this project, we studied the possibility of ZnO nanomaterials as LEDs. We have developed a techniques to fabricated reproducible ZnO nanorod arrays on various substrates with 40 - 100 nm diameters. We have successfully fabricated two-dimensional ZnO film growth on one-dimensional nanorods. We have also systematically studied ZnO nanorod growth on GaN and Al 2 O 3 substrated with different proton treatments to understand the ZnO nanorod growth mechanism. These techniques will be used to develop p-ZnO/n-ZnO nanomaterials as LEDs

  19. Active targeting of tumor cells using light emitting bacteria

    International Nuclear Information System (INIS)

    Moon, Sung Min; Min, Jung Joon; Hong, Yeong Jin; Kim, Hyun Ju; Le, Uuenchi N.; Rhee, Joon Haeng; Song, Ho Chun; Heo, Young Jun; Bom, Hee Seung; Choy, Hyon E

    2004-01-01

    The presence of bacteria and viruses in human tumors has been recognized for more than 50 years. Today, with the discovery of bacterial strains that specifically target tumors, and aided by genomic sequencing and genetic engineering, there is new interest in the use of bacteria as tumor vectors. Here, we show that bacteria injected intravenously into live animals entered and replicated in solid tumors and metastases using the novel imaging technology of biophotonics. Bioluminescence operon (LuxCDABE) or fluorescence protein, GFP) has been cloned into pUC19 plasmid to engineer pUC19lux or pUC19gfp. Engineered plasmid was transformed into different kinds of wild type (MG1655) or mutant E. coli (DH5, ppGpp, fnr, purE, crpA, flagella, etc.) strains to construct light emitting bacteria. Xenograft tumor model has been established using CT26 colon cancer cell line. Light emitting bacteria was injected via tail vein into tumor bearing mouse. In vivo bioluminescence imaging has been done after 20 min to 14 days of bacterial injection. We observed localization of tumors by light-emitting E. coli in tumor (CT-26) bearing mice. We confirmed the presence of light-emitting bacteria under the fluorescence microscope with E. coli expressing GFP. Althoug varying mutants strain with deficient invading function has been found in tumor tissues, mutant strains of movement (flagella) couldn't show any light signal from the tumor tissue under the cooled CCD camera, indicating bacteria may actively target the tumor cells. Based on their 'tumor-finding' nature, bacteria may be designed to carry multiple genes or drugs for detection and treatment of cancer, such as prodrug-converting enzymes, toxins, angiogenesis inhibitors and cytokines

  20. Electroluminescence dependence of the simplified green light organic light emitting diodes on in situ thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Mu, Haichuan, E-mail: hcmu@ecust.edu.cn [Department of Physics, School of Science, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Rao, Lu [Department of Physics, School of Science, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Li, Weiling; Wei, Bin [Key Laboratory of Advanced Display and System Applications, Ministry of Education, School of Mechanics Engineering and Automation, Shanghai University, 149 Yanchang Road, Shanghai 200072 (China); Wang, Keke; Xie, Haifen [Department of Physics, School of Science, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China)

    2015-12-01

    Highlights: • In-situ thermal treating the organic tri-layer (CBP/CBP:Ir(ppy){sub 3}/TPBi) of the green light PHOLED under various temperatures during the organic materials evaporation. • Investigating the effect of in situ thermal treatment on the electroluminescence (EL) performance of the green light PHOLED with tri-layer structures. • Provide an easy and practical way to improve the EL performance of the OLEDs without major modification of the organic materials and OLEDs structures required. - Abstract: Simplified multilayer green light phosphorescent organic light emitting diodes (PHOLED) with the structure of ITO/MoO{sub 3}(1 nm)/CBP(20 nm)/CBP:Ir(ppy){sub 3} (1 wt%) (15 nm)/TPBi(60 nm)/LiF(0.5 nm)/Al were fabricated via thermal evaporation and in situ thermal treatment (heating the OLED substrates to certain temperatures during the thermal evaporation of the organic materials) was performed. The effect of the in situ thermal treatment on the electroluminescence (EL) performance of the PHOLED was investigated. It was found that the OLED exhibited strong EL dependence on the thermal treatment temperatures, and their current efficiency was improved with the increasing temperature from room temperature (RT) to 69 °C and deteriorated with the further increasing temperature to 105 °C. At the brightness of 1000 cd/m{sup 2}, over 80% improvement of the current efficiency at the optimal thermal treatment temperature of 69 °C (64 cd/A) was demonstrated compared to that at RT (35 cd/A). Meanwhile, the tremendous influences of the in situ thermal treatment on the morphology of the multilayer CBP/CBP:Ir(ppy){sub 3}/TPBi were also observed. At the optimal thermal treatment temperature of 69 °C, the improvement of the EL performance could be ascribed to the enhancement of the electron and hole transporting in the CBP:Ir(ppy){sub 3} emitting layer, which suppressed the triplets self-quenching interactions and promoted the charge balance and excitons formation. The

  1. Organic Light-Emitting Diodes with a Perylene Interlayer Between the Electrode-Organic Interface

    Science.gov (United States)

    Saikia, Dhrubajyoti; Sarma, Ranjit

    2018-01-01

    The performance of an organic light-emitting diode (OLED) with a vacuum-deposited perylene layer over a fluorine-doped tin oxide (FTO) surface is reported. To investigate the effect of the perylene layer on OLED performance, different thicknesses of perylene are deposited on the FTO surface and their current density-voltages (J-V), luminance-voltages (L-V) and device efficiency characteristics at their respective thickness are studied. Further analysis is carried out with an UV-visible light double-beam spectrophotometer unit, a four-probe resistivity unit and a field emission scanning electron microscope set up to study the optical transmittance, sheet resistance and surface morphology of the bilayer anode film. We used N,N'-bis(3-methyl phenyl)- N,N'(phenyl)-benzidine (TPD) as the hole transport layer, Tris(8-hydroxyquinolinato)aluminum (Alq3) as a light-emitting layer and lithium fluoride as an electron injection layer. The luminance efficiency of an OLED structure with a 9-nm-thick perylene interlayer is increased by 2.08 times that of the single-layer FTO anode OLED. The maximum value of current efficiency is found to be 5.25 cd/A.

  2. White OLED using {beta}-diketones rare earth binuclear complex as emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Quirino, W.G. [LOEM, Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, PUC-Rio, P.O.Box 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Legnani, C. [LOEM, Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, PUC-Rio, P.O.Box 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Cremona, M. [LOEM, Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, PUC-Rio, P.O.Box 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil)]. E-mail: cremona@fis.puc-rio.br; Lima, P.P. [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, UFPE-CCEN, Recife, PE, 50670-901 (Brazil); Junior, S.A. [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, UFPE-CCEN, Recife, PE, 50670-901 (Brazil); Malta, O.L. [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, UFPE-CCEN, Recife, PE, 50670-901 (Brazil)

    2006-01-03

    In this work, the fabrication and the characterization of a white triple-layer OLED using a {beta}-diketones binuclear complex [Eu(btfa){sub 3}phenterpyTb(acac){sub 3}] as the emitting layer is reported. The devices were assembled using a heterojunction between three organic molecular materials: the N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) as hole-transporting layer, the {beta}-diketones binuclear complex and the tris(8-hydroxyquinoline aluminum) (Alq{sub 3}) as the electron transporting layer. All the organic layers were sequentially deposited under high vacuum environment by thermal evaporation onto ITO substrates and without breaking vacuum. Continuous electroluminescence emission was obtained varying the applied bias voltage from 10 to 22 V showing a wide emission band from 400 to 700 nm with about 100 cd/m{sup 2} of luminance. The white emission results from a combined action between the binuclear complex, acting as hole blocking and emitting layer, blue from NPB and the typical Alq{sub 3} green emission. The intensity ratio of the peaks is determined by the layer thickness and by the bias voltage applied to the OLED, allowing us to obtain a color tunable light source.

  3. White OLED using β-diketones rare earth binuclear complex as emitting layer

    International Nuclear Information System (INIS)

    Quirino, W.G.; Legnani, C.; Cremona, M.; Lima, P.P.; Junior, S.A.; Malta, O.L.

    2006-01-01

    In this work, the fabrication and the characterization of a white triple-layer OLED using a β-diketones binuclear complex [Eu(btfa) 3 phenterpyTb(acac) 3 ] as the emitting layer is reported. The devices were assembled using a heterojunction between three organic molecular materials: the N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) as hole-transporting layer, the β-diketones binuclear complex and the tris(8-hydroxyquinoline aluminum) (Alq 3 ) as the electron transporting layer. All the organic layers were sequentially deposited under high vacuum environment by thermal evaporation onto ITO substrates and without breaking vacuum. Continuous electroluminescence emission was obtained varying the applied bias voltage from 10 to 22 V showing a wide emission band from 400 to 700 nm with about 100 cd/m 2 of luminance. The white emission results from a combined action between the binuclear complex, acting as hole blocking and emitting layer, blue from NPB and the typical Alq 3 green emission. The intensity ratio of the peaks is determined by the layer thickness and by the bias voltage applied to the OLED, allowing us to obtain a color tunable light source

  4. Influence of doping location and width of dimethylquinacridone on the performance of organic light emitting devices

    International Nuclear Information System (INIS)

    Li Jingze; Yahiro, Masayuki; Ishida, Kenji; Matsushige, Kazumi

    2005-01-01

    The influence of doping location and width of fluorescent dimethylquinacridone (DMQA) molecules on the performance of organic light emitting devices has been systematically investigated. While the doped zone is located at the interface of the hole transport layer (HTL) and the light emitting layer (EML), doping in the HTL leads to significant improvement of the external quantum efficiency relative to the undoped device, whereas the efficiency is lower than that of doping in the EML. This phenomenon is explained according to the electroluminescence (EL) process of the doped DMQA, which is dominated by Foerster energy transfer. Additionally, a device with dual doping in both HTL and EML exhibits the highest efficiency. The EL and photoluminescence spectra are also dependent on the doping sites

  5. Photolithography-free fabrication of organic light-emitting diodes for lighting applications

    International Nuclear Information System (INIS)

    Seo, I H; Shin, D C; Park, J W

    2013-01-01

    We investigate the photolithography-free fabrication of organic light-emitting diodes (OLEDs) for lighting applications with an attempt to embed the deposition and patterning process of an indium–tin–oxide (ITO) anode and insulating layer into an in-line-type organic evaporation system. This scheme inevitably brings in leakage current induced by the spike-like surface of ITO. To suppress it, we cover the ITO edges with three different insulation materials (i.e. sputter-deposited inorganic Al 2 O 3 thin film, monomer (polymer) thin film deposited by organic acrylate evaporation or thermally evaporated organic insulation layer (tris-(8-hydroxyquinoline) aluminum (Alq 3 ))). Although small-molecule organic insulation materials that can be thermally evaporated are the most suitable for such a cost-effective fabrication process, yet their insulation capability is low due to the carrier transporting property. In this paper, we demonstrate that it can be boosted to a great extent with an increase of their thickness. It is likely that pinholes existing on the Al 2 O 3 thin film act as leak channels, degrading the device performance. We also verify that the insulation capability of polymer fabricated by organic acrylate evaporation is just comparable with that of polyimide (PI) insulator patterned using a standard photolithography process. (paper)

  6. Light emitting fabric for photodynamic treatment of actinic keratosis

    Science.gov (United States)

    Thecua, E.; Vicentini, C.; Vignion, A.-S.; Lecomte, F.; Deleporte, P.; Mortier, L.; Szeimies, R.-M.; Mordon, S.

    2017-02-01

    The integration of optical fibers into flexible textile structures, by using knitting or weaving processes can allow the development of flexible light sources. The paper aims to present a new technology: Light Emitting Fabrics (LEF), which can be used for example for PDT of Actinic Keratosis in Dermatology. The predetermined macro-bending of optical fibers, led to a homogeneous side emission of light over the entire surface of the fabric. Tests showed that additional curvatures when applying the LEF on non-planar surfaces had no impact on light delivery and proved that LEF can adapt to the human morphology. The ability of the LEF, coupled with a 635nm LASER source, to deliver a homogeneous light to lesions is currently assessed in a clinical trial for the treatment of AK of the scalp by PDT. The low irradiance and progressive activation of the photosensitizer ensure a pain reduction, compared to discomfort levels experienced by patients during a conventional PDT session.

  7. Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

    NARCIS (Netherlands)

    Lucarelli, G.; Di Giacomo, F.; Zardetto, V.; Creatore, M.; Brown, T.M.

    2017-01-01

    This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx, values typically found in indoor environments. Flexible cells were developed using either

  8. How to distinguish scattered and absorbed light from re-emitted light for white LEDs?

    NARCIS (Netherlands)

    Meretska, Maryna; Lagendijk, Aart; Thyrrestrup Nielsen, Henri; Mosk, Allard; IJzerman, Wilbert; Vos, Willem L.

    2017-01-01

    We have studied the light transport through phosphor diffuser plates that are used in commercial solid-state lighting modules (Fortimo). These polymer plates contain YAG:Ce+3 phosphor particles that scatter, absorb and re-emit incident light in the visible wavelength range (400-700 nm). To

  9. White organic light emitting diodes based on fluorene-carbazole dendrimers

    International Nuclear Information System (INIS)

    Usluer, Özlem; Demic, Serafettin; Kus, Mahmut; Özel, Faruk; Serdar Sariciftci, Niyazi

    2014-01-01

    In this paper, we report on theProd. Type: FTP fabrication and characterization of blue and white light emitting devices based on two fluorene-carbazole containing dendrimers and para-sexiphenyl (6P) oligomers. Blue light emitting diodes were fabricated using 9′,9″-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis-9′H-9,3′:6′,9″-tercarbazole (OFC-G2) and 9′,9″-(9,9′-spirobi[fluorene]-2,7-diyl)bis-9′H-9,3′:6′,9″-tercarbazole (SBFC-G2) dendrimers as a hole transport and emissive layer (EML) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as an electron transport layer. White light emitting diodes were fabricated using 6P and these two dendrimers as an EML. OLED device with the structure of ITO/PEDOT:PSS (50 nm)/OFC-G2 (40 nm)/6P (20 nm)/LiF:Al (0.5:100 nm) shows maximum luminance of nearly 1400 cd/m 2 and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.27, 0.30) at 12 V. -- Highlights: • White organic light emitting diodes have been fabricated using two fluorene-carbazole dendrimers and para-sexiphenyl (6P) oligomers. • When only these two dendrimers are used as EML, OLED devices are emitted blue light. • The emission colors of OLED devices change from blue to white when 6P is coated on dendrimer films

  10. White organic light emitting diodes based on fluorene-carbazole dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Usluer, Özlem, E-mail: usluerozlem@yahoo.com.tr [Department of Chemistry, Muğla Sıtkı Koçman University, 48000 Muğla (Turkey); Demic, Serafettin [Department of Materials Science and Engineering, Izmir Katip Çelebi University, 35620 Çiğli, Izmir (Turkey); Kus, Mahmut, E-mail: mahmutkus1@gmail.com [Chemical Engineering Department and Advanced Technology R and D Center, Selçuk University, Konya (Turkey); Özel, Faruk [Chemical Engineering Department and Advanced Technology R and D Center, Selçuk University, Konya (Turkey); Serdar Sariciftci, Niyazi [Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz (Austria)

    2014-02-15

    In this paper, we report on theProd. Type: FTP fabrication and characterization of blue and white light emitting devices based on two fluorene-carbazole containing dendrimers and para-sexiphenyl (6P) oligomers. Blue light emitting diodes were fabricated using 9′,9″-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis-9′H-9,3′:6′,9″-tercarbazole (OFC-G2) and 9′,9″-(9,9′-spirobi[fluorene]-2,7-diyl)bis-9′H-9,3′:6′,9″-tercarbazole (SBFC-G2) dendrimers as a hole transport and emissive layer (EML) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as an electron transport layer. White light emitting diodes were fabricated using 6P and these two dendrimers as an EML. OLED device with the structure of ITO/PEDOT:PSS (50 nm)/OFC-G2 (40 nm)/6P (20 nm)/LiF:Al (0.5:100 nm) shows maximum luminance of nearly 1400 cd/m{sup 2} and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.27, 0.30) at 12 V. -- Highlights: • White organic light emitting diodes have been fabricated using two fluorene-carbazole dendrimers and para-sexiphenyl (6P) oligomers. • When only these two dendrimers are used as EML, OLED devices are emitted blue light. • The emission colors of OLED devices change from blue to white when 6P is coated on dendrimer films.

  11. Smartphone-Driven Low-Power Light-Emitting Device

    Directory of Open Access Journals (Sweden)

    Hea-Ja An

    2017-01-01

    Full Text Available Low-level light (laser therapy (LLLT has been widely researched in the recent past. Existing LLLT studies were performed based on laser. Recently, studies using LED have increased. This study presents a smartphone-driven low-power light-emitting device for use in colour therapy as an alternative medicine. The device consists of a control unit and a colour probe. The device is powered by and communicates with a smartphone using USB On-The-Go (OTG technology. The control unit controls emitting time and intensity of illumination with the configuration value of a smartphone application. Intensity is controlled by pulse width modulation (PWM without feedback. A calibration is performed to resolve a drawback of no feedback. To calibrate, intensity is measured in every 10 percent PWM output. PWM value is linearly calibrated to obtain accurate intensity. The device can control the intensity of illumination, and so, it can find application in varied scenarios.

  12. Light-emitting diode lighting for forest nursery seedling production

    Science.gov (United States)

    R. Kasten Dumroese; Jeremiah R. Pinto; Anthony S. Davis

    2015-01-01

    Crop lighting is an energy-intensive necessity for nursery production of high-quality native plants and forest tree seedlings. During the winter months (especially in northern USA latitudes) or overcast or cloudy days, the amount of solar radiation reaching greenhouse crops is insufficient resulting in growth cessation, early terminal bud formation, and failure of...

  13. Silicon based light-emitting materials and devices

    International Nuclear Information System (INIS)

    Chen Weide

    1999-01-01

    Silicon based light-emitting materials and devices are the key to optoelectronic integration. Recently, there has been significant progress in materials engineering methods. The author reviews the latest developments in this area including erbium doped silicon, porous silicon, nanocrystalline silicon and Si/SiO 2 superlattice structures. The incorporation of these different materials into devices is described and future device prospects are assessed

  14. Effects of electron blocking and hole trapping of the red guest emitter materials on hybrid white organic light emitting diodes

    International Nuclear Information System (INIS)

    Hong, Lin-Ann; Vu, Hoang-Tuan; Juang, Fuh-Shyang; Lai, Yun-Jr; Yeh, Pei-Hsun; Tsai, Yu-Sheng

    2013-01-01

    Hybrid white organic light emitting diodes (HWOLEDs) with fluorescence and phosphorescence hybrid structures are studied in this work. HWOLEDs were fabricated with blue/red emitting layers: fluorescent host material doped with sky blue material, and bipolar phosphorescent host emitting material doped with red dopant material. An electron blocking layer is applied that provides hole red guest emitter hole trapping effects, increases the charge carrier injection quantity into the emitting layers and controls the recombination zone (RZ) that helps balance the device color. Spacer layers were also inserted to expand the RZ, increase efficiency and reduce energy quenching along with roll-off effects. The resulting high efficiency warm white OLED device has the lower highest occupied molecule orbital level red guest material, current efficiency of 15.9 cd/A at current density of 20 mA/cm 2 , and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39)

  15. Effects of electron blocking and hole trapping of the red guest emitter materials on hybrid white organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Lin-Ann; Vu, Hoang-Tuan [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Juang, Fuh-Shyang, E-mail: fsjuang@seed.net.tw [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Lai, Yun-Jr [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Yeh, Pei-Hsun [Raystar Optronics, Inc., 5F No. 25, Keya Rd. Daya Township, Taichung County, Taiwan (China); Tsai, Yu-Sheng [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China)

    2013-10-01

    Hybrid white organic light emitting diodes (HWOLEDs) with fluorescence and phosphorescence hybrid structures are studied in this work. HWOLEDs were fabricated with blue/red emitting layers: fluorescent host material doped with sky blue material, and bipolar phosphorescent host emitting material doped with red dopant material. An electron blocking layer is applied that provides hole red guest emitter hole trapping effects, increases the charge carrier injection quantity into the emitting layers and controls the recombination zone (RZ) that helps balance the device color. Spacer layers were also inserted to expand the RZ, increase efficiency and reduce energy quenching along with roll-off effects. The resulting high efficiency warm white OLED device has the lower highest occupied molecule orbital level red guest material, current efficiency of 15.9 cd/A at current density of 20 mA/cm{sup 2}, and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39)

  16. Surface plasmon enhanced organic light emitting diodes by gold nanoparticles with different sizes

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Chia-Yuan; Chen, Ying-Chung [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); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung, Taiwan (China)

    2015-11-30

    Highlights: • Different varieties, sizes, and shapes for nanoparticles will generate different surface plasmon resonance effects in the devices. • The red-shift phenomenon for absorption peaks is because of an increasing contribution of higher-order plasmon modes for the larger gold nanoparticles. • The mobility of electrons in the electron-transport layer of organic light-emitting diodes is a few orders of magnitude lower than that of holes in the hole-transport layer of organic light-emitting diodes. - Abstract: The influence of gold nanoparticles (GNPs) with different sizes doped into (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) (PEDOT:PSS) on the performance of organic light-emitting diodes is investigated in this study. The current efficiency of the device, at a current density of 145 mA/cm, with PEDOT:PSS doped with GNPs of 8 nm is about 1.57 times higher than that of the device with prime PEDOT:PSS because the absorption peak of GNPs is closest to the photoluminescence peak of the emission layer, resulting in maximum surface plasmon resonance effect in the device. In addition, the surface-enhanced Raman scattering spectroscopy also reveals the maximum surface plasmon resonance effect in the device when the mean particle size of GNPs is 8 nm.

  17. Blue-light emitting triazolopyridinium and triazoloquinolinium salts

    KAUST Repository

    Carboni, Valentina

    2017-01-27

    Compounds that emit blue light are of interest for applications that include optoelectronic devices and chemo/biosensing and imaging. The design and synthesis of small organic molecules that can act as high-efficiency deep-blue-light emitters in the solid state and can be easily processed from solutions represents a significant challenge. Herein we present the preparation and photophysical, photochemical and electrochemical properties of a series of triazolopyridinium and triazoloquinolinium compounds. The compounds are soluble in water or polar organic solvents and exhibit photoluminescence in the blue region of the spectrum in fluid solution, in the solid state and in a frozen matrix.

  18. Pyridine substituted spirofluorene derivative as an electron transport material for high efficiency in blue organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Soon Ok; Yook, Kyoung Soo; Lee, Jun Yeob, E-mail: leej17@dankook.ac.k

    2010-11-01

    The quantum efficiency of blue fluorescent organic light-emitting diodes was enhanced by 20% using a pyridine substituted spirofluorene-benzofluorene derivative as an electron transport material. 2',7'-Di(pyridin-3-yl)spiro[benzofluorene-7,9'-fluorene] (SPBP) was synthesized and it was used as the electron transport material to block the hole leakage from the emitting layer. The improvement of the quantum efficiency and power efficiency of the blue fluorescent organic light-emitting diodes using the SPBP was investigated.

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

    International Nuclear Information System (INIS)

    Bergh, Arpad A.

    2004-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Bergh, Arpad A [Optoelectronics Industry Development Association (OIDA), 1133 Connecticut Avenue, NW, Suite 600, Washington, DC 20036-4329 (United States)

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

  2. A tunable lighting system integrated by inorganic and transparent organic light-emitting diodes

    Science.gov (United States)

    Zhang, Jing-jing; Zhang, Tao; Jin, Ya-fang; Liu, Shi-shen; Yuan, Shi-dong; Cui, Zhao; Zhang, Li; Wang, Wei-hui

    2014-05-01

    A tunable surface-emitting integrated lighting system is constructed using a combination of inorganic light-emitting diodes (LEDs) and transparent organic LEDs (OLEDs). An RB two-color LED is used to supply red and blue light emission, and a green organic LED is used to supply green light emission. Currents of the LED and OLED are tuned to produce a white color, showing different Commission Internationale d'Eclairage (CIE) chromaticity coordinates and correlated color temperatures with a wide adjustable range. Such an integration can compensate for the lack of the LED's luminance uniformity and the transparent OLED's luminance intensity.

  3. Exciplex formation and electroluminescent absorption in ultraviolet organic light-emitting diodes

    International Nuclear Information System (INIS)

    Zhang Qi; Zhang Hao; Xu Tao; Wei Bin; Zhang Xiao-Wen

    2015-01-01

    We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes (UV OLEDs) using different heterojunction structures. It is found that an energy barrier of over 0.3 eV between the emissive layer (EML) and adjacent transport layer facilitates exciplex formation. The electron blocking layer effectively confines electrons in the EML, which contributes to pure UV emission and enhances efficiency. The change in EML thickness generates tunable UV emission from 376 nm to 406 nm. In addition, the UV emission excites low-energy organic function layers and produces photoluminescent emission. In UV OLED, avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency. A maximum external quantum efficiency of 1.2% with a UV emission peak of 376 nm is realized. (paper)

  4. 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.

  5. Application of Surface Plasmonics for Semiconductor Light-Emitting Diodes

    DEFF Research Database (Denmark)

    Fadil, Ahmed

    This thesis addresses the lack of an efficient semiconductor light source at green emission colours. Considering InGaN based quantum-well (QW) light-emitters and light-emitting diodes (LEDs), various ways of applying surface plasmonics and nano-patterning to improve the efficiency, are investigated....... By placing metallic thin films or nanoparticles (NPs) in the near-field of QW light-emitters, it is possible to improve their internal quantum efficiency (IQE) through the Purcell enhancement effect. It has been a general understanding that in order to achieve surface plasmon (SP) coupling with QWs......-QW coupling does not necessarily lead to emission enhancement. The findings of this work show that the scattering and absorption properties of NPs play a crucial role in determining whether the implementation will improve or degrade the optical performance. By applying these principles, a novel design...

  6. White organic light-emitting diodes based on electroplex from polyvinyl carbazole and carbazole oligomers blends

    International Nuclear Information System (INIS)

    Fei-Peng, Chen; Bin, Xu; Wen-Jing, Tian; Zu-Jin, Zhao; Ping, Lü; Chan, Im

    2010-01-01

    White organic light-emitting diodes with a blue emitting material fluorene-centred ethylene-liked carbazole oligomer (Cz6F) doped into polyvinyl carbazole (PVK) as the single light-emitting layer are reported. The optical properties of Cz6F, PVK, and PVK:Cz6F blends are studied. Single and double layer devices are fabricated by using PVK: Cz6F blends, and the device with the configuration of indium tin oxide (ITO)/PVK:Cz6F/tris(8-hydroxyquinolinate)aluminium (Alq 3 )/LiF/A1 exhibits white light emission with Commission Internationale de l'Éclairage chromaticity coordinates of (0.30, 0.33) and a brightness of 402 cd/m 2 . The investigation reveals that the white light is composed of a blue–green emission originating from the excimer of Cz6F molecules and a red emission from an electroplex from the PVK:Cz6F blend films

  7. White organic light-emitting diodes based on electroplex from polyvinyl carbazole and carbazole oligomers blends

    Science.gov (United States)

    Chen, Fei-Peng; Xu, Bin; Zhao, Zu-Jin; Tian, Wen-Jing; Lü, Ping; Im, Chan

    2010-03-01

    White organic light-emitting diodes with a blue emitting material fluorene-centred ethylene-liked carbazole oligomer (Cz6F) doped into polyvinyl carbazole (PVK) as the single light-emitting layer are reported. The optical properties of Cz6F, PVK, and PVK:Cz6F blends are studied. Single and double layer devices are fabricated by using PVK: Cz6F blends, and the device with the configuration of indium tin oxide (ITO)/PVK:Cz6F/tris(8-hydroxyquinolinate)aluminium (Alq3)/LiF/A1 exhibits white light emission with Commission Internationale de l'Éclairage chromaticity coordinates of (0.30, 0.33) and a brightness of 402 cd/m2. The investigation reveals that the white light is composed of a blue-green emission originating from the excimer of Cz6F molecules and a red emission from an electroplex from the PVK:Cz6F blend films.

  8. Continuous light-emitting Diode (LED) lighting for improving food quality

    OpenAIRE

    Lu, C; Bian, Z

    2016-01-01

    Lighting-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and positive impact compared with other artificial lighting. The combined effects of red/blue or/and green, and white LED light on plant growth and physiology, including chlorophyll fluorescence, nitrate content and phytochemical concentration before harvest, were investigated. The results showed that continuous light (CL)\\ud exposure at pre-harvest can effectively redu...

  9. 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.

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

    International Nuclear Information System (INIS)

    Inada, Yasuhisa; Nishiwaki, Seiji; Hirasawa, Taku; Nakamura, Yoshitaka; Hashiya, Akira; Wakabayashi, Shin-ichi; Suzuki, Masa-aki; Matsuzaki, Jumpei

    2014-01-01

    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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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. (paper)

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

    International Nuclear Information System (INIS)

    Oyewole, O. K.; Yu, D.; Du, J.; Asare, J.; Fashina, A.; Anye, V. C.; Zebaze Kana, M. G.; Soboyejo, W. O.

    2015-01-01

    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

  13. Structural, electrical and luminescent characteristics of ultraviolet light emitting structures grown by hydride vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    A.Y. Polyakov

    2017-03-01

    Full Text Available Electrical and luminescent properties of near-UV light emitting diode structures (LEDs prepared by hydride vapor phase epitaxy (HVPE were studied. Variations in photoluminescence and electroluminescence efficiency observed for LEDs grown under nominally similar conditions could be attributed to the difference in the structural quality (dislocation density, density of dislocations agglomerates of the GaN active layers, to the difference in strain relaxation achieved by growth of AlGaN/AlGaN superlattice and to the presence of current leakage channels in current confining AlGaN layers of the double heterostructure.

  14. Ultraviolet light-emitting diodes in water disinfection.

    Science.gov (United States)

    Vilhunen, Sari; Särkkä, Heikki; Sillanpää, Mika

    2009-06-01

    The novel system of ultraviolet light-emitting diodes (UV LEDs) was studied in water disinfection. Conventional UV lamps, like mercury vapor lamp, consume much energy and are considered to be problem waste after use. UV LEDs are energy efficient and free of toxicants. This study showed the suitability of LEDs in disinfection and provided information of the effect of two emitted wavelengths and different test mediums to Escherichia coli destruction. Common laboratory strain of E. coli (K12) was used and the effects of two emitted wavelengths (269 and 276 nm) were investigated with two photolytic batch reactors both including ten LEDs. The effects of test medium were examined with ultrapure water, nutrient and water, and nutrient and water with humic acids. Efficiency of reactors was almost the same even though the one emitting higher wavelength had doubled optical power compared to the other. Therefore, the effect of wavelength was evident and the radiation emitted at 269 nm was more powerful. Also, the impact of background was studied and noticed to have only slight deteriorating effect. In the 5-min experiment, the bacterial reduction of three to four log colony-forming units (CFU) per cubic centimeter was achieved, in all cases. When turbidity of the test medium was greater, part of the UV radiation was spent on the absorption and reactions with extra substances on liquid. Humic acids can also coat the bacteria reducing the sensitivity of the cells to UV light. The lower wavelength was distinctly more efficient when the optical power is considered, even though the difference of wavelengths was small. The reason presumably is the greater absorption of DNA causing more efficient bacterial breakage. UV LEDs were efficient in E. coli destruction, even if LEDs were considered to have rather low optical power. The effect of wavelengths was noticeable but the test medium did not have much impact. This study found UV LEDs to be an optimal method for bacterial

  15. Enhanced Performance of Bipolar Cascade Light Emitting Diodes by Doping the Aluminum Oxide Apertures

    National Research Council Canada - National Science Library

    Siskaninetz, William

    2004-01-01

    Performance improvements in multiple-stage, single-cavity bipolar cascade light emitting diodes including reduced operating voltages, enhanced light generation, and reduced device heating are obtained...

  16. III-nitride based light emitting diodes and applications

    CERN Document Server

    Han, Jung; Amano, Hiroshi; Morkoç, Hadis

    2017-01-01

    The revised edition of this important book presents updated and expanded coverage of light emitting diodes (LEDs) based on heteroepitaxial GaN on Si substrates, and includes new chapters on tunnel junction LEDs, green/yellow LEDs, and ultraviolet LEDs. Over the last two decades, significant progress has been made in the growth, doping and processing technologies of III-nitride based semiconductors, leading to considerable expectations for nitride semiconductors across a wide range of applications. LEDs are already used in traffic signals, signage lighting, and automotive applications, with the ultimate goal of the global replacement of traditional incandescent and fluorescent lamps, thus reducing energy consumption and cutting down on carbon-dioxide emission. However, some critical issues must be addressed to allow the further improvements required for the large-scale realization of solid-state lighting, and this book aims to provide the readers with details of some contemporary issues on which the performanc...

  17. The efficiency challenge of nitride light-emitting diodes for lighting

    KAUST Repository

    Weisbuch, Claude; Piccardo, Marco; Martinelli, Lucio; Iveland, Justin; Peretti, Jacques; Speck, James S.

    2015-01-01

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We discuss the challenges of light-emitting diodes in view of their application to solid-state lighting. The requirement is to at least displace the quite efficient fluorescent, sodium, and high

  18. Finding the Average Speed of a Light-Emitting Toy Car with a Smartphone Light Sensor

    Science.gov (United States)

    Kapucu, Serkan

    2017-01-01

    This study aims to demonstrate how the average speed of a light-emitting toy car may be determined using a smartphone's light sensor. The freely available Android smartphone application, "AndroSensor," was used for the experiment. The classroom experiment combines complementary physics knowledge of optics and kinematics to find the…

  19. Surface Plasmon Enhanced Phosphorescent Organic Light Emitting Diodes

    International Nuclear Information System (INIS)

    Bazan, Guillermo; Mikhailovsky, Alexander

    2008-01-01

    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 especially

  20. Improved power efficiency of blue fluorescent organic light-emitting diode with intermixed host structure

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Shouzhen; Zhang, Shiming; Zhang, Zhensong; Wu, Yukun; Wang, Peng; Guo, Runda; Chen, Yu; Qu, Dalong; Wu, Qingyang; Zhao, Yi, E-mail: yizhao@jlu.edu.cn; Liu, Shiyong

    2013-11-15

    High power efficiency (PE) p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-ph) based fluorescent blue organic light-emitting diode (OLED) is demonstrated by utilizing intermixed host (IH) structure. The PE outperforms those devices based on single host (SH), mixed host (MH), and double emitting layers (DELs). By further optimizing the intermixed layer, peak PE of the IH device is increased up to 8.7 lm/W (1.7 times higher than conventional SH device), which is the highest value among the DSA-ph based blue device reported so far. -- Highlights: • DSA-ph based blue fluorescent OLEDs are fabricated. • The intermixed host structure is first introduced into the blue devices. • Blue device with the highest power efficiency based on DSA-ph is obtained.

  1. 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.

  2. 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.

  3. Compact light-emitting diode lighting ring for video-assisted thoracic surgery.

    Science.gov (United States)

    Lu, Ming-Kuan; Chang, Feng-Chen; Wang, Wen-Zhe; Hsieh, Chih-Cheng; Kao, Fu-Jen

    2014-01-01

    In this work, a foldable ring-shaped light-emitting diode (LED) lighting assembly, designed to attach to a rubber wound retractor, is realized and tested through porcine animal experiments. Enabled by the small size and the high efficiency of LED chips, the lighting assembly is compact, flexible, and disposable while providing direct and high brightness lighting for more uniform background illumination in video-assisted thoracic surgery (VATS). When compared with a conventional fiber bundle coupled light source that is usually used in laparoscopy and endoscopy, the much broader solid angle of illumination enabled by the LED assembly allows greatly improved background lighting and imaging quality in VATS.

  4. Compact light-emitting diode lighting ring for video-assisted thoracic surgery

    Science.gov (United States)

    Lu, Ming-Kuan; Chang, Feng-Chen; Wang, Wen-Zhe; Hsieh, Chih-Cheng; Kao, Fu-Jen

    2014-10-01

    In this work, a foldable ring-shaped light-emitting diode (LED) lighting assembly, designed to attach to a rubber wound retractor, is realized and tested through porcine animal experiments. Enabled by the small size and the high efficiency of LED chips, the lighting assembly is compact, flexible, and disposable while providing direct and high brightness lighting for more uniform background illumination in video-assisted thoracic surgery (VATS). When compared with a conventional fiber bundle coupled light source that is usually used in laparoscopy and endoscopy, the much broader solid angle of illumination enabled by the LED assembly allows greatly improved background lighting and imaging quality in VATS.

  5. 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.

  6. Capturing triplet emission in white organic light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-08-15

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

  7. White polymer light-emitting diode based on polymer blending

    International Nuclear Information System (INIS)

    Lee, Yong Kyun; Kwon, Soon Kab; Kim, Jun Young; Park, Tae Jin; Song, Dae Ho; Kwon, Jang Hyuk; Choo, Dong Jun; Jang, Jin; Jin, Jae Kyu; You, Hong

    2006-01-01

    A series of white polymer light emitting devices have been fabricated by using a polymer blending system of polyfluorene-based blue and MEH-PPV red polymers. A device structure of ITO/PEDOT:PSS/polymer/LiF/Al was employed. The white polymer device exhibited a current efficiency of 4.33 cd/A (4,816 cd/m 2 , Q.E. = 1.9 %) and a maximum luminance of 21,430 cd/m 2 at 9.2 V. The CIE coordinates were (0.35, 0.37) at 5 V and (0.29, 0.30) at 9 V.

  8. Investigation of phosphorescent blue organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Chien-Shu [Department of Electrical Engineering and Information Technology, Technical University of Braunschweig (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Krause, Ralf [Department of Materials Science VI, University of Erlangen-Nuernberg (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Kozlowski, Fryderyk; Hunze, Arvid [Siemens AG, CT MM 1, Erlangen (Germany); Kowalsky, Wolfgang [Department of Electrical Engineering and Information Technology, Technical University of Braunschweig (Germany)

    2008-07-01

    Recently, rapid development of phosphorescent materials has significantly improved the efficiency of organic light emitting diodes (OLEDs). By using efficient phosphorescent emitter materials white OLEDs with high power efficiency values could be demonstrated. But especially blue phosphorescent devices, due to stability issues, need to be further investigated und optimized. In this work, blue OLED devices based on the phosphorescent emitter FIrpic were investigated. Single-carrier hole-only as well as electron-only devices were fabricated and characterized to study the impact of charge carriers on device performance.

  9. Photoresponse of poly(para-phenylenevinylene) light-emitting diodes

    International Nuclear Information System (INIS)

    Wei, X.; Raikh, M.; Vardeny, Z.V.; Yang, Y.; Moses, D.

    1994-01-01

    We have studied the photoresponses of poly(para-phenylene vinylene) (PPV) light-emitting diodes (LED's) with PPV derivatives sandwiched between tin oxide (ITO) and metals including calcium, aluminum, and copper. Under illumination all diodes exhibit relatively large photoconductive I(V) responses which cross the dark I(V) curve at a forward-bias voltage V 0 that scales with the difference in work functions between the ITO and metal electrodes, the open-circuit voltage saturates at V 0 and is temperature independent, and the enhanced electroluminescence intensity of the illuminated LED's correlates with the photocurrent

  10. Printable candlelight-style organic light-emitting diode

    Science.gov (United States)

    Jou, J. H.; Singh, M.; Song, W. C.; Liu, S. H.

    2017-06-01

    Candles or oil lamps are currently the most friendly lighting source to human eyes, physiology, ecosystems, artifacts, environment, and night skies due to their blue light-less emission. Candle light also exhibits high light-quality that provides visual comfort. However, they are relatively low in power efficacy (0.3 lm/W), making them energy-wasting, besides having problems like scorching hot, burning, catching fire, flickering, carbon blacking, oxygen consuming, and release of green house gas etc. In contrast, candlelight organic light-emitting diode (OLED) can be made blue-hazard free and energy-efficient. The remaining challenges are to maximize its light-quality and enable printing feasibility, the latter of which would pave a way to cost-effective manufacturing. We hence demonstrate herein the design and fabrication of a candlelight OLED via wet-process. From retina protection perspective, its emission is 13, 12 and 8 times better than those of the blue-enriched white CFL, LED and OLED. If used at night, it is 9, 6 and 4 times better from melatonin generation perspective.

  11. Effects of doping parameters on the CIE value of flexible white organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Juang Fuhshyang; Lin Mingyein; Yang Chanyi [Institute of Electro-Optical and Materials Science, National Huwei University of Science and Technology, Huwei, Yunlin (Taiwan); Tsai Yusheng [Department of Electro-Optics Engineering, National Huwei University of Science and Technology, Huwei, Yunlin (Taiwan); Lin, David [Windell Corporation, 1F, No. 9, Kung-Yen 7 Road, Industrial Zone, Taichung (Taiwan); Wang Wentunn; Shen Chaiyuan [Electronics Research and Service Organization, Industrial Technology Research Institute, 195 Chung Hsing Rd., Sec. 4 Chu Tung, Hsin Chu (Taiwan)

    2004-09-01

    Red dopants were doped in different emitters, blue and green, respectively, to fabricate white organic light emitting diodes on flexible substrates. The competitive emission between blue and red emitters with various doped-zones was studied. When the DCJT doped zone was located far away from the hole-injection layer, both the blue and red color can be emitted. An appropriate red-dopant position in the device enhanced the green emission from 8-hydroxyquinoline aluminum (Alq3) which was combined with the red and blue emission to generate a white light. Finally, a white emission with the CIE value, (0.30, 0.32), independent of the applied voltage, was obtained with the optimum doped width and location. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Overcoming the electroluminescence efficiency limitations of perovskite light-emitting diodes

    Science.gov (United States)

    Cho, Himchan; Jeong, Su-Hun; Park, Min-Ho; Kim, Young-Hoon; Wolf, Christoph; Lee, Chang-Lyoul; Heo, Jin Hyuck; Sadhanala, Aditya; Myoung, NoSoung; Yoo, Seunghyup; Im, Sang Hyuk; Friend, Richard H.; Lee, Tae-Woo

    2015-12-01

    Organic-inorganic hybrid perovskites are emerging low-cost emitters with very high color purity, but their low luminescent efficiency is a critical drawback. We boosted the current efficiency (CE) of perovskite light-emitting diodes with a simple bilayer structure to 42.9 candela per ampere, similar to the CE of phosphorescent organic light-emitting diodes, with two modifications: We prevented the formation of metallic lead (Pb) atoms that cause strong exciton quenching through a small increase in methylammonium bromide (MABr) molar proportion, and we spatially confined the exciton in uniform MAPbBr3 nanograins (average diameter = 99.7 nanometers) formed by a nanocrystal pinning process and concomitant reduction of exciton diffusion length to 67 nanometers. These changes caused substantial increases in steady-state photoluminescence intensity and efficiency of MAPbBr3 nanograin layers.

  13. Polymer Light-Emitting Diode (PLED) Process Development

    Science.gov (United States)

    2003-12-01

    perature of 95°C, above the Tg (55°C) of un- polymerized SU8 . Baking at this temperature will allow the resin to reflow, which will result in a smoother... SU8 polymerization . An- terface of the SU8 layer and the OG114-4 layer results in a strong reflection of the UV light, which causes this over exposure...post-develop bake is to complete the polymerization and re-flow the coa ing surface. The chemical resistance of the SU8 layer t- depends predominately

  14. Optical design of adjustable light emitting diode for different lighting requirements

    International Nuclear Information System (INIS)

    Lu Jia-Ning; Yu Jie; Tong Yu-Zhen; Zhang Guo-Yi

    2012-01-01

    Light emitting diode (LED) sources have been widely used for illumination. Optical design, especially freedom compact lens design is necessary to make LED sources applied in lighting industry, such as large-range interior lighting and small-range condensed lighting. For different lighting requirements, the size of target planes should be variable. In our paper we provide a method to design freedom lens according to the energy conservation law and Snell law through establishing energy mapping between the luminous flux emitted by a Lambertian LED source and a certain area of the target plane. The algorithm of our design can easily change the radius of each circular target plane, which makes the size of the target plane adjustable. Ray-tracing software Tracepro is used to validate the illuminance maps and polar-distribution maps. We design lenses for different sizes of target planes to meet specific lighting requirements. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  15. Electrical and Optical Enhancement in Internally Nanopatterned Organic Light-Emitting Diodes

    Science.gov (United States)

    Fina, Michael Dane

    Organic light-emitting diodes (OLEDs) have made tremendous technological progress in the past two decades and have emerged as a top competitor for next generation light-emitting displays and lighting. State-of-the-art OLEDs have been reported in literature to approach, and even surpass, white fluorescent tube efficiency. However, despite rapid technological progress, efficiency metrics must be improved to compete with traditional inorganic light-emitting diode (LED) technology. Organic materials possess specialized traits that permit manipulations to the light-emitting cavity. Overall, as demonstrated within, these modifications can be used to improve electrical and optical device efficiencies. This work is focused at analyzing the effects that nanopatterned geometric modifications to the organic active layers play on device efficiency. In general, OLED efficiency is complicated by the complex, coupled processes which contribute to spontaneous dipole emission. A composite of three sub-systems (electrical, exciton and optical) ultimately dictate the OLED device efficiency. OLED electrical operation is believed to take place via a low-mobility-modified Schottky injection process. In the injection-limited regime, geometric effects are expected to modify the local electric field leading to device current enhancement. It is shown that the patterning effect can be used to enhance charge carrier parity, thereby enhancing overall recombination. Current density and luminance characteristics are shown to be improved by OLED nanopatterning from both the model developed within and experimental techniques. Next, the optical enhancement effects produced by the nanopatterned array are considered. Finite-difference time-domain (FDTD) simulations are used to determine positional, spectral optical enhancement for the nanopatterned device. The results show beneficial effects to the device performance. The optical enhancements are related to the reduction in internal radiative

  16. The effects of light-emitting diode lighting on greenhouse plant growth and quality

    Directory of Open Access Journals (Sweden)

    Margit Olle

    2013-06-01

    Full Text Available The aim of this study is to present the light emitting diode (LED technology for greenhouse plant lighting and to give an overview about LED light effects on photosynthetic indices, growth, yield and nutritional value in green vegetables and tomato, cucumber, sweet pepper transplants. The sole LED lighting, applied in closed growth chambers, as well as combinations of LED wavelengths with conventional light sources, fluorescent and high pressure sodium lamp light, and natural illumination in greenhouses are overviewed. Red and blue light are basal in the lighting spectra for green vegetables and tomato, cucumber, and pepper transplants; far red light, important for photomorphogenetic processes in plants also results in growth promotion. However, theoretically unprofitable spectral parts as green or yellow also have significant physiological effects on investigated plants. Presented results disclose the variability of light spectral effects on different plant species and different physiological indices.

  17. [The role of BCP in electroluminescence of multilayer organic light-emitting devices].

    Science.gov (United States)

    Deng, Zhao-Ru; Yang, Sheng-Yi; Lou, Zhi-Dong; Meng, Ling-Chuan

    2009-03-01

    As a hole-blocking layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) is usually used in blue and white light electroluminescent devices. The ability of blocking holes of BCP layer depends on its thickness, and basically holes can tunnel through thin BCP layer. In order to know the role of BCP layer in electroluminescence (EL) of multilayer organic light-emitting diodes (OLEDs), in the present paper, the authors designed a multilayer OLED ITO/NPB/BCP/Alq3 : DCJTB/Alq3/Al and investigated the influence of thickness of BCP on the EL spectra of multilayer OLEDs at different applied voltages. The experimental data show that thin BCP layer can block holes partially and tune the energy transfer between different emissive layers, and in this way, it is easy to obtain white emission, but its EL spectra will change with the applied voltages. The EL spectra of multilayer device will remain relatively stable when BCP layer is thick enough, and the holes can hardly tunnel through when the thickness of BCP layer is more than 15 nm. Furthermore, the stability of EL spectra of the multilayer OLED at different applied voltages was discussed.

  18. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting [Ventura, CA

    2011-04-26

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  19. Using high-power light emitting diodes for photoacoustic imaging

    DEFF Research Database (Denmark)

    Hansen, R. S.

    2011-01-01

    for the experiment consists of a 3mm high x 5mm wide slice of green colored gelatine overlaid by a 3cm layer of colorless gelatine. The light pulses from the LED is focused on the green gelatine. The photoacoustic response from the green gelatine is detected by a single transducer on the opposite (top) surface...

  20. an assessment of ultraviolet radiation components of light emitted ...

    African Journals Online (AJOL)

    Dr

    therefore high for exposure limits of 8 hours for UV-B and UV-C and the 16 minutes for UV-A. The investigation ... has become particularly interesting as the ozone layer ... THEORY. Ultraviolet (UV) light is an electromagnetic radiation with a ...

  1. The application of multispectral light detectors to gauge detonative events by means of their emitted light signature

    CSIR Research Space (South Africa)

    Olivier, Marius

    2016-09-01

    Full Text Available It is well known that reacting explosives emit light of varying intensity across the light spectrum. Measurement of this emitted light could have many applications, i.a. the creation of a database of characteristic light signatures at specific...

  2. Finding the Acceleration and Speed of a Light-Emitting Object on an Inclined Plane with a Smartphone Light Sensor

    Science.gov (United States)

    Kapucu, Serkan

    2017-01-01

    This study investigates how the acceleration and speed of a light-emitting object on an inclined plane may be determined using a smartphone's light sensor. A light-emitting object was released from the top of an inclined plane and its illuminance values were detected by a smartphone's light sensor during its subsequent motion down the plane. Using…

  3. Quantum key distribution with an entangled light emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Dzurnak, B.; Stevenson, R. M.; Nilsson, J.; Dynes, J. F.; Yuan, Z. L.; Skiba-Szymanska, J.; Shields, A. J. [Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-12-28

    Measurements performed on entangled photon pairs shared between two parties can allow unique quantum cryptographic keys to be formed, creating secure links between users. An advantage of using such entangled photon links is that they can be adapted to propagate entanglement to end users of quantum networks with only untrusted nodes. However, demonstrations of quantum key distribution with entangled photons have so far relied on sources optically excited with lasers. Here, we realize a quantum cryptography system based on an electrically driven entangled-light-emitting diode. Measurement bases are passively chosen and we show formation of an error-free quantum key. Our measurements also simultaneously reveal Bell's parameter for the detected light, which exceeds the threshold for quantum entanglement.

  4. Quantum dot superluminescent light emitting diodes: Ideal blackbody radiators?

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Martin; Elsaesser, Wolfgang [Institute of Applied Physics, Darmstadt University of Technology (Germany); Hopkinson, Mark [Dept. E and E.E, University of Sheffield (United Kingdom); Krakowski, Michel [Alcatel Thales, III-V Lab. (France)

    2008-07-01

    Quantum dot (QD) superluminescent light emitting diodes (SLEDs) provide large optical bandwidths at desired wavelengths and are therefore promising devices for incoherent light application. The intensity noise behavior of QD SLEDs is of fundamental physical interest as it provides insight into the photon emission process. We performed high precision intensity noise measurements over several decades of optical output power. For low driving currents spontaneous emission leads to Shot Noise. For high currents we find excess noise behavior with Amplified Spontaneous Emission acting as the dominant source of noise. The QD SLEDs' noise can be described as blackbody radiation noise with a limited number of optical modes. It is therefore possible to identify the SLEDs' relevant intensity noise parameters.

  5. Chemically Addressable Perovskite Nanocrystals for Light-Emitting Applications

    KAUST Repository

    Sun, Haizhu

    2017-07-10

    Whereas organic–inorganic hybrid perovskite nanocrystals (PNCs) have remarkable potential in the development of optoelectronic materials, their relatively poor chemical and colloidal stability undermines their performance in optoelectronic devices. Herein, this issue is addressed by passivating PNCs with a class of chemically addressable ligands. The robust ligands effectively protect the PNC surfaces, enhance PNC solution processability, and can be chemically addressed by thermally induced crosslinking or radical-induced polymerization. This thin polymer shield further enhances the photoluminescence quantum yields by removing surface trap states. Crosslinked methylammonium lead bromide (MAPbBr3) PNCs are applied as active materials to build light-emitting diodes that have low turn-on voltages and achieve a record luminance of over 7000 cd m−2, around threefold better than previous reported MA-based PNC devices. These results indicate the great potential of this ligand passivation approach for long lifespan, highly efficient PNC light emitters.

  6. Surface displacement imaging by interferometry with a light emitting diode

    International Nuclear Information System (INIS)

    Dilhaire, Stefan; Grauby, Stephane; Jorez, Sebastien; Lopez, Luis David Patino; Rampnoux, Jean-Michel; Claeys, Wilfrid

    2002-01-01

    We present an imaging technique to measure static surface displacements of electronic components. A device is supplied by a transient current that creates a variation of temperature, thus a surface displacement. To measure the latter, a setup that is based on a Michelson interferometer is used. To avoid the phenomenon of speckle and the drawbacks inherent to it, we use a light emitting diode as the light source for the interferometer. The detector is a visible CCD camera that analyzes the optical signal containing the information of surface displacement of the device. Combining images, we extract the amplitude of the surface displacement. Out-of-plane surface-displacement images of a thermoelectric device are presented

  7. 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...

  8. Degradation of phosphorescent blue organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Chien-Shu [Department of Electrical Engineering and Information Technology, Technical University of Braunschweig (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Steinbacher, Frank [Department of Materials Science VI, University of Erlangen-Nuernberg (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Krause, Ralf; Hunze, Arvid [Siemens AG, CT MM 1, Erlangen (Germany); Kowalsky, Wolfgang [Department of Electrical Engineering and Information Technology, Technical University of Braunschweig (Germany)

    2009-07-01

    Development of phosphorescent materials has significantly improved the efficiency of organic light-emitting diodes (OLEDs). By using efficient red, green and blue phosphorescent emitter materials high efficient white OLEDs can be achieved. However, due to low stability of blue phosphorescent materials the lifetime of phosphorescent white OLEDs remains an issue. As a result, degradation of blue phosphorescent materials needs to be further investigated and improved. In this work, blue OLED devices based on the phosphorescent emitter FIrpic were investigated. Single-carrier hole-only as well as electron-only devices were fabricated. For investigation of degradation process the devices were stressed with electrical current and UV-light to study the impact of charge carriers as well as excitons and exciton-polaron quenching on the stability of the blue dye.

  9. Applications of Light Emitting Diodes in Health Care.

    Science.gov (United States)

    Dong, Jianfei; Xiong, Daxi

    2017-11-01

    Light emitting diodes (LEDs) have become the main light sources for general lighting, due to their high lumen efficiency and long life time. Moreover, their high bandwidth and the availability of diverse wavelength contents ranging from ultraviolet to infrared empower them with great controllability in tuning brightness, pulse durations and spectra. These parameters are the essential ingredients of the applications in medical imaging and therapies. Despite the fast advances in both LED technologies and their applications, few reviews have been seen to link the controllable emission properties of LEDs to these applications. The objective of this paper is to bridge this gap by reviewing the main control techniques of LEDs that enable creating enhanced lighting patterns for imaging and generating effective photon doses for photobiomodulation. This paper also provides the basic mechanisms behind the effective LED therapies in treating cutaneous and neurological diseases. The emerging field of optogenetics is also discussed with a focus on the application of LEDs. The multidisciplinary topics reviewed in this paper can help the researchers in LEDs, imaging, light therapy and optogenetics better understand the basic principles in each other's field; and hence to stimulate the application of LEDs in health care.

  10. MOLED: Simulation of multilayer organic light emitting diodes

    Science.gov (United States)

    Houili, H.; Tutiš, E.; Lütjens, H.; Bussac, M. N.; Zuppiroli, L.

    2003-12-01

    MOLED solves the dynamics of electrons and holes in multilayer Organic Light Emitting Diodes (OLED). The carriers are injected on the positive and negative electrodes of the device by tunneling through a potential barrier. Thermal excitation processes across the barrier are also included. In the interior of the device the electron-hole recombination occurs when the two carriers are close enough, according to a model inspired from the one of Langevin. A fraction of these recombined pairs gives photons. The charge transport inside the organic material occurs through hopping. Several choices of mobility formulae are available in the code. MOLED can be used for OLEDs with an arbitrary number of layers. The output consists of numerous fields that describe the device performance. For example, there are the current, the recombination and the charge density distributions, the electric field distribution, the current-voltage characteristics and the device internal quantum efficiency. Program summaryTitle of program: MOLED Catalogue identifier: ADSG Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADSG Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Operating systems under which the program has been tested: Unix, Linux Programming language used: FORTRAN 90 Memory required to execute with typical data: 2 MB No. of bytes in distributed program: 26 942 No. of bits in a word: 64 Peripherals used: permanent disk storage No. of lines in distributed program, including test data, etc.: 3695 Distribution format: tar gzip file Nature of the physical problem: Injection of electrons and holes into an organic electroluminescent material occurs through tunneling from metal electrodes. The transport of carriers inside the molecular medium proceeds by hopping from one molecule to another. The emission of light is a result of their radiative Langevin recombination (for a review see [Scott et al., Synthetic Metals 111-112 (2000) 289; Friend et al

  11. Transparent conductive oxide films embedded with plasmonic nanostructure for light-emitting diode applications.

    Science.gov (United States)

    Chuang, Shih-Hao; Tsung, Cheng-Sheng; Chen, Ching-Ho; Ou, Sin-Liang; Horng, Ray-Hua; Lin, Cheng-Yi; Wuu, Dong-Sing

    2015-02-04

    In this study, a spin coating process in which the grating structure comprises an Ag nanoparticle layer coated on a p-GaN top layer of InGaN/GaN light-emitting diode (LED) was developed. Various sizes of plasmonic nanoparticles embedded in a transparent conductive layer were clearly observed after the deposition of indium tin oxide (ITO). The plasmonic nanostructure enhanced the light extraction efficiency of blue LED. Output power was 1.8 times the magnitude of that of conventional LEDs operating at 350 mA, but retained nearly the same current-voltage characteristic. Unlike in previous research on surface-plasmon-enhanced LEDs, the metallic nanoparticles were consistently deposited over the surface area. However, according to microstructural observation, ITO layer mixed with Ag-based nanoparticles was distributed at a distance of approximately 150 nm from the interface of ITO/p-GaN. Device performance can be improved substantially by using the three-dimensional distribution of Ag-based nanoparticles in the transparent conductive layer, which scatters the propagating light randomly and is coupled between the localized surface plasmon and incident light internally trapped in the LED structure through total internal reflection.

  12. Improving the Stability of Metal Halide Perovskite Materials and Light-Emitting Diodes.

    Science.gov (United States)

    Cho, Himchan; Kim, Young-Hoon; Wolf, Christoph; Lee, Hyeon-Dong; Lee, Tae-Woo

    2018-01-25

    Metal halide perovskites (MHPs) have numerous advantages as light emitters such as high photoluminescence quantum efficiency with a direct bandgap, very narrow emission linewidth, high charge-carrier mobility, low energetic disorder, solution processability, simple color tuning, and low material cost. Based on these advantages, MHPs have recently shown unprecedented radical progress (maximum current efficiency from 0.3 to 42.9 cd A -1 ) in the field of light-emitting diodes. However, perovskite light-emitting diodes (PeLEDs) suffer from intrinsic instability of MHP materials and instability arising from the operation of the PeLEDs. Recently, many researchers have devoted efforts to overcome these instabilities. Here, the origins of the instability in PeLEDs are reviewed by categorizing it into two types: instability of (i) the MHP materials and (ii) the constituent layers and interfaces in PeLED devices. Then, the strategies to improve the stability of MHP materials and PeLEDs are critically reviewed, such as A-site cation engineering, Ruddlesden-Popper phase, suppression of ion migration with additives and blocking layers, fabrication of uniform bulk polycrystalline MHP layers, and fabrication of stable MHP nanoparticles. Based on this review of recent advances, future research directions and an outlook of PeLEDs for display applications are suggested. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for InGaN/GaN light-emitting diodes.

    Science.gov (United States)

    Kyaw, Zabu; Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ju, Zhen Gang; Zhang, Xue Liang; Ji, Yun; Hasanov, Namig; Zhu, Binbin; Lu, Shunpeng; Zhang, Yiping; Sun, Xiao Wei; Demir, Hilmi Volkan

    2014-01-13

    N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple quantum wells (MQWs) are systematically studied both experimentally and theoretically to increase the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN layer sandwiched in the NPNPN-GaN structure is completely depleted due to the built-in electric field in the NPNPN-GaN junctions, and the ionized acceptors in these P-GaN layers serve as the energy barriers for electrons from the n-GaN region, resulting in a reduced electron over flow and enhanced the current spreading horizontally in the n- GaN region. These lead to increased optical output power and external quantum efficiency (EQE) from the proposed device.

  14. Experimental study of the organic light emitting diode with a p-type silicon anode

    International Nuclear Information System (INIS)

    Ma, G.L.; Xu, A.G.; Ran, G.Z.; Qiao, Y.P.; Zhang, B.R.; Chen, W.X.; Dai, L.; Qin, G.G.

    2006-01-01

    We have fabricated and studied an organic light emitting diode (OLED) with a p-type silicon anode and a SiO 2 buffer layer between the anode and the organic layers which emits light from a semitransparent top Yb/Au cathode. The luminance of the OLED is up to 5600 cd/m 2 at 17 V and 1800 mA/cm 2 , the current efficiency is 0.31 cd/A. Both its luminance and current efficiency are much higher than those of the OLEDs with silicon as the anodes reported previously. The enhancement of the luminance and efficiency can be attributed to an improved balance between the hole- and electron-injection through two efficient ways: 1) restraining the hole-injection by inserting an ultra-thin SiO 2 buffer layer between the Si anode and the organic layers; and 2) enhancing the electron-injection by using a low work function, low optical reflectance and absorption semitransparent Yb/Au cathode

  15. Hybrid daylight/light-emitting diode illumination system for indoor lighting.

    Science.gov (United States)

    Ge, Aiming; Qiu, Peng; Cai, Jinlin; Wang, Wei; Wang, Junwei

    2014-03-20

    A hybrid illumination method using both daylight and light-emitting diodes (LEDs) for indoor lighting is presented in this study. The daylight can be introduced into the indoor space by a panel-integration system. The daylight part and LEDs are combined within a specific luminaire that can provide uniform illumination. The LEDs can be turned on and dimmed through closed-loop control when the daylight illuminance is inadequate. We simulated the illumination and calculated the indoor lighting efficiency of our hybrid daylight and LED lighting system, and compared this with that of LED and fluorescent lighting systems. Simulation results show that the efficiency of the hybrid daylight/LED illumination method is better than that of LED and traditional lighting systems, under the same lighting conditions and lighting time; the method has hybrid lighting average energy savings of T5 66.28%, and that of the LEDs is 41.62%.

  16. Highly efficient phosphorescent blue and white organic light-emitting devices with simplified architectures

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chih-Hao, E-mail: chc@saturn.yzu.edu.tw [Department of Photonics Engineering, Yuan Ze University, Chung-Li, Taiwan 32003 (China); Ding, Yong-Shung; Hsieh, Po-Wei; Chang, Chien-Ping; Lin, Wei-Chieh [Department of Photonics Engineering, Yuan Ze University, Chung-Li, Taiwan 32003 (China); Chang, Hsin-Hua, E-mail: hhua3@mail.vnu.edu.tw [Department of Electro-Optical Engineering, Vanung University, Chung-Li, Taiwan 32061 (China)

    2011-09-01

    Blue phosphorescent organic light-emitting devices (PhOLEDs) with quantum efficiency close to the theoretical maximum were achieved by utilizing a double-layer architecture. Two wide-triplet-gap materials, 1,3-bis(9-carbazolyl)benzene and 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, were employed in the emitting and electron-transport layers respectively. The opposite carrier-transport characteristics of these two materials were leveraged to define the exciton formation zone and thus increase the probability of recombination. The efficiency at practical luminance (100 cd/m{sup 2}) was as high as 20.8%, 47.7 cd/A and 31.2 lm/W, respectively. Furthermore, based on the design concept of this simplified architecture, efficient warmish-white PhOLEDs were developed. Such two-component white organic light-emitting devices exhibited rather stable colors over a wide brightness range and yielded electroluminescence efficiencies of 15.3%, 33.3 cd/A, and 22.7 lm/W in the forward directions.

  17. Highly efficient phosphorescent blue and white organic light-emitting devices with simplified architectures

    International Nuclear Information System (INIS)

    Chang, Chih-Hao; Ding, Yong-Shung; Hsieh, Po-Wei; Chang, Chien-Ping; Lin, Wei-Chieh; Chang, Hsin-Hua

    2011-01-01

    Blue phosphorescent organic light-emitting devices (PhOLEDs) with quantum efficiency close to the theoretical maximum were achieved by utilizing a double-layer architecture. Two wide-triplet-gap materials, 1,3-bis(9-carbazolyl)benzene and 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, were employed in the emitting and electron-transport layers respectively. The opposite carrier-transport characteristics of these two materials were leveraged to define the exciton formation zone and thus increase the probability of recombination. The efficiency at practical luminance (100 cd/m 2 ) was as high as 20.8%, 47.7 cd/A and 31.2 lm/W, respectively. Furthermore, based on the design concept of this simplified architecture, efficient warmish-white PhOLEDs were developed. Such two-component white organic light-emitting devices exhibited rather stable colors over a wide brightness range and yielded electroluminescence efficiencies of 15.3%, 33.3 cd/A, and 22.7 lm/W in the forward directions.

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

    Science.gov (United States)

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

    2017-02-01

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

  19. On the AlxGa1-xN/AlyGa1-yN/AlxGa1-xN (x>y) p-electron blocking layer to improve the hole injection for AlGaN based deep ultraviolet light-emitting diodes

    Science.gov (United States)

    Chu, Chunshuang; Tian, Kangkai; Fang, Mengqian; Zhang, Yonghui; Li, Luping; Bi, Wengang; Zhang, Zi-Hui

    2018-01-01

    This work proposes the [0001] oriented AlGaN-based deep ultraviolet (DUV) light-emitting diode (LED) possessing a specifically designed p-electron blocking layer (p-EBL) to achieve the high internal quantum efficiency. Both electrons and holes can be efficiently injected into the active region by adopting the Al0.60Ga0.40N/Al0.50Ga0.50N/Al0.60Ga0.40N structured p-EBL, in which a p-Al0.50Ga0.50N layer is embedded into the p-EBL. Moreover, the impact of different thicknesses for the p-Al0.50Ga0.50N insertion layer on the hole and electron injections has also been investigated. Compared with the DUV LED with the bulk p-Al0.60Ga0.40N as the EBL, the proposed LED architectures improve the light output power if the thickness of the p-Al0.50Ga0.50N insertion layer is properly designed.

  20. Development and evaluation of a light-emitting diode endoscopic light source

    Science.gov (United States)

    Clancy, Neil T.; Li, Rui; Rogers, Kevin; Driscoll, Paul; Excel, Peter; Yandle, Ron; Hanna, George; Copner, Nigel; Elson, Daniel S.

    2012-03-01

    Light-emitting diode (LED) based endoscopic illumination devices have been shown to have several benefits over arclamp systems. LEDs are energy-efficient, small, durable, and inexpensive, however their use in endoscopy has been limited by the difficulty in efficiently coupling enough light into the endoscopic light cable. We have demonstrated a highly homogenised lightpipe LED light source that combines the light from four Luminus LEDs emitting in the red, green, blue and violet using innovative dichroics that maximise light throughput. The light source spectrally combines light from highly divergent incoherent sources that have a Lambertian intensity profile to provide illumination matched to the acceptance numerical aperture of a liquid light guide or fibre bundle. The LED light source was coupled to a standard laparoscope and performance parameters (power, luminance, colour temperature) compared to a xenon lamp. Although the total illuminance from the endoscope was lower, adjustment of the LEDs' relative intensities enabled contrast enhancement in biological tissue imaging. The LED light engine was also evaluated in a minimally invasive surgery (MIS) box trainer and in vivo during a porcine MIS procedure where it was used to generate 'narrowband' images. Future work using the violet LED could enable photodynamic diagnosis of bladder cancer.