Browsing by Author "Chang, Yu-Fan"

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All-Solution-Processed Red and Orange-Red Organic Light-Emitting Diodes with High-Efficiencies: The Effect of Mixed-Host Emissive Layers and Thermal Annealing Treatment
(2019-09-01)
Chang, Yu-Fan
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Yang, Lan-Sheng
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Su, Hsiao-Tso
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Liao, Si-Yi
;
Niu, Mu-Chun
The instability of the organic light-emitting diodes (OLEDs) during operation can be attributed to the existence of point defects on the organic layers. In this work, the effect of mixed-host emissive layer and the thermal annealing treatment were investigated to eliminate defects and to boost the device performance. The mixed-host system includes 4,4 ',4 ''-tri (9-carbazoyl) triphenylamine (TCTA) and 2,7-bis(diphenylphosphoryl)-9, 9 '-spirobi[fluorene] (SPPO13). The mixed-host emissive layer with thermal annealing treatment showed low roughness and few pinholes, and the devices fabricated from this emissive layer exhibited high efficiencies, high stabilities, and long lifetimes. The red and orange-red OLEDs exhibited efficiencies of 13.9 cd/A and 24.35 cd/A, respectively. The longest half-lifetime (L-0=500 cd/m(2)) of the red and orange-red OLEDs were 158 h and 180 h, respectively. Efforts were made to solve problems in large-area coating and to reduce the number of defects on in organic layer. Large-active-area (active area=3 cmx4 cm) red phosphorescent OLEDs (PhOLEDs) devices were realized with very high current efficiency up to 9 cd/A.
Blade coating of Tris(8-hydroxyquinolinato)aluminum as the electron-transport layer for all-solution blue fluorescent organic light-emitting diodes
(2016-02-01)
Chang, Yu-Fan
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Meng, Hsin-Fei
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Fan, Gang-Lun
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Wong, Ken-Tsung
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Zan, Hsiao-Wen
Organic light-emitting diodes (OLEDs) with a low driving voltage and efficient blue fluorescence were fabricated through blade coating. Tris(8-hydroxyquinolinato)aluminum (Alq(3)) is a relatively stable electron-transporting material commonly used in evaporation. However, depositing Alq(3) through a solution process is difficult because of its extremely low solubility organic solvents, a result of its symmetrical molecular structure. In this study, Alq(3) was successfully deposited through blade coating at a very low concentration below 0.1wt%. The OLEDs contained co-dopants BUBD-1 and p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph), and a high-band-gap host 2-methyl-9,10-bis(naphthalen-2-yl) anthracene (MADN) as the emission layer with the following structure: ITO/PEDOT:PSS (40 nm)/VB-FNPD (30 nm)/MADN:2% BUBD-1:1% DSA-Ph (50 nm)/TPBI (30 nm)/LiF (0.8 nm)/Al (100 nm)or ITO/PEDOT:PSS (40 nm)/VB-FNPD (30 nm)/MADN:3% BUBD-1 (50 nm)tris(8-hydroxyquinolinato)aluminum (Alq(3); 10 nm)/LiF (0.8 nm)/Al (100 nm). 2,7-disubstituted fluorene-based triaryldiamine(VB-FNPD)is the cross-linking transporting material. The device exhibited a peak current efficiency of 5.67 cd/A for Alq(3) and 5.76 cd/A for TPBI. The device with Alq(3) has operated lifetime seven times higher than the device with TPBI. (C) 2015 Elsevier B.V. All rights reserved.
Continuous blade coating for multi-layer large-area organic light-emitting diode and solar cell
(2011-11-01)
Chen, Chun-Yu
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Chang, Hao-Wen
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Chang, Yu-Fan
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Chang, Bo-Jie
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Lin, Yuan-Sheng
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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3636398]
Deep learning assisted detection of glaucomatous optic neuropathy and potential designs for a generalizable model
(2020-05-14)
Ko, Yu-Chieh
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Wey, Shih-Yu
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Chen, Wei-Ta
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Chang, Yu-Fan
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Chen, Mei-Ju
Purpose To evaluate ways to improve the generalizability of a deep learning algorithm for identifying glaucomatous optic neuropathy (GON) using a limited number of fundus photographs, as well as the key features being used for classification. Methods A total of 944 fundus images from Taipei Veterans General Hospital (TVGH) were retrospectively collected. Clinical and demographic characteristics, including structural and functional measurements of the images with GON, were recorded. Transfer learning based on VGGNet was used to construct a convolutional neural network (CNN) to identify GON. To avoid missing cases with advanced GON, an ensemble model was adopted in which a support vector machine classifier would make final classification based on cup-to-disc ratio if the CNN classifier had low-confidence score. The CNN classifier was first established using TVGH dataset, and then fine-tuned by combining the training images of TVGH and DrishtiGS datasets. Class activation map (CAM) was used to identify key features used for CNN classification. Performance of each classifier was determined through area under receiver operating characteristic curve (AUC) and compared with the ensemble model by diagnostic accuracy. Results In 187 TVGH test images, the accuracy, sensitivity, and specificity of the CNN classifier were 95.0%, 95.7%, and 94.2%, respectively, and the AUC was 0.992 compared to the 92.8% accuracy rate of the ensemble model. For the Drishti-GS test images, the accuracy of the CNN, the fine-tuned CNN and ensemble model was 33.3%, 80.3%, and 80.3%, respectively. The CNN classifier did not misclassify images with moderate to severe diseases. Class-discriminative regions revealed by CAM co-localized with known characteristics of GON. Conclusions The ensemble model or a fine-tuned CNN classifier may be potential designs to build a generalizable deep learning model for glaucoma detection when large image databases are not available.
Efficient, large area organic photovoltaic modules with active layers processed with non-halogenated solvents in air
(2017-04-01)
Lim, Siew-Lay
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Ong, Kok-Haw
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Li, Jun
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Yang, Le
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Chang, Yu-Fan
Organic photovoltaic (OPV) modules with excellent power conversion efficiencies of 4.20% and 5.87% were obtained with blends of novel low bandgap polymers, POD2T-DTBT and PDTBT-alt-1T, respectively, with PCBM as the active layers. Large area polymer:PCBM blend films were deposited by blade coating with high film uniformity, fast processing speed, and low material consumption, without the need for an inert atmosphere. With the requirements of future manufacturing in mind, the effects of air exposure on the active layers and the substitution of chlorinated solvents for polymer processing were investigated. While the decline of V-oc due to air exposure was recovered by appropriate treatment of the completed devices, FFand J(sc) were significantly affected due to interfacial effects, indicating that air exposure should be limited in duration. Active layers of POD2T-DTBT:PCBM processed with less toxic, non-halogenated mixed solvents, comprising non-polaro-xylene with small amounts of polar additive, showed a fine, interpenetrating nanofibrous network that facilitates charge transport in bulk heterojunction photovoltaic cells. The performance of POD2T-DTBT:PCBM photovoltaic cells and modules processed with the new ink formulations were on par with that obtained with chlorinated solvents, with the modules exhibiting impressive power conversion efficiencies above 4%. The results indicated that POD2T-DTBT was an outstanding candidate for future OPV production due to its high performance, processibility in different ink formulations and compatibility with the large area coating techniques. (C) 2017 Elsevier B.V. All rights reserved.
Great improvement of operation-lifetime for all-solution OLEDs with mixed hosts by blade coating
(2017-03)
Chang, Yu-Fan
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Yu, Cheng-Han
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Yang, Shao-Chun
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Hong, I-Hong
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Jiang, Sin-Ciang
We investigated some effective device designs and fabrication methods for long operation-lifetime all solution-processed Phosphorescent OLEDs (PhOLEDs) and fluorescent OLEDs with mixed-hosts system and thin Poly [(9, 9-dioctylfluorenyl-2, 7-diyl)-co-(4, 4\'-(N-(4-sec-butylphenyl) diphenylamine)] (TFB). The all-solution-processed green PhOLEDs had high current efficiency (30.3 cd/A) and long operation lifetime. The best half-lifetime of green PhOLEDs with thin HTL, MH-hosts EML and optimized deposition was 310 h at an initial luminance 1000 cd/m(2), 250 h at an initial luminance 500 cd/m(2) for green PhOLEDs with thin HTL, and MH-hosts EML, and the lifetime of triple layer PhOLEDs device was only 0.5 h for the same materials. The red PhOLEDs exhibited a high current efficiency (10.93 cd/A) and half lifetime with 157.9 h at an initial luminance 500 cd/m(2). For the blue fluorescent OLEDs, the thin polymer TFB, mixed-hosts EMI, double EMLs and optimization deposition yield a high current efficiency (5.68 cd/ A) and long operation-lifetime with 117.7 h at an initial luminance 500 cd/m(2). Single host fluorescent device had half-lifetime of 73.5 h only at an initial luminance 100 cd/m(2). Finally, by doping red emitter Rubrene into stable blue device, we achieved soft yellow OLEDs with high efficiency (10.87 cd/A) and 8 fold improvement operation-lifetime (1200 h). We believe that such all-solution-processed OLEDs which showed greatly improved operational lifetimes would be suitable for the indoor supportive lighting with natural colors. (C) 2016 Elsevier B.V. All rights reserved.
High-efficiency polymer solar cells by blade coating in chlorine-free solvents
(2014-04-01)
Tsai, Pei-Ting
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Tsai, Chia-Ying
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Wang, Chun-Ming
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Chang, Yu-Fan
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Meng, Hsin-Fei
High-performance polymer cells are typically fabricated by employing toxic solvents such as dichlorobenzene and chlorobenzene. In this study, blade coating with the chlorine-free solvents toluene and xylene is applied to polymer solar cells that contained the low band-gap polymer PBDTTT-C-T blended with [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM). The highest efficiencies of the cells fabricated in toluene and xylene solutions were 6.09% and 6.11%, respectively. Atomic force microscopy images show that the films formed by blade coating using toluene and xylene were extremely smooth, with roughness of only 1 nm. This blade coating has a rapid-drying in a few seconds without the long-running thermal or solvent annealing. The possibility of high-volume environmentally-friendly fabrication of efficient polymer solar cells with minimal material waste is thus demonstrated using a combination of chlorine-free solvents and blade coating. (C) 2014 Elsevier B.V. All rights reserved.
Highly efficient and stable organic solar cell modules processed by blade coating with 5.6% module efficiency and active area of 216 cm(2)
(2019-03-01)
Huang, Kuan-Min
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Wong, Ying Qian
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Lin, Man-Chun
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Chen, Chao-Hsuan
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Liao, Chung-Hung
In this study, an efficient and stable large-area blade-coated organic solar cell (OSC) module with an active area of 216 cm(2) (16 elementary cells connected in series) is demonstrated by combining appropriate thermal annealing treatment with the use of 4,4 '-(((methyl(4-sulphonatobutyl)ammonio)bis(propane-3,1-diyl))bis(dimethyl-ammoniumdiyl))bis-(butane-1-sulfonate) (MSAPBS) as the cathode interfacial layer. For the opaque device using poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b ']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PBDTTT-EFT (PTB7-Th)):[6,6]-phenyl C-71-butyric acid methyl ester (PC71BM) blend film as the active layer, the power conversion efficiency (PCE) of 5.6% is achieved under AM 1.5G solar light illumination. Very encouragingly, our strategy can be applicable for semitransparent OSCs, and a remarkable PCE up to 4.5% is observed. To the best of our knowledge, the PCE of 5.6% for opaque device and 4.5% for semitransparent device represent the highest PCE ever reported for OSCs with the active area exceeding 100 cm(2). The devices also show an impressive stability under outdoor environment, where the efficiency decay is less than 30% for 60 days. Our findings can pave the way toward the development of organic solar cell modules with high performance and long-term stability.
Highly efficient solution-processed red organic light-emitting diodes with long-side-chained triplet emitter
(2011-01-01)
Chao, Yu-Chiang
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Huang, Sheng-Yang
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Chen, Chun-Yu
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Chang, Yu-Fan
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Meng, Hsin-Fei
Newly synthesized red It complexes tris[2-(4-n-hexyl-phenyl)quinoline]iridium(III) and tris[(4-n-hexylphenyl)isoquinoline)]iridium(III) with long alkyl side chains are utilized to demonstrate the high efficiency multi-layer solution-processed red organic light-emitting diodes. Solubilities of these triplet emitters are high which enable them to be uniformly dispersed in the polymer host. Blade coating method is utilized to prepare organic multi-layers without mutual dissolution between different layers. 17 cd/A current efficiency, 10 lm/W power efficiency, and 8.8% external quantum efficiency can be achieved for the device with CsF/Al cathode. 10,000 cd/m(2) is reached at 10 V. Similar quantum efficiency is also achieved with an electron-transport layer and LiF/Al cathode. (C) 2010 Elsevier B.V. All rights reserved.
Interface and thickness tuning for blade coated small-molecule organic light-emitting diodes with high power efficiency
(2013-09-28)
Chang, Yu-Fan
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Chiu, Yu-Chian
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Chang, Hao-Wen
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Wang, Yi-Siang
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Shih, Yi-Lun
We developed a general method based on fluorescence microscopy to characterize the interface dissolution in multi-layer organic light-emitting diodes (OLEDs) by blade coating. A sharp bi-layer edge was created before blade coating, with the bottom layer being insoluble and top layer soluble. After blade coating, fluorescence images showed that the edge of the top layer shifted when the layer dissolved completely, whereas the bottom layer's edge remained in place as a positioning mark. The dissolution depth was determined to be 15-20 nm when the emissive-layer host of 2,6-bis (3-(9H-carbazol-9-yl) phenyl) pyridine (26DCzPPy) was coated on the hole-transport layer of N, N'-bis(naphthalen-1-yl)-N, N'-bis(phenyl)-benzidine(NPB), which was consistent with a sudden drop in efficiency of orange OLEDs with layer thickness below 20 nm. Thus, the layer thickness of OLEDs was optimized to stay more than 20 nm for blade coating. For a two-color white OLED with the structure TCTA/26DCzPPy:PO-01-TB:FIrpic/TPBI, efficiency was 24 cd/A and 8.5 lm/W at 1000 cd/m(2). For a three-color white OLED with Os(fptz)(2)(dhpm) added as the emitter, the efficiency was 12.3 cd/A and 3.7 lm/W at 1000 cd/m(2). For a green device with the structure TCTA/26DCzPPy: Ir(mppy)(3)/TPBI, the efficiency was 41.9 cd/A and 23.4 lm/W at 1000 cd/m(2). VC 2013 AIP Publishing LLC.
Leakage-free solution-processed organic light-emitting diode using a ternary host with single-diode emission area up to 6 x 11.5 cm(2)
(2019-01-01)
Liao, Si-Yi
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Su, Hsiao-Tso
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Hsiao, Yung-Hung
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Chang, Yu-Fan
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Chang, Chiung-Wen
The electrical current leakage and stability are studied for solution-processed OLEDs with areas of 4.45 mm(2), 3 x 3.2 cm(2), and 6 x 11.5 cm(2). The emission layer of the OLED has a ternary or binary mixed host with hole-transporting molecules tris(4-carbazoyl-9-ylphenyl)amine (TCTA) and 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), together with the electron-transporting molecule 2,7-bis(diphenylphosphoryl)-9,9-spirobi[fluorene] (SPPO13). The phosphorescent emitters are Ir(mppy)(3) for green and bis[4-(4-tert-butylphenyl)thieno[3,2-c]pyridine][N,N-diisopropylbenamidinato]iridium(iii) (PR-02) for orange. Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) is used as the hole transport layer and PEDOT:PSS is used as the hole injection layer. On top of the emission layer, CsF/Al is deposited by thermal evaporation as the cathode. All organic layers are deposited by blade coating and the initial current leaking defects can be avoided by careful control of the coating conditions. The detrimental burning point caused by a local current short developed after long-time operation can be avoided by reducing the operation voltage using a ternary mixed host. The operation voltage is only 4 V at 100 cd m(-2) and 5 V at 250 cd m(-2) for the green emitting device. Furthermore, the crystallization defect is reduced by the ternary host. For the orange emitting device, the binary host is good enough with an operating voltage of 5 V at 100 cd m(-2). For an area as large as 6 x 11.5 cm(2), the OLED shows good stability and there is no burning point after an operation of over 1600 hours.
Multilayer rapid-drying blade coating for organic solar cells by low boiling point solvents
(2014-06-01)
Chen, En-Chen
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Tsai, Pei-Ting
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Chang, Bo-Jie
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Wang, Chun-Ming
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Meng, Hsin-Fei
A bulk heterojunction organic solar cell with poly(3-hexylthiophene) (P3HT) as the donor and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor is deposited using blade coating on a hot plate at 80 degrees C with hot air of 70 degrees C applied from above. In contrast to the 30 min of conventional dichlorobenzene solvent annealing, the rapid-drying blade coating forms a dry film in 1 s. The fabrication throughput is substantially enhanced. The blade-coated film has a smoother surface roughness of 3.5nm compared with 10.5nm for solvent annealing; however, the desired phase separation in the 50nm scale forms despite the rapid drying. A single layer solar cell exhibits power conversion efficiency of 4.1% with blade coating in chlorobenzene, which is the same as solvent annealing device. A multilayer device with carrier blocking layers fabricated entirely of the less toxic toluene also exhibits efficiency of 4.1%. (C) 2014 The Japan Society of Applied Physics
Rear interface engineering of hybrid organic-silicon nanowire solar cells via blade coating
(2016-01-25)
Lai, Yi-Chun
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Chang, Yu-Fan
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Tsai, Pei-Ting
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Chang, Jan-Kai
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Tseng, Wei-Hsuan
In this work, we investigate blade-coated organic interlayers at the rear surface of hybrid organic-silicon photovoltaics based on two small molecules: Tris(8-hydroxyquinolinato) aluminium (Alq(3)) and 1,3-bis(2-(4-tert- butylphenyl)-1,3,4-oxadiazol-5-yl) benzene (OXD-7). In particular, soluble Alq3 resulting in a uniform thin film with a root-mean-square roughness < 0.2nm is demonstrated for the first time. Both devices with the Alq3 and OXD-7 interlayers show notable enhancement in the open-circuit voltage and fill-factor, leading to a net efficiency increase by over 2% from the reference, up to 11.8% and 12.5% respectively. The capacitance-voltage characteristics confirm the role of the small-molecule interlayers resembling a thin interfacial oxide layer for the Al-Si Schottky barrier to enhance the built-in potential and facilitate charge transport. Moreover, the Alq3 interlayer in optimized devices exhibits isolated phases with a large surface roughness, in contrast to the OXD-7 which forms a continuous uniform thin film. The distinct morphological differences between the two interlayers further suggest different enhancement mechanisms and hence offer versatile functionalities to the advent of hybrid organic-silicon photovoltaics. (C)2016 Optical Society of America
Soldering of solution-processed organic vertical transistor and light-emitting diode on separate glass substrates by tin micro-balls
(2013-11-01)
Lin, Yu-Hsin
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Chang, Yu-Fan
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Meng, Hsin-Fei
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Zan, Hsiao-Wen
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Hsu, Wensyang
The vertical organic space-charge-limited transistor made of P3HT and small-molecule phosphorescent organic light-emitting diode (OLED) are made on two separate glass substrate by blade coating, then soldered vertically together by tin balls with 40 mu m diameter. The soldering is done by hot wind of 150 degrees C for 5 min Contact resistance is only 10 Omega. The vertical transistor is annealed at 150 degrees C for 5 min before soldering to enhance the output current up to 25 mA/cm(2) and give high thermal stability. Both OLED and the annealed vertical transistor are not affected by the soldering process. The vertical transistor has 1/4 of the OLED area and turns on the bottom-emission white OLED up to 300 cd/m(2) and orange OLED up to 600 cd/m(2). The entire operation is within 8 V. OLED and transistor array can therefore be made on separate glass substrates then soldered together to form the display. (C) 2013 Elsevier B. V. All rights reserved.
Stable and efficient blue fluorescent organic light-emitting diode by blade coating with or without electron-transport layer
(2017-12-01)
Yang, Lan-Sheng
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Meng, Hsin-Fei
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Chang, Yu-Fan
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Lien, Cheng-Hsin
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Zan, Hsiao-Wen
Multi-layer small-molecule blue fluorescent organic light-emitting diode (OLED) is fabricated by blade coating. The emission layer is based on a mixed host of 1-(7-(9,90-bianthracen-10-yl)-9,9-dioctyl-9H-fluoren- 2-yl) pyrene (PT-404) and electron-transport material 2,7-Bis(diphenylphosphoryl)-9,90 -spirobifluorene (SPPO13), and the blue guest emitter is 4-40-(1E, 10E)-2,20-(naphthalene-2,6-diyl) bis(ethane-2,1diyl) bis(N, N-bis(4-hexyl-Phenyl) aniline) (Blue D). A hole-transport layer of Poly-(9, 9-dioctylfluorenyl2, 7-diyl)-co-(4, 4-(N-(4-sec-butylphenyl)) diphenylamine) (TFB) is added on top of PEDOT: PSS anode. The electrons are blocked away from TFB by a layer of pure host emission layer of PT-404 between TFB and the mixed ehost emission layer. For the devicewith the electron transport layer of Tris(8-hydroxyquinolinato) aluminum (Alq3) blade-coated over the emission layer the efficiency and lifetime at initial brightness of 500 cd m(-2) are 7.5 cd A(-1) and 150 h for Alq3/CsF/Al cathode. When the Alq3/CsF/Al is replaced by simply CsF/Al over the mixed-host emission layer the efficiency and lifetime are 6.4 cd A(-1) and 300 h (2 times longer than that of the Alq3/CsF/Al cathode). The lifetime depends on the electron-hole balance tuned by the mixed-host blending ratio as well as the electron injection from the cathode. This work shows good stability is possible for all-solution-processed blue OLED. (C) 2017 Published by Elsevier B.V.
Unmodified small-molecule organic light-emitting diodes by blade coating
(2012-10-01)
Chang, Yu-Fan
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Chiu, Yu-Chian
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Yeh, Han-Cheng
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Chang, Hao-Wen
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Chen, Chun-Yu
Blade coating with substrate heating and hot wind is demonstrated to be a general platform for multi-layer deposition of unmodified small-molecule organic semiconductors. Most unmodified small molecules, originally designed for vacuum evaporation, can be blade coated while the solubility is above 0.5 wt.%. High uniformity is achieved for scale over 5 cm. Orange devices by evaporation and blade coating are compared with 4,4'-bis(carbazol-9-yl)biphenyl (CBP) as the host, iridium(III) bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C-2') acetylacetonate (PO-01-TB) as the emitter. The efficiency difference is within 10%. When 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) is used as the host, the current efficiencies are 40 cd/A for orange, 32 cd/A for green, and 20 cd/A for blue. The optimized organic light-emitting diodes (OLED) structure developed for vacuum deposition can therefore be exactly copied by the low cost blade coating method in solution. (C) 2012 Elsevier B.V. All rights reserved.
Vacuum-free lamination of low work function cathode for efficient solution-processed organic light-emitting diodes
(2012-03-01)
Chang, Yu-Fan
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Chen, Chun-Yu
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Luo, Fang-Tsai
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Chao, Yu-Chiang
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Meng, Hsin-Fei
The low work function cathode of blade-coated organic light-emitting diode is transferred from a soft polydimethylsiloxane (PDMS) mold by lamination without vacuum. The cathode is a bilayer of polyethylene glycol (PEG) (< 10 nm) and Al (100 nm). A sacrificial layer of polystyrene with low Mw 1500 and melting point of 120 degrees C is inserted between the cathode and PDMS for the subsequent mold removal at 150 degrees C by melting polystyrene. Current efficiency of 3 cd/A (1.1%) and luminance of 2500 cd/m(2) are achieved for green polyfluorene fluorescent emitter. 25 cd/A (8.2%) and 3200 cd/m(2) are achieved for green phosphorescent tris[2-(p-tolyl) pyridine] iridium(III) (Ir(mppy)(3)) emitter in polymer blend host. The efficiency is about 70% of the devices with thermally evaporated cathode. The turn-on voltage is about 5 V higher. (C) 2011 Elsevier B. V. All rights reserved.