Browsing by Author "Chiu, Yu-Chian"

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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.
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.