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.
Improving light harvesting in polymer photodetector devices through nanoindented metal mask films J. Appl. Phys.External quantum efficiency versus charge carriers mobility in polythiophene/methanofullerene based planar photodetectors
New low band gap thiophene-phenylene-thiophene (TPT)-based donor-acceptor-donor random copolymers were synthesized for optoelectronic device applications by a palladium-catalyzed Stille coupling reaction under microwave heating. The acceptors included 2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,8-bis[5 0 -bromo-dithien-2-yl-quinoxalines] (DTQ) and 3,6-bis(5bromothiophen-2-yl)-2,5-bis(2-ethyl-hexyl)-pyrrolo[3,4-c]-pyrrole-1,4-dione (DPP). The prepared random copolymers were named as PTPTDTQ 0.55 , PTPTDTQ 0.34 DPP 0.14 , and PTPTDTQ 0.26 DPP 0.34 depending on the copolymer ratio. The optical band gaps (E opt g ) of PTPTDTQ 0.55 , PTPTDTQ 0.34 DPP 0.14 , and PTPTDTQ 0.26 DPP 0.34 were 1.74, 1.56, and 1.48 eV, respectively. The hole mobility obtained from the field-effect transistor devices prepared from PTPTDTQ 0.55 , PTPTDTQ 0.34 DPP 0.14 , and PTPTDTQ 0.26 DPP 0.34 were 2.2 Â 10 À3 , 2.4 Â 10 À3 , and 4.7 Â 10 À3 cm 2 V À1 s À1 , respectively, with the on-off ratios of 4.0 Â 10 4 , 4.0 Â 10 4 , and 5.3 Â 10 4 . It suggested that the significant intramolecular charge transfer between the TPT and acceptor led to the band gap reduction and hole mobility enhancement. Polymer solar cells of these TPT-based copolymers blended with 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-71 (PC 71 BM) under illumination of AM 1.5G (100 mW cm À2 ) solar simulator exhibited a power conversion efficiency (PCE) as high as 3.71%. Besides, the near-infrared photodetector device prepared from PTPTDTQ 0.26 DPP 0.34 showed a high external quantum efficiency exceeding 32% at 700 nm (under À3 V bias) and fast-speed response. This study suggests that the prepared TPT-based donoracceptor random copolymers exhibited promising and versatile applications on optoelectronic devices. V
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