Alkoxy- and Alkyl-Side-Chain-Functionalized Terpolymer Acceptors for All-Polymer Photovoltaics Delivering High Open-Circuit Voltages and Efficiencies |
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Authors: | Yu-Che Lin Chung-Hao Chen Bing-Shiun Tsai Ting-Fang Hsueh Cheng-Si Tsao Shaun Tan Bin Chang Yu-Ning Chang Ting-Yi Chu Ching-En Tsai Cheng-Sheng Chen Yang Yang Kung-Hwa Wei |
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Affiliation: | 1. Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, 30010 Taiwan;2. Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617 Taiwan
Institute of Nuclear Energy Research, Taoyuan, 32546 Taiwan;3. Department of Material Science and Engineering, University of California, Los Angeles, CA, 90095 USA |
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Abstract: | A new terpolymer acceptor is presented, comprising various ratios of the same dithienothienopyrrolobenzothiadiazole (BTP) core with different side chains—alkoxy side chains (BTPO-IC) and alkyl side chains (BTP-IC)—and thiophene units, for use in all-polymer organic photovoltaics. Devices incorporating binary blends of this terpolymer and the polymer PM6 as the active layer displayed open-circuit voltages (VOC) that increase linearly upon increasing the molar ratio of BTPO-IC. For example, the optimized device incorporating PM6:PY-0.2OBO (i.e., with 20 mol% of BTPO-IC) (1:1.2 wt.%) blend, with the smallest domain sizes but largest coherence length and combined face-on and edge-on orientation fractions among all blends, have a champion power conversion efficiency (PCE) of 16.7% (VOC = 0.97 V; JSC = 25.2 mA cm−2; FF = 0.68), whereas the device containing a similar blend ratio of the PM6:PY-OD:PY-OBO ternary blend (1:0.96:0.24 wt.%) displayed a PCE of 8.6% (VOC = 0.969 V; JSC = 18.7 mA cm−2; FF = 0.48). The device with PM6:PY-0.2OBO displays better thermal stability than the devices with PM6: PY-OD or PY-OBO. Thus, employing terpolymer acceptors with differently functionalized side-chain units can be an effective approach for simultaneously optimizing the aggregation domain and enhancing the PCEs and thermal stabilities of all-polymer devices. |
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Keywords: | alkoxy side chains all polymer organic photovoltaics high open-circuit voltages polymer acceptors terpolymers |
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