P3HT‐Based Polymer Solar Cells with 8.25% Efficiency Enabled by a Matched Molecular Acceptor and Smart Green‐Solvent Processing Technology

• Published in: Advanced materials (Weinheim) 2019-12, Vol.31 (52), p.e1906045-n/a
• Main Authors: Xu, Xiaopeng, Zhang, Guangjun, Yu, Liyang, Li, Ruipeng, Peng, Qiang
• Format: Article
• Language: English
• Subjects: Aging; Charge transport; Energy levels; Excitons; green solvents; Interpenetrating networks; Malononitrile; Matching; MATERIALS SCIENCE; Nanowires; nonfullerene acceptors; nonfullerene polymer solar cells; Phase separation; Photovoltaic cells; poly(3‐hexylthiophene); Polymers; Room temperature; Solar cells; solvent aging; Solvents; Trimethylbenzene
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201906045

A novel molecular acceptor of TrBTIC (2,7,12‐tris((2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile‐7‐benzothiadiazole‐2‐)truxene) is designed by attaching the 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile‐benzothiadiazole (BTIC) electron‐deficient unit to an electron‐rich truxene core. TrBTIC has excellent solubility in common solvents and features good energy level matching with poly(3‐hexylthiophene) (P3HT). Interestingly, P3HT can be readily dissolved in warm 1,2,4‐trimethylbenzene (TMB), a green solvent, but crystallizes slowly with long‐term aging in TMB at room temperature. A prephase separation can thus occur before active blend film deposition, and the separation degree can be easily controlled by varying the aging time. After 40 min of aging, the resulting active blend has the most appropriate phase separation with uniform nanowires, which forms favorable interpenetrating networks for exciton dissociation and charge transport. As a result, the device performance is improved from 6.62% to 8.25%. Excitingly, 8.25% is a new record for P3HT‐based solar cells. The study not only provides an efficient nonfullerene acceptor for matching P3HT donors but also develops a promising processing technology to realize high‐performance P3HT‐based polymer solar cells with an efficiency over 8%. A power conversion efficiency of 8.25% for poly(3‐hexylthiophene)‐based polymer solar cells is realized by pairing a novel star‐shaped small‐molecular acceptor 2,7,12‐tris((2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile‐7‐benzothiadiazole‐2‐)truxene with a smart solution‐processing technology in the green solvent 1,2,4‐trimethylbenzene.