An Isomeric Solid Additive Enables High‐Efficiency Polymer Solar Cells Developed Using a Benzo‐Difuran‐Based Donor Polymer

• Published in: Advanced materials (Weinheim) 2023-06, Vol.35 (26), p.e2301231-n/a
• Main Authors: Chen, Lu, Yi, Jicheng, Ma, Ruijie, Ding, Lu, Dela Peña, Top Archie, Liu, Heng, Chen, Jian, Zhang, Cuifen, Zhao, Chaoyue, Lu, Wen, Wei, Qi, Zhao, Bin, Hu, Huawei, Wu, Jiaying, Ma, Zaifei, Lu, Xinhui, Li, Mingjie, Zhang, Guangye, Li, Gang, Yan, He
• Format: Article
• Language: English
• Subjects: benzo[1,2‐b:4,5‐b′]difuran; Donor materials; Efficiency; Energy levels; isomeric solid additives; organic solar cells; Photovoltaic cells; Polymers; power conversion efficiency; Solar cells; Steric hindrance
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202301231

Currently, nearly all high‐efficiency organic photovoltaic devices use donor polymers based on the benzo‐dithiophene (BDT) unit. To diversify the choices of building blocks for high‐performance donor polymers, the use of benzo‐difuran (BDF) units is explored, which can achieve reduced steric hindrance, stronger molecular packing, and tunable energy levels. In previous research, the performance of BDF‐based devices lagged behind those of BDT‐based devices. In this study, a high efficiency (18.4%) is achieved using a BDF‐based polymer donor, which is the highest efficiency reported for BDF donor materials to date. The high efficiency is enabled by a donor polymer (D18‐Fu) and the aid of a solid additive (2‐chloronaphthalene), which is the isomer of the commonly used additive 1‐chloronaphthalene. These results revealed the significant effect of 2‐chloronaphthalene in optimizing the morphology and enhancing the device parameters. This work not only provides a new building block that can achieve an efficiency comparable to dominant BDT units but also proposes a new solid additive that can replace the widely used 1‐chloronaphthalene additive. The efficiency of benzo‐difuran‐based polymer‐donor‐enabled solar cells is improved a lot in this work thanks to rational material combination and isomeric solid additive type morphology tuning. A series of characterizations, in situ technique, vertical distribution calculation, transient absorption spectra, and GIWAXS/SAXS + RSoXS, reveal the basic mechanism, producing fruitful insights to this work with record efficiency.