Achieving 19% efficiency in non-fused ring electron acceptor solar cells via solubility control of donor and acceptor crystallization

• Published in: Nature energy 2024-09, Vol.9 (9), p.1117-1128
• Main Authors: Zeng, Rui, Zhang, Ming, Wang, Xiaodong, Zhu, Lei, Hao, Bonan, Zhong, Wenkai, Zhou, Guanqing, Deng, Jiawei, Tan, Senke, Zhuang, Jiaxin, Han, Fei, Zhang, Anyang, Zhou, Zichun, Xue, Xiaonan, Xu, Shengjie, Xu, Jinqiu, Liu, Yahui, Lu, Hao, Wu, Xuefei, Wang, Cheng, Fink, Zachary, Russell, Thomas P., Jing, Hao, Zhang, Yongming, Bo, Zhishan, Liu, Feng
• Format: Article
• Language: English
• Subjects: 639/301/299; 639/4077/909/4101/4096/946; Acceptor materials; Cell morphology; Charge transport; Chloroform; Control systems; Crystallinity; Crystallization; Economics and Management; Efficiency; Energy; Energy Policy; Energy Storage; Energy Systems; Evaporation; Evaporation rate; Fibrillogenesis; Interpenetrating networks; Materials for energy and catalysis; Morphology; Phase separation; Photovoltaic cells; Polymers; Renewable and Green Energy; Solar cells; SOLAR ENERGY; Solubility; Solvents; Xylene
• ISSN: 2058-7546; 2058-7546
• DOI: 10.1038/s41560-024-01564-0

Non-fused ring electron acceptors (NFREAs) potentially have lower synthetic costs than their fused counterparts. However, the low backbone planarity and the presence of bulky substituents adversely affect the crystallinity of NFREAs, impeding charge transport and the formation of bicontinuous morphology in organic solar cells. Here we show that a binary solvent system can individually control the crystallization and phase separation of the donor polymer (for example, D18) and the NFREA (for example, 2BTh-2F-C 2 ). We select solvents such as chloroform and o -xylene that evaporate at different temperatures and rates and have different solubility for D18. Upon evaporation of chloroform, D18 starts to assemble into fibrils. Then, the evaporation of o -xylene induces the rapid formation of a fibril network that phase segregates 2BTh-2F-C 2 into pure domains and leads to a bicontinuous morphology. The well-defined interpenetrating network morphology affords an efficiency of 19.02% on small-area cells and 17.28% on 1 cm 2 devices. Non-fused ring electron acceptors may have low synthetic costs but also exhibit poor crystallinity in organic solar cells. Zeng et al. use a binary solvent system to control the crystallization and phase separation of donor and acceptor materials, achieving over 19% efficiency.