15.3% efficiency all-small-molecule organic solar cells enabled by symmetric phenyl substitution

• Published in: Science China materials 2020-07, Vol.63 (7), p.1142-1150
• Main Authors: Qin, Jinzhao, An, Cunbin, Zhang, Jianqi, Ma, Kangcqiao, Yang, Yang, Zhang, Tao, Li, Sunsun, Xian, Kaihu, Cui, Yong, Tang, Yabing, Ma, Wei, Yao, Huifeng, Zhang, Shaoqing, Xu, Bowei, He, Chang, Hou, Jianhui
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; Chemistry/Food Science; Crystal structure; Crystallinity; Energy conversion efficiency; Fullerenes; Materials Science; Materials substitution; Morphology; Optimization; Photovoltaic cells; Solar cells; Strong interactions (field theory); X-ray scattering
• ISSN: 2095-8226; 2199-4501
• DOI: 10.1007/s40843-020-1269-9

Synergistic optimization of donor-acceptor blend morphologyis a hurdle in the path of realizing efficient non-fullerene small-molecule organic solar cells (NFSM-OSCs) due to the anisotropic conjugated backbones of both donor and acceptor. Therefore, developing a facile molecular design strategy to effectively regulate the crystalline properties of photoactive materials, and thus, enable the optimization of blend morphology is of vital importance. In this study, a new donor molecule B1, comprising phenyl-substituted benzodithiophene (BDT) central unit, exhibits strong interaction with the non-fullerene acceptor BO-4Cl in comparison with its corresponding thiophene-substituted BDT-based material, BTR. As a result, the B1 is affected and induced from an edge-on to a face-on orientation by the acceptor, while the BTR and the acceptor behave individually for the similar molecular orientation in pristine and blend films according to grazing incidence wide angle X-ray scattering results. It means the donor-acceptor blend morphology is synergistically optimized in the B1 system, and the B1:BO-4Cl-based devices achieve an outstanding power conversion efficiency (PCE) of 15.3%, further certified to be 15.1% by the National Institute of Metrology, China. Our results demonstrate a simple and effective strategy to improve the crystalline properties of the donor molecule as well as synergistically optimize the morphology of the all-small-molecule system, leading to the high-performance NFSM-OSCs.