Simple non-fused ring electron acceptors with well-controlled terminal group stacking
Xinming Zheng, Wenlong Liu, Hang Wang, Xuyan Man, Guangliu Ran, Xiaodi Yu, Hao Lu, Zhaozhao Bi, Yahui Liu, Andong Zhang, Wei Ma, Xinjun Xu, Zheng Tang, Wenkai Zhang, Zhishan Bo
Abstract
Producing high-performance and inexpensive non-fullerene acceptors is a great challenge in the field of organic photovoltaics. Herein, three non-fused ring electron acceptors (NFREAs), TT-O-2F, TT-S-2F, and TT-Se-2F, have been designed and can be modularly synthesized with a few high-productivity steps. According to our results, TT-S-2F and TT-Se-2F have planar molecular backbones because of the existence of S⋅⋅⋅O and Se⋅⋅⋅O intramolecular non-covalent interactions, whereas TT-O-2F has a twisted molecular backbone. In particular, TT-S-2F exhibits the largest terminal group overlapping area and exciton diffusion length among these acceptors, which could facilitate charge transport. The devices based on TT-S-2F can generate an excellent power conversion efficiency (PCE) of 15.29%, much higher than TT-O-2F (10.43%) and TT-Se-2F (12.23%), which are also among the highest PCEs based on NFREAs. Our work highlights the importance of well-controlled terminal packing in designing high-performance NFREAs.