Single photovoltaic material solar cells with enhanced exciton dissociation and extended electron diffusion
Zhenzhen Zhang, Li Li, Chaoying Xu, Pengfei Jin, Miaofei Huang, Yawen Li, Hong Wang, Yuanping Yi, Chuang Zhang, Ye Yang, Weigao Xu, Yuze Lin
Abstract
Typical organic photovoltaic semiconductors exhibit high exciton binding energy (Eb, typically >300 meV), hindering the development of organic solar cells based on a single photovoltaic material (SPM-OSCs). Herein, compared with the control molecule (Y6), Y6Se with selenium substitution exhibits reduced Eb and faster relaxation of the exciton state or the intermediate intra-moiety excimer state, indicating that the exciton dissociation in Y6Se film can be driven by lower energy. The SPM-OSCs based on Y6Se film without and with 1 wt % p-type polymer additive exhibit long charge-carrier lifetime, and extended electron diffusion length, leading to impressive power conversion efficiencies of 3.07% and 3.94%, respectively, which are significantly higher than those values reported for SPM-OSCs based on single photovoltaic small molecules in the literature. In addition, the SPM-OSCs based on Y6Se show superior thermal stability, relative to the typical bulk heterojunction OSCs based on Y6Se blending with polymer donor.