Single photovoltaic material solar cells with enhanced exciton dissociation and extended electron diffusion

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.