2D g‐C3N5 p‐Doping of Donor Material for High‐Efficiency Organic Solar Cells

Abstract Molecular doping of organic semiconductor is a great strategy for significantly regulating the electronic band structure of organic semiconductor while increasing charge mobility and carrier concentration. Here, a facile strategy is presented by introducing 2D g‐C 3 N 5 as a p‐dopant into PM6, improving the charge mobility and hole carrier concentration of PM6. Moreover, the electron transfer between PM6 and g‐C 3 N 5 can effectively downshift the Fermi energy level and highest occupied molecular orbital (HOMO) energy level of PM6, which leads to the increase the built‐in electric field of organic solar cells (OSCs). The addition of g‐C 3 N 5 also effectively enhances the crystallization of active layer, thereby improving the stability of OSCs. As a result, a champion bulk‐heterojunction (BHJ) and layer‐by‐layer (LbL) structure OSCs are successfully achieved featuring a high‐power conversion efficiency of 18.10%/18.25%, simultaneously having excellent device stability. This work shows that introducing a low concentration dopant into organic donor is an effective method for improving the electrical performance of organic donor and the efficiency of OSCs.