Multifunctional Two-Dimensional Polymers for Perovskite Solar Cells with Efficiency Exceeding 24%

The passivation of the intrinsic surface defects of perovskites by organic functional materials has a great potential to retard charge recombination and enhance charge extraction. However, unsatisfactory device performance and a lack of in-depth understanding of the defect passivation mechanism make rational molecule design for efficient solar cells a great challenge. Herein, two solution-processable two-dimensional (2D) conjugated polymers, namely, 2DP-F and 2DP-O, have been synthesized for perovskite solar cells (PSCs). It is found that these materials could passivate surface defects, transport and extract hole carriers, hamper moisture invasion, and impede diffusion of Li+ cations into the perovskite film. As a result, champion efficiencies of 23.31% and 24.08% were achieved for 2DP-F- and 2DP-O-based devices, respectively, coupled with dramatically improved stability. These results indicate that our proposed 2D polymers could be promising multifunctional materials for further boosting the efficiency and improving the stability of PSCs.