Ultrahigh open-circuit voltage for high performance mixed-cation perovskite solar cells using acetate anions

Abstract

Mixed-cation perovskite solar cells have a much higher power conversion efficiency than traditional mono-cation perovskite solar cells. However, fabrication of high-quality mixed cation-halide perovskite films is still challenging due to the formation of point defects in the annealing process, resulting in a large loss in the potential of solar cells. In this work, formamidine acetate, as an additive, is introduced into the perovskite-precursor solution to overcome this issue. The prolonged time-resolved photoluminescence lifetime indicates fewer defects in the optimized perovskite film with formamidine acetate than those in the control sample. The solar cells using the optimized perovskite layer achieve a maximum power conversion efficiency of 21.9% with a large open-circuit voltage of 1.19 V. For another perovskite film with a low band gap (1.53 eV), the optimized device also shows a large open-circuit voltage of 1.14 V. Our work provides a new strategy to realize the commercial applications of perovskite solar cells.