Abstract
Fabricating high-performance perovskite solar cells (PSCs) with solution processing is conducive to low-cost commercial production, it is therefore rather critical to stabilize perovskite in both solution and solid phases. For this purpose, the speed-up ageing of perovskite solution in air was systematically studied and its severe spontaneous degradation was observed. To address this issue, we introduce 4-(trifluoromethyl) phenylhydrazine (TFPH) to modify the perovskite solution, which presents enhanced storage stability. Consequently, when the modified solution was used to prepare PSCs, we obtained much improved and well consistent power conversion efficiencies (PCEs, ~ 26.0%) regardless of the perovskite solution ageing time, as well as exciting operational stability, which maintains PCE ≥ 92% for 1830 hours. These results are attributed to TFPH's multifunctionality: a) hydrazine groups inhibit perovskite decomposition by dual-pathway mechanism; b) trifluoromethyl boosts dipole moment, aiding crystallization and strain relaxation; c) impurity reduction and high-quality film jointly lower charge traps. This work substantially assists understanding and modifying perovskite degradation in both solution and solid phases. The developed performance stability and consistency on the TFPH modified device batches is of great significance for commercial production of PSCs.