Realization of ultra-flat perovskite films with surprisingly large-grain distribution using high-pressure cooking

A novel perovskite film post-treatment method, denoted high-pressure cooking (HPC) process, was developed to prepare perovskite films with ultra-flat surface, highly ordered perovskite grains, and large grain distribution. The inverted PSC with HPC treatment achieved an excellent PCE of 23.07% with remarkably high light-operation stability. • A novel post-treatment method was developed to optimize perovskite films. • Ultra-flat, highly ordered and large grain distribution were achieved. • A fascinating method FRAP was conducted to study the light stability. • The PSC with HPC treatment shows high light-operation stability. • The inverted PSC with HPC treatment achieved an excellent PCE of 23.07%. High-quality perovskite absorber is the basis for obtaining high-performance perovskite solar cells (PSCs). Herein, a novel perovskite film post-treatment method, called high-pressure cooking (HPC) process, was developed to prepare ultra-flat perovskite films, with highly ordered perovskite grains and monolayer structures. The various carrier dynamic characterizations indicated high-quality perovskite grains from HPC treatment contributing to the improvement of transmission speed and collection efficiency of the photogenerated carriers, as well as reducing the defects assisted recombination loss. As a result, the inverted PSC with HPC treatment achieved an excellent PCE of 23.07% with fully optimized photovoltaic performance parameters. Furthermore, fluorescence recovery after photobleaching (FRAP) measurements suggested large grain size by HPC treatment to possess better resistance to halide-ion movement and photochemical decomposition. Among samples, HPC PSC possessed remarkably high light-operation stability at maximum power output coupled with long-term stability when stored in air condition.