Achieving the high phase purity of CH_3NH_3PbI_3 film by two-step solution processable crystal engineering

摘要

To date,it is still a great challenge for highly efficient perovskite devices to realize the high quality perovskite films with high purity,high coverage ratio and good crystallization by two-step scalable solution method.In this study,a series Pb I_2films with tunable micro-architecture of Pb I_2crystals are prepared via solution processable crystal engineering.The perovskite film,prepared by optimized pit spacing in gas pumped Pb I_2film at 1000 Pa,shows the highest film quality,including no residual Pb I_2phase,compact morphology,and improved photoluminescence intensity.A transformation kinetics shows that the pit spacing strongly influences both the mass transfer and the sequential intercalation reaction between CH_3NH_3I and Pb I_2crystals,which ultimately determines the full reaction state of the perovskite film.The perovskite solar cells assembled by the perovskite film show both high power-conversion efficiency and good reproducibility of photovoltaic performance due to the restrained charge recombination arising from the high quality perovskite film.