A modified two-step sequential deposition method for preparing perovskite CH3NH3PbI3 solar cells

Abstract

Two-step sequential deposition of CH₃NH₃PbI₃ (MAPI) films is widely used in the preparation of perovskite solar cells, but still suffers from some drawbacks such as residual PbI₂ and uncontrollable surface morphology of MAPI films. Here a modified two-step sequential deposition is reported to prepare MAPI films with pure phase and smooth surface. The process involves the deposition of a low-crystallinity PbI₂ film firstly and subsequent spraying of CH₃NH₃I solution. A well-converted and extremely surface-smooth MAPI film was successfully prepared via this two-step method. The weak crystallinity of raw PbI₂ film leads to the pure MAPI film. The following spraying of CH₃NH₃I solution in a spin-coating process results in MAPI films with much smoother surface, better crystallization and higher absorption compared with the traditional method of immersing in CH₃NH₃I solution. Consequently, the corresponding mesostructured perovskite solar cells based on these MAPI films achieve a high efficiency of 14.3% and good reproducibility, which demonstrates the advantages and promising applications of this modified two-step sequential deposition method.