Vacuum co-deposited CH3NH3PbI3 films by controlling vapor pressure for efficient planar perovskite solar cells

Abstract Physical vacuum deposition (PVD) of organo-metal halide thin film has advantages of uniform and large scale deposition for emerging perovskite solar cell technology. Evaporation of organic halides such as CH 3 NH 3 I (MAI) is crucial for obtaining phase pure perovskite thin films. However, controlling the evaporation rate of MAI remains difficult owing to its “vapor-gas” like nature upon sublimation. Here we report, highly crystalline CH 3 NH 3 PbI 3 (MAPbI 3 ) films with micrometer grains can be prepared by gradually controlling the MAI vapor pressure rather than evaporation rate in co-evaporation method. When integrating an optimal film into a planar heterojunction solar cell, the best device achieved a power conversion efficiency of 15.74% by deploying TiO 2 as an electron transport layer. This strategy alleviates the strict calibration of MAI evaporation rate and led to obtain phase pure MAPbI 3 films for high performance solar cells.