Resolving the detrimental interface in co-evaporated MAPbI3 perovskite solar cells by hybrid growth method

Abstract Among various processing methods for growing perovskite thin layers, dual-source vacuum deposition was once regarded as the most economical and high throughput method. However, co-evaporation of MAI and PbI 2 often leads to an inevitable PbI 2 interfacial layer formed by the initial growth of evaporation resulting in a compromised efficiency of vacuum deposited MAPbI 3 solar cell. Here, two modified growth methods based on vacuum co-evaporation, namely solution-vacuum hybrid method (SVHM) and soaking-assistant fully-vacuum method (SAFVM), are developed to grow a completely converted MAPbI 3 perovskite layer at the interface prior to the co-evaporation of MAPbI 3 perovskite layer. Upon these two methods, the unwanted PbI 2 layer can be removed from the interface resulting in much improved power conversion efficiency up to 14.35%. Our result shows that, while unwanted interfacial PbI 2 layer is the main cause of low performing co-evaporated perovskite solar cell devices, by removing the PbI 2 interfacial layer we can unlock the full potential of vacuum-based perovskite solar cells to industrial mass production.