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 PbI2 often leads to an inevitable PbI2 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 PbI2 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 PbI2 layer is the main cause of low performing co-evaporated perovskite solar cell devices, by removing the PbI2 interfacial layer we can unlock the full potential of vacuum-based perovskite solar cells to industrial mass production.