Thermal evaporated PbI2 enables high-quality perovskite films and improves their solar cell performance

The quality of the light-absorbing perovskite layer is essential for fabricating highly efficient and stable perovskite solar cells (PSCs). The utilization of vacuum-deposited PbI₂, instead of spin-coated PbI₂, significantly enhanced the quality of the perovskite film in a two-step deposition process. A uniform and agglomeration-free formation of the PbI₂ layer achieved through the vacuum-deposition method promoted the efficient intercalation of MAI and led to the formation of a high-quality MAPbI₃ perovskite layer with enhanced optical properties and surface morphology. Through electrochemical impedance spectroscopy, we discovered that PSCs with vacuum-deposited PbI₂ demonstrate suppressed ion migration compared to devices with spin-coated PbI₂. With the application of vacuum-deposited PbI₂, the power conversion efficiency (PCE) of the device is superior to devices using spin-coated PbI₂. Moreover, after a 40 h thermal stability test, the device with vacuum-deposited PbI₂ maintained a PCE of over 50% of its initial efficiency, while the PSC with spin-coated PbI₂ dropped to 10%.