Universal defects elimination for high performance thermally evaporated CsPbBr₃ perovskite solar cells

Inorganic CsPbBr₃ perovskite has emerged as a promising material for fabricating highly stable perovskite solar cell devices. However, during the formation of thermally evaporated CsPbBr₃ film, an all-solid reaction between CsBr and PbBr₂ leads to non-uniform interfaces and high defect density in the perovskite film. In this work, we utilize a two-step sintering (TSS) method which successfully modifies the morphologies of thermally evaporated CsPbBr₃ films and the power conversion efficiency of a champion CsPbBr₃ perovskite solar cell achieves 9.35%. Steady-state photoluminescence, time-resolved photoluminescence and space-charge-limited-current results prove that the TSS process can effectively reduce defect densities also. Besides these improvements, the TSS device maintains 94% of initial efficiency after being heated at 100 °C without encapsulation for over 40 days under ambient lab condition. In comparison, the untreated device reduces about 15%. Transmission electron microscope results further prove the reduction of line defects in CsPbBr₃ crystals after TSS treatment.