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 degrees 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.