Prebedded Sacrificing Layer for Developing Strain Released and Phase Pure CsPbBr3 Perovskite Solar Cells

In this study, strain-induced cracks and a lead-rich impurity phase (CsPb₂Br₅) have been detected at the buried interface of the two-step prepared CsPbBr₃ films. To solve this problem, a sacrificing layer (CsAc) was introduced before the deposition of the PbBr₂ precursors. This provides enough cesium precursors for the afterward CsPbBr₃ growth. Besides, the CsAc sacrificing layer brings more holes in the prepared PbBr₂ films, which benefits the volume expansion during the PbBr₂ to CsPbBr₃ conversion. Thus, residual strain released films can be expected. With the assistance of the CsAc sacrificing layer, the performance of our CsPbBr₃ devices can be improved from 7.70% (control) to 10.07% (6% CsAc assisted) with enhanced stability. Finally, we introduce a sacrificing layer assisted strategy for preparing strain released and phase pure CsPbBr₃ films, and this strategy might also be applicable to other types of PSCs.