In Situ Grain Boundary Functionalization for Stable and Efficient Inorganic CsPbI2Br Perovskite Solar Cells

Abstract

AbstractThe phase instability and large energy loss are two obstacles to achieve stable and efficient inorganic‐CsPbI3−xBrxperovskite solar cells. In this work, stable cubic perovskite (α)‐phase CsPbI2Br is successfully achieved by Pb(Ac)2functioning at the grain boundary under low temperature. Ac−strongly coordinates with CsPbI2Br to stabilize the α‐phase and also make the grain size smaller and film uniform by fast nucleation. PbO is formed in situ at the grain boundary by decomposing Pb(Ac)2at high‐temperature annealing. The semiconducting PbO effectively passivates the surface states, reduces the interface recombination, and promotes the charge transport in CsPbI2Br perovskite solar cells. A 12% efficiency and good stability are obtained for in situ PbO‐passivated CsPbI2Br solar cells, while Pb(Ac)2‐passivated device exhibits 8.7% performance and the highest stability, much better than the control device with 8.5% performance and inferior stability. This article highlights the extrinsic ionic grain boundary functionalization to achieve stable and efficient inorganic CsPbI3−xBrxmaterials and the devices.