Efficient and Stable CsPbI3 Inorganic Perovskite Photovoltaics Enabled by Crystal Secondary Growth

Defect-triggered phase degradation is generally considered as the main issue that causes phase instability and limited device performance for CsPbI3 inorganic perovskites. Here, a defect compensation in CsPbI3 perovskite through crystal secondary growth of inorganic perovskites is demonstrated, and highly efficient inorganic photovoltaics are realized. This secondary growth is achieved by a solid-state reaction between a bromine salt and defective CsPbI3 perovskite. Upon solid-state reaction, the Br- ions can diffuse over the entire CsPbI3 perovskite layer to heal the undercoordinated Pb2+ and conduct certain solid-state I/Br ion exchange reaction, while the organic cations can potentially heal the Cs+ cation vacancies through coupling with [PbI6](4-) octahedra. The carrier dynamics confirm that this crystal secondary growth can realize defect compensation in CsPbI3. The as-achieved defect-compensated CsPbI3 not only improves the charge dynamics but also enhances the photoactive phase stability. Finally, the CsPbI3-based solar cell delivers 20.04% efficiency with excellent operational stability. Overall, this work proposes a novel concept of defect compensation in inorganic perovskites through crystal secondary growth induced by solid-state reaction that is promising for various optoelectronic applications.