Crystallization regulation and defect suppression of CsPbI2Br perovskite using a dual-functional additive

Inorganic CsPbI2Br perovskite solar cells have attracted widespread attention due to their outstanding performance and photo-thermal stability. However, the rapid crystallization of the solution-processed CsPbI2Br film often results in poor crystallinity and a high density of defects, which seriously restrict the improvement of the device performance. Here, we introduce a dual-functional additive, 4-amino-5-aminomethyl-2-methylpyrimidine (AMP), to regulate the crystallization and reduce the defect density of the CsPbI2Br film. The introduction of AMP notably improves the crystallinity and morphology of the CsPbI2Br film and promotes a preferred crystal orientation. The C=N and amino groups in AMP interact with Pb2+ and Br- in the perovskite, respectively, effectively passivating the defects and improving the carrier lifetime. As a result, the power conversion efficiency of the optimized carbon-based hole-transport layer-free device reaches 13.30%, which exceeds the 10.66% of the control device. The environmental and light stability of the device is also significantly improved. This work provides valuable insights into the development of high-performance all-inorganic perovskite solar cells via additive strategies.