4-Bromoaniline Passivation for Efficient and Stable All-Inorganic CsPbI2Br Planar Perovskite Solar Cells

In this work, 4-bromoaniline (BrAL) is employed to modify the CsPbI2Br/carbon electrode interface to passivate defects of all-inorganic CsPbI2Br perovskite solar cells (PSCs). The effects of BrAL modification on the structure, light absorption, and trap-state density (N-trap) of CsPbI2Br films and the carrier recombination process, photoelectrical characteristics, and air stability of the PSCs are systematically studied. The results show that the hydrophobic BrAL interlayer modification can lead to a better matched energy-level alignment, reduce the N-trap to construct uniform CsPbI2Br films, and suppress carrier recombination to promote charge transport and collection. Thus, the modified PSC achieves a higher power conversion efficiency (PCE) of 11.34% with less hysteresis (reference-PSC, 9.50%) and better stability in ambient air. The BrAL passivation provides a good strategy to enhance the photoelectrical performance and air stability of all-inorganic PSCs.