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 (Ntrap) 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 Ntrap 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.