Passivating iodine interstitials to suppress nonradiative recombination at CsPbI₃ surface

The efficiency of CsPbI 3 perovskite solar cells is limited by nonradiative carrier recombination induced by surface defects, yet the precise nature of these defects remains elusive. By performing rigorous first-principles calculations for the surface defects of CsPbI 3 , we demonstrate that the dominant nonradiative recombination center is the iodine interstitial. Importantly, we show that the iodine interstitial exhibits amphoteric behavior and can be effectively passivated with either F − or Cs + , contingent upon the synthesis conditions. These findings not only pinpoints the critical target for surface passivation to further improve the performance of CsPbI 3 but also offers guidelines for the passivation of the relevant defect.