Organic iodides in efficient and stable perovskite solar cells: strong surface passivation and interaction

Abstract

Surface passivation with organic iodides has become a necessary strategy for realizing high-performance perovskite solar cells (PSCs). However, stability degradation of PSCs is always triggered by the migration of iodine interstitial (I_i) defects on the perovskite surface after such treatment. Here, we found that even if the surface treatment is not annealed, it induces the formation of I_i and leads to the subsequent migration behavior. We emphasized the importance of cation selection for organic iodides, and revealed that a strong interaction between cations and perovskite surfaces can suppress the I_i migration through increasing the migration energy barrier. Detailed investigation of four classical phenylalkylammonium iodides demonstrates that the alkyl chain length of cations has an effect on the suppression of I_i migration. Owing to effective defect passivation on the perovskite surface and successful I_i migration inhibition, the phenylpropylammonium iodide-treated PSCs achieve enhanced efficiency and stability simultaneously, obtaining a champion efficiency of 24.20% and retaining about 92% of their initial efficiency after 240 h of continuous illumination during operational stability testing.