Investigating the effects of modified anchoring groups on the surface structure of perovskites for enhanced stability

Abstract

Utilizing organic small molecules to passivate the surface of perovskites is regarded as the most flexible and effective strategy for enhancing the performance of perovskite solar cells (PSCs). Understanding the passivation effects of experimental passivators, along with the theoretical design of enhanced passivators, is crucial for achieving further improvements in the efficiency and stability of perovskite devices. In this study, a series of novel BHT–X–R passivators were designed using BHT–OH–CH₃; these passivators have various anchoring groups (X = SH, NH₂, CN, CHO, or COOH) and carbon chain lengths (R = CH₃ or C₂H₅). We used first-principles calculations to determine the effects of eight passivation molecules (PMs) with distinct configurations on the surface structure and electronic properties of perovskites. The results indicated that the designed molecules enhance charge transfer and adsorb strongly on the perovskite surface. Ab initio molecular dynamics simulations confirmed that the optimal PM, namely BHT–COOH–C₂H₅, not only diminished the positional fluctuation of Pb and I particles on the perovskite surface but also served as an effective waterproof barrier. This “static–dynamic” evaluation strategy shows that modifying the anchoring group and extending the alkyl chain can further increase the longevity of PSCs under humid conditions.