Manipulating Intermediate Surface Energy for High-Performance All-Inorganic Perovskite Photovoltaics

The complete phase transition from DMAPbI₃ and Cs₄PbI₆ intermediates to the final CsPbI₃ perovskite phase is pivotal for fabricating high-quality inorganic perovskite films. In this study, the reaction energy barrier between DMAPbI₃ and Cs₄PbI₆ is sought to be reduced by increasing their surface energy, where a perfluorinated compound is designed using DFT modeling to saturate the surface of the intermediates to effectively prevent their crystalline growth. Consequently, the smaller intermediates with ultrahigh surface energy react more energetically to facilitate a rapid conversion to the desired perovskite phase. It is found that the resultant inorganic perovskite shows improved crystallinity and morphology, as demonstrated by suppressed non-radiative recombination and prolonged carrier lifetimes. As a result, the optimized inorganic perovskite solar cells (PSCs) achieve a power conversion efficiency (PCE) of over 20%, along with significantly improved light and thermal stability. This work provides a way to regulate crystallization dynamics for advanced quality of inorganic perovskites.