Transient Interphase Assisted Crystallization of Antisolvent-Free Perovskite for Enhanced Device Performance

Antisolvent-free perovskite solar cells (PSCs) are a promising technology for scalable manufacturing. Due to a more complicated crystallization process, a key factor limiting device performance is phase segregation induced by the varying crystallization rates of the various components. Herein, we propose a transient interphase strategy to manipulate the nucleation process and crystal growth for enhanced device performance without an antisolvent. We found that tetramethylurea (TMU) induces instantaneous nucleation with a Cs-rich component and forms a transient interphase, which balances the integrated crystallization for the formation of α-Cs_XFA_1-XPbI₃ phase. This approach enhances device performance with an efficiency up to 25.63% and a module efficiency of 19.62%. Crucially, suppressed phase segregation endows exceptional stability: devices show negligible degradation after 1700 h (ISOS-L-1) and retain 90% of their initial efficiency after 3500 h. It represents the longest reported MPPT stability for antisolvent-free Cs_XFA_1-XPbI₃-based PSCs to date.