Dual-intermediator guided methodical molecular exchange towards optimized crystallization kinetics of advanced perovskite solar cells

Sequential deposition has been demonstrated to provide a maneuverable and reproducible crystallization process for formamidinium-lead triiodide (FAPbI₃) perovskite solar cells (PSCs). However, the uncontrollable PbI₂ transformation by organic cations brings great challenges to ideal perovskite films. The state-of-the-art studies predominantly emphasize either PbI₂-intermediate phases or the use of FA⁺-retardants to slow down intramolecular exchange, lacking of comprehensive investigation into bilateral coordination enabled methodical molecular exchange for the rational growth of α-FAPbI₃ films. In this study, we launch a dual-intermediator strategy involving 1,3-propanediamine (DAP) and 4-aminobutyric acid (GABA) to bilaterally regulate the crystallization kinetics of FAPbI₃. This dual-intermediator line synergistically advances efficient and direct α-FAPbI₃ phase transition with preferred orientation and fewer defects, generating improved energetic alignment and charge transport dynamics in PSCs. Encouragingly, the best PSC free of encapsulation delivers a champion efficiency of 25.52 % and retains 95.2 % efficiency after 1200 h of maximum power point tracking under continuous AM 1.5 G illumination in N₂ at 50 ℃.