Tailoring the Interface with a Multifunctional Ligand for Highly Efficient and Stable FAPbI₃ Perovskite Solar Cells and Modules

Perovskite solar cells (PeSCs) using FAPbI₃ perovskite films often exhibit unfavorable phase transitions and defect-induced nonradiative interfacial recombination, resulting in considerable energy loss and impairing the performance of PeSCs in terms of efficiency, stability, and hysteresis. In this work, a facile interface engineering strategy to control the surface structure and energy-level alignment of perovskite films by tailoring the interface between the FAPbI₃ film and hole-transporting layer using 4-hydroxypicolinic acid (4HPA) is reported. According to density functional theory studies, 4HPA has prominent electron delocalization distribution properties that enable it to anchor to the perovskite film surface and facilitate charge transfer at the interface. By enabling multiple bonding interactions with the perovskite layer, including hydrogen bonds, Pb-O, and Pb.N dative bonds, 4HPA passivation significantly reduces the trap density and efficiently suppresses nonradiative recombination. The obtained perovskite films exhibit superior optoelectronic properties with improved crystallinity, pure α-phase FAPbI₃, and favorable energy band bending. Following this strategy, 4HPA post-treatment PeSCs achieve a champion power conversion efficiency of 23.28% in 0.12 cm² cells and 19.26% in 36 cm² modules with excellent environmental and thermal stabilities.