Modulation of Buried Interface by 1‐(3‐aminopropyl)‐Imidazole for Efficient Inverted Formamidinium‐Cesium Perovskite Solar Cells

Abstract Considering the direct influence of substrate surface nature on perovskite (PVK) film growth, buried interfacial engineering is crucial to obtain ideal perovskite solar cells (PSCs). Herein, 1‐(3‐aminopropyl)‐imidazole (API) is introduced at polytriarylamine (PTAA)/PVK interface to modulate the bottom property of PVK. First, the introduction of API improves the growth of PVK grains and reduces the Pb 2+ defects and residual PbI 2 present at the bottom of the film, contributing to the acquisition of high‐quality PVK film. Besides, the presence of API can optimize the energy structure between PVK and PTAA, which facilitates the interfacial charge transfer. Density functional theory (DFT) reveals that the electron donor unit (R‐C ═ N) of the API prefers to bind with Pb 2+ traps at the PVK interface, while the formation of hydrogen bonds between the R‐NH 2 of API and I − strengthens the above binding ability. Consequently, the optimum API‐treated inverted formamidinium‐cesium (FA/Cs) PSCs yields a champion power conversion efficiency (PCE) of 22.02% and exhibited favorable stability.