Synergetic Regulation of Oriented Crystallization and Interfacial Passivation Enables 19.1% Efficient Wide‐Bandgap Perovskite Solar Cells

Abstract Wide‐bandgap (WBG) perovskite solar cells (PSCs) suffer from severe voltage loss, which significantly limits the enhancement of photovoltaic performance. Here, 4‐fluoro‐phenylethylammonium iodide (FPEAI) is used as a dual‐functional agent for oriented crystallization and comprehensive passivation of WBG PSCs. The additive of FPEAI promotes crystals to grow along with the (100) orientation with improved crystallinity and to spontaneously form Ruddlesden–Popper 2D perovskite on the grain boundary and surface of 3D crystals, which can passivate defects and protect the perovskite film from moisture erosion as well as suppressed ion migration. In addition, the 2D/3D heterostructure induces a matched energy‐level alignment, which mitigates the detrimental interfacial charge recombination at the interface of the 3D perovskite and hole transport layer. Consequently, the modified WBG PSCs exhibit an improved open‐circuit voltage to 1.3 V and a fill factor of 77.8%, leading to a remarkable power conversion efficiency of 19.1% with negligible hysteresis. Furthermore, the WBG PSCs maintain 85% of the original efficiency after 1000 h in air, demonstrating outstanding humidity stability. This work indicates that FPEAI can be used as a dual‐functional agent to significantly enhance the efficiency of WBG PSCs.