Synergistic Dual‐Defect Passivation via Iodoethoxyethane for High‐Efficiency Inverted Inorganic Perovskite Solar Cells

Abstract Inorganic perovskite solar cells (PSCs) have attracted significant attention due to their excellent photothermal stability and potential for integration with silicon solar cells in tandem devices, offering great promise for future commercialization. However, the presence of numerous defects on the perovskite surface and poor energy level alignment between functional layers and perovskite in inverted PSCs result in power conversion efficiencies (PCE) that are still lower than those of conventional PSCs. Herein, an effective interfacial passivation strategy is proposed by introducing 1,2‐bis(2‐iodoethoxy)ethane (BIEE) molecules as an interfacial passivator for inverted PSCs. The oxygen atoms in BIEE can coordinate with undercoordinated lead ions, while iodide simultaneously occupies adjacent halide vacancies. This dual interaction effectively reduces defect density, suppresses ion migration, and improves energy level alignment at the interface. With this surface engineering approach, the inverted CsPbI 3−x Br x PSCs achieved a PCE of 21.9% under 1‐sun equivalent illumination and 42.6% under indoor light emiting diode (LED) lighting (1000 lux, 281 µW cm −2 ). Furthermore, under maximum power point (MPP) tracking with continuous one sun illumination for 1170 h in N 2 environment, the PCEs of the BIEE‐modified device maintain 95.8% of the initial efficiency.