Suppressing NiO x /CsPbIBr ₂ Interfacial Redox Reactions and Band Energy Misalignment in Perovskite Solar Cells

Inverted inorganic CsPbIBr 2 perovskite solar cells (PSCs) employing NiO x as the hole‐transport layer are promising long‐term stable and semi‐transparent photovoltaic devices. Nevertheless, their performance is often constrained by unfavorable interfacial phenomena, including detrimental redox reactions between Ni 3+ in NiO x and I − in perovskite, as well as band energy misalignment at the NiO x /CsPbIBr 2 interface. In this work, we introduce an N‐dodecylphosphonic acid (NDPA) interfacial modification strategy, where the phosphonic groups of NDPA anchor onto the NiO x surface. This tailored interface not only suppresses interfacial redox reactions but also alleviates energy level mismatch and releases the residual tensile stress, thereby facilitating charge transport and reducing non‐radiative recombination losses. As a result, the optimized PSCs deliver a champion power conversion efficiency of 9.28% with a high open‐circuit voltage ( V oc ) of 1.12 V, positioning it among the best‐performing inverted CsPbIBr 2 PSCs reported to date. The modified devices retain 79% of their initial efficiency after 1300 h of storage in a nitrogen‐filled glovebox, underscoring their potential for practical photovoltaic applications.