Fully Inorganic Hole Contacts Enabled by CeI3 for High-Performance Perovskite Solar Modules.

Inorganic oxides are widely recognized as stable interfacial materials that can mitigate degradation of perovskite absorbers and prolong device lifetime. However, conventional nickel oxide (NiOx)-based hole-transport layers often suffer from unfavorable energy-level alignment and reactive interfacial defects, while commonly used organic surface modifiers can complicate scalable processing and long-term stability. Here, we introduce cerium iodide (CeI3) as an inorganic interfacial modifier to construct a fully inorganic hole-contact architecture. CeI3 modulates perovskite nucleation and crystallization under ambient processing conditions, producing compact, pinhole-free films with improved coverage. Correlated changes in the oxidation states of Ce, Ni, and Pb after aging, together with reduced iodine loss, support the involvement of Ce species in redox-mediated interfacial regulation. CeI3 modification also improves energy-level alignment and suppresses nonradiative recombination. The resulting devices achieve power conversion efficiencies of 25.19% for 0.113 cm2 cells and 23.37% for 21 cm2 modules, with a geometric fill factor of 98.3%. Encapsulated modules retain 92.3% of their initial efficiency after 1000 h of continuous 1-sun illumination and 95.2% after 1000 h of damp-heat aging at 85 °C/85% RH. Outdoor measurements over one month further demonstrate stable module operation. This ambient-compatible and cost-effective strategy provides a scalable route toward efficient and durable perovskite photovoltaics.