Donor–Acceptor Competition via Halide Vacancy Filling for Oxygen Detection of High Sensitivity and Stability by All‐Inorganic Perovskite Films

Abstract Oxygen detection by organic–inorganic halide perovskites (OIHPs) has demonstrated advantages in operating temperature, response time, and reversibility over traditional materials. However, OIHPs can only sense O₂ in light and the unavoidable O₂ exposure during detection easily induces the degradation of OIHPs. The trade‐off between sensitivity and stability makes the OIHP‐based oxygen sensors impractical. By replacing organic groups with Cs, the compact films of all‐inorganic halide perovskites (AIHPs) that can adsorb O₂ at grain boundaries in dark are developed. AIHPs show conductance increase of 1875.5% from 1 × 10⁻⁵ to 700 Torr of O₂ pressure, associated with full reversibility and long‐term stability. Combining experiments and modeling, this work reveals the donor–acceptor competition via halide vacancy filling leading to the modulation of carrier concentration and mobility. This work offers understandings on oxygen sensing by perovskite materials and paves the way for further optimization of AIHPs as promising oxygen sensors with high sensitivity and stability.