Deuterated FAPbI3 Perovskite Films with Suppressed Deprotonation for Durable Solar Cells

• • Deuteration reduces the deprotonation rate constant of FAPbI3 from 5.15 × 10−8 to 2.42 × 10−8 s−1, a 53% suppression that directly mitigates the primary intrinsic degradation pathway and extends operational lifetime. • • The deuterated devices achieve a power conversion efficiency of 25.08%, comparable to state-of-the-art PSCs, demonstrating that isotopic substitution does not compromise charge transport or light absorption. • • A T97 lifetime of 1264 h under continuous one-sun illumination at 55 °C is reported, exceeding typical FA-based device stability and approaching the industrial requirement of <0.5% annual output loss for commercial silicon cells. • • The kinetic isotope effect arises from the lower ground-state energy of the N–D bond, providing a thermodynamically driven stabilization mechanism that operates without extrinsic additives or encapsulation, thus simplifying device architecture.