Locating Non‐Radiative Recombination Losses and Understanding Their Impact on the Stability of Perovskite Solar Cells During Photo‐Thermal Accelerated Ageing

Abstract Commercialization of perovskite solar cells (PSCs) requires further breakthroughs in stability, but the complex degradation mechanisms and the interplay of the underlying stress factors complicate insight‐driven improvement of long‐term stability. This study establishes a quantitative link between potential degradation—specifically open‐circuit voltage ( V OC ) and quasi‐Fermi level splitting (QFLS)—and the photo‐thermal stability of PSCs. It is highlighted that an increase in non‐radiative recombination losses induces the seemingly negligible decrease in V OC and QFLS, though it causes a significant decrease in fill factor (FF) and/or short circuit current ( J SC ) instead, leading to an overall performance decline. By combining non‐destructive photoluminescence imaging and drift‐diffusion simulations, it is revealed that during photo‐thermal ageing, unstable low‐dimensional passivation fails within tens of hours, generating bulk defects, while unstable hole‐transport‐layer contacts induce interface defects within hours. Building on these findings, a robust hole‐transport‐layer polymer interface is employed and enhanced perovskite crystal quality to suppress both interface and bulk defect generation during ageing, achieving a T 80 lifetime exceeding 1000 h under accelerated ageing conditions (85 °C and two‐sun illumination).