Maximum Stability Point Tracking Stabilizes Wide‐Bandgap Mixed‐Halide Perovskite Solar Cells

ABSTRACT Mixed‐halide wide‐bandgap (WBG) perovskites with bandgaps above 1.65 eV are essential top‐cell absorbers for tandem photovoltaics. However, bromide‐rich WBG perovskites suffer from photo‐induced halide segregation, while its origin under operating conditions remains unclear. Here, we identify trapped‐charge accumulation as a key factor triggering phase segregation during operation and develop a practical operational strategy to mitigate this process. Time‐evolving photoluminescence and depth‐profiling x‐ray photoelectron spectroscopy reveal that trapped‐charge accumulation accelerates ionic redistribution and halide segregation under illumination. Based on this insight, we introduce a maximum stability point tracking (MSPT) strategy that periodically relieves charge accumulation during device operation. WBG perovskite solar cells (PSCs) operated under MSPT retain approximately 90% of their initial power after 700 h of continuous operation, whereas devices operated under conventional maximum power point tracking (MPPT) rapidly degrade during the early stages of operation. Post‐operational analyses further reveal that MSPT preserves the alloyed perovskite phase, whereas MPPT induces pronounced phase segregation. As an operation‐stage strategy that mitigates charge accumulation without altering material composition, MSPT is compatible with existing material approaches and offers a route toward more stable perovskite photovoltaics. These findings provide an operational guideline for stabilizing WBG PSCs and advancing tandem photovoltaic technologies.