Surface Co-passivation for 1.7 eV wide-bandgap perovskite solar cells with minimal voltage loss to achieve over 23% efficiency

The high non-radiative recombination caused by lattice defects and photoinduced phase segregation remains a major challenge hindering the development of wide-bandgap perovskite solar cells (PSCs), severely impairing their open-circuit voltage (VOC), efficiency, and long-term stability. Herein, we propose a co-passivation strategy to address lattice defects associated with Br-I ions in 1.7 eV bandgap Cs0.22FA0.78PbI2.25Br0.75 perovskite material. This approach effectively suppresses surface defects and reduces the non-radiative recombination rate of the perovskite material, increasing the VOC from 1.13 V to a record 1.29 V. Based on this strategy, we achieved a record-breaking efficiency of exceeding 23% for wide-bandgap PSCs. The unencapsulated devices retained 98.5% of their initial efficiency after more than 2000 h of testing at room temperature and maintained over 80% efficiency after 900 h at 85 °C. These significant improvements in both efficiency and stability are attributed to targeted passivation against the uneven nucleation unique to wide-bandgap perovskite. By introducing iodine-rich passivators, the imbalanced Br and I distribution in the film was balanced, which provides a promising pathway for enhancing the performance of mixed-halide perovskite materials.