Mixed halide wide-bandgap perovskites are suitable for integration in tandem photovoltaics such as perovskite/organic tandem solar cells. However, halide phase segregation originating from halogen vacancy-assisted ion migration in wide-bandgap perovskites limits the device efficiency and lifetime. Here we incorporate pseudo-halogen thiocyanate (SCN) ions in iodide/bromide mixed halide perovskites and show that they enhance crystallization and reduce grain boundaries. Trace amount of SCN ions in the bulk enter the perovskite lattice, forming an I/Br/SCN alloy, and occupy iodine vacancies, blocking halide ion migration via steric hindrance. Taken together, these effects retard halide phase segregation under operation and reduce energy loss in the wide-bandgap perovskite cells. The resulting perovskite/organic tandem solar cell achieves a power conversion efficiency of 25.82% (certified 25.06%) and an operational stability of 1,000 h.

混合卤化物宽带隙钙钛矿适合集成在串联光伏电池中，例如钙钛矿/有机串联太阳能电池。然而，宽带隙钙钛矿中卤素空位辅助离子迁移产生的卤化物相偏析限制了器件的效率和寿命。在这里，我们将拟卤素硫氰酸根（SCN）离子掺入碘化物/溴化物混合卤化物钙钛矿中，并表明它们可以增强结晶并减少晶界。块体中的微量SCN离子进入钙钛矿晶格，形成I/Br/SCN合金，并占据碘空位，通过空间位阻阻止卤化物离子迁移。综上所述，这些效应可延迟运行时的卤化物相分离，并减少宽带隙钙钛矿电池中的能量损失。由此产生的钙钛矿/有机串联太阳能电池实现了25.82%的功率转换效率（认证为25.06%）和1,000小时的运行稳定性。