Mixed iodide‐bromide organolead perovskites with a bandgap of 1.70–1.80 eV have great potential to boost the efficiency of current silicon solar cells by forming a perovskite‐silicon tandem structure. Yet, the stability of the perovskites under various application conditions, and in particular combined light and heat stress, is not well studied. Here, FA_0.15Cs_0.85Pb(I_0.73Br_0.27)₃, with an optical bandgap of ≈1.72 eV, is used as a model system to investigate the thermal‐photostability of wide‐bandgap mixed halide perovskites. It is found that the concerted effect of heat and light can induce both phase segregation and decomposition in a pristine perovskite film. On the other hand, through a postdeposition film treatment with benzylamine (BA) molecules, the highly defective regions (e.g., film surface and grain boundaries) of the film can be well passivated, thus preventing the progression of decomposition or phase segregation in the film. Besides the stability improvement, the BA‐modified perovskite solar cells also exhibit excellent photovoltaic performance, with the champion device reaching a power conversion efficiency of 18.1%, a stabilized power output efficiency of 17.1% and an open‐circuit voltage (V _oc) of 1.24 V.

中文翻译：

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经苄胺处理的宽带隙钙钛矿，具有高的热光稳定性和光伏性能

带隙为1.70-1.80 eV的混合碘化物-溴化物有机铅钙钛矿具有巨大的潜力，可以通过形成钙钛矿-硅串联结构来提高当前硅太阳能电池的效率。然而，钙钛矿在各种应用条件下的稳定性，特别是光和热应力的结合，还没有得到很好的研究。在此，FA _0.15 Cs _0.85 Pb（I _0.73 Br _0.27）₃具有约1.72 eV的光学带隙的模型系统被用作研究宽带隙混合卤化物钙钛矿的热光稳定性的模型系统。发现热和光的协同作用可以在原始钙钛矿膜中引起相偏析和分解。另一方面，通过用苄胺（BA）分子进行后沉积膜处理，可以很好地钝化膜的高度缺陷区域（例如，膜表面和晶界），从而防止膜中的分解或相偏析的进行。 。除了改善稳定性外，BA改性的钙钛矿太阳能电池还表现出出色的光伏性能，冠军设备达到了18.1％的功率转换效率，17.1％的稳定功率输出效率和开路电压（V _oc）为1.24V。