Hybrid lead halide perovskites such as MAPbI₃ (MA = CH₃NH₃⁺) and their mixed halide analogues represent an emerging class of materials for solar energy conversion. Intriguing aspects include sizable carrier diffusion lengths, large optical absorption coefficients, and certified power conversion efficiencies that now exceed 22%. Halide-composition-tunable band gaps also make MAPb(I_1–xBr_x)₃ systems ideal candidates for tandem solar cells. Unfortunately, preventing the effective integration of MAPb(I_1–xBr_x)₃ into working devices are intrinsic instabilities due to light-induced halide phase segregation. Namely, under illumination, mixed halide perovskites reversibly segregate into low-band-gap I-rich and high-band-gap Br-rich domains. Under electrical bias, halide migration has also been proposed as the source of undesirable charge injection barriers that degrade photovoltaic performance. In this Perspective, we review the origin of light-induced halide phase segregation, its effects on photovoltaic response, and ongoing research to suppress its influence on the optical and electronic response of mixed halide perovskites.

中文翻译：

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混合卤化物钙钛矿中的光诱导阴离子相偏析

杂化的卤化钙钛矿如MAPbI ₃（MA = CH ₃ NH ₃ ⁺）及其混合的卤化物类似物代表了新兴的一类用于太阳能转换的材料。引人入胜的方面包括相当大的载流子扩散长度，较大的光吸收系数以及现已超过22％的认证功率转换效率。卤化物成分可调节的带隙也使MAPb（I _{1 – x} Br _x）₃系统成为串联太阳能电池的理想候选者。不幸的是，阻止了MAPb（I _{1 – x} Br _x）₃的有效整合由于光诱导的卤化物相偏析，进入工作装置是固有的不稳定性。即，在照明下，混合的卤化物钙钛矿可逆地分离成低带隙的富I和高带隙的富Br的域。在电偏压下，也提出了卤化物迁移作为不期望的电荷注入势垒的来源，其降低了光伏性能。在此观点中，我们回顾了光诱导卤化物相分离的起源，其对光伏响应的影响，以及正在进行的研究以抑制其对混合卤化物钙钛矿的光学和电子响应的影响。