Organic-inorganic metal-halide perovskite materials offer a promising route to reducing the dollars-per-watt cost of solar energy due to their good optoelectronic properties and facile, scalable processing. Compositional tuning allows for the preparation of absorbers with band gaps tailor-made for specific tandem and single-junction applications, but photoinduced phase segregation in mixed-halide materials leads to the formation of low-band-gap regions that reduce the voltage of devices. This work explores the structural origins of photoinduced phase segregation in FA_yCs_1−yPb(Br_xI_1−x)₃ perovskite alloys. We use synchrotron X-ray diffraction to map the solvus between the cubic and cubic-tetragonal mixed-phase region and time-dependent photoluminescence to assess stability under illumination. We show that the correlation between crystallographic phase and phase-segregation behavior is imperfect, so phase is not the sole determinant of optical stability. Instead, we consider several possible mechanisms that could underlie the dependence of optical stability on perovskite composition.

有机-无机金属卤化物钙钛矿材料具有良好的光电性能和便捷，可扩展的加工工艺，为降低太阳能的每瓦成本提供了一条有希望的途径。成分调谐允许制备具有针对特定串联和单结应用量身定制的带隙的吸收体，但是混合卤化物材料中的光致相分离导致形成低带隙区域，从而降低了器件的电压。这项工作探索了FA _y Cs _{1 － y} Pb（Br _x I _{1 －x}）₃中光致相分离的结构起源。钙钛矿合金。我们使用同步加速器X射线衍射来绘制立方和立方四方混合相区域和时间相关的光致发光之间的溶解度，以评估光照下的稳定性。我们表明，结晶相和相偏析行为之间的相关性是不完善的，因此，相并不是光学稳定性的唯一决定因素。相反，我们考虑了几种可能的机理，这些机理可能是光学稳定性对钙钛矿成分的依赖性的基础。