Mixed-halide perovskites are ideal materials for the demanding applications of tandem solar cells and emission-tunable light-emitting diodes (LEDs) because of their high compositional flexibility and optoelectronic performance. However, one major obstacle to their use is the compositional instability some mixed-halide perovskites experience under illumination or charge-carrier injection, during which the perovskite material demixes into regions of differing halide content. Such segregation of halide ions adversely affects the electronic properties of the material and severely limits the prospects of mixed-halide perovskite technology. Accordingly, a considerable amount of research has been performed aiming to uncover the underlying mechanisms and mitigating factors of the halide segregation process. Here we present a perspective of strategies designed to reduce the effects of halide segregation in working mixed-halide perovskite devices, based on recent literature reports. We discuss a multitude of mitigating techniques, and conclude that a combination of stoichiometric engineering, crystallinity control and trap state passivation is clearly imperative for abating halide segregation. In addition, the reduction of halide vacancies and control over illumination and temperature can, to a certain extent, mitigate halide segregation. Less direct approaches, such as a change in atmospheric environment, perovskite incorporation into a nanocrystalline composition, or direct control over the crystallographic structure of the perovskite, may however prove too cumbersome to be of practical use. This perspective paves the way for the design and creation of phase-stable, mixed-halide perovskite materials for photovoltaic and LED applications.

中文翻译：

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预防混合卤化物钙钛矿中的相分离：一个观点

混合卤化物钙钛矿因其高的组成灵活性和光电性能而成为串联太阳能电池和发射可调发光二极管（LED）苛刻应用的理想材料。然而，使用它们的一个主要障碍是一些混合卤化物钙钛矿在光照或电荷载流子注入下所经历的组成不稳定性，在此期间钙钛矿材料分解成卤化物含量不同的区域。卤离子的这种偏析对材料的电子性能产生不利影响，并严重限制了混合卤化物钙钛矿技术的前景。因此，已经进行了大量的研究，旨在揭示卤化物偏析过程的潜在机理和缓解因素。在此，根据最近的文献报道，我们提出了旨在减少工作混合卤化物钙钛矿装置中卤化物偏析影响的策略的观点。我们讨论了多种缓解技术，并得出结论，化学计量工程，结晶度控制和陷阱态钝化相结合显然对于减少卤化物的偏析是必不可少的。此外，减少卤化物空位以及控制光照和温度可以在一定程度上减轻卤化物的偏析。然而，不太直接的方法，例如改变大气环境，将钙钛矿掺入纳米晶体组合物中或直接控制钙钛矿的晶体学结构，可能证明太麻烦而不能实际使用。