Potassium addition to mixed‐halide perovskites is found to be a promising way to overcome their major stability issue, the segregation of the mixed phase to iodide and bromide‐rich regions. To fully exploit the potential of potassium addition, it is essential to achieve a better understanding of its working mechanism, and understand the limitations of the stabilization it provides. Photoluminescence emission spectra of MAPb(Br_0.6I_0.4)₃ films are studied upon addition of KBr and KI under nitrogen and air atmosphere. The halide exchange between the added potassium salts and the perovskite is demonstrated. It is shown that the potassium addition does not passivate the surface, and it is therefore prone to oxygen and water absorption. The significant contribution of the adsorbed water to the prevention of halide segregation is discussed, which should be taken into account when the stability of the mixed‐halide films is evaluated under ambient conditions.

中文翻译：

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钾在不同环境下对MAPb（Br0.6I0.4）3混合卤化物钙钛矿离析的作用

人们发现，将钾添加到混合卤化物钙钛矿中是解决其主要稳定性问题（将混合相分离到富含碘化物和溴化物的区域）的一种有前途的方法。为了充分利用钾添加的潜力，必须对钾的工作机理有一个更好的了解，并了解其提供的稳定性的局限性。MAPb（Br _0.6 I _0.4）_3的光致发光光谱在氮气和空气气氛下，通过添加KBr和KI来研究薄膜。证明了添加的钾盐和钙钛矿之间的卤化物交换。结果表明，钾的添加不会钝化表面，因此易于吸收氧气和水分。讨论了吸附水对防止卤化物偏析的重要作用，在环境条件下评估混合卤化物薄膜的稳定性时应考虑到这一点。