Alloying structurally similar perovskites to form mixed-cation lead iodide perovskites, e.g., ${\mathrm{Cs}}_x\mathrm{F}{\mathrm{A}}_{(1-x)}\mathrm{Pb}{\mathrm{I}}_3, \mathrm{M}{\mathrm{A}}_x\mathrm{F}{\mathrm{A}}_{(1-x)}\mathrm{Pb}{\mathrm{I}}_3$, and ${\mathrm{Cs}}_x\mathrm{M}{\mathrm{A}}_y\mathrm{F}{\mathrm{A}}_{(1-x-y)}\mathrm{Pb}{\mathrm{I}}_3$, could improve the performance of perovskite-based solar cells and light-emitting diodes. However, a phase diagram of them and a clear understanding of the underlying atomic-scale mechanism are still lacking. Using ab initio calculations combined with high-throughput experimentation, we demonstrate the phase diagram of mixed-cation lead iodide perovskites. Only a small proportion of monovalent cations (${\mathrm{Cs}}^{+}/{\mathrm{Rb}}^{+}/{\mathrm{MA}}^{+}$) could be incorporated into the ${\mathrm{FAPbI}}_3/{\mathrm{MAPbI}}_3$ matrix; otherwise it will be separated into δ-${\mathrm{CsPbI}}_3$, δ-${\mathrm{RbPbI}}_3$, MAI, etc. The smaller the radius of doping cations, the harder it is to incorporate them into a perovskite lattice and the easier it is to stabilize the perovskite phase. In ${\mathrm{FAPbI}}_3$-based multication perovskites, moreover, over 10 mol % alloying is needed to convert δ phase to α phase at room temperature. The combined upper and lower limits for doping concentration restrict the appropriate alloying ratio to a narrow window. We further plot the relative energy diagram for triple-cation perovskite ${\mathrm{Cs}}_x\mathrm{M}{\mathrm{A}}_y\mathrm{F}{\mathrm{A}}_{(1-x-y)}\mathrm{Pb}{\mathrm{I}}_3$, which reveals the ideal doping ratio for uniform stable alloying. This theory-experiment-combined study provides a clear microscopic picture of phase stability and segregation for mixed-cation perovskite solids.

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混合阳离子碘化铅钙钛矿的相图和稳定性：理论与实验相结合的研究

将结构相似的钙钛矿合金化以形成混合阳离子碘化铅钙钛矿，例如， ${\mathrm{Cs}}_X\mathrm{F}{\mathrm{一种}}_{（\mathrm{1个}-X）}\mathrm{铅含量}{\mathrm{一世}}_3， \mathrm{中号}{\mathrm{一种}}_X\mathrm{F}{\mathrm{一种}}_{（\mathrm{1个}-X）}\mathrm{铅含量}{\mathrm{一世}}_3$和 ${\mathrm{Cs}}_X\mathrm{中号}{\mathrm{一种}}_{ÿ}\mathrm{F}{\mathrm{一种}}_{（\mathrm{1个}-X-ÿ）}\mathrm{铅含量}{\mathrm{一世}}_3$可以改善钙钛矿基太阳能电池和发光二极管的性能。但是，仍然缺乏它们的相图和对潜在原子尺度机理的清晰理解。使用从头算与高通量实验相结合的方法，我们证明了混合阳离子碘化铅钙钛矿的相图。仅一小部分单价阳离子（${\mathrm{Cs}}^{+}/b^{+}/{嘛}^{+}$）可以并入 ${\mathrm{FAPbI}}_3/{\mathrm{马比}}_3$矩阵; 否则将被分解为δ-$P_3$，δ-$b_3$，MAI等。掺杂阳离子的半径越小，将它们掺入钙钛矿晶格的难度就越大，并且稳定钙钛矿相的难度也就越大。在${\mathrm{FAPbI}}_3$此外，在室温下需要超过10 mol％的合金化钙钛矿，以将δ相转变为α相。掺杂浓度的组合上限和下限将适当的合金化比例限制在一个狭窄的窗口内。我们进一步绘制了三阳离子钙钛矿的相对能图${\mathrm{Cs}}_X\mathrm{中号}{\mathrm{一种}}_{ÿ}\mathrm{F}{\mathrm{一种}}_{（\mathrm{1个}-X-ÿ）}\mathrm{铅含量}{\mathrm{一世}}_3$，揭示了均匀稳定合金化的理想掺杂比。这项理论与实验相结合的研究为混合阳离子钙钛矿固体的相稳定性和偏析提供了清晰的微观图像。