Anomalous Alloy Properties in Mixed Halide Perovskites.
Anomalous Alloy Properties in Mixed Halide Perovskites.
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DOI：
10.1021/jz501896w
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发表时间：
2014-10
期刊：
影响因子：
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通讯作者：
W. Yin;Yanfa Yan;S. Wei
中科院分区：
文献类型：
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作者：
W. Yin;Yanfa Yan;S. Wei
通过混合卤素元素，如CH3NH3PbI3-xClx和CH3NH3PbI3-xBrx，工程卤化钙钛矿是调整其电子和光学性质的可行方法。尽管出现了许多关于混合卤化物钙钛矿的实验，但合金的基本电子和结构性质尚未被理解，一些关键问题仍然存在，例如，CH3NH3PbI3中可以掺入多少Cl仍然不清楚。本文以CsPbX3 （X = I, Br, Cl）为例，采用第一原理计算结合团簇展开方法系统研究了混合卤化物钙钛矿的结构、电子和光学性质，发现与传统半导体合金不同，混合卤化物钙钛矿在某些浓度下表现出很小甚至负的形成能，在高温下表现出可以忽略甚至负的带隙弯曲参数。结果表明，混合（I,Cl）钙钛矿在625 K以下的温度下很难形成，而混合（Br,Cl）和（I,Br）合金在室温下很容易形成。
Engineering halide perovskite through mixing halogen elements, such as CH3NH3PbI3-xClx and CH3NH3PbI3-xBrx, is a viable way to tune its electronic and optical properties. Despite many emerging experiments on mixed halide perovskites, the basic electronic and structural properties of the alloys have not been understood and some crucial questions remain, for example, how much Cl can be incorporated into CH3NH3PbI3 is still unclear. In this Letter, we chose CsPbX3 (X = I, Br, Cl) as an example and use a first-principle calculation together with cluster-expansion methods to systematically study the structural, electronic, and optical properties of mixed halide perovskites and find that unlike conventional semiconductor alloys, they exhibit many anomalous alloy properties such as small or even negative formation energies at some concentrations and negligible or even negative band gap bowing parameters at high temperature. We further show that mixed-(I,Cl) perovskite is hard to form at temperature below 625 K, whereas forming mixed-(Br,Cl) and (I,Br) alloys are easy at room temperature.