Atomistic and Electronic Origin of Phase Instability of Metal Halide Perovskites
Atomistic and Electronic Origin of Phase Instability of Metal Halide Perovskites
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DOI：
10.1021/acsaem.0c00791
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发表时间：
2020-12-28
影响因子：
6.4
通讯作者：
Tao, Shuxia
中科院分区：
文献类型：
--
作者：
Jiang, Junke;Liu, Feng;Tao, Shuxia
金属卤化物钙钛矿(MHPS)优异的光电性能引起了人们的广泛兴趣，并推动了其在光电子器件中的应用。尽管它们具有诱人的光电性能，但它们在环境条件下的低稳定性仍然是阻碍其大规模实际应用的主要挑战。特别是，一些MHPS经历了从钙钛矿到非钙钛矿的自发相变。通过混合阳离子或阴离子的组成工程已被广泛报道为有效地抑制这种不需要的相变。然而，稳定效应的原子和电子来源仍未被探索。在这里，我们用密度泛函理论计算了原始钙钛矿(FAPbI(3)、CsPbI3和CsSnI3)的非理想相变，揭示了混合化合物[Cs(X)Fa(1-x)PbI(3)、CsSnyPb1-yI3和CSSN(BrzI1-z)(3)]提高相稳定性的机理。我们发现，相变与钙钛矿和非钙钛矿相中M-X键和氢键(对于杂化组成)的相对强度有关。混合离子可以抑制这种相变，导致钙钛矿的键合强度增加或非钙钛矿的键合强度降低，或者抑制了锡铅混合钙钛矿的空位缺陷的形成。我们的结果对MHPS的相不稳定机理有了全面的理解，并为工程上相稳定的钙钛矿相成分的设计提供了规则。
The excellent optoelectronic properties of metal halide perovskites (MHPs) have attracted extensive scientific interest and boosted their application in optoelectronic devices. Despite their attractive optoelectronic properties, their poor stability under ambient conditions remains the major challenge, hindering their large-scale practical applications. In particular, some MHPs undergo spontaneous phase transitions from perovskites to nonperovskites. Compositional engineering via mixing cations or anions has been widely reported to be effective in suppressing such unwanted phase transitions. However, the atomistic and electronic origins of the stabilization effect remain unexplored. Here, by using density functional theory calculations, we provide insights for the undesired phase transition of pristine perovskites (FAPbI(3), CsPbI3, and CsSnI3) and reveal the mechanisms of the improved phase stability of the mixed compounds [Cs(x)FA(1-x)PbI(3), CsSnyPb1-yI3, and CsSn(BrzI1-z)(3)]. We identify that the phase transition is correlated with the relative strength of the M-X bonds as well as that of the hydrogen bonds (for hybrid compositions) in perovskite and nonperovskite phases. The phase transition can be suppressed by mixing ions, giving rise to either an increased bond strength for the perovskite or a decreased bond strength in their nonperovskite counterparts, or suppressed vacancy defect formation for Sn-Pb mixed perovskites. Our results present a comprehensive understanding of the mechanisms for the phase instability of MHPs and provide design rules for engineering phase-stable perovskite compositions.y