Rotational Energy Barriers and Relaxation Times of the Organic Cation in Cubic Methylammonium Lead/Tin Halide Perovskites from First Principles
Rotational Energy Barriers and Relaxation Times of the Organic Cation in Cubic Methylammonium Lead/Tin Halide Perovskites from First Principles
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DOI：
10.1021/acs.jpcc.7b04589
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发表时间：
2017-06
影响因子：
3.7
通讯作者：
S. Kanno;Y. Imamura;A. Saeki;M. Hada
中科院分区：
文献类型：
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作者：
S. Kanno;Y. Imamura;A. Saeki;M. Hada
有机-无机杂化钙钛矿（如CH3NH3PbI3）中的有机阳离子动力学已被报道在载流子寿命和铁电性中起重要作用，但尚未得到充分的理论研究。我们从第一性原理出发，考虑PbX6或SnX6无机骨架的完全弛豫，比较了MABX3 （B = Pb或Sn， X = Cl， Br或I）立方相中甲基铵阳离子（CH3NH3， MA）的旋转能垒和弛豫时间。我们成功地再现了MA的C-N轴的4重旋转对称（C4）的实验旋转势垒。我们的计算表明，MA可以相对自由地旋转，因为柔性无机骨架表现出类似液体的行为，通过氢键诱导金属阳离子(B)和卤素(X)的协同位移，并降低了旋转势垒高度。我们还证明了MA的旋转势垒（6-11 kJ mol-1）与温度密切相关。
Organic cation dynamics in organic–inorganic hybrid perovskite such as CH3NH3PbI3 have been reported to play an important role in the charge carrier lifetime and ferroelectricity but have not been fully investigated by theoretical approach. We have compared the rotational energy barriers and relaxation times of the methylammonium cation (CH3NH3, MA) in the cubic phases of MABX3 (B = Pb or Sn, X = Cl, Br, or I) by considering full relaxation of the PbX6 or SnX6 inorganic framework from first principles. We successfully reproduced the experimental rotational barrier for the 4-fold rotational symmetry (C4) of the C—N axis of MA. Our calculations suggest that the MA can rotate relatively freely because the flexible inorganic framework exhibits liquid-like behavior, which induces cooperative displacement of the metal cation (B) and the halogen (X) via a hydrogen bond and lowers the rotational barrier height. We also demonstrate that the rotational barrier of MA (6–11 kJ mol–1), which is closely correlated to t...