Influence of intrinsic defects on the structure and dynamics of the mixed Pb–Sn perovskite: first-principles DFT and NAMD simulations
Influence of intrinsic defects on the structure and dynamics of the mixed Pb–Sn perovskite: first-principles DFT and NAMD simulations
复制标题
固有缺陷对混合 Pb-Sn 钙钛矿结构和动力学的影响：第一性原理 DFT 和 NAMD 模拟
DOI：
10.1039/d1ta09027e
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发表时间：
2021
影响因子：
11.9
通讯作者：
Liang, WanZhen
中科院分区：
文献类型：
--
作者：
Liu, Qi;Li, Akang;Chu, Weibin;Prezhdo, Oleg V.;Liang, WanZhen
与纯Sn卤化物钙钛矿相比，混合的锡（Sn）和铅（Pb）钙钛矿组合物由于显著增强的材料稳定性和延长的载流子寿命而在钙钛矿光伏器件中显示出巨大的潜力。尽管越来越多的兴趣，光生电荷和本征点缺陷，如金属阳离子空位（VSn和VPb）和间隙卤素（iI）的行为，还没有得到很好的理解，在这类材料。我们报告的第一性原理密度泛函理论（DFT）计算结合从头算非绝热分子动力学（NAMD）模拟的静态和动态结构的MA2SnPbI6有和没有这些固有的缺陷。我们讨论了缺陷态的性质，揭示了本征点缺陷对MA2SnPbI6的结构、光电性能和载流子动力学的影响。iI缺陷通过产生提供新的复合途径的中间带隙状态而显著缩短载流子寿命。相比之下，空位缺陷对载流子寿命的影响要小得多。VSn和VPb都产生刚好低于价带最大值（VBM）的缺陷态，并且不改变带隙。它们通过改变VBM的能量色散和导带最低点（CBM）来影响载流子寿命。我们建议在钙钛矿的合成中应使用过量的阳离子，以避免间隙卤素缺陷的出现。
The mixed tin (Sn) and lead (Pb) perovskite compositions have shown great potential in perovskite photovoltaic devices due to the significantly enhanced material stability and prolonged carrier lifetime, compared to the pure Sn halide perovskites. In spite of the increasing interest, the behaviors of photo-generated charges and of the intrinsic point defects, such as the metal cation vacancies (VSn and VPb) and the interstitial halogen (iI), have not been well understood in this class of materials. We report first-principles density functional theory (DFT) calculations combined with ab initio non-adiabatic molecular dynamics (NAMD) simulations on the static and dynamic structures of MA2SnPbI6 with and without these intrinsic defects. We discuss the nature of the defect states and unveil the influence of the intrinsic point defects on the structure, optoelectronic properties, and charge carrier dynamics of MA2SnPbI6. The iI defect significantly shortens the carrier lifetime by creating mid-gap states that provide new recombination pathways. In comparison, the vacancy defects have much weaker influence on the carrier lifetime. Both VSn and VPb produce the defect states just below the valence band maxima (VBMs), and do not alter the band gap. They affect the carrier lifetime through changing the energy dispersions of VBMs and the conduction band minima (CBMs). We suggest that excess cations should be used in the synthesis of perovskites to avoid the appearance of interstitial halogen defects.