Cohen Ayala V, Egger David A, Rappe Andrew M, Kronik Leeor
Department of Materials and Interfaces , Weizmann Institute of Science , Rehovoth 76100 , Israel.
Institute of Theoretical Physics , University of Regensburg , 93040 Regensburg , Germany.
J Phys Chem Lett. 2019 Aug 15;10(16):4490-4498. doi: 10.1021/acs.jpclett.9b01855. Epub 2019 Jul 25.
We consider the Br vacancy in CsPbBr as a prototype for the impact of structural dynamics on defect energetics in halide perovskites (HaPs). Using first-principles molecular dynamics based on density functional theory, we find that the static picture of defect energetics breaks down; the energy level associated with a Br vacancy is found to be intrinsically dynamic, oscillating by as much as 1 eV on the picosecond time scale at room temperature. These significant energy fluctuations are correlated with the distance between the neighboring Pb atoms across the vacancy and with the electrostatic potential at these Pb atomic sites. We expect this unusually strong coupling of structural dynamics and defect energetics to bear important implications for both experimental and theoretical analyses of defect characteristics in HaPs. It may also hold significant ramifications for carrier transport and defect tolerance in this class of photovoltaic materials.
我们将CsPbBr中的Br空位视为结构动力学对卤化物钙钛矿（HaPs）中缺陷能量学影响的一个范例。基于密度泛函理论使用第一性原理分子动力学，我们发现缺陷能量学的静态图景不再成立；与Br空位相关的能级本质上是动态的，在室温下的皮秒时间尺度上振荡幅度高达1 eV。这些显著的能量波动与空位两侧相邻Pb原子之间的距离以及这些Pb原子位点处的静电势相关。我们预计结构动力学与缺陷能量学之间这种异常强的耦合对HaPs中缺陷特性的实验和理论分析都具有重要意义。它可能对这类光伏材料中的载流子传输和缺陷容忍度也有重大影响。
