Low-frequency lattice phonons in halide perovskites explain high defect tolerance toward electron-hole recombination
Low-frequency lattice phonons in halide perovskites explain high defect tolerance toward electron-hole recombination
复制标题
卤化物钙钛矿中的低频晶格声子解释了电子空穴复合的高缺陷容限
DOI：
10.1126/sciadv.aaw7453
复制
发表时间：
2020-02-01
期刊：
影响因子：
13.6
通讯作者：
Saidi, Wissam A.
中科院分区：
文献类型：
--
作者：
Chu, Weibin;Zheng, Qijing;Saidi, Wissam A.
基于低成本溶液的金属卤化物钙钛矿（MHPs）合成总是会在系统中引入缺陷，这些缺陷可能形成Shockley-Read-Hall （SRH）电子-空穴复合中心，不利于太阳能转换效率。在这里，我们用从头算非绝热分子动力学研究了甲基卤化铅（MAPbI(3)）钙钛矿中由于天然点缺陷引起的非辐射重组过程。无论缺陷是引入浅带态还是深带态，我们都发现MAPbI(3)中的电荷重组并没有增强，这与SRH理论的预测相反。我们证明了这种对缺陷的强耐受性，从而导致SRH的击穿，是因为光生成的载流子只与低频声子耦合，并且电子和空穴态重叠微弱。这两个因素都明显降低了非绝热耦合。我们认为具有小体积模量的无机晶格的柔软性质是缺陷容忍度的关键，因此，这些发现对其他MHPs具有普遍性。
Low-cost solution-based synthesis of metal halide perovskites (MHPs) invariably introduces defects in the system, which could form Shockley-Read-Hall (SRH) electron-hole recombination centers detrimental to solar conversion efficiency. Here, we investigate the nonradiative recombination processes due to native point defects in methylammonium lead halide (MAPbI(3)) perovskites using ab initio nonadiabatic molecular dynamics within surface-hopping framework. Regardless of whether the defects introduce a shallow or deep band state, we find that charge recombination in MAPbI(3) is not enhanced, contrary to predictions from SRH theory. We demonstrate that this strong tolerance against defects, and hence the breakdown of SRH, arises because the photogenerated carriers are only coupled with low-frequency phonons and electron and hole states overlap weakly. Both factors appreciably decrease the nonadiabatic coupling. We argue that the soft nature of the inorganic lattice with small bulk modulus is key for defect tolerance, and hence, the findings are general to other MHPs.