Large polarons in lead halide perovskites.
Large polarons in lead halide perovskites.
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DOI：
10.1126/sciadv.1701217
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发表时间：
2017-08
期刊：
影响因子：
13.6
通讯作者：
Zhu XY
中科院分区：
文献类型：
--
作者：
Miyata K;Meggiolaro D;Trinh MT;Joshi PP;Mosconi E;Jones SC;De Angelis F;Zhu XY
杂化和全无机卤化铅钙钛矿中的电荷载流子都形成了大的极化子。卤化铅钙钛矿具有优异的光电性能，具有明显的缺陷容忍性。这些性质可能可以用大极化子的形成来解释，但它们是如何形成的，以及有机阳离子是否必不可少，仍然是悬而未决的问题。我们提供了单晶溴化铅钙钛矿CH3NH3PbBr3和CsPbBr3中大极化子形成的直接时间域图。我们发现，无论阳离子类型如何，大极化子的形成主要来自PbBr3−骨架的形变。不同之处在于极化子的形成时间，在CH3NH3PbBr3(0.3ps)中，不到CsPbBr3(0.7ps)的一半。第一性原理计算证实了大极化子的形成，确定了铅-溴-铅的变形模式，并定量解释了CH3NH3PbBr3和CsPbBr3之间的速率差异。研究结果揭示了软[PbX3]−亚晶格在电荷载流子保护方面的总体优势，并表明使用全无机或混合阳离子卤化铅钙钛矿来克服不稳定性问题和调节电荷载流子保护和迁移率之间的平衡可能没有机械上的限制。
Charge carriers in both hybrid and all-inorganic lead halide perovskites form large polarons. Lead halide perovskites show marked defect tolerance responsible for their excellent optoelectronic properties. These properties might be explained by the formation of large polarons, but how they are formed and whether organic cations are essential remain open questions. We provide a direct time domain view of large polaron formation in single-crystal lead bromide perovskites CH3NH3PbBr3 and CsPbBr3. We found that large polaron forms predominantly from the deformation of the PbBr3− frameworks, irrespective of the cation type. The difference lies in the polaron formation time, which, in CH3NH3PbBr3 (0.3 ps), is less than half of that in CsPbBr3 (0.7 ps). First-principles calculations confirm large polaron formation, identify the Pb-Br-Pb deformation modes as responsible, and explain quantitatively the rate difference between CH3NH3PbBr3 and CsPbBr3. The findings reveal the general advantage of the soft [PbX3]− sublattice in charge carrier protection and suggest that there is likely no mechanistic limitations in using all-inorganic or mixed-cation lead halide perovskites to overcome instability problems and to tune the balance between charge carrier protection and mobility.
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