Monitoring Electron-Phonon Interactions in Lead-Halide Perovskites Using Time-Resolved THz Spectroscopy.
Monitoring Electron-Phonon Interactions in Lead-Halide Perovskites Using Time-Resolved THz Spectroscopy.
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DOI：
10.1021/acsnano.9b02049
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发表时间：
2019-07
期刊：
影响因子：
17.1
通讯作者：
Daming Zhao;Hongwei Hu;R. Haselsberger;R. Marcus;M. Michel-beyerle;Y. Lam;Jian-Xin Zhu;C. La-o-vorakiat;M. Beard;E. Chia
中科院分区：
文献类型：
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作者：
Daming Zhao;Hongwei Hu;R. Haselsberger;R. Marcus;M. Michel-beyerle;Y. Lam;Jian-Xin Zhu;C. La-o-vorakiat;M. Beard;E. Chia
卤化铅钙钛矿半导体在卤化铅亚晶格内具有低频声子模式，因此被认为是软的。软晶格被认为是重要的，在定义他们有趣的光电性能。电子-声子耦合控制热载流子弛豫、载流子迁移率、载流子寿命以及其他重要的电子特性。直接观察自由电荷载流子和声子之间的相互作用可以提供声子如何影响这些性质的细节，例如激子种群和其他集体模式。在这里，我们观察到一个微妙的相互作用之间的载流子，声子和激子在混合阳离子和混合卤化物钙钛矿薄膜，同时解决时间分辨太赫兹光电导谱中的电荷载流子和声子的贡献。我们能够直接观察到的声子人口在载流子冷却过程中的增加，并讨论如何热平衡人口的载流子和声子调制的载流子输运性质，以及减少人口的带尾内的载流子。我们也能够直接观察到自由载流子的形成时，激子与声子相互作用和解离，并描述如何自由载流子和激子人口交换通过声子相互作用。最后，我们还解决了时间如何通过库仑相互作用在低温和室温下的载体筛选。我们的研究揭示了电荷载流子如何与低能声子相互作用，并讨论了影响。
Lead-halide perovskite semiconductors have low-frequency phonon modes within the lead-halide sublattice and thus are considered to be soft. The soft lattice is considered to be important in defining their interesting opto-electronic properties. Electron-phonon coupling governs hot-carrier relaxation, carrier mobilities, carrier lifetimes, among other important electronic characteristics. Directly observing the interplay between free-charge carriers and phonons can provide details on how phonons impact these properties, e.g. exciton populations and other collective modes. Here, we observe a delicate interplay among carriers, phonons and excitons in mixed-cation and mixed-halide perovskite films by simultaneously resolving the contribution of charge carriers and phonons in the time-resolved terahertz photoconductivity spectra. We are able to observe directly the increase in phonon population during carrier cooling and discuss how thermal equilibrium populations of carriers and phonons modulate the carrier transport properties, as well as reduce the population of carriers within band tails. We are also able to observe directly the formation of free-charge carriers when excitons interact with phonons and dissociate, and to describe how free carriers and exciton populations exchange through phonon interactions. Finally, we also time-resolve how the carriers are screened via the Coulomb interaction at low and room temperatures. Our studies shed light on how charge carriers interact with the low-energy phonons and discuss implications.