Electron–Phonon Couplings Inherent in Polarons Drive Exciton Dynamics in Two-Dimensional Metal-Halide Perovskites
Electron–Phonon Couplings Inherent in Polarons Drive Exciton Dynamics in Two-Dimensional Metal-Halide Perovskites
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DOI：
10.1021/acs.chemmater.9b02267
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发表时间：
2019-06
影响因子：
8.6
通讯作者：
F. Thouin;A. R. Srimath Kandada;David A. Valverde-Ch'avez;D. Cortecchia;I. Bargigia;A. Petrozza;Xunmo Yang;E. Bittner;Carlos Silva
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文献类型：
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作者：
F. Thouin;A. R. Srimath Kandada;David A. Valverde-Ch'avez;D. Cortecchia;I. Bargigia;A. Petrozza;Xunmo Yang;E. Bittner;Carlos Silva
我们报告了单层二维碘化铅钙钛矿中光载流子注入后的激子形成和弛豫动力学。我们通过时间分辨光致发光和瞬态吸收光谱探测了四种不同激子共振的时间演化，发现在 5\,K 时，激子子集在 $\lesssim$ 1-ps 时间尺度上形成，并且这些激子随后在 $\sim$ 5--10\,ps 上弛豫为较低能量激子，并在 $<$100\,K 上具有明显的温度依赖性。我们实施模式投影分析，确定所有观察到的频率为 $\leq$50\,cm$^{-1}$ 的声子对激子间非绝热耦合的相对贡献，这反过来又决定了激子弛豫速率。该分析对参与极化晶格畸变的声子对激子相互转换动力学的相对贡献进行排序，从而确定它们在激子态非绝热混合中的作用，以及在激子弛豫率中的作用。
We report on the exciton formation and relaxation dynamics following photocarrier injection in a single-layer two-dimensional lead-iodide perovskite. We probe the time evolution of four distinct exciton resonances by means of time-resolved photoluminescence and transient absorption spectroscopies, and find that at 5\,K a subset of excitons form on a $\lesssim$ 1-ps timescale, and that these relax subsequently to lower-energy excitons on $\sim$ 5--10\,ps with a marked temperature dependence over $<$ 100\,K. We implement a mode projection analysis that determines the relative contribution of all observed phonons with frequency $\leq$50\,cm$^{-1}$ to inter-exciton nonadiabatic coupling, which in turn determines the rate of exciton relaxation. This analysis ranks the relative contribution of the phonons that participate in polaronic lattice distortions to the exciton inter-conversion dynamics and thus establishes their role in the nonadiabatic mixing of exciton states, and this in the exciton relaxation rate.