Phonon coherences reveal the polaronic character of excitons in two-dimensional lead halide perovskites
Phonon coherences reveal the polaronic character of excitons in two-dimensional lead halide perovskites
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DOI：
10.1016/0022-3093(95)00355-x
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发表时间：
2019-04-01
期刊：
影响因子：
41.2
通讯作者：
Kandada, Ajay Ram Srimath
中科院分区：
文献类型：
--
作者：
Thouin, Felix;Valverde-Chavez, David A.;Kandada, Ajay Ram Srimath
由于晶体的离子特性和分子部分与无机网络之间的非共价键产生的柔软性，混合有机-无机半导体具有复杂的晶格动力学特征。在这里，我们建立了这样的动态结构的复杂性，在一个原型的二维碘化铅钙钛矿引起共存的各种激子共振，每个具有不同程度的极化特征。通过高分辨率的共振脉冲受激拉曼光谱，我们确定振动波包动力学演化沿着不同的构型坐标为不同的激子和光载流子。采用密度泛函理论计算，我们分配所观察到的相干振动模式的各种低频（小于或接近50厘米（-1））的光学声子涉及碘化铅层中的运动。因此，我们得出结论，不同的激子诱导特定的晶格重组，这是极化子结合的签名。这种对涉及全局中性初级光激发的能量/构型景观的洞察可能与更广泛的新兴混合半导体材料有关。
Hybrid organic-inorganic semiconductors feature complex lattice dynamics due to the ionic character of the crystal and the softness arising from non-covalent bonds between molecular moieties and the inorganic network. Here we establish that such dynamic structural complexity in a prototypical two-dimensional lead iodide perovskite gives rise to the coexistence of diverse excitonic resonances, each with a distinct degree of polaronic character. By means of high-resolution resonant impulsive stimulated Raman spectroscopy, we identify vibrational wavepacket dynamics that evolve along different configurational coordinates for distinct excitons and photocarriers. Employing density functional theory calculations, we assign the observed coherent vibrational modes to various low-frequency (less than or similar to 50 cm(-1)) optical phonons involving motion in the lead iodide layers. We thus conclude that different excitons induce specific lattice reorganizations, which are signatures of polaronic binding. This insight into the energetic/configurational landscape involving globally neutral primary photoexcitations may be relevant to a broader class of emerging hybrid semiconductor materials.