Exploring the Electronic Band Structure of Organometal Halide Perovskite via Photoluminescence Anisotropy of Individual Nanocrystals.
Exploring the Electronic Band Structure of Organometal Halide Perovskite via Photoluminescence Anisotropy of Individual Nanocrystals.
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DOI：
10.1021/acs.nanolett.6b02012
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发表时间：
2016-08
期刊：
影响因子：
10.8
通讯作者：
Daniela Täuber;A. Dobrovolsky;Rafael Camacho;I. Scheblykin
中科院分区：
文献类型：
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作者：
Daniela Täuber;A. Dobrovolsky;Rafael Camacho;I. Scheblykin
了解有机金属卤化物钙钛矿、蓬勃发展的光伏材料和发光材料中的电子过程需要解开它们电子跃迁的起源。光偏振研究可以提供有关跃迁偶极矩方向的重要信息。研究单个甲基铵三碘化铅钙钛矿纳米晶体使我们能够通过整体平均检测隐藏在大块样品中的光致发光强度和光致发光激发的偏振。晶体的偏振特性与其光致发光光谱和电子显微镜图像相关。我们认为 PbI6 八面体的畸变导致了靠近能带边缘的电子能带结构的特殊性。即，最低能带跃迁具有沿顶端 Pb-I-Pb 键的跃迁偶极矩，导致偏振光致发光。带隙之上的光致发光的激发是非偏振的，因为它涉及在钙钛矿八面体的顶角和赤道方向上离域的分子轨道。令人惊讶的是，77 K 下的陷阱辅助发射的偏振与带隙发射类似。
Understanding electronic processes in organometal halide perovskites, flourishing photovoltaic, and emitting materials requires unraveling the origin of their electronic transitions. Light polarization studies can provide important information regarding transition dipole moment orientations. Investigating individual methylammonium lead triiodide perovskite nanocrystals enabled us to detect the polarization of photoluminescence intensity and photoluminescence excitation, hidden in bulk samples by ensemble averaging. Polarization properties of the crystals were correlated with their photoluminescence spectra and electron microscopy images. We propose that distortion of PbI6 octahedra leads to peculiarities of the electronic band structure close to the band-edge. Namely, the lowest band transition possesses a transition dipole moment along the apical Pb-I-Pb bond resulting in polarized photoluminescence. Excitation of photoluminescence above the bandgap is unpolarized because it involves molecular orbitals delocalized both in the apical and equatorial directions of the perovskite octahedron. Trap-assisted emission at 77 K, rather surprisingly, was polarized similar to the bandgap emission.