Spectral and Dynamical Properties of Single Excitons, Biexcitons, and Trions in Cesium-Lead-Halide Perovskite Quantum Dots
Spectral and Dynamical Properties of Single Excitons, Biexcitons, and Trions in Cesium-Lead-Halide Perovskite Quantum Dots
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DOI：
10.1021/acs.nanolett.5b05077
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发表时间：
2016-04-01
期刊：
影响因子：
10.8
通讯作者：
Klimov, Victor I.
中科院分区：
文献类型：
--
作者：
Makarov, Nikolay S.;Guo, Shaojun;Klimov, Victor I.
有机无机卤化铅钙钛矿由于其异常强大的光伏性能而成为最近人们强烈关注的主题。钙钛矿家族的新成员是全无机铯铅卤化物钙钛矿纳米晶体或量子点，通过中温胶体合成制造。虽然这些纳米材料最近才被引入研究界，但它们已经显示出了从颜色转换磷光体和发光二极管到激光器，甚至室温单光子源等一系列应用的前景。关于钙钛矿量子点光学性质的知识仍然非常不完整。在这里，我们应用各种时间分辨光谱技术对 CsPbX3 纳米晶中单激子态和多激子态的光谱和动力学特性进行全面研究，其中 X 是 Br、I 或其混合物。具体来说，我们测量激子辐射寿命、吸收截面，并推导带边电子和空穴态的简并性。我们还表征了带内冷却和非辐射俄歇复合的速率，并评估了激子耦合的强度。这项工作的总体结论是，Cs Pb 卤化物量子点的光谱特性与 CdSe 和 PbSe 等更传统半导体的量子点非常相似。与此同时，我们观察到一些区别，例如，卤化物特性对辐射寿命的明显影响，双激子俄歇寿命显着缩短，以及其尺寸依赖性与先前在许多传统纳米晶体系统中观察到的“通用体积缩放”的明显偏差。钙钛矿量子点的俄歇衰变效率高，不利于其在发光器件和激光器中的潜在应用。这表明需要开发有效抑制这些纳米材料中俄歇重组的方法，或许可以利用之前对 II VI 纳米晶体的研究获得的见解。
Organic inorganic lead-halide perovskites have been the subject of recent intense interest due to their unusually strong photovoltaic performance. A new addition to the perovskite family is all-inorganic Cs Pb-halide perovskite nanocrystals, or quantum dots, fabricated via a moderate temperature colloidal synthesis. While being only recently introduced to the research community, these nanomaterials have already shown promise for a range of applications from color-converting phosphors and light-emitting diodes to lasers, and even room-temperature single-photon sources. Knowledge of the optical properties of perovskite quantum dots still remains vastly incomplete. Here we apply various time resolved spectroscopic techniques to conduct a comprehensive study of spectral and dynamical characteristics of single- and multiexciton states in CsPbX3 nanocrystals with X being either Br, I, or their mixture. Specifically, we measure exciton radiative lifetimes, absorption cross-sections, and derive the degeneracies of the band-edge electron and hole states. We also characterize the rates of intraband cooling and nonradiative Auger recombination and evaluate the strength of exciton exciton coupling. The overall conclusion of this work is that spectroscopic properties of Cs Pb-halide quantum dots are largely similar to those of quantum dots of more traditional semiconductors such as CdSe and PbSe. At the same time, we observe some distinctions including, for example, an appreciable effect of the halide identity on radiative lifetimes, considerably shorter biexciton Auger lifetimes, and apparent deviation of their size dependence from the "universal volume scaling" previously observed for many traditional nanocrystal systems. The high efficiency of Auger decay in perovskite quantum dots is detrimental to their prospective applications in light-emitting devices and lasers. This points toward the need for the development of approaches for effective suppression of Auger recombination in these nanomaterials, using perhaps insights gained from previous studies of II VI nanocrystals.