Strandell Dallas, Mora Perez Carlos, Wu Yifan, Prezhdo Oleg V, Kambhampati Patanjali
Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada.
Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
Nano Lett. 2024 Jan 10;24(1):61-66. doi: 10.1021/acs.nanolett.3c03180. Epub 2023 Dec 19.
The decay of excited states via radiative and nonradiative paths is well understood in molecules and bulk semiconductors but less so in nanocrystals. Here, we perform time-resolved photoluminescence (t-PL) experiments on CsPbBr metal-halide perovskite nanocrystals, with a time resolution of 3 ps, sufficient to observe the decay of both excitons and biexcitons as a function of temperature. The striking result is that the radiative rate constant of the single exciton increases at low temperatures with an exponential functional form, suggesting quantum coherent effects with dephasing at high temperatures. The opposing directions of the radiative and nonradiative decay rate constants enable enhanced brightening of PL from excitons to biexcitons due to quantum effects, promoting a faster approach to the quantum theoretical limits of light emission. quantum dynamics simulations reproduce the experimental observations of radiation controlled by quantum spatial coherence enhanced at low temperatures.
激发态通过辐射和非辐射路径的衰变在分子和体相半导体中已得到很好的理解，但在纳米晶体中了解较少。在此，我们对CsPbBr金属卤化物钙钛矿纳米晶体进行了时间分辨光致发光（t-PL）实验，时间分辨率为3皮秒，足以观察到激子和双激子的衰变随温度的变化。引人注目的结果是，单激子的辐射速率常数在低温下以指数函数形式增加，这表明存在量子相干效应，且在高温下会发生退相。辐射和非辐射衰变速率常数的相反方向使得由于量子效应，从激子到双激子的光致发光增强变亮，促进了更快地接近发光的量子理论极限。量子动力学模拟重现了低温下增强的量子空间相干控制辐射的实验观测结果。
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