Lin Kailai, Jasrasaria Dipti, Yoo Jason J, Bawendi Moungi, Utzat Hendrik, Rabani Eran
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02143, United States.
J Phys Chem Lett. 2023 Aug 17;14(32):7241-7248. doi: 10.1021/acs.jpclett.3c01630. Epub 2023 Aug 8.
Single-molecule photoluminescence (PL) spectroscopy of semiconductor nanocrystals (NCs) reveals the nature of exciton-phonon interactions in NCs. Understanding the homogeneous spectral line shapes and their temperature dependence remains an open problem. Here, we develop an atomistic model to describe the PL spectrum of NCs, accounting for excitonic effects, phonon dispersion relations, and exciton-phonon couplings. We validate our model using single-NC measurements on CdSe/CdS NCs from = 4 to 290 K, and we find that the slightly asymmetric main peak at low temperatures is comprised of a narrow zero-phonon line (ZPL) and acoustic phonon sidebands. Furthermore, we identify the specific phonon modes that give rise to the optical phonon sidebands. At temperatures above 200 K, the spectral line width shows a stronger dependence upon the temperature, which we demonstrate to be correlated with higher order exciton-phonon couplings. We also identify the line width dependence upon reorganization energy, NC core sizes, and shell thicknesses.
半导体纳米晶体（NCs）的单分子光致发光（PL）光谱揭示了纳米晶体中激子 - 声子相互作用的本质。理解均匀光谱线形状及其温度依赖性仍然是一个悬而未决的问题。在这里，我们开发了一个原子模型来描述纳米晶体的PL光谱，该模型考虑了激子效应、声子色散关系和激子 - 声子耦合。我们使用对CdSe/CdS纳米晶体在4至290 K范围内的单纳米晶体测量来验证我们的模型，并且我们发现低温下略微不对称的主峰由一条窄的零声子线（ZPL）和声学声子边带组成。此外，我们确定了产生光学声子边带的特定声子模式。在高于200 K的温度下，光谱线宽对温度的依赖性更强，我们证明这与高阶激子 - 声子耦合相关。我们还确定了线宽对重组能、纳米晶体核心尺寸和壳层厚度的依赖性。
