Ultrafast exciton transport at early times in quantum dot solids.
Ultrafast exciton transport at early times in quantum dot solids.
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量子点固体早期的超快激子传输。
DOI：
10.1038/s41563-022-01204-6
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发表时间：
2022
期刊：
影响因子：
41.2
通讯作者：
Zhang Z
中科院分区：
文献类型：
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作者：
Zhang Z
量子点（QD）固体是用于开发一系列光电器件的新兴平台。因此，理解激子动力学对于开发和优化QD器件至关重要。在这里，使用瞬态吸收显微镜，我们揭示了初始激子动力学量子点与飞秒时间尺度。我们观察到高激子扩散率（~ 102 cm ~ 2s ~（-1））在铅硫族化物量子点在光激发后的前几百飞秒内，随后过渡到较慢的制度（~10 ~（-1）~ 1cm ~ 2s ~（-1））。具有较大点间距离的量子点固体表现出较高的初始扩散率和延迟过渡到较慢的制度，而较高的量子点堆积密度和异质性加速这种转变。快速传输制度只发生在激子玻尔半径远大于量子点尺寸的材料，这表明在这个制度的离域激子的运输和过渡到较慢的运输激子本地化。这些发现提出了控制量子点固体光电性质的途径。
Quantum dot (QD) solids are an emerging platform for developing a range of optoelectronic devices. Thus, understanding exciton dynamics is essential towards developing and optimizing QD devices. Here, using transient absorption microscopy, we reveal the initial exciton dynamics in QDs with femtosecond timescales. We observe high exciton diffusivity (~102cm2s–1) in lead chalcogenide QDs within the first few hundred femtoseconds after photoexcitation followed by a transition to a slower regime (~10–1–1 cm2s–1). QD solids with larger interdot distances exhibit higher initial diffusivity and a delayed transition to the slower regime, while higher QD packing density and heterogeneity accelerate this transition. The fast transport regime occurs only in materials with exciton Bohr radii much larger than the QD sizes, suggesting the transport of delocalized excitons in this regime and a transition to slower transport governed by exciton localization. These findings suggest routes to control the optoelectronic properties of QD solids.