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Updated: May 16, 2026

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Published on: October 13, 2017
Probing Hole-State Splitting and Relaxation in Gradient Alloyed CdSe Core-Shell Quantum Dots Using Two-Dimensional
Xiaolu Bai1, Chenhui Wang2, Weijian Li1
1School of Optics and Photonics, Beijing Institute of Technology, Beijing, 100081, China.
Abstract:
Gradient alloyed Type-I CdSe quantum dots have been demonstrated to suppress Auger recombination, enabling highly efficient photoluminescence and enhanced optical gain. However, the influence of these gradient-alloyed shells on the band-edge structure and associated relaxation mechanisms remains poorly understood. In this work, we employed two-dimensional electronic spectroscopy to resolve the band-edge hole structure and the corresponding relaxation mechanism of continuously graded CdSe/CdxZn1-xSe/ZnSe core-shell quantum dots (QDs). Analysis of an early-time two-dimensional electronic spectrum resolved three band-edge optical transitions, which are assigned as 1Se-2Shh, 1Se-1Slh, and 1Se-1Shh excitons. These findings suggest that the gradient alloyed shells on CdSe quantum dots cause symmetry breaking, which results in the light-hole and heavy-hole states splitting. Furthermore, ultrafast (<1 ps) relaxation processes via hole cooling across these three hole states are observed. The hole-state splitting provides a spectroscopic basis for the observed cooling dynamics and may serve as a contributing factor to the enhancement of photoluminescence and optical gain, offering a potential pathway for optimizing excitonic structure in next-generation QD-based optoelectronic devices.
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