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Auger and Carrier Trapping Dynamics in Core/Shell Quantum Dots Having Sharp and Alloyed Interfaces
Gary A Beane1, Ke Gong1, David F Kelley1
1Chemistry and Chemical Biology, University of California Merced , 5200 North Lake Road, Merced, California 95343, United States.
ACS Nano
|February 20, 2016
Summary
Interface sharpness in CdSe/ZnSe quantum dots controls excited state dynamics. A sharp interface enhances fast biexciton decay via Auger recombination, linked to lattice strain.
Area of Science:
- Quantum dots
- Materials science
- Spectroscopy
Background:
- Cadmium selenide/zinc selenide (CdSe/ZnSe) core/shell quantum dots are synthesized with controlled interface sharpness.
- Interface sharpness is crucial for tuning excited-state properties in nanomaterials.
Purpose of the Study:
- To investigate the influence of core-shell interface sharpness on excited-state dynamics in CdSe/ZnSe quantum dots.
- To correlate interface properties with biexciton recombination pathways.
Main Methods:
- Synthesis of CdSe/ZnSe core/shell quantum dots with varying interface sharpness via controlled temperature and annealing.
- Characterization using transmission electron microscopy (TEM) and absorption spectroscopy.
- Time-resolved absorption spectroscopy to measure one- and two-photon dynamics.
Main Results:
- Biexcitons exhibit biexponential decay, with fast and slow components.
- A sharper core-shell interface correlates with a larger fast decay component amplitude.
- Annealing softens the interface, reducing lattice strain and diminishing the fast decay component.
- The slow decay component, attributed to Auger recombination of band-edge carriers, remains largely unaffected by interface modification.
Conclusions:
- Interface sharpness in CdSe/ZnSe quantum dots is a critical factor in controlling excited-state dynamics.
- Lattice strain at sharp interfaces contributes to defect-mediated Auger recombination.
- Controlled interface engineering offers a pathway to tune quantum dot photophysics.
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