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Insight into Strain Effects on Band Alignment Shifts, Carrier Localization and Recombination Kinetics in CdTe/CdS Core/Shell Quantum Dots
- Source :
- Journal of the American Chemical Society. 137:2073-2084
- Publication Year :
- 2015
- Publisher :
- American Chemical Society (ACS), 2015.
-
Abstract
- The impact of strain on the optical properties of semiconductor quantum dots (QDs) is fundamentally important while still awaiting detailed investigation. CdTe/CdS core/shell QDs represent a typical strained system due to the substantial lattice mismatch between CdTe and CdS. To probe the strain-related effects, aqueous CdTe/CdS QDs were synthesized by coating different sized CdTe QD cores with CdS shells upon the thermal decomposition of glutathione as a sulfur source under reflux. The shell growth was carefully monitored by both steady-state absorption and fluorescence spectroscopy and transient fluorescence spectroscopy. In combination with structural analysis, the band alignments as a consequence of the strain were modified based on band deformation potential theory. By further taking account of these strain-induced band shifts, the effective mass approximation (EMA) model was modified to simulate the electronic structure, carrier spatial localization, and electron-hole wave function overlap for comparing with experimentally derived results. In particular, the electron/hole eigen energies were predicted for a range of structures with different CdTe core sizes and different CdS shell thicknesses. The overlap of electron and hole wave functions was further simulated to reveal the impact of strain on the electron-hole recombination kinetics as the electron wave function progressively shifts into the CdS shell region while the hole wave function remains heavily localized in CdTe core upon the shell growth. The excellent agreement between the strain-modified EMA model with the experimental data suggests that strain exhibits remarkable effects on the optical properties of mismatched core/shell QDs by altering the electronic structure of the system.
- Subjects :
- Models, Molecular
Optical Phenomena
Molecular Conformation
Shell (structure)
Analytical chemistry
Electrons
Electronic structure
Sulfides
Biochemistry
Molecular physics
Catalysis
Fluorescence spectroscopy
Colloid and Surface Chemistry
Quantum Dots
Cadmium Compounds
Absorption (electromagnetic radiation)
Wave function
Chemistry
technology, industry, and agriculture
General Chemistry
equipment and supplies
Cadmium telluride photovoltaics
Kinetics
Quantum dot
Quantum Theory
Tellurium
Deformation (engineering)
Subjects
Details
- ISSN :
- 15205126 and 00027863
- Volume :
- 137
- Database :
- OpenAIRE
- Journal :
- Journal of the American Chemical Society
- Accession number :
- edsair.doi.dedup.....a1b2f4daec881d46c739c0b65ddb7c98