研究目的
Investigating the exciton-phonon coupling and the role of trap states formed at the interface of structural dislocations in CdSe quantum dots synthesized by kinetic growth method.
研究成果
The study concludes that temperature dependent PL spectroscopy is an efficient tool for monitoring trap states in QDs. The presence of interface states associated with crystal dislocation in aliquoted QDs samples and the lack of systematics in exciton-phonon coupling with size of QDs are due to structural defects introduced by aliquoting. Uninterrupted reaction for long time results in QDs free of such defects due to annealing in solution phase.
研究不足
The study is limited by the resource-intensive techniques required for investigating structural defects in nanocrystals. The methodology for easy identification of such defects needs further development to eliminate their adverse effects on optical properties of QDs.
1：Experimental Design and Method Selection:
The synthesis method for CdSe QDs was adapted and modified from the literature. A mixture of CdO, oleic acid, and 1-octadecene was heated to 280°C, then cooled to 240°C before adding a solution of Selenium metal powder in Trioctylphosphine and 1-octadecene. Aliquots were collected at different time intervals for spectroscopic measurements.
2：Sample Selection and Data Sources:
QD samples were size sorted by aliquoting at different time intervals during the reaction.
3：List of Experimental Equipment and Materials:
PerkinElmer LAMBDA 950 UV/Vis/NIR spectrometer, Varian Cary Eclipse Fluorescence Spectrophotometer, 325 nm He-Cd laser, Acton Spectra Pro 2500i monochromator, back thinned cooled CCD detector.
4：Experimental Procedures and Operational Workflow:
Absorption and PL spectra at room temperature were recorded for QDs dispersed in chloroform. For temperature dependent PL measurements, samples were drop casted on silicon substrate and cooled with closed cycle He-refrigerator.
5：Data Analysis Methods:
Temperature dependence of PL intensity and line width were analyzed to extract parameters related to inhomogeneous line broadening, exciton-phonon interaction, and defect states.
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