Bandgap of the core-shell CdSe/ZnS nanocrystal within the temperature range 300-373 K

The bandgap of a core-shell CdSe/ZnS quantum dot (QD) is investigated within a temperature range 300-373 K. In this study, the visible absorption and photoluminescence spectra of the QD dispersed in toluene are measured. The obtained results indicate a red shift of 4-6 nm of the peak wavelength associated with a shrinking bandgap of the QD, as the temperature increases from 300 to 373 K. Varshni's law commonly used to describe the bandgap of bulk semiconductors is found also applicable to the QD materials mentioned. Varshni's coefficients are determined as alpha = (2.0 +/- 0.2) x 10(-4) eV/K, and beta = 200 +/- 30 K, for the temperature range 300-373 K. This shows a smaller alpha but a similar beta value in comparison with the bulk semiconductors, suggesting a better thermal stability of the QD. (C) 2009 Elsevier B.V. All rights reserved.