Strain-induced effects in colloidal quantum dots: lifetime measurements and blinking statistics.
A series of samples of CdSe/Cd(x)Zn(1-x)S core/shell quantum dots have been synthesized in order to measure the influence of lattice-mismatch-induced strain on the photoluminescence (PL) and blinking behaviour. The PL spectra show a significant variation of the fluorescence wavelength even though the colloidal quantum dots (cQDs) are similar in size. The PL excitation spectra show a gradual splitting of the first exciton level as the proportion of Zn is increased in the shell and as the shell grows. On the other hand, blinking studies clearly demonstrate a significant dependence on the amount of Zn present in the shell. Distributions of on and off times go from the usual power-law distributions to power-law distributions with exponential cut-offs. These cut-offs become increasingly pronounced as the proportion of Zn increases. We interpret these results in the framework of diffusion-controlled electron transfer. Exciton relaxation lifetime measurements strongly suggest that lattice mismatch is responsible for a greater number of defects in core/shell cQDs. Therefore, strain and lattice mismatch are shown to be parameters of significant importance for the electronic structure of nanocrystals, influencing the photoluminescence, exciton relaxation lifetime and blinking behaviour.
Veilleux
V
V
Centre d'optique, photonique et laser (COPL), Université Laval, QC, Canada.
Lachance-Quirion
D
D
Doré
K
K
Landry
D B
DB
Charette
P G
PG
Allen
C Nì
CN