BARC/PUB/2022/0875

 
 

Exciton Dynamics in Colloidal CdS Quantum Dots with Intense and Stokes Shifted Photoluminescence in a Single Decay Channel

 
     
 
Author(s)

Gogoi, H.; Pathak, S. S.; Dasgupta, S.; Nath, S.; and others
(RPCD)

Source

Journal of Physical Chemistry Letters, 2022. Vol. 13: pp. 6770-6776

ABSTRACT

CdS quantum dots (QDs), synthesized by a sol−gel method, exhibit significantly Stokes shifted bright photoluminescence (PL), predominantly from the trap states. Surprisingly, the PL decay at the emission maximum is single-exponential. This is an unusual observation for as-prepared QDs and indicates a narrow distribution in the nature of trap states. A closer look reveals an additional fast component for the decays at shorter emission wave lengths, presumably due to the band edge emission, which remains elusive in the steady-state spectra. Indeed, a significantly narrower and blue-shifted emission band is observed in the decay-associated spectra. The contribution of this component to the steady-state PL intensity is shown to be over whelmed by that of the significantly stronger trap emission. Exciton dynamics in the quantum dots is elucidated using transient absorption spectra, in which the stimulated emission is observed even at low pump power.

 
 
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