Journal of Physical Studies 14(2), Article 2701 [10 pages] (2010)
DOI: https://doi.org/10.30970/jps.14.2701

STOKES SHIFT IN CdTe QUANTUM DOTS

I. M. Kupchak¹, D. V. Korbutyak¹, S. M. Kalytchuk¹, Yu. V. Kryuchenko¹, A. Chkrebtii²
¹V. Lashkaryov Institute of Semiconductor Physics, NAS Ukraine,
Nauky pr. 45, Kyiv, 03028, e-mail: div47@isp.kiev.ua
²University of Ontario Institute of Technology, 2000 Simcoe Street North,
Oshawa, ON, Canada, L1H 7K4

Absorption and photoluminescence spectra of colloidal CdTe quantum dots (QD) as well as CdTe QDs incorporated into PDDA polymer matrix (polidialildymetylamoniy chloride) have been studied experimentally. A theoretical model of resonant (due to singlet-triplet splitting of ‟bright” and ‟dark” exciton states) and non-resonant Stokes shift (due to exciton-phonon interaction and the QD size dispersion) has been developed. The calculated Stokes shift depends on mean QD size, QD size dispersion, characteristics of phonon spectrum and the height of potential barrier for charge carriers at QD-environment heterointerface. It has been shown that in the studied QD size range from 3.1 nm to 1.8 nm theoretically calculated Stokes shifts for colloidal CdTe QDs are close to the experimentally measured values from 170 to 200 meV which correspond to the energy distance between the absorption and photoluminescence band peaks. To explain the giant Stokes shift $\sim0.6$ eV in CdTe QDs incorporated into the polymer matrix an assumption has been made on the formation of additional QD interface states participating in the process of light absorption.

PACS number(s): 73.20.Mf, 73.21.La, 78.67.Hc, 78.30.Fs