Temperature Dependent Luminescent Decay Properties of CdTe Quantum Dot Monolayers: Impact of Concentration on Carrier Trapping

TL;DR

This study examines how temperature and concentration affect the luminescent decay and trapping mechanisms in CdTe quantum dot monolayers, revealing the need for an extended model to accurately describe high-temperature behavior.

Contribution

It introduces an extended model including trap states to better fit temperature-dependent luminescence decay data of CdTe quantum dots.

Findings

Trap state interaction efficiency increases with concentration.

A simple three-level model suffices only at low temperatures.

Extended model accurately fits data above 150 K.

Abstract

We have investigated the temperature dependence of the photoluminescence spectra and average photoluminescence decay rate of CdTe quantum dot monolayers of different sizes as a function of concentration in the range 77 K to 296 K. It is shown that a simple three level analytic model involving bright and dark exciton states can only describe the lower temperature data but is unable to satisfactorily fit the data over the full temperature range. An extended model which includes external trap states is necessary to fit the data above approximately 150 K. Parameters for the model are obtained using both temporal and spectral data. The model indicates that the efficiency of interaction with trap states increases as the QD monolayer concentration increases, which is likely due to an increase in the density of available traps.