Two-dimensional Förster resonant energy transfer in a mixed quantum dot monolayer: Experiment and theory

Abstract

Energy transfer in monolayers of CdTe quantum dots (QDs), comprised of QDs of two different sizes, has been investigated. Förster resonant energy transfer (FRET) from QD donors to QD acceptors was observed and characterized using absorption and photoluminescence spectroscopy, as well as time-resolved photoluminescence measurements. A theory of FRET in two dimensions, taking into account random donor and acceptor distributions and exclusion zones around the donors, was used to fit the donor decays in mixed films. In this way the value of the Förster radius calculated from the spectral overlap was confirmed and a method for determining all important FRET parameters for QD monolayers from time-resolved photoluminescence measurements alone was found. The dependence of the measured FRET efficiency on the acceptor concentration can also be explained within this theory. Additionally, the rise in the acceptor emission enhancement for low acceptor:donor ratios indicates that energy is not only transferred from nearest neighbors but that donors at larger distances also contribute.