Characterising quantum dot concentrators

Luminescent collectors have advantages over geometric concentrators in that tracking is unnecessary and both direct and diffuse radiation can be collected. However, their development has been limited by the performance of luminescent dyes. The authors have recently proposed a novel concentrator in which the dyes are replaced by quantum dots (QDs). The advantages over dyes are: the absorption threshold can be tuned by choice of dot diameter, the red-shift between absorption and luminescence is related to the spread of dot sizes and high luminescence quantum efficiency (QE) has been observed. In this paper, the authors discuss how they have adapted a thermodynamic model to allow for re-absorption in QDs. They find that the amount of overlap of the absorption and luminescence has a strong effect on the efficiency. They show how to use the model to characterise the QDs and the concentrator by measuring the luminescence as a function of position