Ray-trace modelling of reflectors for quantum dot solar concentrators

Quantum Dot Solar Concentrators (QDSCs) are static, non-imaging concentrators which do not require expensive solar tracking and concentrate both direct and diffuse light. Optical efficiencies (η_opt) and concentration ratios (C) of a single plate QDSC were calculated by Monte-Carlo ray-trace modelling. Consideration of reflection, refraction, quantum dot (QD) photon emission and absorption and light attenuation in the device matrix were included in the analysis. In this paper, the effect of placing plane and diffuse reflectors at the rear surface was analyzed. Mirrors with a structured surface (saw-tooth shaped) were also modelled and the effect of each reflector type on C was determined, for direct and diffuse incident light. The diffuse and structured reflectors perform better than the plane reflector under direct light, but there is no significant difference under diffuse light. A spectrally selective reflector, placed at the top surface, reflects light emitted by QDs inside the escape cone back into the concentrator. For a particular set of model parameters, the model results show an increase in C of 13% due to the inclusion of a spectrally selective reflector.