Quantum dot solar concentrator: Optical transportation and doping concentration optimization

This research investigated optical transport properties, quantum dot doping, and size optimization for Quantum Dot Solar Concentrators (QDSCs) through correlating spectroscopic and electrical characterization, and model predictions. QDSC plates of 60 x 40 x 2 mm containing; 0.005, 0.01, 0.03, 0.05, and 0.07 wt% of CdSe/ZnS quantum dot were fabricated by a drop casting technique and the edges were optically smoothed by polishing. QD fluorescence emission transport properties in QDSC plates were examined with varying optical path-length using laser lines 405, 488 and 532 nm, and white light with a cut-off wavelength of 600 nm. Emerging fluorescence emission falls off as the optical path-length increases and the rate of fall-off is increased for higher QD concentration; the emission is nearly negligible above the 25 mm optical path-length for 0.05 and 0.07 wt% QDSC plates. Re-absorption is mainly responsible for reduced emission in lower QD concentration QDSCs for fixed optical path-lengths. In higher concentration QDSCs, scattering and re-absorption both contribute to the reduced emission, which is verified through the white light scattering profile of QDSCs. Emission is reduced by up to 70% for >20 mm optical path-length where emission is lost before reaching the edge. The optimum concentration of QD doping has been found while balancing the QDSC device dimensions, and also ensuring sufficient absorption of the incident light. (C) 2015 Elsevier Ltd. All rights reserved.