Photo-stability and performance of CdSe/ZnS quantum dots in luminescent solar concentrators

The performances of luminescent solar concentrators (LSCs) made with two versions of quantum dots (QDs) with CdSe cores and ZnS shells are compared to LSCs containing the organic dye, Lumogen^® F Red 300 (LR), to assess the viability of QD LSCs. In addition to spectroscopic and light collection measurements, the photo-degradation response of the version I (vI) QD LSC is compared to the LR LSC. The measured fluorescence quantum yield of the version II (vII) QDs (57%) is about half that of LR (>90%) and twice that of the vI QDs (31%). Though the quantum yield for vII QDs is lower than LR, the vII QD LSC has nearly twice the short-circuit current of the LR LSCs or the vI QD LSCs when their respective red-peak optical densities are the same in 6.2 × 6.2 × 0.6 cm LSCs. This is a reflection of the main advantage of QDs for use in LSCs, that QDs collect considerably more sunlight than LR due to their broad absorption spectrum. Despite the fact that the QD LSCs absorbs more photons than the LR LSCs, the slow phase of the photo-degradation rate of the QD LSC is approximately five times slower than the LR LSC under nearly constant light exposure. Most surprising is the observation that the photo-degradation of the QD LSC's absorption completely recovers during a prolonged dark cycle. In a normal day/night cycle, this will benefit the performance of the QD LSC.