On improving the short-wavelength response and efficiency of photovoltaic modules via luminescent down-shifting of the incident light
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This thesis investigates the technology of luminescent down-shifting (LDS) of light for improving the short-wavelength response and efficiency of photovoltaic (PV) modules. A critical literature review of previously published work is presented identifying the opportunity to include the luminescent species in the encapsulation layer of certain PV technologies. A range of luminescent materials and mixtures thereof were tested in ethylene vinyl acetate (EVA) host. They all exhibited very high luminescent efficiencies and did not impair the transmittance of the encapsulant. LDS EVA sheets were used to encapsulate multi-crystalline silicon (mc-Si) and chalcopyrite (CIGS) solar cells. An increase in short-λ external quantum efficiency of up to 25 % was achieved for mc-Si devices. For CIGS, the increase was up to 25 % and 40 % for 50-nm- and 100-nm-thick buffers respectively. The overall efficiency of mc-Si devices was improved by 0.2 % in the best case and gains of up to 0.2 mA / cm2 and 0.6 mA / cm2 were achieved for 50-nm- and 100-nm-thick buffer CIGS devices. LDS offers the additional benefit of device colouration, which can encourage the further uptake of PV in applications where colour is a desirable property.