Hybrid sol-gel layers containing CeO2 nanoparticles as UV-protection of plastic lenses for concentrated photovoltaics

Fresnel lenses made of polymethylmethacrylate (PMMA) represent a cost-effective approach for concentrated photovoltaic (CPV) panels. The lens must sustain suitable working performance during the whole lifetime of the photovoltaic plant, as UV photodegradation is the main issue to be avoided. In this work, PMMA sheets were covered with a hybrid organic-inorganic sol-gel coating consisting of a matrix of an organically modified silicate (ORMOSIL) in which CeO2 nanoparticles 10-20 nm in size were dispersed, acting as the UV-absorbing agent. Ceria contents up to 40% w/w were studied and blended with the precursor ORMOSIL solution before deposition and in-situ polymerization at 80 °C. The UV-visible spectra were analyzed between 200 and 800 nm. Furthermore, the effect of the aging on outdoor weathering was investigated for the coated PMMA sheets and compared to the unprotected sample. The results show that a load of 30% w/w of ceria nanoparticles provides a reasonable compromise in terms of UV protection and absorption in the visible range. The weathering test also demonstrates enhanced protection against UV degradation for the coated PMMA sheet compared to the bare substrate, although the adherence should be further improved for optimum performance.