Abstract: Photovoltaic device comprising an anti-reflective coating on a light incident side of a transparent cover layer, the anti-reflective coating comprising a layer of diatom frustules, each of the frustules comprising two adjacent and connected porous silica layers, the first porous silica layer having a pore diameter and pore pitch defining a first layer porosity, the second porous silicon layer having a pore diameter and pore pitch defining a second layer porosity, the second layer porosity being less than the first layer porosity, the layer of diatom frustules being arranged such that the first porous silica layer is light incident with respect to the second porous silica layer.

Abstract: A cosmetic composition comprising: at least one sunscreen active agent; and, benthic pennate diatom frustules. A method of boosting the SPF of a sunscreen composition. A method of producing a sunscreen by providing an active sunscreen agent, and benthic pennate diatom frustules.

Abstract: A method of extracting frustules from benthic pennate diatoms is disclosed. The method includes culturing benthic pennate diatoms in an industrial biofilm process, wherein in the industrial biofilm process the benthic pennate diatoms are growing on at least one surface in a water-containing compartment and wherein the benthic pennate diatoms forms a biofilm on the at least one surface; harvesting the benthic pennate diatoms from the at least one surface; and extracting the frustules by separating the frustules from organic biomass contained in the benthic pennate diatoms.