Anti-reflection and self-cleaning meso-porous TiO2 coatings as solar systems protective layer: Investigation of effect of porosity and roughness

Abstract

Anti-reflection and self-cleaning coatings on the glass substrate are used to improve the performance of solar systems. TiO2 are one of the most used semiconductors for this application. In this research meso-porous TiO2 coatings (that synthesized by the sol-gel process) with the various extent of porosity (using different concentrations of Pluronic F127, as pore-forming agent) have been investigated. The coating's thickness and porosity and anti-reflective properties were studied by FE-SEM and UV/VIS spectrometer (transmission spectra test), respectively. It was found that the use of F127 leads to the formation of pores smaller than 30 nm and increases the surface roughness from 1.5 (for F127 free coating) to 2.4 (for coating with 1.6 × 10−3 M of F127). and the transmittance of waves in the range of visible spectrum for TiO2 coated glass with 1.6 × 10−3 and 2 × 10−3 (M) was higher than the bare glass. The etching of TiO2 coating with HF (5%) is another beneficial way to improve the anti-reflective properties. Self-cleaning properties of super-hydrophilic TiO2 coating were investigated by contact angle and fatty acid decomposition tests. The contact angle of meso-porous TiO2 coating (4.2°) was less than dense coating (5.8°) and by increasing the coating surface roughness, the rate of fatty acid contaminations decomposition on the surface was increased.