Visible light active and self-cleaning SiO2/N-TiO2 heterostructure surface with high transmittance for solar module glass cover: Experimental and DFT insights

Abstract

Transparent, anti-reflective, visible-light-driven photocatalytically active and superhydrophilic heterostructure coating have been synthesized on glass substrates. Heterostructures consist of SiO2 as an anti-reflective layer at the bottom and nitrogen-doped TiO2 (N-TiO2) with varying concentrations (0, 2.5, 5, 7.5 and 10 wt%) at the top for visible-light-driven photocatalytic active surface. Porosity is induced in both materials by introducing a suitable pore-forming agent for better anti-reflective properties. Doped samples exhibited excellent photocatalytic activity in the sunlight owing to the significant absorption in the visible region, confirmed by experimental and theoretical studies. Disintegration and cleaning of pollutants are demonstrated by photodegradation of methylene blue (MB) dye solution. Optimized heterostructure exhibited 5% greater optical transmittance than pristine TiO2. The hydrophilicity of heterostructure also varies with nitrogen doping concentration and is found to be minimum (11.9º) for SiO2/2.5 N-TiO2. Simultaneous self-cleaning and high optical transmittance of SiO2/N-TiO2 support the removal of fine contaminants under sunlight irradiation. At the same time, it contributes to the enhancement of transmitting incident light to the absorber layer of the solar cell. These heterostructures are highly suitable for bifunctional, self-cleaning and anti-reflective coating applications on building glass and photovoltaic glass covers.