Tailoring photonic and wetting properties through multilayer titania films fabricated by sol-gel spin coating

Abstract

Thin films composed of titanium dioxide (TiO₂) are renowned for their exceptional optical and surface characteristics, making them crucial in various applications including solar cells, LEDs, and self-cleaning surfaces. Nevertheless, fine-tuning these properties through precise manipulation of coating layers remains problematic. This research examines the effects of single, double, and triple TiO₂ coatings on photonic and wetting properties, utilizing an economical sol–gel spin-coating technique. The findings demonstrated that increasing the number of layers led to enhanced surface roughness, with measurements rising from 11 nm for a single layer to 26 nm for a triple layer, as determined by atomic force microscopy (AFM). Field emission scanning electron microscopy (FESEM) cross-sectional analysis verified thicknesses of 182 nm, 201/230 nm, and 203/180/225 nm for single, double, and triple coatings, respectively. UV–VIS spectroscopy showed improved optical transmittance and a red shift in the stop band with additional layers, which is advantageous for anti-reflective applications. Water contact angle measurements revealed a transition from hydrophobic (110° for a single layer) to hydrophilic (55° for a triple layer) behavior, attributed to increased roughness and surface irregularities. These results establish a clear correlation between the number of layers and improved photonic and self-cleaning properties, underscoring the potential of TiO₂ multilayers for advanced solar cell coatings and optical devices.