Abstract

Transparent titania coatings have self-cleaning and anti-reflection properties (AR) that are of great importance to minimize soiling effect on photovoltaic modules. In this work, TiO2 nanocolloids prepared by polyol reduction method were successfully used as coating thin films onto borosilicate glass substrates via adsorptive self-assembly process. The nanocolloids were characterized by transmission electron microscopy and x-ray diffraction. The average particle size was around 2.6 nm. The films which have an average thickness of 76.2 nm and refractive index of 1.51 showed distinctive anti soiling properties under desert environment. The film surface topography, uniformity, wettability, thickness and refractive index were characterized using x-ray diffraction, atomic force microscopy, scanning electron microscopy, water contact angle measurements and ellipsometry. The self-cleaning properties were investigated by optical microscopy and UV-Vis spectroscopy. The optical images show 56% reduction of dust deposition rate over the coated surfaces compared with bare glass substrates after 7 days of soiling. The transmission optical spectra of these films collected at normal incidence angle show high anti-reflection properties with the coated substrates having transmission loss of less than 6% compared to bare clean glass.

Highlights

  • Sunlight is an abundant energy source that is not distributed evenly on earth’s surface

  • Photocatalytic TiO2 coatings are known for their excellent self-cleaning behavior and anti-reflection properties, where very thin water layer formed on the hydrophilic surface can wash-off the dirt particles

  • We reported on a costly efficient and simple preparation method of the optically transparent, good wettability towards water and photocatalytic TiO2 coatings on glass substrate for self-cleaning applications

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Summary

Results and Discussion

The titania coating deposited using TiO2 colloidal nanoparticles shows less accumulation of dust particles compared with uncoated glass sample. This value is in good agreement with the film thickness obtained by Xi et al.[8] who first proposed this technique for self-cleaning applications. The measured contact angles of the deposited films show medium hydrophilicity and the values are in total agreement with what was reported earlier for anatase TiO2 thin films deposited on glass substrates as summarized in Table 3 21–23. The average of dust deposition rate for seven days on uncoated versus coated samples with TiO2

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