  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.
