Light scattering behavior of oxide nanoparticles

Titanium dioxide (TiO₂) has high optical refractive index and is transparent to visible light. No strong reflection is expected from a single layer of continuous TiO₂ film. In this work, we report the unusually high reflection from a thick layer of TiO₂ nanoparticles. TiO₂ nanoparticles of different sizes (~ 21 nm and ~ 400 nm) were deposited on indium tin oxide (ITO) coated glass substrate by electrophoretic process in atmosphere. It was observed that the film characteristics such as morphology and thickness were affected by the electrophoretic process conditions like voltage, deposition time, and electrolyte concentration. The electrolyte had the most significant effect on the deposition rate of the nanoparticles. The film thickness was proportional to the deposition time, which in turn determined the diffused reflectance of the TiO₂ particle films. It was observed that the 400 nm TiO₂ nanoparticle films lead to much stronger light scattering as compared to the 21 nm particles. The diffuse reflectance was compared to sputtering deposited Ag/ZnO back reflectors that are used in thin film solar cells. The TiO₂ nanoparticle film showed higher reflectance, making it a potential candidate to replace the unstable Ag/ZnO back reflector.