Antireflection and photocatalytic single layer and double layer ZnO and ZnO–TiO2 thin films

Abstract

Due to climate change and the need to use renewable energy resources, solar cell modification is being considered by scientists around the world. Photocatalytic and anti-reflective coatings on solar cells can affect the efficiency and stability of solar cells. In this study, single-layer zinc oxide thin films and double-layer ZnO–TiO2 thin films were investigated to study their photocatalytic and optical properties. In fact, the effect of porosity and the application of double-layer thin films on the optical and photocatalytic properties of coated glass were studied. Mesoporous thin films thinner than 100 nm were synthesized using a sol-gel process and the ZnO thin film with 2 × 10-2 M pore-forming agent (CTAB) in the coating solution had the highest transparency and ultraviolet absorption, and the ZnO thin film with 4 × 10-2 M pore-forming agent had the best antireflection performance. The double-layer thin film consisted of dense (interlayer) and mesoporous (top layer) ZnO layers had the best anti-reflection performance. It reduced the reflection of the glass substrate by 2.05%. Investigation of the effect of the coating thickness on optical properties showed that higher film thickness can lead to a shift of the visible wavelength with the highest transparency such that the increase of withdrawal speed from 1 mm/s to 5 mm/s resulted in an increase of this wavelength from 530 nm to 590 nm. The photocatalytic studies of the ZnO double-layer coatings showed that 120 min of ultraviolet irradiation could completely recover the transparency of the samples contaminated with fatty acid.