Sol-Gel Synthesis of SiO2-TiO2 Film as Antireflection Coating on Silicon for Photovoltaic Application

Abstract

Application of thin films of SiO2 and TiO2 using the sol-gel process were utilized as antireflection coating on monocrystalline silicon wafers. The aim of this study is to validate this process as a procedure to prepare antireflective films for monocrystalline silicon by dip-coating. The coating was carried out by dip-coating process using tetraethoxysilane (TEOS) as precursor for SiO2 and titanium isopropoxide (TIPT) as precursor for TiO2. In order to study the influence of the thickness on the reflectance and the optical parameters, several coatings with different thickness were deposited onto silicon wafers. The refractive index and the thickness were adjusted by controlling the number of dipping. The refractive index increases from 2.10 up to 2.22 by increasing the film thickness from 36 to 137 nm. It was found that the sample coated with two layers exhibits a lower reflection (1.86 % at λ = 602 nm). This result was improved by a single sub-layer of SiO2 (36.75 nm) to reach 1.08 % at λ = 674 nm). Furthermore, the low values of the extinction coefficient (k) (approach to Zero at λ = 632.8 nm) indicate that TiO2 and SiO2 films deposited by sol-gel method can be used as ARC for Si solar cells.