Antireflective Coatings with Nanostructured TiO<sub>2</sub> Thin Films for Silicon Solar Cells

Abstract

This paper presents the preparation and characterization of nanostructured TiO2 films designated to the integration of antireflective (AR) layers into the fabrication process of the silicon solar cells. The nanostructured titanium dioxide (TiO2) layers have been obtained by the anodization of the Ti layer deposited by sputtering technique on glass substrates and silicon wafers. The obtained TiO2 films were optically characterized using the Spectroscopic Ellipsometry (SE) and the values of the refractive index are in a range of 1.66-1.76 at 632 nm radiation wavelength. The transmittance of 90 nm TiO2 thin films deposited on transparent substrate, evaluated by the spectrophotometry method, is over 70%. The TiO2 band gap of 3.3 eV was evaluated from the spectral transmittance characteristic. Silicon solar cells with various AR coatings of TiO2, SiO2 and SiO2 - TiO2 have been fabricated. The optoelectrical characterization proved that the output maximum power (Pmax) for the solar cell with a 90 nm TiO2 layer is with 28% greater than Pmax for the solar cells with SiO2 as AR layer and with 15.5 % greater than Pmax for the solar cells having a two-layer antireflective coating of SiO2 - TiO2.