Porous Silicon & Titanium Dioxide Coatings Prepared by Atmospheric Pressure Plasma Jet Chemical Vapour Deposition Technique-A Novel Coating Technology for Photovoltaic Modules

Atmospheric Pressure Plasma Jet (APPJ) is an alternative for wet processes used to make anti reflection coatings and smooth substrate surface for the PV module. It is also an attractive technique because of it’s high growth rate, low power consumption, lower cost and absence of high cost vacuum systems. This work deals with the deposition of silicon oxide from hexamethyldisiloxane (HMDSO) thin films and titanium dioxide from tetraisopropyl ortho titanate using an atmospheric pressure plasma jet (APPJ) system in open air conditions. A sinusoidal high voltage with a frequency between 19-23 kHz at power up to 1000 W was applied between two tubular electrodes separated by a dielectric material. The jet, characterized by Tg ~ 600-800 K, was mostly laminar (Re ~ 1200) at the nozzle exit and became partially turbulent along the jet axis (Re ~ 3300). The spatially resolved emission spectra showed OH, N₂, N₂₊ and CN molecular bands and O, H, N, Cu and Cr lines as well as the NO₂ chemiluminescence continuum (450-800 nm). Thin films with good uniformity on the substrate were obtained at high deposition rate, between 800 -1000 nm.s^-1, and AFM results revealed that coatings are relatively smooth (Ra ~ 2 nm). The FTIR and SEM analyses were better used to monitor the chemical composition and the morphology of the films in function of the different experimental conditions.