In this study, SiOx layers were fabricated by spray pyrolysis deposition (SPD) and aerosol spraying as diffusion barriers between the stainless steel (SS) substrate (SUS430) and the molybdenum back contact layer in CuIn1-xGaxSe2 (CIGS) thin-film solar cells. SPD and aerosol spraying for SiOx layers are attractive processes for the deposition of thin films due to their low cost and controllable properties especially for solar cells on SS foils since a good barrier layer is required to prevent the Fe impurities (ions) defusing from SS substrate to the cells. The properties of SiOx barriers including thermal stability, microstructure content, electrical insulation and thickness of SiOx layers were investigated. The surface morphology and surface roughness were observed by scanning electron microscope and atomic force microscope. A transmission electron microscopy and X-ray diffractometer are adopted to measure the microstructural characteristics, grain size, and residual stresses of films. The chemical composition of the dielectric barriers was analyzed by X-ray photoelectron spectroscopy. The experimental results shows the specific thickness at 200 nm of SiOx layer will cause the absorber layer has the single chalcopyrite phase structure with (112) preferred orientation. The effects from the results revealed that the cells with a SiOx barrier layer fabricated by aerosol spraying provided a promising process in obtaining better CIGS cell performance.