Wide gap, high quality hydrogenated intrinsic amorphous silicon (i-a-Si:H) alloy films are essentially required for multi-junction solar cells fabrication to enhance the open-circuit voltage (V-oc) of the top cell. In this paper, intrinsic hydrogenated amorphous silicon oxide films (i-a-SiOx:H) have been prepared using a very high frequency plasma-enhanced chemical vapor deposition technique for use as an absorber layer of the top cell for double-junction amorphous silicon thin film solar cells. We studied the effects of the carbon dioxide (CO2) to silane (SiH4) ratio on the properties of the i-a-SiOx:H films and also optimized these films for application in a-SiOx:H/a-Si:H double-junction solar cells. The Voc of the a-SiOx:H/a-Si:H double-junction solar cells was higher than that of conventional a-Si:H/a-Si: H double-junction solar cells. Using an optimized deposition condition, a-SiOx:H/a-Si:H double-junction solar cell with an initial cell efficiency (eta) of 10.2% was produced. (C) 2013 Elsevier B.V. All rights reserved.