Light-induced stability of various p-i-n type wide-gap a-Si1 - xCx:H solar cells has been systematically investigated. The i-layers of all a-Si1 - xCx:H solar cells were prepared using a 60 MHz VHF-PECVD technique with monomethyl silane (SiH3CH3, MMS) as the carbon source. It was confirmed that device structures, especially the type of buffer layer and thickness of i-layer, strongly affect the degradation behavior of a-Si1 - xCx:H solar cells. The fabricated a-Si1 - xCx:H solar cells showed efficiency degradation of about 11-22% depending on device structure. Efficiency degradation of optimized a-Si1 - xCx:H solar cells was much better compared with those reported by other groups even with thinner i-layer. These results revealed that a-Si1 - xCx:H solar cells with optimized buffer layer and prepared using MMS as the carbon source have high light-induced stability. Moreover, we have also fabricated a-Si1 -xCx:H/a-Si:H tandem cells with a SiOx intermediate layer to examine the benefit of a-Sii Cx:H top cells. Up to now, V-oc as high as 1.81 V and fill factor (FF) as high as 0.70 have been achieved. Thus, the fabricated a-Si1 - xCx:H solar cell is promising to be used as the top cell in multijunction solar cells. (C) 2010 Elsevier B.V. All rights reserved.