In this study design and optimization of a-S:H/c-Si heterojunction solar cell was done with AFORS-HET simulation program. Detailed simulation studies of I-V characterization of solar cells have been carried out with TCO/(n) a-Si: H/(i) a-Si: H/(p) c-Si/BSF/Ag structure. Back surface field (BSF) layer created with (p+) a-Si: H layers. Various efforts such as changes in thicknesses, and doping concentrations of all layers, the quality of amorphous layer have been done to achieve higher efficiency. The results of these simulation studies have been obtained to be in a good agreement with the reported studies in the literature, and it is possible to propose some design parameters for HIT cell fabrication. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Organizers of European Materials Research Society (EMRS) Conference: Symposium on Advanced Inorganic Materials and Concepts for Photovoltaics.