Current hydrogenated amorphous and micro-crystalline silicon solar cells use textured substrates for enhancing the light absorption and (graded) buffer layers in order to improve the overall performance of the cells. The resulting solar cell structures are very complex and for understanding the role of these layers and for further optimization of the solar cell structures computer modeling is a useful tool. Integrated electrical and optical modeling was used to optimize hydrogenated amorphous silicon-germanium (a-SiGe:H) solar cells. Using simulations various mobility gap profiling schemes of the intrinsic a-SiGe:H layer were analyzed. On the basis of these simulations a new mobility gap profile (modified V type profile) for the intrinsic layer of a-SiGe:H solar cells is proposed. (C) 2003 Elsevier B.V. All rights reserved.