Abstract: A process for producing a thin film semiconductor solar cell, said solar cell at least comprising: a p-type layer, and an n-type layer, which are deposited on carrier material, wherein the composition of the p-type layer, especially the optical band gap and/or the specific conductivity, and/or the composition of the n-type layer, especially the optical band gap and/or the specific conductivity thereof, are varied on a continuous way in time and/or space, by controlling the composition and/or flow of predetermined gases at the location where the respective semiconductor layer is formed.