Abstract: The present invention relates to a thin film solar cell and a method of manufacturing such cells. In particular the invention relates to the use of a composite back contact (314) in Cu(In,Ga)Se2 (CIGS) based thin film solar cells with thin absorber layers. The composite back contact (314) is provided between the substrate (105) and the absorber (115) and comprises: a back reflector layer (311) that enhance the reflectance at the absorber/composite back contact interface; and at least a contact layer that contact layer (310, 313) that ensures suitable electrical properties of the back contact with respect to the absorber; and/or a conductance layer (312) that ensures low sheet resistance for the in-plane current flow.

Abstract: An in-line production apparatus and a method for composition control of copper indium gallium diselenide (CIGS) solar cells fabricated by a co-evaporation deposition process. The deposition conditions are so that a deposited Cu-excessive overall composition is transformed into to a Cu-deficient overall composition, the final CIGS film. Substrates with a molybdenum layer move through the process chamber with constant speed. The transition from copper rich to copper deficient composition on a substrate is detected by using sensors which detect a physical parameter related to the transition. A preferred embodiment sensors are provided that detect the composition of elements in the deposited layer. A controller connected to the sensors adjusts the fluxes from the evaporant sources in order provide a CIGS layer with uniform composition and thickness over the width of the substrate.