NOVELTY - Preparation of a copper-indium-gallium-selenide thin film, usable as absorber layer in copper-indium-gallium-selenide/cadmium sulfide solar cells, involves sputtering deposition of a copper-gallium alloy, in which copper content is 70 to 30 atomic% and correspondingly gallium content is 30 to 70 atomic%, on a copper-indium-selenide film deposited on a molybdenum-coated substrate; and subsequent selenization.    USE - For preparation of a CuInGaSe2 thin film, usable as absorber layer in CuInGaSe2/CdS solar cells (claimed) such as CdS thin film solar cells.    ADVANTAGE - The process is suitable for industrial level production of CdS thin film solar cells in which the absorber layer is constituted by CuInGaSe2. The CuInGaSe2 film reveals stoichiometric uniformity from one zone to another i.e. the resulting film is homogeneous. The CuInGaSe2 layer formed has a Ga content which varies through its thickness i.e. more Ga is contained at the layer surface than within the layer. This allows the prohibited gap of the material to be larger at the surface than in the material itself and thus the open circuit potential that can be obtained in the solar cell is higher in the case where Ga is distributed uniformly over the whole material thickness. The process only uses sputtering and selenization, it neither uses layer evaporation nor any chemical bath which is usually used for preparing CdS film. The use of sputtering alone for deposition of all layers facilitates the aligning of the process to be used for industrial production on a large area of substrate. Given the high reproducibility and stability of the sputtering technique, both stoichiometric and thickness uniformity of the layers is guaranteed.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a process (P1) for the production of a copper-indium-gallium-selenide (CuInGaSe2)/cadmium sulfide (CdS) thin film solar cell involving preparing CuInGaSe2 absorber film deposited on a Mo-coated substrate by the method; and depositing by RF sputtering a CdS film on the absorber film.