Abstract: A method for manufacturing solar cells, more specifically thin-film solar cells, particularly thin-film solar cells on which CuInSe.sub.2 is deposited. A substrate is provided on which a multi-layer structure is formed by depositing thereon a layer defined by a compound including several basic substances, such as copper-indium-diselenide (CuInSe.sub.2), or a closely-related compound where copper (Cu) and indium (In) can be replaced totally or partially with Silver (Ag) and gallium (Ga), respectively, and where selenium (Se) can be replaced totally or partially with sulphur (S) and tellurium (Te), and where the concentration of the basic substances in the layer varies. The substrate is placed on the inside of a rotatable, tubular carrier device, after which the substrate is heated, and substance sources are provided for depositing the basic substances on the substrate.