Method of providing a layer of solid material on a substrate in which liquid from which the solid material can be formed, is spread over the substrate surface

A method of providing a layer of solid polycrystalline semiconductor material on a flat substrate surface, for use as a solar cell in which a liquid material from which said solid polycrystalline semiconductor material is formed, is supplied dropwise to the substrate, while said substrate is given a rotating movement, characterized in that the rotating movement of said substrate is combined with at least one other periodic movement which produces a change of the position of the plane of said substrate surface, such that the points of the surface which are situated outside the point of intersection of the axis of the rotating movement change in height periodically with respect to said point of intersection.