Method of forming chalcopyrite thin film solar cell

In a method of forming a CIGS film absorption layer, a first precursor is provided including a first substrate having a major process precursor film formed thereon, the major process precursor film containing two or more of Cu, In, Ga, and Se. A second precursor is provided including a second substrate having an element supplying precursor film formed thereon, the element supply precursor film containing two or more of Cu, In, Ga and Se. The precursors are oriented with the major process precursor film and element supplying precursor film facing one another so as to allow diffusion of elements between the films during annealing. The oriented films are annealed and then the precursors are separated, wherein the CIGS film is formed over the first substrate and either a CIGS film or a precursor film containing two or more of Cu, In, Ga, and Se remains over the second substrate.