The possibilities of using highly absorbing chalcopyrite semiconductors of the type Cu(In,Ga)Se2 in a quantum well solar cell structure are explored. Thin alternating layers of 50 nm CuInSe2 and CuGaSe2 were grown epitaxially on a GaAs(100) substrate. The optical properties of a resulting structure of three layers indicate charge carrier confinement in the low band gap CuInSe2 layer. By compositional analysis interdiffusion of In and Ga at the interfaces was found. The compositional profile was converted into a conduction-band diagram, for which the quantization of energy levels was numerically confirmed using the effective-mass approximation. The results provide a promising basis for the future development of chalcopyrite-type quantum well structures and their application, i.e. in quantum well solar cells.