Homogeneous single phase Cu(InGa)Se2films with Ga/(In+Ga)=0.25–0.75 were formed by reacting Cu–Ga–In precursor films in H2Se followed by an anneal in Ar. X‐ray diffraction and Auger analysis show that the metal precursors reacted only in H2Se were multiphase films having a layered CuInSe2/CuGaSe2structure. Solar cells made with the multiphase films have properties similar to CuInSe2devices. Cells made with the annealed single phase films behave like Cu(InGa)Se2devices with the band gap expected for the precursor composition. ©1995 American Institute of Physics.