A method for synthesizing Cu(InxGa1-x)S2 and Cu(InxGa1-x)Se2 nanopowders using flame spray pyrolysis to form solar cell absorber materials. The flame spray product is the oxide nanoparticles of the absorber materials (copper indium gallium oxide). The oxide nanoparticles may be deposited directly onto glass substrates. The oxide nanoparticles are then sulfurdized or selenized with a post deposition anneal directly on the substrate to form the absorber layer for a solar cell device.