A novel non-vacuum process in which water based inks formulated using nanoparticles of mixed oxides of Cu, In and Ga are used to deposit a precursor layer of fixed Cu/(In+Ga) ratio on a rigid or a flexible substrate of choice using printing techniques. The precursor layer is converted to a CuIn1-xGaxSe2 (CIGS) absorber layer of uniform composition via two sequential gas solid reactions of reduction and selenization. Solar cells fabricated in CIGS films prepared by this technique have conversion efficiency approaching 13.6% on glass substrate and over 10% on Mo foil. Compositional uniformity, high materials' utilization and the use of low-cost equipment make this process suitable for large-scale production of low-cost CIGS modules. (C) 2003 Elsevier Science B.V. All rights reserved.