In this paper, we report a novel and simple solution-based approach for the fabrication of chalcopyrite Cu(In,Ga)Se2 thin film solar cells. An aqueous co-precipitation method based on metal selenites, M2(SeO3)x (M = Cu, In, Ga) precursors was investigated. The resulting powder, dispersed in a binder to form an ink, was coated on a substrate by doctor blade technique. A soft annealing treatment allowed the reduction of metal selenites into selenides. Further rapid thermal processing (RTP) achieved crystalline chalcopyrite absorber. The obtained layer provides good compositional control and adequate morphology for solar cell applications. The water-based synthesis is a sustainable and simple procedure, and together with doctor blade printing, provides a potential cost-effective advantage over conventional fabrication processes (vacuum-based deposition techniques). The short circuit current (JSC), open circuit voltage (VOC), fill factor (FF), and total area power conversion efficiency (Eff.) of the device are 26 mA/cm2, 450 mV, 62%, and 7.2%, respectively. The effective band gap of 1.12 eV confirmed Ga-incorporation in the CIGS crystal lattice.