P-type CIGS (CuIn 1-x Ga x Se 2) thin films are electro-deposited on a p-type c-Si substrate with a galvanostatic mode to form CIGS(p)/c-Si(p) hetero-junction. The Ga content is varied up to x = 30%. The physical properties of formed CIGS films are characterized by XRD, SEM, EDS and UV-Visible spectroscopy. With x = 30%, we obtain a single chalcopyrite phase of CIGS with a tetragonal crystal structure, a high crystallinity, an orientation toward the (112) direction and a band gap energy of 1.40 eV. AM1.5 J-V performed on the CuI 0.7 G 0.3 Se 2 /c-Si hetero-junction reveals interesting photovoltaic parameters with an efficiency of 3.75%. In addition, using the energy diagram of the hetero-junction calculated with the Anderson model, we show that it could play a dual role when combined to a c-Si cell in a Ag-Al/c-Si(n +)/c-Si (p)/CIGS(p)/Al new architecture. Therefore, in addition to its interesting photovoltaic parameters, this heterojunction can substitute the BSF.