Electroless nucleation and growth of Cu-Se phases on molybdenum in Cu(II)-In(III)-Se(IV) solutions

Surface reactions of molybdenum-covered glass plates, used as back contact for thin Cu (In,Ga) (S,Se)2 solar cells, are examined at open circuit in acidic electrolytes used for plating CuIn Se2 layers. A multinary element cementation reaction occurs, leading to the corrosion of molybdenum and the formation of Cu Sex electroless deposit (x from 0.2 to 0.8), with well-defined compositions. Immediately after immersion, small nuclei appear on the surface, which then grow to form a quasi-continuous layer. The time evolution of the open-circuit potential of Mo and the SeCu surface atomic ratio are correlated and are in agreement with thermodynamic data predictions.