One-Step Electrodeposited Cu-In-Ga Thin Films and Cu(In,Ga)Se2 Absorber Synthesis for Solar Cells

Cu-In-Ga electrodeposition on Mo substrate is carried out in acidic aqueous media. Subsequent selenization leads to Cu(In,Ga)Se2 absorber for thin film solar cells. First, conditions to achieve onestep Cu-In-Ga electrodeposition are analysed. Then, Cu-In and CuGa systems are studied. Cu-In electrodeposition is realized under diffusion-control conditions. For Cu-Ga system, first Cu(II) diffusion-controlled reduction occurs, followed by kinetic underpotential deposition (UPD) of Ga, leading to the formation of CuGa2 compound. Finally Cu-In-Ga electrodeposition is investigated. For Cu-In-Ga system, CuGa2 compound is not noticed, Ga-O codeposition is favored. In presence of citrate, Ga metal is deposited without oxide. Cu(II) and In(III) reductions are both diffusion-controlled, and Ga(III) kinetically controlled, allowing composition control at fixed pH and potential, but with dendritic growth. After selenization, complete Ga insertion is noticed in the formed chalcopyrite absorber. Solar cells with 4% efficiency were achieved despite porous morphology of the absorber.