Cyclic voltammetric study and nucleation of electrodeposited Cu(In,Al)Se₂ Thin Films with Sodium Dodecyl Sulfate Additive

Cu(In,Al)Se₂ films have been fabricated by electrodeposition technique in chloride solutions with sodium dodecyl sulfate (SDS) additive. The effects of SDS additive on the reduction potentials of Cu²⁺, In ³⁺, Al³⁺ and H₂SeO₃ were studied by cyclic voltammerty. The corresponding chemical reactions were defined according to the XRD analysis. SDS additive promotes the deposited potential of each element closing to each other for a better co-elecorodeposition environment. Besides, the chemical mechanism of Cu(In,Al)Se₂ films were investigated by chronoamperometry. The nucleation mechanism of Cu(In,Al)Se ₂ films change from instantaneous nucleation to progressive nucleation as SDS additive is added. Scanning electron microscopy and energy dispersive X-ray spectroscopy reveal the surface morphology and stoichiometry of Cu(In,Al)Se₂ films at various potentials from -0.5 V to -1.0 V. The excess indium content inhibits the aluminum's incorporation into Cu(In,Al)Se₂ films, and induces the surface morphology to change from round-like structure into cauliflower-like structure. Raman spectra shows the quality and composition phase of Cu(In,Al)Se₂ films at various potentials. The shift in the optical band gap evidences the incorporation of aluminum element into CuInSe₂ structure to form Cu(In,Al)Se ₂ film. The corresponding optical bandgap of Cu(In,Al)Se₂ film with the composition Al/(In+Al) = 0.219 is about 1.17 eV.