Electrodeposition of Cu-In Alloys as Precursors of Chalcopyrite Absorber Layers

Copper-Indium alloy films were electrodeposited from sulfate based acidic solutions onto Au and Mo substrates at room temperature and at 50°C. Composition analysis confirmed that In could be deposited at potentials more positive than its elemental reduction potential, as a result of the alloy formation with Cu. The alloys form supersaturated solid solution of Indium in Cu, with In up to ∼ 15 at% at relatively positive potentials. At more negative potentials, both intermetallic phases and the elemental In phase were detected. Crystal structure of alloy films was relatively stable over time, in contrast with bilayer Cu/In films. The formation of intermetallic phases could be enhanced by using short time pulses at more negative potentials followed by potentiostatic deposition at potentials corresponding to the intermetallic compositions. Near equiatomic films grown on Mo at high temperature present a relatively smooth surface, potentially providing suitable precursors for the formation of chalcopyrite compounds.