Cu(In,Ga)(Se,Te)2 films formed on metal foil substrates by a two-stage process employing electrodeposition and evaporation

Abstract

Cu(In,Ga)(Se,Te)2 or CIGST films were grown over molybdenum coated stainless steel foil substrates using a two-stage technique. The process involved deposition of a Cu-In-Ga/Se-Te precursor stack over the Mo layer using electrodeposition for the metals and evaporation for the chalcogens. The stack was then annealed at 600 °C to initiate reaction between the constituent elements. The reacted films were characterized in terms of their structural, compositional, electrical and optical properties. Results were compared to films obtained using all-evaporated precursor stacks formed on glass substrates. It was observed that the compositional control and the morphological properties of the compound layers grown on the metal foil substrates employing electrodeposition and rapid thermal annealing were superior to the films obtained on glass substrates using evaporated precursors and slower temperature ramp rate during annealing. Glancing angle XRD measurements at the front and back surfaces of the layers showed that Ga distribution through the CIGT films was much more uniform than that through the CIGS layers. CIGST films, which contained both Se and Te had slightly Se-rich surface compared to their bulk.