Christopher J. Hibberd

Incorporation of copper into indium gallium selenide layers from solution

A chemical method for the incorporation of copper into indium gallium selenide (IGS) layers has been developed. The resulting copper-containing precursor layers have been annealed in the presence of selenium vapour with the goal of forming Cu(In, Ga)Se2 (CIGS) layers. It is found that copper ions in solution are incorporated into IGS layers during immersion, resulting in the formation of a precursor layer containing both copper selenides and IGS. When aqueous solutions are used for this process, corrosion of the molybdenum back contact occurs by reduction of copper ions in the solution. Use of an ethylene glycol solution prevents corrosion of the Mo and allows higher process temperatures, corresponding to higher reaction rates. During annealing, the precursor layers are converted into CIGS and the morphology of these layers is strongly affected by the availability of selenium whilst the substrate temperature is ramped up.