In and Ga diffusion in Cu(In, Ga)Se2 and Cu(In, Ga)S2 films instantaneously prepared in a non-vacuum process

When Cu(In,Ga)(S,Se)2 is prepared by heating metal precursor films in chalcogen atmosphere (sequential process) the resulting films typically show a gradient in the Ga/(In+Ga) ratio over the depth of the film. This is generally observed for reaction periods ranging from a few minutes (rapid thermal processing) to several hours. In this work we have investigated the Ga distribution in films where the reaction period was reduced to one second. The ultra-fast reaction was achieved by passing a high electrical current through the Mo foil substrate after depositing metal and chalcogen precursors.