The diffusion behaviour of Zn in solar-grade Cu(In,Ga)Se2 was found to be similar to that in epitaxial CuInSe2, which indicated that grain boundaries only played a minor role as segregation sites and fast-transport pathways. The diffusivity obeyed,

D(cm2/s)  = 3.8  x  10−3exp[-1.24(eV)∕kT]

Surprisingly, the 65Zn diffusion profiles obtained by the radiotracer technique exhibited anomalous shapes with a second maximum near the Cu(In,Ga)Se2 Se-substrate interface. The observations might be indicative of an interstitial-substitutional diffusion mechanism.

Zinc Diffusion in Polycrystalline Cu(In,Ga)Se2 and Single-Crystal CuInSe2 Layers. J.Bastek, N.A.Stolwijk, R.Wuerz, A.Eicke, J.Albert, S.Sadewasser: Applied Physics Letters, 2012, 101[7], 074105