Zinc diffusion in polycrystalline Cu(In,Ga)Se2 and single-crystal CuInSe2 layers

The diffusion behavior of Zn in solar-grade Cu(In,Ga)Se-2 (CIGSe) is found to be similar to that in epitaxial CuInSe2 (CISe), which indicates that grain boundaries only play a minor role as segregation sites and fast-transport pathways. The diffusivity obeys the Arrhenius equation D-Zn = 3.8 x 10(-3)exp(-1.24 eV/k(B)T) cm(2) s(-1). Surprisingly, the Zn-65 diffusion profiles obtained by the radiotracer technique exhibit anomalous shapes with a second maximum near the CI(G)Se-substrate interface. The observations may be indicative of an interstitial-substitutional diffusion mechanism. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745927]