Advanced X-ray analysis of polycrystalline CuInSe2 thin films

Advanced X-ray powder diffraction (XRD) analysis of polycrystalline semiconductor thin-films such as CuInSe₂ is able to give detailed information of the thin-film structure. A (112) peak profile fitting and pole figure measurements were chosen to give a set of structural data such as integrated intensities, full width at half maximum (FWHM), peak position, Pearson VII exponent and residual error factors, and a quantitative measure of crystallite orientation. These structural data were combined with EDS measurements and solar cell efficiencies. It is shown that for the standard bilayer deposition of lateral Cu/In gradient layers, the maximum efficiency is correlated with maximum texture effects and the point of Cu/In-ratio=1. Discontinuities of changes in peak position, FWHM, and error factors indicate a secondary nucleation process during the overgrowth of the In-rich top layer. Increasing the Cu evaporation temperature step causes increased tendency of the secondary nucleation process. Texture measurements expose the crystallite orientation effect as a fiber texture parallel to [221]