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(Color online) XANES spectra at the sulfur K-edge (μ norm(E)) of CZTS and secondary phases normalized to an edge step of one. Sulfur-containing adhesive tape used as a substrate for transmission measurements does not influence the XANES spectra in the evaluated region (2467–2478 eV).
(Color online) Measured and edge step normalized XANES spectra at the sulfur K-edge (μ norm(E)) of a sample series with varying Sn/Zn-ratio together with the spectrum of the CZTS reference. The first maximum increases with increasing Sn/Zn-ratio, while the second maximum decreases as indicated by arrows.
(Color online) Measured and edge step normalized XANES at the sulfur K-edge (μ norm(E)) of one particular thin film (squares) together with the least square fit obtained from a superposition of the spectra of CZTS and ZnS with ratios 88%:12%. In order to demonstrate the dependence of the XANES on the ZnS:CZTS ratio, linear combinations with 15%, 25%, and 50% ZnS content are plotted additionally.
(Color online) Results of the ZnS quantification in CZTS samples by XANES and its relation to the Sn/Zn composition ratio (left axis) determined by XRF (error bars from relative error of atomic composition). The normalized efficiencies of the solar cells (right axis) strongly correlate with their ZnS volume fraction. Each data point consists of the averaged efficiency of eight cells per sample, with the standard deviation indicated by the error bars.
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