Composition dependence of structure and optical properties of Cu2ZnSn(S,Se)4 solid solutions: An experimental study

The evolution of structure and optical properties of Cu2ZnSn (SxSe1-x)(4) (CZTSSe) solid solutions in a wide composition range (0 <= x <= 1) has not been fully elucidated. We have performed comprehensive characterization on the CZTSSe powders with different S/Se ratios, which were synthesized by the solid state reaction method. X-ray diffraction patterns demonstrate that the lattice parameters a and c of CZTSSe decrease lineally when S replace Se gradually, which obeys the Vegard's rule. The A(1) Raman modes of CZTSSe show a typical two-mode behavior. The absorption spectra reveal that the band gap of CZTSSe can be tuned monotonously between 0.96 and 1.5 eV with almost linearity, and a small band gap bowing constant (b approximate to 0.08 eV) is deduced. (C) 2011 Elsevier B. V. All rights reserved.