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

Highlights: → The CZTSSe solid solutions were synthesized by solid state reaction method. → EDX, XRD and Raman spectra confirm that the atomic Se and S are highly miscible in CZTSSe solid solutions. → The absorption spectra reveal that the band gap of CZTSSe can be tuned linearly between 0.96 and 1.5 eV. - Abstract: 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 A1 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 ∼ 0.08 eV) is deduced.