Crystal structures and band-gap energies of Cu2Sn(S, Se)3 (0≤ x ≤ 1.0) solid solution

Cu2Sn(S-1-xSex)(3) (CTSSe) solid solutions with 0 <= x <= 1.0 were synthesized by mixing the elemental powders and post-annealing at 600 degrees C. The crystal structure of Cu2SnS3 (CTS), Cu2SnSe3 (CTSe), and their solid solution were determined by Rietveld refinement of the powder X-ray diffraction data. CTSSe solid solution had a monoclinic crystal system [space group: Cc (No. 9)]. The refined lattice parameters of CTS were a=6.654(8) angstrom, b=11.534(2) angstrom, c=6.659(4) angstrom, and beta=109.40(5)degrees and those of CTSe were a=6.964(6) angstrom, b=12.056(6) angstrom, c=6.972(4) angstrom, and beta=109.49(1)degrees. The lattice parameters, a, b, and c of CTSSe solid solution monotonically increased with increasing Se content. The band gap of the CTSSe solid solution linearly decreased from 0.87 eV (x=0.0) to 0.67 eV (x=0.60) with increasing Se content.