Crystallographic and optical properties of CuSbS₂ and CuSb(S_1-xSe_x)₂ solid solution

We synthesized CuSbS₂ (CAS), CuSbSe₂ (CASe), and their solid solutions by only a mechanochemical process. CAS powder with good crystallinity was obtained by post-heating at 400 and 500 °C. CASe powder with good crystallinity was obtained by post-heating at 400 and 450 °C. The CuSb(S_1-xSe_x)₂ (CASSe) solid solutions with 0.0 ≤ x ≤ 1.0 were synthesized by post-heating at 450 °C. The crystal structure of CASSe was analyzed by Rietveld refinement using X-ray diffraction data. CAS, CASe, and CASSe solid solutions have a chalcostibite structure with an orthorhombic system of space group (Pnma). Both indirect and direct band gap energies of CASSe solid solutions were estimated by the diffuse reflectance spectra of ultraviolet/visible/near-infrared (UV-vis-NIR) spectroscopy. The indirect band gap of the CASSe solid solution linearly decreased from 1.40 eV of CuSbS₂ (x = 0.0) to 1.04 eV of CuSbSe₂ (x = 1.0). The direct band gap of the CASSe solid solution linearly decreased from 1.45 eV of CuSbS₂ (x = 0.0) to 1.08 eV of CuSbSe₂ (x = 1.0). CuSbS_0.8Se_1.2 (x = 0.6) and CuSbS_0.4Se_1.6 (x = 0.8) had a suitable band gap of about 1.15 eV for an absorber material of a high-efficiency thin-film polycrystalline solar cell. - Highlights: • We synthesized CuSbS₂ and CuSbSe₂ by only a mechanochemical process. • The CuSb(S_1-xSe_x)₂ solid solutions were synthesized by post-heating at 450 °C. • Indirect and direct band gaps of CuSb(S_1-xSe_x)₂ solid solutions were estimated. • Indirect and direct band gaps of CuSbS₂ were 1.40 and 1.45 eV, respectively. • Indirect and direct band gaps of CuSbSe₂ were 1.04 and 1.08 eV, respectively