Crystallographic and optical properties of CuInS2-Cu2ZnSnS4 crystals

CuInS2-Cu2ZnSnS4 crystals were synthesized by the pressure-less sintering method using CuInS2 and Cu2ZnSnS4 powders grown from each melt. The x values in Cu2(2In)x(ZnSn)(1.00−x)S4 were evaluated by energy dispersive spectroscopy. Lattice constants were derived from powder X-ray diffraction analysis by Rietveld method. Lattice constants of CuInS2 phase changed linearly at x ≥ 0.49. On the other hand, lattice constants of Cu2ZnSnS4 phase changed almost linearly at x ≤ 0.37. In Raman spectra, peak positions of A (I4¯) or A1 (I4¯2m) mode of Cu2ZnSnS4 phase changed toward the lower wavenumber side linearly with increasing x. A1 mode of CuInS2 phase became weaker with decreasing x, and disappeared below x = 0.49. In PL spectra measured at 15 K, broad peaks at about 1.26 eV were observed at 0.00 ≤ x ≤ 0.85.