β-In 2 S 3 and β-In 2 S 3 :Co 2+ single crystals were grown by the chemical transport reaction method using In 2 S 3 , S, and ZnS as starting materials and (ZnCl 2 + I 2 ) as a transport agent. The single crystals crystallized into a tetragonal structure. The indirect optical energy band gaps of the single crystals at 298 K were found to be 2.240 eV and 1.814 eV for β-In 2 S 3 and β-In 2 S 3 :Co 2+ , respectively. The direct optical energy band gaps were found to be 2.639 eV and 2.175 eV for β-In 2 S 3 and β-In 2 S 3 :Co 2+ , respectively. Impurity optical absorption peaks were observed for the β-In 2 S 3 :Co 2+ single crystal. These impurity absorption peaks were assigned, based on the crystal field theory, to the electron transitions between the energy levels of the Co 2+ ion sited in T d symmetry.

α- Ga 2 S 3 and α-Ga2S3:Fe2+ single crystals were grown by the two-zone sublimation method. The optical energy gaps of α-Ga2S3 and α-Ga2S3:Fe2+ at 10 K were found to be 3.440 and 3.392 eV, respectively. From the absorption spectra of α-Ga2S3:Fe2+, the crystal field parameter Dq of 345 cm−1 and Racah parameters B of 700 and C of 3365 cm−1 were obtained for tetrahedral Fe2+ ions. From the photoluminescence spectra at 10 K, the blue and red emissions at 424 and 643 nm, respectively, for α-Ga2S3 and the violet and yellow emissions at 400 and 580 nm, respectively, for α-Ga2S3:Fe2+ were observed. All the emission lines observed in the photoluminescence spectra were identified.

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CuAl 2 S 4 single crystals were grown with the constituent elements copper, aluminium and sulphur (purity 6N) as the starting material by the chemical transport reaction method using iodine as a transport agent. Layer-type colourless transparent single crystals were obtained, and the crystal structure of the single crystals was found to be cubic with the lattice constant a = 9.954 Å. The energy bandgap of the CuAl 2 S 4 single crystal was revealed to be direct bandgap, and the optical energy gap was found to be 4.10 eV at 10 K.

MnAl 2 S 4 and MnAl2Se4 single crystals were grown by the chemical transport reaction method. Optical energy gaps of the MnAl2S4 and MnAl2Se4 single crystals were 3.75 and 3.21 eV, respectively, at 300 K. Emission peaks due to donor-acceptor pair recombinations were observed at 450 and 603 nm in the MnAl2S4 single crystal and at 488 and 655 nm in the MnAl2Se4 single crystal. Optical absorption peaks and emission peaks described as appearing due to Mn2+ ion sited in Td symmetry were observed at 414, 450, 482, and 527 nm in the MnAl2S4 single crystal and at 416, 455, 488, and 532 nm in the MnAl2Se4 single crystal.