Alkali halide flux synthesis, crystal structure, and photoelectric response of quaternary thiosilicates K3Ga3Si7S20 and K2ZnSi3S8

Two new quaternary thiosilicate crystalline compounds namely K3Ga3Si7S20 (1) and K2ZnSi3S8 (2) with distinct dimensions were successfully synthesized by the alkali halide flux synthesis method. Both structures feature an anionic M-S-Si (M = Ga or Zn) network constructed from interconnected MS4 and SiS4 tetrahedral units with charge balancing K+ cations. The anionic architecture of 1 is a three-dimensional (3-D) anionic open framework of [(Ga/Si)(10)S-20](n)(3n-) with large channels in which K+ ions are located, while that of 2 presents a two-dimensional (2-D) anionic layer of [ZnSi3S8](n)(2n-) and K+ cations reside in the interlayered spaces. Their physicochemical performances including optical bandgap and thermal behavior were investigated, and the photoelectric response and impedance of 1 were explored. The optical absorption edges of the two compounds are determined to be 3.60 eV (1) and 2.57 eV (2), respectively. In particular, 1 shows good photoelectric response performance, which endows it with broad application prospects in the photoelectric field.