Solvothermal syntheses, characterization and photoluminescence properties of layered quaternary sulfides ACuZnS2 (A = K, Rb, Cs)

Abstract

Three layered quaternary sulfides, ACuZnS₂ (A = K, Rb, Cs) have been synthesized by a facile solvothermal method using ethylenediamine as solvent and characterized by a combination of structural, magnetic, and optical measurements. They adopt the ThCr₂Si₂-type structure (space group I4/mmm) and are composed of alternating two-dimensional [CuZnS₂]⁻¹ layers and alkali metal layers. Based on magnetization and optical measurements, these three compounds are found to be paramagnetic semiconductors. The optical band gap is around 2.75 eV and for the first time two photoluminescence bands are observed for each compound. The green luminescence can be ascribed to a localized Cu⁺ emitting level and the red one to an excitonic state.