Two Novel Large Birefringent Sulfide Crystals, Cs2znge3s8 and Cs2cdge3s8, Showcase Wide Band Gaps and Distinct Structural Symmetries

Investigating highly birefringent crystals with an extended wavelength range is crucial for expanding their applications in optoelectronic research. Guided by insights into the interplay between the structure and properties of sulfide materials, this study successfully synthesized two sulfur compounds, Cs2ZnGe3S8 and Cs2CdGe3S8, which exhibit large birefringence of 0.134 and 0.11, as well as wide bandgaps of 3.34 eV and 3.35 eV, respectively. Through the incorporation of elements with higher electronegativity and the manipulation of anion group distortion, the band gap of this compound series was effectively widened, while the structural symmetry was changed. Cs2ZnGe3S8 and Cs2CdGe3S8 exhibit promising potential as large birefringence crystals suitable for UV band applications. These findings offer valuable insights for the design of birefringent crystals with extended wavelength ranges, thus diversifying their potential applications.