Cs₂ZnSn₃S₈: A Sulfide Compound Realizes a Large Birefringence by Modulating the Dimensional Structure

Birefringence, an important optical performance parameter for optoelectronic functional materials, is mainly influenced by the types of anion groups and their spatial arrangement. Inspired by the relationship between the structure and properties of chalcogenides, combined with the dimensional transformation, we successfully synthesized a sulfide compound (Cs₂ZnSn₃S₈) with a two-dimensional layered structure and a large birefringence. The experimental results showed that, compared with Rb₁₀Zn₄Sn₄S₁₇, Cs₂ZnSn₃S₈ achieved the structural transition from a zero-dimensional arrangement to a two-dimensional lamellar arrangement and achieved a breakthrough of birefringence from 0 to 0.12, which was determined by both experiments and first-principles calculations. These findings demonstrated that Cs₂ZnSn₃S₈ was a potential birefringent material and provided instructions for the study of the synthesis of birefringent materials.