A Hybrid Antiperovskite with Strong Linear and Second‐Order Nonlinear Optical Responses

Antiperovskites have been studied since the 1980s because of their rich physical and chemical properties, but their linear and second-order nonlinear optical responses remain largely unknown. Here we report a new polar crystal, Cs3 Cl(HC3 N3 S3 ) (I), which features a quasi-one-dimensional antiperovskite structure composed of ClCs6 polyhedra and A-site [HC3 N3 S3 ]2- rings. To our best knowledge, this kind of antiperovskite structure is reported for the first time. Remarkably, I exhibits a very strong nonlinear optical response up to 11.4 times that of the benchmark KH2 PO4 and exceptionally large birefringence of 0.52. The first-principles calculations and structural analyses reveal that [HC3 N3 S3 ]2- is the "material gene" while the antiperovskite structural feature making it in a favorable arrangement. This work provides a new structural platform for the rational design of integrated optoelectronic materials with linear and second-order nonlinear optical responses.