Oxygen‐Substitution Induced High‐Performance Nonlinear Optical Properties: Witnessed by the First Quaternary Oxythiostannate

Oxychalcogenides can combine the large second-harmonic generation (SHG) effects of chalcogenides with the wide bandgaps of oxides to obtain high-performance infrared (IR) nonlinear optical (NLO) crystal materials. Here, the first quaternary oxythiostannate NLO crystal material Sr6Sn3OS11 crystallized in the trigonal noncentrosymmetric space group P3m1 is synthesized by a high-temperature solid-state method. Its 0D structure features isolated [SnS4] and [SnOS3] tetrahedra, which can be derived from parent 0D Sr2SnS4 (Ama2) via anion partial substitution. The SHG response of Sr6Sn3OS11 primarily contributed by [SnS4] tetrahedra is increased to be 0.82 × benchmark AgGaS2 compared with 0.5 × AgGaS2 for Sr2SnS4. The experimental bandgap of Sr6Sn3OS11 is 2.81 eV, which is mainly determined by the Sr 4d and S 3p orbitals according to the theoretical calculation results. This work not only expands oxythiostannates as promising IR NLO materials but also contributes a facile strategy to improve the NLO properties from known ones.