Infrared (IR) nonlinear optical (NLO) material is one of the core device of all-solid-state lasers, which show wide applications in long distance laser communication, environmental monitoring and photonic technologies, etc. Currently, the commercially available IR NLO materials are mainly composed of chalcopyrite-like (CL) compounds, like AgGaS₂ (AGS), AgGaSe₂ (AGSe), and ZnGeP₂ (ZGP), which are built by tetrahedral structure units. Nevertheless, the small band gaps (E_g) induced low LIDT and two-photon absorption (TPA) in these materials have limited their further applications in current far-IR laser techniques. Hence, break through the property limitations of CL compounds, developing high performance IR NLO materials based on advantageous structural motifs or new strategies becomes an urgent need.

Recently, a research group led by Prof. Shilie Pan and Prof. Junjie Li at Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Science, designed and fabricated 11 new compounds in the AIBII6CIII6QVI16 family by simple high-temperature solid-state reaction. Among them, Sn_0.5Mg₃Ga₃S₈achieves a strongSHGresponse (1.5× AGS), a wide bandgap (2.62 eV), and a high LIDT (3.0 × AGS) as one of the promising candidates for IR all-solid-state laser technology. Additionally, it shows broad blue-green photoluminescence with a FWHM of 112 nm (456–568 nm) under 396 nm excitation.The DFT calculations reveal the pivotal role of triangular prismatic [SnS₆] in governing the optical bandgap, SHG response, and PL properties of Sn_0.5Mg₃Ga₃S₈. This study broadens the structural diversity of Sn-based chalcogenides and offers novel insights for designing advanced optoelectronic materials, such as photoelectric detector, light-emitting diodes, and chemical sensors, through a lattice confinement-engineered approach, leveraging the novel triangular prismatic [SnS6] structural units.

The paper was published in Advanced Functional Materialswith the title: Lattice Confinement-Stabilized Triple-Connected Sn(II) Chalcogenides for Strong Second-Harmonic Generation and Broadband-Tunable Photoluminescence. This work was financially supported by National Youth Talent Program of China, the Strategic Priority Research Program of the Chinese Academy of sciences, National Natural Science Foundation of China, and Xinjiang Key Research and Development Program.

Figure 1.The design of Sn(II) bifunctional materials based on the windmill-shaped anion framework's lattice confinement effect.