Infrared (IR) nonlinear optical (NLO) crystals with outstanding properties are crucial for extending the laser wavelengths through frequency conversion technology and have been employed in many fields such as civil industry, medicine, and military affairs. Among the studied IR NLO crystals, Ag-based chalcogenides are one of the most favorable candidates, not only owing to their compositional or structural relationship with the benchmark IR NLO materials AgGaS₂ and AgGaSe₂, but also due to their diverse structures, large NLO intensities, wide IR transparent regions, and suitable birefringences for phase matching. So far, many Ag-based chalcogenides and derivatives (AChDs) with prominent NLO properties have been reported; however, a systematic summary of them is absent, which is significantly needed to facilitate the ever-increasing research on IR NLO materials. Herein, we summarized AChDs by classifying the investigated materials into three groups, based on their chemical composition and expounding the chemical composition-NCS structure-NLO performance relationship. In this review, the following features of AChDs with IR NLO properties were summarized. (1) Quaternary Ag-based chalcogenides were much more abundant compared to the ternary ones. (2) Although Ag possessed various coordination modes (linear or V-shaped, triangular, and tetrahedral), AgQ₄ tetrahedra were much more common than the AgQ₂ and AgQ₃ (Q = S, Se) units. (3) The cations of AChDs tended to construct one type of conventional IR NLO structural unit, namely, MQ₄ tetrahedra (M = Zn, Cd, Hg, Ga, In, Si, Ge, Sn, P; Q = S, Se), making great contributions to the microscopic NLO responses. Finally, the exploration directions and development prospects of AChDs as promising IR NLO candidates were discussed from the deduced structure–property relationship.

具有优异性能的红外（IR）非线性光学（NLO）晶体对于通过频率转换技术扩展激光波长至关重要，并已应用于民用工业，医学和军事等许多领域。在研究的 IR NLO 晶体中，Ag 基硫族化物是最有利的候选者之一，这不仅是因为它们与基准 IR NLO 材料 AgGaS ₂和AgGaSe _{2的组成或结构关系}, 但也由于它们的不同结构、大的 NLO 强度、宽的 IR 透明区域以及适合相位匹配的双折射。到目前为止，已经报道了许多具有显着 NLO 特性的 Ag 基硫族化物和衍生物 (AChDs)；然而，缺乏对它们的系统总结，这对于促进对 IR NLO 材料不断增加的研究是非常需要的。在此，我们通过将研究的材料根据其化学成分分为三组并阐述化学成分-NCS 结构-NLO 性能关系来总结 AChD。在这篇综述中，总结了具有 IR NLO 属性的 AChD 的以下特征。(1) 与三元相比，季银基硫族化物的含量要丰富得多。(2) 虽然 Ag 具有多种配位模式（线性或 V 形，₄四面体比 AgQ ₂和 AgQ ₃ (Q = S, Se) 单元更常见。(3) AChDs的阳离子倾向于构建一类常规IR NLO结构单元，即MQ ₄四面体(M = Zn, Cd, Hg, Ga, In, Si, Ge, Sn, P; Q = S, Se ), 为微观 NLO 响应做出了巨大贡献。最后，从推导的结构-性质关系讨论了 AChDs 作为有前途的 IR NLO 候选者的探索方向和发展前景。