Selenoborates: a latent structure resource for infrared functional crystal materials

Optoelectronic functional crystal materials are crucial components in laser systems and could be applied as polarized light converters, modulators, photorefractive devices, window materials etc. Borates and chalcogenides are well-established sources of ultraviolet (UV) and infrared (IR) optoelectronic functional crystal materials. The selenoborate system combines the structural diversity of borates with the extensive optical transmission range of metal selenides, showing potential as IR functional materials. However, research on selenoborates remains limited. This review aims to stimulate further research into IR optoelectronic functional crystal materials within the selenoborate system. First, this work offers a comprehensive review of all selenoborates (21) reported to date, categorizing them according to their structural motifs from zero to three dimensions. Second, the unique synthesis methods of selenoborates are summarized. Additionally, first-principles calculations are utilized to analyze the bandgaps and nonlinear optical (NLO) properties of these materials. As a result, it is concluded that selenoborates possess considerable potential for further investigation as IR functional materials, especially in terms of the structures and properties regulated by excellent microstructural groups.