Selenides are compounds containing the selenide anion, Se2-. As selenium is a member of group 16 on the periodic table, it is considered a chalcogen, and selenide compounds belong to a class of compounds known as chalcogenides.
Alkali metal and alkaline earth chalcogenides are typically colorless, water-soluble compounds used primarily as reagents in chemical synthesis. In contrast, transition metal chalcogenides exhibit a more covalent bond character and useful electronic and optical properties, and many are brightly colored. These are the chalcogenides most often used directly as functional materials; they are found as pigments, catalysts, optical materials, phase change materials, solid electrolytes, or semiconductors. The properties of main-group chalcogenides are less generalizable, but like transition metal halides, they exhibit covalent bonding and many have direct applications. Many chalcogenides compounds occur naturally as minerals such as pyrite (iron sulfide) and calaverite (gold telluride).
Most commercially important selenides are inorganic semiconducting solids, and are found in a variety of optical and/or electronic applications. Copper indium gallium selenide (CIGS), which is a solid solution of copper indium selenide and copper gallium selenide, is an important thin-film solar cell material. Cadmium selenide is a well-researched material used primarily in the form of quantum dots for applications in solar cells, LEDs, and biofluorescent tagging. Lead selenide is a thermoelectric semiconductor that is widely used for infrared detectors in thermal imaging applications.
Additionally, there are a number of organic selenides that are used primarily in depositing thin films of selenium compounds through processes such as metal organic vapor epitaxy.