copperindium

Copperindium is a chemical system comprising copper and indium elements. It is encountered most commonly in several classes of compounds: discrete intermetallics such as CuIn and CuIn2 (binary copper–indium intermetallics), and a family of copper–indium chalco- and selenides with the formula CuInS2 and CuInSe2, as well as solid solutions with gallium used in photovoltaic absorbers.

Intermetallics in the copper–indium system form ordered compounds with a range of stoichiometries. They are typically crystalline solids that can be high-melting and brittle. These materials are primarily of interest in solid-state chemistry and materials science, where they are studied for fundamental properties and potential electronic applications. They are not widely used as commercial metals outside of research contexts.

Copper indium sulfide (CuInS2) and copper indium selenide (CuInSe2) are semiconductors with direct band gaps around 1.5 eV and 1.04 eV, respectively. They are p-type materials and can form solid solutions with gallium to produce copper indium gallium sulfide/selenide (Cu(In,Ga)S2, Cu(In,Ga)Se2). The solid solutions are used to tune the band gap for photovoltaic absorbers, especially in thin-film solar cells.

Applications and synthesis: CuInS2 and CuInSe2, as well as their Cu(In,Ga)S2/Se2 counterparts, are typically prepared by solid-state reactions or thin-film deposition techniques, such as co-evaporation or chemical vapor deposition, followed by sulfurization or selenization. The Cu(In,Ga)Se2 family (CIGS) is a leading absorber material in flexible, thin-film solar cells due to strong light absorption and tunable band gaps.

Economic and environmental considerations: Indium is relatively scarce and costly, affecting material availability and price. Recycling, reuse, and efficient manufacturing are important. Ongoing research seeks to improve efficiency, stability, and integration of copper–indium absorbers in photovoltaic devices.