Indium(III) selenide is a compound of indium and selenium. It has potential for use in photovoltaic devices and has been the subject of extensive research. The two most common phases, ñ and ò, have a layered structure, while ó has a "defect wurtzite structure." In all, five polymorphs are known: ñ, ò, ó, ô, ú. The ñ-ò phase transition is accompanied by a change in electrical conductivity. The band gap of ó-In<sub>2</sub>Se<sub>3</sub> is approximately 1.9 eV.
The method of production influences the polymorph generated. For example, thin films of pure ó-In<sub>2</sub>Se<sub>3</sub> have been produced from trimethylindium (InMe<sub>3</sub>) and hydrogen selenide via MOCVD techniques.
A conventional route entails heating the elements in a sealed tube: