Indium tin oxide (ITO, or tin-doped indium oxide) is a solid solution

Solid solution

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...

 of indium(III) oxide

Indium(III) oxide

Indium oxide is a chemical compound, an amphoteric oxide of indium.-Crystal structure:Amorphous indium oxide is insoluble in water but soluble in acids, whereas crystalline indium oxide is insoluble in both water and acids. The crystalline form exist in two phases, cubic and rhombohedral . Both...

 (In₂O₃) and tin(IV) oxide (SnO₂), typically 90% In₂O₃, 10% SnO₂ by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey. In the infrared region of the spectrum it is a metal-like mirror.

Indium tin oxide is one of the most widely used transparent conducting oxides because of its two chief properties, its electrical conductivity and optical transparency, as well as the ease with which it can be deposited as a thin film.