The density functional theory is approached for the study of structural, electronic and optical properties of an active material of Indium oxide (In2O3) which is used in a single layer organic light emitting diode. The structural analysis gives a small variation in the bond lengths of cubic, orthorhombic and in trigonal structures; there is s–p and p–p hybridizations, density of states explains optical metallic nature of cubic and orthorhombic structures and a semiconducting nature of trigonal structure. Charge density analysis explains highly ionic and partial covalent bonds between In–O atoms, and there is a high reflectance of incident photons in the range of 12–15 eV. There are broader optical absorption and optical conducting regions in cubic and orthorhombic structures; hence these are optically metallic conductors, no significant contribution made by trigonal structure. [ABSTRACT FROM AUTHOR]