Inorganic benzenes with inverted singlet-triplet gaps.

Inorganic-type benzenes have attracted significant attention due to their unique physical and chemical properties that are different from organic benzene. In this study, we theoretically investigate the possibility of inorganic benzenes as wide-gap materials with inverted singlet and triplet (iST) excited states. Since iST materials are expected to allow extremely efficient triplet to singlet conversion, they are promising as fluorescent and assist dopant materials for light-emitting diodes. From theoretical calculations, borazine (B3N3H6), one of the most well-known inorganic benzenes, and its derivatives are expected not only to show iST but also to exhibit fast radiative decays surpassing those of typical iST materials: azaphenalene derivatives. Borthiin (B3S3H3), boroselenol (B3Se3H3), and the gallium-nitride analogue of benzene (Ga3N3H6) are also expected to show iST with wide optical gaps.