Design approach of exciplexes enhancing the singlet and triplet energy by managing electron transport type host

A high singlet energy and triplet energy exciplex host was developed by synthesizing an electron transport type host with a controlled lowest unoccupied molecular orbital (LUMO) level and intermolecular interaction. A diphenyltriazine derived host was designed by substituting t-butyl functional moieties to the electron transporting core structure to make the LUMO shallow for high exciplex emission energy. An exciplex host with a singlet energy of 3.49 eV and a triplet energy of 3.02 eV was derived by mixing the t-butyl modified diphenyltriazine type host with a hole transport type host. The comparison of the newly developed t-butyl modified host with a previous host without the t-butyl group clarified that the t-butyl group had a singlet and triplet energy boosting effect. A high external quantum efficiency of 17.3% was demonstrated in the blue phosphorescent device using the high triplet energy exciplex host.