Organic Long-Persistent Luminescence from a Thermally Activated Delayed Fluorescence Electron Donor-Acceptor Binary System

Organic long-persistent luminescence (OLPL) based on long-lived charge-separated (CS) states shows considerable emission persistence time owing to the ability to store absorbed photon energy. Herein, a novel electron donor-acceptor (D-A) binary system consisting of electron donor 4,4,4-tris[3methylphenyl(phenyl)amino]triphenylamine and electron acceptor tris-[3-(3-pyridyl)mesityl]borane is designed and investigated for outstanding OLPL performance. It is found that the proposed binary system exhibits effective OLPL emission that lasted for more than 100 s after 1 min of ultraviolet light irradiation at room temperature (292 K). Moreover, this electron D-A binary system also exhibits thermally activated delayed fluorescence emission prior to OLPL emission. Both emission types are found to be temperature-sensitive, which are believed to result from the occurrence of reverse intersystem crossing and the formation of a CS state, respectively. The findings enrich the electron D-A system OLPL materials and clarify the rich excited-state transitions during OLPL emission of electron D-A systems.