Fluorenone-based thermally activated delayed fluorescence materials for orange-red emission.

Herein, two orange-red emitters, 3,6-bis(9,9-dimethylacridin-10(9H)-yl)-9H-fluoren-9-one (DMAC-FO) and 3,6-di(10H-SP[acridine-9,9′-fluoren]-10-yl)-9H-fluoren-9-one (SPAC-FO), based on fluorenone have been designed and synthesized. As compared to the widely reported benzophenone acceptor, fluorenone has deeper lowest unoccupied molecular orbital (LUMO) because of its more conjugated skeleton and thus it can red-shift the emission maximum. The molecular simulation exhibits both emitters has separated highest occupied molecular orbitals (HOMOs) (@donors) and LUMOs (@acceptor), indicating they could act as thermally activated delayed fluorescence (TADF) materials which are further confirmed by the transient spectra. Consequently, external quantum efficiencies (EQEs) of 10.0% for DMAC-FO and 14.2% for SPAC-FO are achieved in the organic light-emitting diodes (OLEDs). Image 1 • Two orange-red emitters, DMAC-FO and SPAC-FO, based on fluorenone have been designed and synthesized. • TADF properties were realized in DMAC-FO and SPAC-FO due to the highly twisted structure. • High EQEs of 10.0% for DMAC-FO and 14.2% for SPAC-FO were achieved in OLEDs. [ABSTRACT FROM AUTHOR]