Novel triazine derivatives with deep LUMO energy levels as the electron-accepting components of exciplexes

Although a variety of electron-accepting molecules (acceptors) have been reported to develop exciplexes, their LUMO energy levels are still limited from -2.9 to -3.3 eV. This narrow range seriously restricts the development of exciplexes. In this work, three novel triazine-based acceptors, 2,4-diphenyl-6-(3-(phenylsulfonyl)phenyl)-1,3,5triazine (TRZ-1SO(2)), 2-phenyl-4,6-bis(3-(phenylsulfonyl)phenyl)-1,3,5-triazine (TRZ-2SO(2)) and 2,4,6tris(3-(phenylsulfonyl)phenyl)-1,3,5-triazine (TRZ-3SO(2)), were developed with deep LUMO energy levels of -3.38, -3.58 and -3.74 eV, respectively. Particularly, TRZ-3SO(2) exhibits the deepest LUMO energy level of -3.74 eV among the reported acceptors so far. By combining with an electron-donating molecule, 1,3-bis(9,9-dimethylacridin-10(9H)-yl)benzene (13AB), three exciplexes, 13AB:TRZ-1SO(2), 13AB:TRZ-2SO(2) and 13AB:TRZ-3SO(2), were constructed with the emission from green to orange-red. The OLED using 13AB:TRZ-3SO(2) as the emitter exhibits an orange-red emission peaking at 572 nm with a maximum external quantum efficiency of 5.5%. Meanwhile, green and red phosphorescent OLEDs (PhOLEDs) were fabricated using interfacial exciplex hosts by combining these acceptors with 4,40-bis(carbazole-9-yl) biphenyl (CBP), which successfully exhibits superior performance compared with that of reference devices. These results demonstrate that the three novel acceptors have great potential in the development of exciplexes.