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

Abstract

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)-1,3,5-triazine (TRZ-1SO₂), 2-phenyl-4,6-bis(3-(phenylsulfonyl)phenyl)-1,3,5-triazine (TRZ-2SO₂) and 2,4,6-tris(3-(phenylsulfonyl)phenyl)-1,3,5-triazine (TRZ-3SO₂), were developed with deep LUMO energy levels of −3.38, −3.58 and −3.74 eV, respectively. Particularly, TRZ-3SO₂ 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-1SO₂, 13AB:TRZ-2SO₂ and 13AB:TRZ-3SO₂, were constructed with the emission from green to orange-red. The OLED using 13AB:TRZ-3SO₂ 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 4,4′-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.