Development of novel acceptors with deep LUMO energy levels

Abstract

Pure-organic red exciplex emitters are far from satisfactory in terms of quantity and efficiency. The narrow lowest unoccupied molecular orbital (LUMO) energy levels range of reported acceptors together with the intrinsic exciton non-radiative decay are the dominant factors restricting the progress of red exciplexes. Herein, two acceptor molecules operating at unique LUMO of -3.51 and -3.56 eV, namely 4-(6-([1, 1’: 3’, 1”-terphenyl]-5’-yl)-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) benzonitrile (CNAI-tPh) and 4-(6-(4-(4, 6-diphenyl-1, 3, 5-triazin-2-yl)phenyl)-1, 3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) benzonitrile (CNAI-TRz), were developed. Through binding to a donor whose HOMO energy level is -5.53 eV, the CNAI-TRz-related OLEDs attained a higher device efficiency amounting to 7.7% with a red-shifted spectrum compared to the CNAI-tPh-related devices. These results are remarkable among the reported pure-organic red exciplex-based OLEDs and demonstrate the tremendous potential of our synthesized acceptors in efficient red exciplexes.