Novel 2,4-difluorophenyl-functionalized arylamine as hole-injecting/hole-transporting layers in organic light-emitting devices

Novel 2,4-difluorophenyl-functionalized triphenylamine and its dimer, namely tris(2′,4′-difluorobiphenyl-4-yl)-amine (3FT) and N4,N4,N4′,N4′-tetrakis-(2′,4′-difluorobiphenyl-4-yl)-biphenyl-4,4′-diamine (4FDT), have been synthesized and characterized. The device with the configuration of ITO/4FDT/Alq3/LiF/Al yields maximum current efficiency of 4.3 cd/A. Moreover, with 4FDT as the hole-injecting layer, the maximum efficiency and luminance of the device was further improved to be 5.0 cd/A and 19 880 cd/m2, respectively. The good performance of devices with 4FDT as HTL or HIL was attributed to the incorporation of the strong electron-withdrawing fluorinated substituents into the arylamine moiety, which reduced holes mobility of HTL and HIL and then balanced the injected carriers in devices.