Versatile fluorinated derivatives of triphenylamine as hole-transporters and blue-violet emitters in organic light-emitting devices

A series of triphenylamine derivatives end-capped with various fluorinated phenyl (TPAF) have been designed and synthesized for the application in organic light-emitting devices (OLEDs). By changing the substitution pattern of electron-withdrawing groups, such as F and CF ₃, the ability of hole-transport, energy levels, and thermal stability of these, TPAF are tuned, which are supported by density functional study of their geometry and electronic structure. TPAF can be used as either hole-transporters or blue-violet emitters in OLEDs. Among TPAF, the device with TPA-(2)-F as hole-transport material achieved the maximum current efficiency of 4.7 cd A ^-1, which was much higher than that of the typical N,N′-di(1-naphthalenyl)-N,N′- diphenyl-4,4′-diamine-based device. This good performance of the TPA-(2)-F-based device was attributed to the more balanceable injected carriers in the device by tuning hole injection and transport. More importantly, nondoped blue OLEDs utilizing TPAF as the emitters exhibited blue-violet emissions peaking between 408 and 428 nm with Commission Internationale de L'Eclairage coordinates in a range of (0.16-0.18, 0.06-0.12), which were also expected to be a new material class with an enhanced current efficiency/color purity compromise for future blue light-emitting devices.