Preparation and characterization of highly efficient blue TPBI:FIrpic organic light-emitting devices

Blue phosphorescent organic light-emitting devices (PhOLEDs) using 1,3,5-tris(N-phenyl-benzimiazole-2-yl) benzene [TPBI] as the host and bis((4,6-difluorophenyl)-pyridinate-N,C2')picolinate [FIrpic] as the dopant in the emitter were fabricated with different treatments of the hole-transport layers and doping levels. Among the experimental devices, the best electroluminescent characteristics were obtained in the device with the combined hole-transport layer of N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolylamino)-phenyl]-biphenyl-4,4'-diamine [DNTPD]/1,1-bis-(di-4-polyaminophenyl)-cyclo-hexane [TAPC] and a doping level of 10-vol.% FIrpic. The device with a structure of DNTPD/TAPC/TPBI:Firpic (10%) showed a luminance of 1300 cd/m(2) at an applied voltage of 10 V, a maximum current efficiency of 18 cd/A, and color coordinates of (0.17, 0.43) on the Commission Internationale de I'Eclairage (CIE) chart.