Electrical and Optical Properties of Phosphorescent Organic Light-Emitting Devices with a TAPC Host

We fabricated phosphorescent organic light-emitting devices with a 1,1-bis[(di-4-tolylamino) phenyl] cyclohexane (TAPC) host layer. Two kinds of devices, one of ITO/TAPC/TAPC: FIrpic/TAZ/LiF/Al (device A) and one of ITO/TAPC: FIrpic/TAPC/TAZ/LiF/Al (device B), were prepared to investigate electrical and optical properties. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N, C-2'] picolinate (FIrpic) and 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)1,2,4- triazole (TAZ) were used as a blue phosphorescent guest material and an electron transport layer, respectively. The TAPC layer in device B strongly contributes to whitish emission, higher driving voltage, and lower current efficiency characteristics compared with device A. The mechanisms of these electrical and optical characteristics of the devices were investigated.