Highly efficient blue phosphorescent organic light-emitting devices using simple structures with thin 1,1-bis[(di-4-tolyamino)phenyl]cyclohexane layers

We have developed highly efficient blue phosphorescent organic light-emitting devices with thin 1,1-bis[(di-4-tolyamino)phenyl]cyclohexane (TAPC) layers. We used simple three organic layers: TAPC, iridium(III) bis[[4,6-di-fluorophenyl]-pyridinato-N,C2′] picolinate (FIrpic) doped N,N′-dicarbazolyl-3,5-benzene (mCP), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) layers. The device structure was ITO/TAPC (x nm)/mCP:FIrpic (5 nm, 10%)/BCP (55 nm)/LiF/Al. The 4 nm TAPC device shows current efficiency and power efficiency of 34 cd/A and 15.1 lm/W, respectively, at a luminance of 1540 cd/m2. We investigate the effect of TAPC thickness on the current efficiency, power efficiency, driving voltage, and electroluminescence characteristics.