High efficiency simple white phosphorescent organic light-emitting diodes using a phosphine oxide host

Highly efficient simple white organic light-emitting diodes (WOLEDs) were fabricated using a mixed host of 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and 2,7-bis(diphenylphosphoryl)-9,9'-spirobi[fluorene] (SPPO13) in the light-emitting layer. A two layer WOLED structure of TAPC hole transport layer and TAPC:SPPO13 emitting layer was developed. Red and blue phosphorescent emitters were doped in the TAPC:SPPO13 mixed host emitting layer and a high quantum efficiency of 16.0% was obtained. In addition, the maximum power efficiency of the WOLEDs was 37.5 Im/W and color coordinate was (0.43, 0.41). The color coordinate could be kept stable irrespective of the luminance of the device.