High power efficiency in simplified two layer blue phosphorescent organic light-emitting diodes

High power efficiency blue phosphorescent organic light-emitting diodes (PHOLEDs) with only two organic layers were developed using a spirobifluorene based phosphine oxide (SPPO13) host material. Two layer blue PHOLEDs with only 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) hole transport layer and TAPC:SPPO13:blue dopant mixed host emitting layer were fabricated. A high power efficiency of 26.0 lm/W at 1000 cd/m2 were achieved in the simple blue device due to the high quantum efficiency of 17.5% and a low driving voltage of 4.1 V at 1000 cd/m2. In addition, a maximum power efficiency of 48.5 lm/W and a high quantum efficiency of 19.6% were demonstrated from the simple blue PHOLEDs with only two organic layers.