A Solution-Processable Small-Molecule Host for Phosphorescent Organic Light-Emitting Devices

The phosphorescent organic light-emitting devices (OLEDs) consisting of the solution-processed four organic layers: hole injection layer, electron blocking layer, emissive layer, and electron injection layer were fabricated. The small-molecule host material used in the device, 3,3',6,6'-tetrakis(9-phenyl-9H-carbazol-3-yl)benzophenone (TCzBP), is insoluble in alcohol solvents such as methanol, ethanol, and 2-propanol. Therefore, alcohol soluble electron injection materials can be coated onto small-molecule TCzBP based-phosphorescent emissive layer from alcohol solution. Power efficiency of 22 lm/W and external quantum efficiency of 14.6% were achieved at 1000 cd/m(2) with spin-coated cesium carbonate (Cs2CO3) as an electron injection layer.