Organic Light-Emitting Diodes with F16CuPC as an Efficient Hole-Injection Layer

We report a new hole-injection material, copper hexadecafluorophthalocyanine (F16CuPC) for organic light-emitting diodes (OLEDs) consisting of N,N’-di(1-naphthyl)-N,N’-diphenylbenzidine (α-NPD) as a hole-transport layer and 8-tris-hydroxyquinoline aluminum (Alq3) as a light-emitting and electron-transport layer. The insertion of the F16CuPC between indium-tin oxide (ITO) and α-NPD reduces the operating voltage significantly and thereby increases the luminous efficiency. By measuring the device characteristics for various F16CuPC thicknesses, we find that an optimum F16CuPC thickness is about 15 nm. At a luminance of 1000 cd/m , the device with 15-nm-thick F16CuPC shows a luminous efficiency of 1.5 lm/W and a device operating voltage of 7.2 V while the device without the F16CuPC layer shows 1.1 lm/W and 10.4 V. The significant decrease in a driving voltage and increase in the luminous efficiency can be attributed to the high hole-injection efficiency when F16CuPC is inserted between ITO and α-NPD.