High-efficiency green phosphorescence from spin-coated single-layer dendrimer light-emitting diodes

We demonstrate very high-efficiency green phosphorescence from a single-layer dendrimer organic light-emitting diode formed by spin-coating. A first generation fac-tris(2-phenylpyridine) iridium cored dendrimer doped into a wide-gap 4,4'-bis(N-carbazole) biphenyl host displays a peak external quantum efficiency of 8.1% (28 Cd/A) at a brightness of 3450 Cd/m(2) and a current density of 13.1 mA/cm(2). A peak power efficiency of 6.9 lm/W was measured at 1475 Cd/m(2) and 5 mA/cm(2). We attribute this exceptionally high quantum efficiency for a single-layer device to the excellent film forming properties and high photoluminescence quantum yield of the dendrimer blend and efficient injection of charge into the emissive layer. These results suggest that dendrimers are an effective method for producing efficient phosphorescent devices by spin-coating. (C) 2002 American Institute of Physics.