An all-columnar bilayer light-emitting diode

The first organic light-emitting diode with both an electron-rich columnar liquid crystal as hole transport material and an electron-deficient fluores cent columnar liquid crystal as electron transport material is presented. R ed fluorescence is observed above 10 V from the configuration indium-tin ox ide (ITO)/hexabutoxy-triphenylene/tetraethyl perylenetetracarboxylate/Al. T he excellent charge transport properties of columnar phases are thus exploi ted for light-emitting diodes. Both organic materials exhibit their columna r liquid crystal phase well above room temperature and the underlying order ed solid columnar phase is used in the diode. The I(V) and L(V) characteris tics are very reproducible from device to device, with an emission peak at 620 nm and an FWHM of 80 nm, a current rectification ratio of about 30, I s imilar to V-2 at low voltages and I similar to L similar to V-7 at higher v oltages. Initial lifetime measurements are encouraging. (C) 2000 Elsevier S cience S.A. All rights reserved.