Effect of annealing on the electrical properties and morphology of a conducting polymer used as an anode in organic light-emitting devices

The surface sheet resistance of conducting films of glycerol-doped poly(3,4-ethylenedioxy-thiophene)-poly(styrene sulfonate) is largely dependent on the annealing temperature. The presence of free glycerol in insufficiently baked films, as indicated by infrared spectra and thermogravimetric analysis, results in conducting polymer films with poor morphology and low electrical conductivity. The device performance of organic light-emitting diodes using this modified poly(3,4-ethylenedioxy-thiophene)-poly(styrene sulfonate) as an anode is also greatly affected by the baking conditions of the conducting films. The maximum light output, current density, and luminous power efficiency are observed from devices using anodes baked at a high temperature close to the boiling point of glycerol. (C) 2003 Wiley Periodicals, Inc.