Direct Measurement of Conjugated Polymer Electronic Excitation Energies Using Metal/Polymer/Metal Structures

We report electroabsorption measurements of built-in electric fields and internal photoemission measurements of Schottky barriers to determine the charge transfer and single-particle energy gaps of the conjugated polymer poly2-methoxy, 5- (2'-ethyl-hexyloxy) -1, 4-phenylene vinylene (MEH-PPV). For MEH-PPV, with an exciton absorption peak of 2. 25 eV, or results yield a single-particle energy gap of 2. 45 eV and a charge transfer energy gap of at least 2. 35 eV. Therefore the exciton binding energy is 0. 2 eV and the bipolaron binding energy is less than 0. 1 eV.