ELECTRONIC-PROPERTIES AND ORIENTATION STUDIES OF POLY-3-ALKYLSELENOPHENE ELECTROCHEMICALLY DEPOSITED ON PT AS OBSERVED BY NEXAFS

The electronic properties and orientation of films of poly-3-alkylselenophenes (poly-3-(CH2)n(CH3)-selenophenes) electrochemically deposited onto Pt have been studied by NEXAFS. The C—K edge characteristics reveal that several major effects occur when n is increased from 0 to 9: (i) In the undoped semiconducting form, a continuous decrease in the polymeric 1s → π* intensity is observed due to an overlap between the π* antibonding band from the polymer and the σ*(C2p—H1s) band which develop when the alkyl chain length increases, (ii) The doping to the conducting state proceeds via a narrowing of the bandgap causing the appearance of metallic-like behavior. However, the changes in the unoccupied antibonding π* band become less pronounced for a long alkyl chain length, (iii) The orientation of the selenophene ring structure switches from a “lying-down” to an “on-edge” configuration with the long alkyl chain being oriented perpendicular to the Pt surface. © 1990, The Electrochemical Society, Inc. All rights reserved.