Optical absorption and electrical conductivity of electron acceptor doped poly-3-octylthiophene films

Russell LeRoy Lidberg, University of Nevada, Las Vegas


Optical absorption and electrical conductivity measurements of solution-doped poly-3-octylthiophene (P3OT) films were studied. Chloroform solutions of P3OT were doped with the organic electron-acceptors, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ); and with the inorganic electron acceptor, ferric chloride (FeCl{dollar}\sb3{dollar}). Charge transfer was observed in P3OT solutions doped with FeCl{dollar}\sb3{dollar} and DDQ. TCNQ-doped solutions showed no optical evidence of charge transfer. Thin films of the doped P3OT were examined at various doping levels. Spectroscopic and electrical conductivity measurements of P3OT films, doped with DDQ, TCNQ, and FeCl{dollar}\sb3{dollar}, at different doping levels, are presented. Optical absorption measurements provided information on the degree of charge transfer occurring for the various dopants. Electrical conductivity measurements showed that the conductivity of P3OT increased with the various dopants in the order of TCNQ {dollar}<{dollar} DDQ {dollar}<{dollar} FeCl{dollar}\sb3{dollar}, for the same dopant concentration level. Results are discussed in relation to the electrochemical properties of the prepared films and the structural properties of P3OT.