Electrochemical n-doping of polyfluorenone films

The n-doping electrochemistry of polyfluorenone (PFO) films prepared by electrochemical polymerization of fluoren-9-one in boron trifluoride diethyl etherate (BFEE) has been characterized. Cyclic voltammetry in acetonitrile showed rapid and reversible n-doping. The potential dependence of the capacitance, measured by impedance spectroscopy, shows that PFO behaves primarily as a redox polymer during n-doping, with localized, non-interacting redox sites. However the potential dependence of the resistance suggests that there are long range effects of conjugation. Deactivation due to charge (cation) trapping occurred during repeated cycling through the n-doping wave. The n-doping capacity can be partially restored by p-doping. Use of polyethylene glycol as a stabilizer decreased the rate of charge trapping, and increased the recovery of n-doping capacity. Scanning electron microscopy revealed that charge trapping was associated with notable changes in the morphology of the PFO film that are characteristic of an annealing process.