Transport of holes in uniformly and non-uniformly protonated poly(o-methoxyaniline)

Steady-state and transient currents were measured in bulk- and surface-protonated poly(o-methoxyaniline) emeraldine. The results obtained demonstrate that in surface-doped samples the protonated surface acts as a contact injecting holes into the bulk. The hole mobilities estimated from time-of-flight experiments performed on such samples amount to 3 x 10(-4) cm(2)/Vs at ambient temperature. In uniformly protonated samples, we observed a transient decrease in the currents following the Light pulse, recovering exponentially with a time constant equal to ca. 17 ms. Such a behaviour ('negative photoconductivity') was attributed to the production of long-lived excited species acting as localization centres.