Hole transport in polyphenylenevinylene-ether under bulk photoexcitation and sensitized injection

Employing the time-of-flight (TOF) technique, the hole mobility in films of polyphenylenevinylene-ether has been measured as a function of electric field and temperature. Charge carriers were generated upon either photoexcitation into the S1←S0 transition of the polymer or via sensitized injection from a thin rhodamine 6G layer. The results will be interpreted in terms of the concept of hopping among polymer segments featuring a Gaussian distribution of energies, its variance being 91 meV. While TOF signals generated via sensitized injection are similar to those in molecularly doped polymers bearing out a transition from nondispersive to dispersive transport, intrinsically generated TOF signal features a cusp at higher temperature and almost no dispersion. The latter phenomenon turns out to be a consequence of charge generation at the tail of the density distribution of hopping states.