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 fi eld and temperature. Charge carriers were generated upon either photoexcita tion into the S-1 <-- S-0 transition of the polymer or via sensitized injec tion from a thin rhodamine 6G layer. The results will be interpreted in ter ms of the concept of hopping among polymer segments featuring a Gaussian di stribution of energies, its variance being 91 meV. While TOF signals genera ted via sensitized injection are similar to those in molecularly doped poly mers bearing out a transition from nondispersive to dispersive transport, i ntrinsically 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 sta tes. (C) 2000 American Institute of Physics. [S0021-9606(00)70233-9].