We describe photoinduced charge transfer process in a bilayer device comprised of poly(p-phenylene vinylene) (PPV) layer and a trap-free molecularly doped polymer containing diaryldiamine (TPD) dispersed in polycarbonate (PC). The time resolved charge transfer from PPV to TPD:PC in the presence of an electric field is analyzed. The injection (transfer) efficiency of the photoinduced holes from PPV into TPD:PC is about 25% holes/photons at electric fields at 4×105 V/cm or higher. Minimal trapping of photocarriers at the interface region between the two polymer layers is associated with this transfer.
In near-field scanning optical microscopy (NSOM), understanding the near-field distribution is important for the interpretation of the images. In this paper, we present a new method to measure the two-dimensional intensity distribution by use of photochemical reactions.
Molecular quantum chemical calculations were performed both at the ab initio and at the semi-empirical level to model the molecular conformations and electronic structure of oligomers of poly(phenylene vinylene) during the early stages of interface formation with Al, Ca and Mg. We found that the divalent metals, Mg and Ca, disrupt the conformation of the oligomers less than Al does. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) move into the energy gap both for Ca- and for Mg-doped systems, resulting in gap-state formation. This is consistent with the polaron/bipolaron picture. The electron density plots indicate that the de-localization of electrons is reduced more significantly by Al than it is by Ca and Mg. Our simulation results have been confirmed experimentally via XPS and NEXAFS.
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