Electronic structure of pristine and sodium doped poly(p- pyridine)

The Journal of Chemical Physics (Impact Factor: 3.12). 03/2001; 114:4243-4252. DOI: 10.1063/1.1343485

ABSTRACT The electronic structure of pristine and sodium-doped poly(p- pyridine) has been studied using both ultraviolet and x-ray photoelectron spectroscopy. The spectra are interpreted with the help of the results of quantum-chemical calculations. Electronic band-structure calculations are performed for isolated chains with different connectivity patterns (head-to- tail and head-to-head), using the valence effective Hamiltonian (VEH) method, with geometries derived from optimizations using the Austin Model 1 Hamiltonian. The density-of-valence-states are derived directly from the VEH band structure. Excellent agreement is obtained between the theoretical simulations and the experimental data, which allows for a detailed assignment of the different peaks in the spectra. The C(1s) and N(1s) shake-up spectra of poly(p-pyridine) are analyzed on the basis of corresponding data for pyridine in the gas phase. Upon sodium doping of poly(p-pyridine), new states are observed within the otherwise forbidden energy gap. These new states can be assigned to the formation of bipolarons. (C) 2001 American Institute of Physics.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: Self-localized nonlinear excitations (solitons, polarons, and bipolarons) are fundamental and inherent features of quasi-one-dimensional conducting polymers. Their signatures are evident in many aspects of the physical and chemical properties of this growing class of novel materials. As a result, these polymers represent an opportunity for exploring the novel phenomena associated with topological solitons and their linear confinement which results from weakly lifting the ground-state degeneracy. The authors review the theoretical models that have been developed to describe the physics of polyacetylene and related conducting polymers and summarize the relevant experimental results obtained for these materials. An attempt is made to assess the validity of the soliton model of polyacetylene and its generalization to related systems in which the ground-state degeneracy has been lifted.
    Review of Modern Physics 07/1988; 60(3):781-850. · 44.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The efficient operation of polymer light-emitting diodes (LEDs) requires balanced injection and transport of electrons and holes. This has stimulated much research into suitable electron-injecting and transporting materials. We report the use of polypyridine as an efficient electron-transporting polymer. We have achieved much-improved LED performance by incorporating polypyridine as an electron-transporting layer in a poly(p-phenylene vinylene) (PPV) LED and optimizing layer thicknesses to balance transport of electrons and holes. The external quantum efficiency of these LEDs is 0.25%, 60 times greater than similar devices without the electron-transporting layer.
    Journal of Physics Condensed Matter 06/1998; 10(23):5171-5178. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The electronic structure of sodium-doped poly (p-phenylenevinylene), or PPV, has been studied using photoelectron spectroscopy, UPS and XPS. Upon doping, two new states are created in the previously forbidden electronic bandgap. No finite density- of-states is observed at the Fermi energy. The UPS spectra are analysed with the help of VEH-level quantum chemical calculations. It is determined that the Na-doping of PPV results in the formation of bipolaron bands in the otherwise forbidden energy gap at saturation doping. These results are in contrast with the case of poly-hexyl-thiophene doped from NOPF6, where the existence of a finite density-of-states at EF and a stable polaron lattice was observed at saturation doping at room temperature. This work represents the first direct measure of multiple, resolved gap states in a doped conjugated polymer.
    Chemical Physics Letters 01/1993; · 2.15 Impact Factor

Full-text (2 Sources)

Available from
May 26, 2014