Article

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
 · 
59 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: X-ray photoelectron (XPS) and UV photoelectron (UPS) spectroscopies were used to characterize the electrochemically n- and p-doped states of poly (3-(4-fluorophenyl) thiophene), PFPT. The polymer was electrochemically grown on platinum electrode from the corresponding monomer. The polymer was characterized by cyclic voltammetry in an electrochemical cell that was attached to the antechamber of the spectrometer in order to avoid as much as possible exposure to ambiant air since the n-doped state is very air and water sensitive. UPS was used to evaluate the position of the Fermi level of the doped PFPT’s which allows for the determination of their work functions. The work functions of p- and n-doped PFPT are 4.3 and 2.6 eV, respectively. The S 2p core level spectrum of the n-doped polymer shows a main doublet at absolute binding energies of about 167.6 (2p3/2) and 168.9 (2p1/2) eV and a second doublet at lower binding energy which disappears upon oxidation to the p-doped state and is only observed for the reduced n-doped polymer. The presence of this low binding energy doublet can be explained by a higher charge localization for the n-doped state relative to the p-doped state and is consistent with the lower conductivity (by a factor of about 10) of the former. XPS was also used to investigate ion-exchange during redox switching of polymers and evaluate the doping levels of polymer. In most cases, the later values were found to be in relatively good agreement with those computed from the electrochemical data.
    Synthetic Metals 12/2002; 132(1):71-79. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The chemical state and electronic properties of hybrid material based on poly (3, 4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and pyridine-capped CdSe nanocrystals have been investigated using photoemission spectroscopy, near-edge x-ray absorption fine structure, and ultraviolet photoelectron spectroscopy. With a high dipole moment as well as high physical momentum, CdSe nanocrystals hindered the rearrangement of PEDOT:PSS and induced PSS-rich surface during film formation. Thus, the work function value was decreased by dedoping of PEDOT or charge localization in PEDOT. Through heat treatment, the behavior of π-π<sup>*</sup> transition in C  1s and the work function value was nearly restored, gradually; these mean recovery of electrostatic bonding nature between PEDOT and PSS. However, the ionization potential (IP) was slightly increased by 0.3 eV with CdSe nanocrystal incorporation and interpreted as dielectric property and local electron transfer from highest occupied molecular orbital of PEDOT to valence band of CdSe nanocrystals. Subsequent addition of CdSe nanocrystal and degree of capping with pyridine allows for a well-controlled electronic structure of PEDOT:PSS, work function, and IP.
    Journal of Applied Physics 02/2009; · 2.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The phenyl-capped 3,4-ethylenedioxythiophene (EDOT) trimer is a well-defined oligomer of the related poly(3,4-ethylenedioxythiophene), the conjugated polymer that forms the basis of the commercialized conducting polymer “PEDOT-PSS.” EDOT-based oligomers are themselves potential candidates for applications in molecular electronics, such as organic field effect transistors and organic solar cells. Well controlled chemical doping is of importance in such applications, since it enables tuning of important properties such as the electrical conductivity, the position of the Fermi-level, the optical absorption edge, and the quantum efficiency for photovoltaic devices. The effects of chemical doping, both p-type doping with iodine, and n-type doping with lithium, on the electronic structure of condensed molecular solid films of EDOT trimer have been studied using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy. The results are discussed in terms of parameters important for device applications. © 2003 American Institute of Physics.
    The Journal of Chemical Physics. 04/2003; 118(14):6495-6502.

Full-text (2 Sources)

Download
53 Downloads
Available from
May 26, 2014