Ultraviolet photoelectron spectroscopy of poly(pyridine-2,5-diyl), poly(2,2′-bipyridine-5,5′-diyl), and their K-doped states

Abstract

Articles you may be interested inImpedance spectroscopy characterization of inverted type organic solar cells based on poly(3-hexylthiophene-2,5-diyl) AIP Conf.Electronic structure of poly(1,10-phenanthroline-3,8-diyl) and its K-doped state studied by photoelectron spectroscopy Ultraviolet photoelectron spectra were measured using synchrotron radiation for two kinds of -conjugated polymers, poly͑pyridine-2,5-diyl͒ ͑PPy͒ and poly͑2,2Ј-bipyridine-5,5Ј-diyl͒ ͑PBPy͒ which exhibit n-type electrically conducting properties. The two compounds show similar spectra and they were analyzed with MO calculations and the comparison with the data of related molecules. The ionization threshold energies of PPy and PBPy were found to be 6.3 and 6.35 eV, respectively. These values are higher than those of -conjugated conducting polymers capable of p doping. Upon potassium doping of PBPy, two new states appeared in the originally empty energy gap and the intensity of the state at 0.65 eV from E F grows as the doping proceeds. This finding and the change of optical absorption spectra upon doping indicate that bipolaron bands are formed in K-doped PBPy. While K-doped PPy also shows similar gap states, it requires higher dopant concentration to create bipolaron bands than in the case of K-doped PBPy. The difference of the dependence on dopant concentration between K-doped PPy and K-doped PBPy is discussed based on the conformational difference between these polymers.

The electronic structure of poly(pyridine-2,5-diyl) investigated by soft X-ray absorption and emission spectroscopies

“…By subtracting the energy of this edge structure in the non-resonant spectrum with that of the elastic peak of the resonant spectrum an alternative way of obtaining the band gap experimentally is obtained which also was demonstrated in our previous paper [15]. The band gap so obtained is 3.2 eV which agrees fairly well with the value of 2.82 eV estimated from the edge of the absorption spectra of solid fillm PPY [3]. …”

“…5 and 7. It can be noted that a comparison between the computed density-of-states distribution with the measured UPS spectrum of PPy by Miyamae et al, gives some preference to the HH form [3]. …”

“…Detailed experimental studies of the uppermost π-valence levels at the valence and conducting band edges of such polymers are important for the understanding of these properties. Such studies have been carried out by many techniques, for instance by photoelectron spectroscopy using photon excitation in both the X-ray and ultraviolet wavelength regimes [2][3][4]. The purpose of the present work is to use X-ray emission (XE) spectroscopy to investigate the electronic structure of poly(pyridine-2,5-diyl) (PPy) which is an aza-substituted poly(p-phenylene) with a sufficiently large bandgap to allow electroluminescence in the blue wavelength region [5,6].…”

Resonant inelastic soft X-ray scattering spectra at the nitrogen and carbon K-edges of poly(pyridine-2,5-diyl)

“…In the polymer case, the bands are broader due to a large number of transitions involved in each band. It is also interesting to note that the bands A--E observed in these RIXS spectra correspond well in energy with the five bands observed in ultraviolet photoelectron spectra (UPS) [7]. However, the intensities are different owing to the different nature of the transition moments between the spectroscopies.…”

Eletropolymerization of Niacinamide for Fabrication of Electrochemical Sensor: Simultaneous Determination of Dopamine, Uric Acid and Ascorbic Acid

“…From Figure 1a, we can find that two oxidation peaks were generated at 0.4 V (a1) and 1.3 V (a2) in the anodic scan and two reduction peaks were correspondingly generated at about 0.45 V (c1) and -0.45 V (c2) in the reverse cathodic scan in the scan range of -1.0 to 1.7 V. The peak heights of all these four peaks were all increased from cycle to cycle, indicating the accumulation of electroactive polymeric materials on the electrode surface. The possible polymerization mechanism is expressed in the reaction (1) Because the NA units can form H-H and H-T connections, 24 the generated polymeric materials have a complicated molecular structure, which is interesting for further study. The redox reactions of a1, a2, c1 and c2 peaks ( Figure 1a) can be assigned to the ring centered reactions with doping-didoping processes.…”