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Electronic structure and properties of poly- and oligoazulenes

Nöll, Gilbert LU ; Lambert, Christoph; Lynch, Michelle; Porsch, Michael and Daub, Jörg (2008) In Journal of Physical Chemistry C 112(6). p.2156-2164
Abstract
One of the most important research interests in the field of organic photovoltaic devices (OPVs) is the development of new materials which can serve as light-absorbing electron donors and hole-conducting (p-type) semiconductors. In this context, 1,3-polyazulenes were synthesized chemically and electrochemically. Their spectroscopic and electrochemical properties are compared with those of the 1,3-oligoazulenes Az(1)-Az(6). The UV-vis spectra of the neutral azulenes Az(1)-Az(6) show a linear correlation between the lowest absorption maximum and the inverse chain length 1/n leading to a band gap of E-g = 1.90 eV for infinite chain length. Derived from this correlation the effective conjugation length of chemically synthesized polyazulene is... (More)
One of the most important research interests in the field of organic photovoltaic devices (OPVs) is the development of new materials which can serve as light-absorbing electron donors and hole-conducting (p-type) semiconductors. In this context, 1,3-polyazulenes were synthesized chemically and electrochemically. Their spectroscopic and electrochemical properties are compared with those of the 1,3-oligoazulenes Az(1)-Az(6). The UV-vis spectra of the neutral azulenes Az(1)-Az(6) show a linear correlation between the lowest absorption maximum and the inverse chain length 1/n leading to a band gap of E-g = 1.90 eV for infinite chain length. Derived from this correlation the effective conjugation length of chemically synthesized polyazulene is only about 10. By an alternative approach, a band gap of E-g = 1.46 eV was determined. Depending on the applied potential the oligomers Az(2)-Az(6) undergo up to two reversible oxidation processes or further polymerization which results in the formation of polymer films at the electrode. The potentiodynamic oxidation of chemically synthesized polyazulene leads to electrocrystallization at the electrode, whereas films of polyazulenes are obtained directly upon oxidation of Az(1)-Az(6). Chemically and electrochemically generated polyazulenes adsorbed on Pt show similar electrochemical behavior upon positive doping. The spectroelectrochemical investigations in combination with density functional theory (DFT) calculations lead to the conclusion that polyazulene can be oxidized up to a doping level of one charge per three or four azulene units. At this stage polarons or polaron pairs are formed (depending on the doping level) but not bipolarons. At higher doping levels the polymers start to decompose. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
112
issue
6
pages
2156 - 2164
publisher
The American Chemical Society
external identifiers
  • wos:000252968100066
  • scopus:40049083970
ISSN
1932-7447
DOI
10.1021/jp074376b
language
English
LU publication?
yes
id
1497352c-a082-4504-a36a-d4c494367a5f (old id 1198669)
date added to LUP
2008-09-10 16:10:41
date last changed
2017-08-13 03:39:11
@article{1497352c-a082-4504-a36a-d4c494367a5f,
  abstract     = {One of the most important research interests in the field of organic photovoltaic devices (OPVs) is the development of new materials which can serve as light-absorbing electron donors and hole-conducting (p-type) semiconductors. In this context, 1,3-polyazulenes were synthesized chemically and electrochemically. Their spectroscopic and electrochemical properties are compared with those of the 1,3-oligoazulenes Az(1)-Az(6). The UV-vis spectra of the neutral azulenes Az(1)-Az(6) show a linear correlation between the lowest absorption maximum and the inverse chain length 1/n leading to a band gap of E-g = 1.90 eV for infinite chain length. Derived from this correlation the effective conjugation length of chemically synthesized polyazulene is only about 10. By an alternative approach, a band gap of E-g = 1.46 eV was determined. Depending on the applied potential the oligomers Az(2)-Az(6) undergo up to two reversible oxidation processes or further polymerization which results in the formation of polymer films at the electrode. The potentiodynamic oxidation of chemically synthesized polyazulene leads to electrocrystallization at the electrode, whereas films of polyazulenes are obtained directly upon oxidation of Az(1)-Az(6). Chemically and electrochemically generated polyazulenes adsorbed on Pt show similar electrochemical behavior upon positive doping. The spectroelectrochemical investigations in combination with density functional theory (DFT) calculations lead to the conclusion that polyazulene can be oxidized up to a doping level of one charge per three or four azulene units. At this stage polarons or polaron pairs are formed (depending on the doping level) but not bipolarons. At higher doping levels the polymers start to decompose.},
  author       = {Nöll, Gilbert and Lambert, Christoph and Lynch, Michelle and Porsch, Michael and Daub, Jörg},
  issn         = {1932-7447},
  language     = {eng},
  number       = {6},
  pages        = {2156--2164},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry C},
  title        = {Electronic structure and properties of poly- and oligoazulenes},
  url          = {http://dx.doi.org/10.1021/jp074376b},
  volume       = {112},
  year         = {2008},
}