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Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices

Persson, N-K; Sun, Mengtao LU ; Kjellberg, Pär LU ; Pullerits, Tönu LU and Inganas, O (2005) In Journal of Chemical Physics 123(20). p.9-204718
Abstract
In a joint experimental and theoretical work the optical response and excited-state character of two novel conjugated polymers for photovoltaic applications are studied. The polymers, alternating polyfluorene (APFO) Green 1 and APFO Green 2, are both copolymers of fluorene, thiophene, and electron accepting groups. The band gaps are extended into the red and near infrared with onsets of 780 and 1000 nm, respectively, due to alternating donor and acceptor moieties along the polymer chain. Spectroscopic ellipsometry and subsequent modeling made it possible to extract the dielectric function in the range of 260–1200 nm. Semiempirical quantum chemical calculations (ZINDO) revealed the character of the main electronic transitions in the studied... (More)
In a joint experimental and theoretical work the optical response and excited-state character of two novel conjugated polymers for photovoltaic applications are studied. The polymers, alternating polyfluorene (APFO) Green 1 and APFO Green 2, are both copolymers of fluorene, thiophene, and electron accepting groups. The band gaps are extended into the red and near infrared with onsets of 780 and 1000 nm, respectively, due to alternating donor and acceptor moieties along the polymer chain. Spectroscopic ellipsometry and subsequent modeling made it possible to extract the dielectric function in the range of 260–1200 nm. Semiempirical quantum chemical calculations (ZINDO) revealed the character of the main electronic transitions in the studied spectral region. The spectral band just above 400 nm was assigned to a delocalized –* transition for both polymers. The red band lying at 622 and 767 nm in the two polymers corresponds to an electronic state mainly occupying the acceptor units and having a strong charge-transfer character. We show that the ZINDO transition energies are valuable input to the application of Lorentz oscillators in modeling of the dielectric function of the polymer material. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Chemical Physics
volume
123
issue
20
pages
9 - 204718
publisher
American Institute of Physics
external identifiers
  • wos:000233661000073
  • scopus:28344433852
ISSN
0021-9606
DOI
10.1063/1.2087367
language
English
LU publication?
yes
id
96b59a3c-ef63-4987-8a93-b0a5b6a8ad80 (old id 157823)
date added to LUP
2007-07-03 14:42:44
date last changed
2017-09-10 03:38:53
@article{96b59a3c-ef63-4987-8a93-b0a5b6a8ad80,
  abstract     = {In a joint experimental and theoretical work the optical response and excited-state character of two novel conjugated polymers for photovoltaic applications are studied. The polymers, alternating polyfluorene (APFO) Green 1 and APFO Green 2, are both copolymers of fluorene, thiophene, and electron accepting groups. The band gaps are extended into the red and near infrared with onsets of 780 and 1000 nm, respectively, due to alternating donor and acceptor moieties along the polymer chain. Spectroscopic ellipsometry and subsequent modeling made it possible to extract the dielectric function in the range of 260–1200 nm. Semiempirical quantum chemical calculations (ZINDO) revealed the character of the main electronic transitions in the studied spectral region. The spectral band just above 400 nm was assigned to a delocalized –* transition for both polymers. The red band lying at 622 and 767 nm in the two polymers corresponds to an electronic state mainly occupying the acceptor units and having a strong charge-transfer character. We show that the ZINDO transition energies are valuable input to the application of Lorentz oscillators in modeling of the dielectric function of the polymer material.},
  author       = {Persson, N-K and Sun, Mengtao and Kjellberg, Pär and Pullerits, Tönu and Inganas, O},
  issn         = {0021-9606},
  language     = {eng},
  number       = {20},
  pages        = {9--204718},
  publisher    = {American Institute of Physics},
  series       = {Journal of Chemical Physics},
  title        = {Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices},
  url          = {http://dx.doi.org/10.1063/1.2087367},
  volume       = {123},
  year         = {2005},
}