Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices

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Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices. / Persson, N-K; Sun, Mengtao; Kjellberg, Pär; Pullerits, Tönu; Inganas, O.

I: Journal of Chemical Physics, Vol. 123, Nr. 20, 2005, s. 204718-204718-9.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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Persson, N-K ; Sun, Mengtao ; Kjellberg, Pär ; Pullerits, Tönu ; Inganas, O. / Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices. I: Journal of Chemical Physics. 2005 ; Vol. 123, Nr. 20. s. 204718-204718-9.

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TY - JOUR

T1 - Optical properties of low band gap alternating copolyfluorenes for photovoltaic devices

AU - Persson, N-K

AU - Sun, Mengtao

AU - Kjellberg, Pär

AU - Pullerits, Tönu

AU - Inganas, O

N1 - The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Chemical Physics (S) (011001060)

PY - 2005

Y1 - 2005

N2 - 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.

AB - 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.

U2 - 10.1063/1.2087367

DO - 10.1063/1.2087367

M3 - Article

VL - 123

SP - 204718-204718-9

JO - Journal of Chemical Physics

T2 - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 20

ER -