Universal ultrafast signatures of photoexcitations in conjugated polymers: Excitons and charge-transfer polarons

D. W. McBranch; B. Kraabel; S. Xu; H. L. Wang; Victor I Klimov

Universal ultrafast signatures of photoexcitations in conjugated polymers: Excitons and charge-transfer polarons

D. W. McBranch, B. Kraabel, S. Xu, H. L. Wang, Victor I Klimov

Los Alamos National Laboratory

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

Abstract

Using subpicosecond transient absorption spectroscopy, we have investigated the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer. We identify two features in the transient absorption spectra and dynamics that are common to all of the materials which we have studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV which has intensity-dependent dynamics which match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, which is longer-lived than the 1 eV exciton PA band, and which has dynamics that are independent (or weakly-dependent) on excitation density. This feature is attributed to charge separated (interchain) excitations. These excitations are generated through a bimolecular process. By comparing to samples in which charged excitations are created deliberately by doping with C₆O, we assign these secondary species as bound polarons.

Original language	English
Title of host publication	Proceedings of SPIE - The International Society for Optical Engineering
Publisher	Society of Photo-Optical Instrumentation Engineers
Pages	17-25
Number of pages	9
Volume	3797
Publication status	Published - 1999
Event	Proceedings of the 1999 Organic Light-Emitting Materials and Devices III - Denver, CO, USA Duration: Jul 19 1999 → Jul 21 1999

Other

Other	Proceedings of the 1999 Organic Light-Emitting Materials and Devices III
City	Denver, CO, USA
Period	7/19/99 → 7/21/99

ASJC Scopus subject areas

Electrical and Electronic Engineering
Condensed Matter Physics

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McBranch, D. W., Kraabel, B., Xu, S., Wang, H. L., & Klimov, V. I. (1999). Universal ultrafast signatures of photoexcitations in conjugated polymers: Excitons and charge-transfer polarons. In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 3797, pp. 17-25). Society of Photo-Optical Instrumentation Engineers.

Universal ultrafast signatures of photoexcitations in conjugated polymers : Excitons and charge-transfer polarons. / McBranch, D. W.; Kraabel, B.; Xu, S.; Wang, H. L.; Klimov, Victor I.

Proceedings of SPIE - The International Society for Optical Engineering. Vol. 3797 Society of Photo-Optical Instrumentation Engineers, 1999. p. 17-25.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

McBranch, DW, Kraabel, B, Xu, S, Wang, HL & Klimov, VI 1999, Universal ultrafast signatures of photoexcitations in conjugated polymers: Excitons and charge-transfer polarons. in Proceedings of SPIE - The International Society for Optical Engineering. vol. 3797, Society of Photo-Optical Instrumentation Engineers, pp. 17-25, Proceedings of the 1999 Organic Light-Emitting Materials and Devices III, Denver, CO, USA, 7/19/99.

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title = "Universal ultrafast signatures of photoexcitations in conjugated polymers: Excitons and charge-transfer polarons",

abstract = "Using subpicosecond transient absorption spectroscopy, we have investigated the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer. We identify two features in the transient absorption spectra and dynamics that are common to all of the materials which we have studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV which has intensity-dependent dynamics which match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, which is longer-lived than the 1 eV exciton PA band, and which has dynamics that are independent (or weakly-dependent) on excitation density. This feature is attributed to charge separated (interchain) excitations. These excitations are generated through a bimolecular process. By comparing to samples in which charged excitations are created deliberately by doping with C6O, we assign these secondary species as bound polarons.",

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N2 - Using subpicosecond transient absorption spectroscopy, we have investigated the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer. We identify two features in the transient absorption spectra and dynamics that are common to all of the materials which we have studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV which has intensity-dependent dynamics which match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, which is longer-lived than the 1 eV exciton PA band, and which has dynamics that are independent (or weakly-dependent) on excitation density. This feature is attributed to charge separated (interchain) excitations. These excitations are generated through a bimolecular process. By comparing to samples in which charged excitations are created deliberately by doping with C6O, we assign these secondary species as bound polarons.

AB - Using subpicosecond transient absorption spectroscopy, we have investigated the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer. We identify two features in the transient absorption spectra and dynamics that are common to all of the materials which we have studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV which has intensity-dependent dynamics which match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, which is longer-lived than the 1 eV exciton PA band, and which has dynamics that are independent (or weakly-dependent) on excitation density. This feature is attributed to charge separated (interchain) excitations. These excitations are generated through a bimolecular process. By comparing to samples in which charged excitations are created deliberately by doping with C6O, we assign these secondary species as bound polarons.

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