Charge transfer dynamics in squaraine-naphthalene diimide copolymers

The synthesis of an alternating squaraine-naphthalene diimide donor-acceptor low band gap polymer (1.14-1.40 eV) as well as its monomolecular analogue is presented. Spectroelectrochemistry experiments and transient absorption spectroscopy in the fs-time regime reveal an ultrafast population of a cha...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2013-12, Vol.15 (45), p.19831-19844
Main Authors: Völker, Sebastian F, Schmiedel, Alexander, Holzapfel, Marco, Böhm, Christoph, Lambert, Christoph
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Charge
Charge transfer
Chemistry
Copolymers
Diimide
Energy transfer
Exact sciences and technology
General and physical chemistry
Monomers
Physical chemistry
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Summary:The synthesis of an alternating squaraine-naphthalene diimide donor-acceptor low band gap polymer (1.14-1.40 eV) as well as its monomolecular analogue is presented. Spectroelectrochemistry experiments and transient absorption spectroscopy in the fs-time regime reveal an ultrafast population of a charge separated state for both polymer and monomer. Local excitation of the squaraine moiety is followed by population of intermediate states, presumably charge transfer states, followed by full charge separation, which occurs within a ca. 2 ps. Charge recombination takes place within 5.2 ps, probably because the system is close to the Marcus optimal region for barrierless ET. For the polymer, measurements of the transient absorption anisotropy show that neither charge nor does energy transfer take place within the lifetime of the charge separated state, indicating that this state is essentially confined within one donor-acceptor pair. fs-Time resolved transient absorption spectroscopy of an alternating squaraine-naphthalene diimide donor-acceptor low band gap (1.14-1.40 eV) polymer shows confinement of a charge separated state within one donor-acceptor pair.
ISSN:1463-9076
1463-9084
DOI:10.1039/c3cp53455c