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Polarization anisot...
Polarization anisotropy of charge transfer absorption and emission of aligned polymer: fullerene blend films
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- Vandewal, Koen (author)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska fakulteten
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- Tvingstedt, Kristofer (author)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska högskolan
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- Inganäs, Olle (author)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska högskolan
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(creator_code:org_t)
- American Physical Society, 2012
- 2012
- English.
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 86:3, s. 035212-
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Abstract
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- An improved understanding of the electronic structure of interfacial charge transfer (CT) states is of importance due to their crucial role in charge carrier generation and recombination in organic donor-acceptor (DA) solar cells. DA combinations with a small difference between the energy of the CT state (E-CT) and energy of the donor exciton (E-D*) are of special interest since energy losses due to electron transfer are minimized, resulting in an optimized open-circuit voltage. In that case, the CT state can be considered as a resonance mixture, containing character of a fully ionic state (D+ A(-)) and of the local polymer excited state (D* A). We show that the D* A contribution to the overall CT state wave function can be determined by measurements of the polarization anisotropy of CT absorption and emission of polymer: fullerene blends with aligned polymer chains. We study two donor polymers, P3HT and TQ1, blended with fullerene acceptors with different ionization potentials, allowing variation of the E-D* -E-CT difference. We find that, upon decreasing E-D* -E-CT, the local excitonic D* A character of the CT state increases, resulting in a decreased fraction of charge transferred and an increased transition dipole moment. For typical polymer: fullerene systems, this effect is expected to become detrimental for device performance if E-D* - E-CT andlt; 0.1 eV. This however, depends on the electronic coupling between D* A and D+ A(-), which we experimentally estimate to be similar to 6 meV for the TQ1: PCBM system.
Keyword
- TECHNOLOGY
- TEKNIKVETENSKAP
Publication and Content Type
- ref (subject category)
- art (subject category)
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