Photoinduced charge transfer in poly(<i>p</i>-phenylene vinylene)

Mizes, H. A.; Conwell, E. M.

doi:10.1103/physrevb.50.11243

Cited by 111 publications

(51 citation statements)

References 19 publications

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“…While it is commonly accepted that hole and electron polarons have similar if not identical absorption spectra in homopolymers 31,37 , this might not hold true in co-polymers. Figure 4a shows the hole polaron spectrum from Fig.…”

Section: Lowmentioning

confidence: 95%

“…Optical signatures of polarons are evident in the infrared and originate from the bandgap renormalization on removal of charge neutrality on the π-conjugated system 30,31 . We have determined the energetic position of the polaron absorption bands in the infrared by chemical doping with the oxidizing dopant SbCl 5 and quantum-chemical calculations 32,33 .…”

Section: Lowmentioning

confidence: 99%

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Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

et al. 2012

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Polymeric semiconductors are materials where unique optical and electronic properties often originate from a tailored chemical structure. This allows for synthesizing conjugated macromolecules with ad hoc functionalities for organic electronics. In photovoltaics, donoracceptor co-polymers, with moieties of different electron affinity alternating on the chain, have attracted considerable interest. The low bandgap offers optimal light-harvesting characteristics and has inspired work towards record power conversion efficiencies. Here we show for the first time how the chemical structure of donor and acceptor moieties controls the photogeneration of polaron pairs. We show that co-polymers with strong acceptors show large yields of polaron pair formation up to 24% of the initial photoexcitations as compared with a homopolymer (η = 8%). π-conjugated spacers, separating the donor and acceptor centre of masses, have the beneficial role of increasing the recombination time. The results provide useful input into the understanding of polaron pair photogeneration in low-bandgap co-polymers for photovoltaics.

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Section: Lowmentioning

confidence: 95%

Section: Lowmentioning

confidence: 99%

Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

et al. 2012

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“…Furthermore, in the film sample, the restricted motion of the polymer chains and the stronger effect of torsional disorder limit the exciton size and reduce the exciton polarizability by a factor of 3. The possible effects of interchain species 2,6,14,18,27 on the observed excitation properties are discussed.…”

Section: Introductionmentioning

confidence: 99%

“…In the thin-film phase interchain interactions are present. 2,6,8,11,18,27,28 On short ͑subpicosecond͒ times, only a small number ͑Ͻ1%͒ of free charges is generated in the solid film, while this number is even smaller ͑by approximately 2 orders of magnitude͒ in solution. On longer timescales ͑Ͼ5 ps͒ mobile charges are not observed and the photoinduced changes in the THz wave form are mainly due to the polarizability of excitons.…”

Section: Introductionmentioning

confidence: 99%

Interchain effects in the ultrafast photophysics of a semiconducting polymer:THztime-domain spectroscopy of thin films and isolated chains in solution

et al. 2005

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We compare the generation and decay dynamics of charges and excitons in a model polymer semiconductor ͑MEH-PPV͒ in solution and drop-cast thin films, by recording the sub-ps transient complex conductivity using THz time-domain spectroscopy. The results show that the quantum efficiency of charge generation is two orders of magnitude smaller in solution ͑ϳ10−5 ͒ than in the solid film ͑ϳ10 −3 ͒. The proximity of neighboring chains in the films apparently facilitates ͑hot͒ exciton dissociation, presumably by allowing the electron and hole to separate on different polymer strands. For both samples, photoexcitation leads to the predominant formation of bound charge pairs ͑excitons͒ that can be detected through their polarizability. Surprisingly, the polarizability per absorbed photon is a factor of 3 larger in solution than in the film, suggesting that interchain interactions in the film do not result in a substantial delocalization of the exciton wave function.

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“…As discussed below, to a large extent this is because the experimental results themselves, or their interpretations, are controversial and confusing. Theoretical investigations of the effects of interchain interactions 17,[20][21][22][23][24][25][26][27][28] have until now focused largely on the lowest interchain species near the optical edge and the role of such interchain species on the emissive behavior of films. The goal of this work is to re-examine interchain interaction in PCPs within a semiempirical Hamiltonian with realistic parameters, focusing on ultrafast photoinduced absorption ͑PA͒ measurements and related experimental results that appear to be mutually contradictory.…”

Section: Introductionmentioning

confidence: 99%

Photophysics of charge-transfer excitons in thin films ofπ-conjugated polymers

2008

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We develop a theory of the electronic structure and photophysics of interacting chains of -conjugated polymers to understand the differences between solutions and films. While photoexcitation generates only the intrachain exciton in solutions, the optical exciton as well as weakly allowed charge-transfer excitons are generated in films. We extend existing theories of the lowest polaron pair and charge-transfer excitons to obtain descriptions of the excited states of these interchain species, and we show that a significant fraction of ultrafast photoinduced absorptions in films originates from the lowest charge-transfer exciton. Our proposed mechanism explains the simultaneous observation of polaronlike-induced absorption features peculiar to films in ultrafast spectroscopy and the absence of mobile charge carriers as deduced from other experiments. We also show that there is a 1:1 correspondence between the essential states that describe the photophysics of single chains and of interacting chains that constitute thin films.

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Photoinduced charge transfer in poly(p-phenylene vinylene)

Cited by 111 publications

References 19 publications

Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

Structural correlations in the generation of polaron pairs in low-bandgap polymers for photovoltaics

Interchain effects in the ultrafast photophysics of a semiconducting polymer:THztime-domain spectroscopy of thin films and isolated chains in solution

Photophysics of charge-transfer excitons in thin films ofπ-conjugated polymers

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