Electronic Energy Transfer and Quantum-Coherence in π-Conjugated Polymers

Hwang, Inchan; Scholes, Gregory D.

doi:10.1021/cm102360x

Cited by 233 publications

(335 citation statements)

References 132 publications

(281 reference statements)

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“…Control of donor/acceptor domain sizes is crucial for OPV efficiency because charge separation occurs at the interface between donor and acceptor, and because the distance that an exciton can diffuse during its lifetime is around 10 nm. 5 Ideal domain sizes are between 10 and 20 nm, 6 small enough that most excitons can reach an interface, but large enough to minimize recombination between the free charges.…”

Section: Introductionmentioning

confidence: 99%

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Mitchell

Wong

Thelakkat

et al. 2016

Polym J

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Nanoscale domains of donor and acceptor materials are crucial for charge generation in organic photovoltaic devices. These domains are difficult to achieve reproducibly in blended materials, but could be engineered into single-material active layers composed of donor-acceptor block copolymers (BCPs). In this work, we report the synthesis and purification of two novel fully conjugated BCPs, P3HT-b-PF TEG TBT and P3HT-b-PF TEG T6BT. To enhance phase separation and self-assembly, these two polymers incorporate tetraethylene glycol side chains into the PFTBT acceptor block, generating an amphiphilic system. The chemical disparity of the donor and acceptor blocks allowed the development of a purification strategy capable of isolating the desired BCP from homopolymer contaminants. This is a significant improvement over previous systems in which homopolymer contaminants can dominate the reaction mixture, affecting performance and morphology. We show that preliminary morphological analysis indicates spontaneous phase separation in thin films, demonstrating the efficacy of this design strategy and the potential application of these materials in organic photovoltaic devices.

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Section: Introductionmentioning

confidence: 99%

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Mitchell

Wong

Thelakkat

et al. 2016

Polym J

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“…A quantitative understanding of exciton migration in conjugated polymers is important for applications in organic photovoltaics, lightemitting diodes and lasers [1][2][3][4][5] . In polymer films excitons migrate along conjugated chains as well as between chains [6][7][8][9][10] .…”

Section: Introductionmentioning

confidence: 99%

Subpicosecond Exciton Dynamics in Polyfluorene Films from Experiment and Microscopic Theory

et al. 2015

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Electronic energy transfer (EET) in organic materials is a key mechanism that controls the efficiency of many processes, including light harvesting antenna in natural and artificial photosynthesis, organic solar cells, and biological systems. In this paper we have examined EET in solid-state thin-films of polyfluorene, a prototypical conjugated polymer with ultrafast photoluminescence experiments and theoretical modelling. We observe EET occurring on a 680 ± 300 fs timescale by looking at the depolarisation of photoluminescence. An * To whom correspondence should be addressed independent, predictive microscopic theoretical model is built by defining 125 000 chromophores containing both spatial and energetic disorder appropriate for a spin-coated thin film. The model predicts time-dependent exciton dynamics, without any fitting parameters, using the incoherent Förster-type hopping model. Electronic coupling between the chromophores is calculated by an improved version of the usual line-dipole model for resonant energy transfer. Without the need for higher level interactions, we yet find that the model is in general agreement with the experimentally observed 680 ± 300 fs depolarisation caused by EET. This leads us to conclude that femtosecond EET in polyfluorene can be well described by conventional resonant energy transfer, as long as the relevant microscopic parameters are well captured. The implications of this finding are that dipole-dipole resonant energy transfer can in some circumstances be fully adequate to describe ultrafast EET without needing to invoke strong or intermediate coupling mechanisms.1

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“…orphology and excitonic coupling are among the most important factors dictating the functions and performance of conjugated polymers (CPs) in a variety of optoelectronic applications (1)(2)(3)(4). To tune and optimize the morphological and optoelectronic properties of CPs, chemical structure modification of the backbone and side chains is one of the main and most effective approaches (5)(6)(7).…”

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confidence: 99%

Impact of backbone fluorination on nanoscale morphology and excitonic coupling in polythiophenes

Haws

Fei

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Fluorination represents an important strategy in developing highperformance conjugated polymers for photovoltaic applications. Here, we use regioregular poly(3-ethylhexylthiophene) (P3EHT) and poly(3-ethylhexyl-4-fluorothiophene) (F-P3EHT) as simplified model materials, using single-molecule/aggregate spectroscopy and molecular dynamic simulations, to elucidate the impacts of backbone fluorination on morphology and excitonic coupling on the molecular scale. Despite its high regioregularity, regioregular P3EHT exhibits a rather broad distribution in polymer chain conformation due to the strong steric hindrance of bulky ethylhexyl side chains. This conformational variability results in disordered interchain morphology even between a few chains, prohibiting long-range effective interchain coupling. In stark contrast, the experimental and molecular dynamic calculations reveal that backbone fluorination of F-P3EHT leads to an extended rod-like single-chain conformation and hence highly ordered interchain packing in aggregates. Surprisingly, the ordered and close interchain packing in F-P3EHT does not lead to strong excitonic coupling between the chains but rather to dominant intrachain excitonic coupling that greatly reduces the molecular energetic heterogeneity.fluorinated polythiophenes | photophysics | single-molecule spectroscopy | morphology | organic electronics M orphology and excitonic coupling are among the most important factors dictating the functions and performance of conjugated polymers (CPs) in a variety of optoelectronic applications (1-4). To tune and optimize the morphological and optoelectronic properties of CPs, chemical structure modification of the backbone and side chains is one of the main and most effective approaches (5-7). It has been revealed that the position, size, and length of side chains dramatically affect the morphology and optoelectronic properties of CPs. In the efforts to develop high-performance photovoltaic CPs, the introduction of fluorine atoms onto aromatic comonomers, i.e., the fluorination of polymer backbone, offers a very appealing strategy to tune the electronic properties, morphology, and photochemical stability (6-8). It is proposed that the inherent electronwithdrawing nature of fluorine atoms lowers the highest energy occupied molecular orbital energy levels, thereby increasing the open-circuit voltage in photovoltaics. In addition, the strong electronegativity might induce F-S and F-H interactions and potentially modifies the molecular conformation and intermolecular organization (6). Furthermore, it has been shown that fluorination often leads to enhanced thermal and oxidative stability (9-11). Given a combination of these desirable properties, fluorine-containing CPs have led to most of the best-performing polymer-based solar cells to date (12-15).For typical CPs, the primarily created exciton is Coulombically bound upon photoexcitation mainly due to the low dielectric constant and strong electron-phonon interaction in polymers. The interchain and intrachain morp...

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Electronic Energy Transfer and Quantum-Coherence in π-Conjugated Polymers

Cited by 233 publications

References 132 publications

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Subpicosecond Exciton Dynamics in Polyfluorene Films from Experiment and Microscopic Theory

Impact of backbone fluorination on nanoscale morphology and excitonic coupling in polythiophenes

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