Stable Polythiophene Semiconductors Incorporating Thieno[2,3-<i>b</i>]thiophene

Heeney, Martin; Bailey, Clare; Genevičius, K.; Shkunov, Maxim; Sparrowe, David; Tierney, Steve; McCulloch, Iain

doi:10.1021/ja043112p

Cited by 353 publications

(307 citation statements)

References 19 publications

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“…41,42 Alternatively introducing a non-or less-conjugated unit as a component of the polymer backbone has also been shown to increase the polymer IP. [43][44][45] On the basis of these strategies, we have prepared a series of polythiophenes with IPs ranging from 4.8 to 5.6 eV.…”

Section: Introductionmentioning

confidence: 99%

Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy

et al. 2008

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Abstract:We report herein a comparison of the photophysics of a series of polythiophenes with ionization potentials ranging from 4.8 to 5.6 eV as pristine films and when blended with 5 wt% 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]C 61 (PCBM). Three polymers are observed to give amorphous films, attributed to a non-planar geometry of their backbone whilst the other five polymers, including poly(3-hexylthiophene), give more crystalline films. Optical excitation of the pristine films of the amorphous polymers is observed by transient absorption spectroscopy to give rise to polymer triplet formation. For the more crystalline pristine polymers, no triplet formation is observed, but rather a short-lived (~ 100 ns), broad photoinduced absorption feature assigned to polymer polarons. For all polymers, the addition of 5 wt% PCBM resulted in 70 -90% quenching of polymer photoluminescence (PL), indicative of efficient quenching of polythiophene excitons. Remarkably, despite this efficient exciton quenching, the yield of dissociated polymer + and PCBM − polarons, assayed by the appearance of a long-lived, powerlaw decay phase assigned to bimolecular recombination of these polarons, was observed to vary by over two orders of magnitude depending upon the polymer employed. In addition to this power-law decay phase, the blend films exhibited short-lived decays assigned, for the amorphous polymers, to neutral triplet states generated by geminate recombination of bound radical pairs and, for the more crystalline polymers, to the direct observation of the geminate recombination of these bound radical pairs to ground. These observations are discussed in terms of a two-step kinetic model for charge generation in polythiophene/PCBM blend films analogous to that reported to explain the observation of exciplex-like emission in poly(p-phenylenevinylene)-based blend films. Remarkably, we find a excellent correlation between the free energy difference for charge separation (ΔG CS rel ) and yield of the long-lived charge generation yield, with efficient charge generation requiring a much larger ΔG CS rel than that required to achieve efficient PL 3 quenching. We suggest this observation is consistent with a model where the excess thermal energy of the initially formed polarons pairs is necessary to overcome their coulomb binding energy. This observation has important implications for synthetic strategies to optimize organic solar cell performance, as it implies that, at least devices based on polythiophene/PCBM blend films, a large ΔG CS rel (or LUMO level offset) is required to achieve efficient charge dissociation.4

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Section: Introductionmentioning

confidence: 99%

Charge Carrier Formation in Polythiophene/Fullerene Blend Films Studied by Transient Absorption Spectroscopy

et al. 2008

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“…Recently, a hybrid thiophene-acene semiconductor has been investigated and revealed high mobility and increased air stability, indicating that the properties of the two fragments (acene and thiophene) can be combined to design a material with overall superior performance (Kwon et al 2004;Heeney et al 2005;Merlo et al 2005;Coropceanu et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Hole-vibronic coupling in oligothiophenes: impact of backbone torsional flexibility on relaxation energies

Filho

Coropceanu

Fichou

et al. 2007

Phil. Trans. R. Soc. A.

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Density functional theory calculations together with highly resolved gas-phase ultraviolet photoelectron spectroscopy have been applied to oligothiophene chains with up to eight thiophene rings. One of the important parameters governing the charge transport properties in the condensed phase is the amount of energy relaxation upon ionization. Here, we investigate the impact on this parameter of the backbone flexibility present in oligothiophenes as a result of inter-ring torsional motions. With respect to oligoacenes that are characterized by a coplanar and rigid backbone, the torsional flexibility in oligothiophenes adds to the relaxation energy and leads to the broadening of the first ionization peak, making its analysis more complex.

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“…Here we show that water-gated OTFTs using the organic semiconductor PBTTT poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno [3,2-b]thiophene), Fig (1), originally synthesised by McCulloch et al [6], show sensitivity to water-borne divalent cations, and selectivity between mono-and divalent cations, without further sensitising. Sensitivity and selectivity are innate to the semiconductor itself.…”

Section: Introductionmentioning

confidence: 70%