Solid‐State Processing of Organic Semiconductors

Baklar, Mohammed A.; Koch, Felix P.; Kumar, Avinesh; Domingo, Ester Buchaca; Campoy‐Quiles, Mariano; Feldman, Kirill; Yu, Liyang; Wöbkenberg, Paul H.; Ball, James M.; Wilson, Rory M.; McCulloch, Iain; Kreouzis, Theo; Heeney, Martin; Anthopoulos, Thomas D.; Smith, Paul; Stingelin, Natalie

doi:10.1002/adma.200904448

Cited by 48 publications

(63 citation statements)

References 36 publications

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“…The relative contribution of molecularly ordered and disordered regions to transport is manipulated using different thermal treatments, resulting in different degrees of energetic disorder within FETs and thus in a strong modulation of the thermal barriers to electron transport. A transport improvement with lamellar thickening, obtained upon annealing at T2, is generally expected in semicrystalline polymers, 62 but it has been rarely demonstrated, 63,64 especially in solution processed films and FET architectures. Owing to the retention of backbone orientation upon annealing at T2, energetic barriers for charge transfer are strongly reduced exclusively in the direction of chain alignment, where effective interconnectivity of ordered regions can be more easily gained, leading to temperature-independent electron transport near to 300 K. In contrast, in the direction perpendicular to the backbone, thermal charge transport barriers are independent whether the material is annealed at T1 or T2, which is not surprising as in the -stacking direction coherence length is much smaller in any case.…”

Section: Discussionmentioning

confidence: 99%

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

et al. 2019

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Recent demonstrations of inverted thermal activation of charge mobility in polymer field-effect transistors have excited the interest in transport regimes not limited by thermal barriers. However, rationalization of the limiting factors to access such regimes is still lacking. An improved understanding in this area is critical for development of new materials, establishing processing guidelines, and broadening of the range of applications. Here we show that precise processing of a diketopyrrolopyrrole-tetrafluorobenzene-based electron transporting copolymer results in single crystal-like and voltage-independent mobility with vanishing activation energy above 280 K. Key factors are uniaxial chain alignment and thermal annealing at temperatures within the melting endotherm of films. Experimental and computational evidences converge toward a picture of electrons being delocalized within crystalline domains of increased size. Residual energy barriers introduced by disordered regions are bypassed in the direction of molecular alignment by a more efficient interconnection of the ordered domains following the annealing process.

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Section: Discussionmentioning

confidence: 99%

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

et al. 2019

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“…1,2 In OPVs, dissociation of excitons at the interface between donor and acceptor is one of the important processes that determines the photoconversion efficiency. The short exciton diffusion length is an important factor that limits the number of excitons that can reach the interface.…”

Section: Introductionmentioning

confidence: 99%

Tuning crystalline ordering by annealing and additives to study its effect on exciton diffusion in a polyalkylthiophene copolymer

Chowdhury

Sajjad

Savikhin

et al. 2017

Phys. Chem. Chem. Phys.

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aThe influence of various processing conditions on the singlet exciton diffusion is explored in films of a conjugated random copolymer poly-(3-hexylthiophene-co-3-dodecylthiophene) (P3HT-co-P3DDT) and correlated with the degree of crystallinity probed by grazing incidence X-ray scattering and with exciton bandwidth determined from absorption spectra. The exciton diffusion coefficient is deduced from exciton-exciton annihilation measurements and is found to increase by more than a factor of three when thin films are annealed using CS 2 solvent vapour. A doubling of exciton diffusion coefficient is observed upon melt annealing at 200 1C and the corresponding films show about 50% enhancement in the degree of crystallinity. In contrast, films fabricated from polymer solutions containing a small amount of either solvent additive or nucleating agent show a decrease in exciton diffusion coefficient possibly due to formation of traps for excitons. Our results suggest that the enhancement of exciton diffusivity occurs because of increased crystallinity of alkyl-stacking and longer conjugation of aggregated chains which reduces the exciton bandwidth.

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“…Building on the report of Baklar et al, 15 in this work we present a simple and novel approach for producing pure P3HT fibers without the use of solvents and at temperatures well below the polymer's melting temperature. The process is reminiscent of the initial stages of more conventional polymer melt-extrusion.…”

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“…Recently, Baklar et al 15 have shown that a large class of organic conjugated systems can be solid state processed at temperatures well below their corresponding melting temperatures through application of an appropriate combination of temperature and pressure. In this work, the authors also observed that solid state processing can induce dramatic improvements in crystallinity in numerous conjugated pure compounds and showed that over macroscopic distances no grain boundaries were observed.…”

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confidence: 99%

“…It was assumed that the remarkable improvement in crystallinity is associated with "repair" of these boundaries due to self-diffusion. 15 When pressure is applied to semi-crystalline polymers, it not only induces 'plastic crystal' flow, 16 but can also improve the polymer crystallinity by allowing greater chain extension in the lamella. These effects are exploited commercially in the processing of poly(tetrafluorine ethylene) (PTFE) 17 and ultra-high molecular weight polyethylene (UHMWPE).…”

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Low temperature solid state processing of pure P3HT fibers

et al. 2013

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Fibers of pure poly(3-hexylthiophene) (P3HT) of 1 and 2 mm diameter, were produced from solid state processing at temperatures of 200, 150 and 100ºC, i.e. up to more than 100 ºC below the melting point of P3HT (∼240 ºC), using a small device reminiscent with the early stage polymer extrusion machines. The fibers produced by this method are continuous and mechanically robust. WAXS results show that the macromolecular chains of P3HT are preferably oriented along the fiber axis. This study clearly shows, for the first time, that P3HT fibers can be processed without solvents well below the polymer's melting temperature

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Solid‐State Processing of Organic Semiconductors

Cited by 48 publications

References 36 publications

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

Tuning crystalline ordering by annealing and additives to study its effect on exciton diffusion in a polyalkylthiophene copolymer

Low temperature solid state processing of pure P3HT fibers

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