Polarized X-ray scattering reveals non-crystalline orientational ordering in organic films

Collins, Brian A.; Cochran, Justin E.; Yan, Hongping; Gann, Eliot; Hub, C.; Fink, R.; Wang, Cheng; Schuettfort, Torben; McNeill, Christopher R.; Chabinyc, Michael L.; Ade, Harald

doi:10.1038/nmat3310

Cited by 281 publications

(328 citation statements)

References 43 publications

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“…Going from solution to the solid phase shifts the spectrum by over 100 nm (0.4 eV) to the red and modifies the spectral form. The bulk spectrum has been interpreted to show a shift of oscillator strength from the 0-0 to the 0-1 transition, assigned to H-aggregation (22), because bulkphase P3HT exhibits a high level of structural ordering in electron microscopy (5), scanning-probe microscopy (45), and other elastic scattering techniques (11,46,47). The large spectral shift between solution and bulk has been assigned to the occurrence of a crystal shift in the H-aggregated chromophores embedded in an ordered environment of many other conjugated polymer chains (23).…”

Section: Resultsmentioning

confidence: 99%

Unraveling the chromophoric disorder of poly(3-hexylthiophene)

Thiessen

Vogelsang

Adachi

et al. 2013

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

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The spectral breadth of conjugated polymers gives these materials a clear advantage over other molecular compounds for organic photovoltaic applications and is a key factor in recent efficiencies topping 10%. However, why do excitonic transitions, which are inherently narrow, lead to absorption over such a broad range of wavelengths in the first place? Using single-molecule spectroscopy, we address this fundamental question in a model material, poly(3-hexylthiophene). Narrow zero-phonon lines from single chromophores are found to scatter over 200 nm, an unprecedented inhomogeneous broadening that maps the ensemble. The giant red shift between solution and bulk films arises from energy transfer to the lowest-energy chromophores in collapsed polymer chains that adopt a highly ordered morphology. We propose that the extreme energetic disorder of chromophores is structural in origin. This structural disorder on the single-chromophore level may actually enable the high degree of polymer chain ordering found in bulk films: both structural order and disorder are crucial to materials physics in devices.structure-property relations | conformational disorder | photophysics | organic solar cells D espite half a century of research into organic photovoltaics (1), the promise of versatile paint-on solar-cell modules based on conjugated polymers has prompted a present flurry of activity in the field (2-5). A particular appeal of such excitonic solar cells is that very little material is needed to efficiently absorb light. This is due to the fact that the oscillator strength of primary photoexcitations, electron-hole pairs with binding energies far exceeding kT, is focused in the excitonic transition. The obvious downside is that this concentration also means excitonic transitions are inherently narrow and usually offer only mediocre spectral overlap with the broad solar spectrum. How then can excitonic solar cells be designed with appropriate spectral breadth? Merely introducing energetic disorder in the underlying excitonic material should lead to low-energy traps, impeding charge harvesting.Although the optical and electronic properties of conjugated polymers are not perfectly suited to photovoltaics, their absorption spectra are surprisingly broad despite the excitonic nature of the transitions. Moreover, the diversity in functional characteristics revealed by varying processing conditions has fueled the quest to formulate robust structure-property relationships between the electronic and optical properties and the underlying polymer structure (6-12). Polythiophene derivatives have evolved into one of the chosen workhorse materials for solar-cell research (13,14). Early spectroscopic studies established extraordinary solvatochromic and thermochromic characteristics, which were attributed to large conformational changes in response to the immediate environment (15-17). It is little surprise then that such diversity in device characteristics exists when using these materials (4). Poly(3-hexylthiophene) (P3HT) (structure show...

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Section: Resultsmentioning

confidence: 99%

Unraveling the chromophoric disorder of poly(3-hexylthiophene)

Thiessen

Vogelsang

Adachi

et al. 2013

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

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“…Indeed, a detailed characterization of this polymer reveals a rather unique solid-state microstructure displaying the simultaneous presence of disordered phases and highly interconnected, fiber-like ordered phases, where the polymer backbones lay preferentially faceon with respect to the substrate (12) and characterized by a dihedral angle between the NDI and thiophene units (13). Whereas a face-on orientation is observed in the bulk of the film, a more edge-on orientation is revealed at the film surface (14,15). This particular morphology allows good electron transport in both organic diodes and field-effect transistors (OFETs), with high in-plane mobilities of ∼0.1-0.6 cm 2 ·V -1 ·s -1 even in the presence of a substantial degree of disorder (11).…”

mentioning

confidence: 99%

Experimental evidence that short-range intermolecular aggregation is sufficient for efficient charge transport in conjugated polymers

Wang

Fabiano

Himmelberger

et al. 2015

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

180

206

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Efficiency, current throughput, and speed of electronic devices are to a great extent dictated by charge carrier mobility. The classic approach to impart high carrier mobility to polymeric semiconductors has often relied on the assumption that extensive order and crystallinity are needed. Recently, however, this assumption has been challenged, because high mobility has been reported for semiconducting polymers that exhibit a surprisingly low degree of order. Here, we show that semiconducting polymers can be confined into weakly ordered fibers within an inert polymer matrix without affecting their charge transport properties. In these conditions, the semiconducting polymer chains are inhibited from attaining longrange order in the π-stacking or alkyl-stacking directions, as demonstrated from the absence of significant X-ray diffraction intensity corresponding to these crystallographic directions, yet still remain extended along the backbone direction and aggregate on a local length scale. As a result, the polymer films maintain high mobility even at very low concentrations. Our findings provide a simple picture that clarifies the role of local order and connectivity of domains.organic electronics | conjugated polymers | aggregation | charge transport C onjugated polymers have received significant scientific attention as the active material in devices for printed and flexible organic electronics (1, 2). Owing to their versatile chemical synthesis, inexpensive processability from solution, and unique mechanical flexibility, these materials are in fact promising for a vast array of devices in future low-cost and distributed technologies, such as integrated systems for electronic labels targeting safety, security, and surveillance applications (3). The rational design of new organic semiconductors has been guided by a thorough investigation of their limitations in charge transport, leading to the development of high-performance materials for next-generation electronic applications such as low-cost displays, solar cells, sensors, and logic circuits (4, 5). For more than a decade research has primarily focused on increasing the long-range order and the crystallinity of conjugated polymers as a strategy to improve the solid-state charge transport properties. As a result, the charge carrier mobility has increased by several orders of magnitude through the design and synthesis of highly ordered polymers. However, recent studies have suggested that the key to designing high-mobility polymers is not to increase their crystallinity but rather to improve their tolerance for disorder by allowing more efficient intra-and intermolecular charge transport pathways (6). This observation explains why mobility values obtained from recently designed seemingly disordered organic semiconductors often exceed those of polymers having a high degree of crystallinity (∼1 cm 2 ·V -1 ·s -1 ) (7-10). Indeed, polymers may exhibit little longrange order, as measured by X-ray diffraction (XRD), and yet display a remarkable degree of short-range or...

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“…ÂÍ, ËÔÒÑÎßÊÖâ ÓÂÊÎËÚËâ Ä NEXAFS-ÔÒÇÍÕÓÂØ ×ÂÊ Fe(III) Ë Fe(II), ÂÄÕÑÓÞ ÓÂÃÑÕÞ [196], ËÊÖÚÂâ ÃËÑÏËÐÇÓÂ- [227].°Ó ËÇÐÕÂÙËÑÐÐÂâ ÚÖÄÔÕÄËÕÇÎßÐÑÔÕß NEXAFS-ÔÒÇÍÕ-ÓÑÄ ËÔÒÑÎßÊÑÄÂÎÂÔß Ä ÔÒÇÍÕÓÑÏËÍÓÑÔÍÑÒËË AEÎâ ËÔÔÎÇAEÑ-ÄÂÐËÌ ÑÓËÇÐÕÂÙËË ÏÑÎÇÍÖÎ Ä ÑÓÅÂÐËÚÇÔÍËØ ÐÂÐÑÏÂÕÇÓËÂ-ÎÂØ [228,229], ÃÎÑÚÐÑÌ ÔÕÓÖÍÕÖÓÞ ÑÓÅÂÐËÚÇÔÍËØ ÒÎÈÐÑÍ [230,231], ÑÓÅÂÐËÚÇÔÍËØ ÒÑÎÖÒÓÑÄÑAEÐËÍÑÄ [232], ÕÓÂÐÊË-ÔÕÑÓÑÄ [233,234], ÑÓËÇÐÕÂÙËË ÏÑÎÇÍÖÎ Ä ËÔÍÖÔÔÕÄÇÐÐÞØ Ë ÒÓËÓÑAEÐÞØ ÄÑÎÑÍÐÂØ [226,235,236], Â ÕÂÍÉÇ ÔÕÓÖÍÕÖÓÞ ÉËAEÍËØ ÍÓËÔÕÂÎÎÑÄ [227,237], ÖÅÎÇÓÑAEÐÞØ ÐÂÐÑÕÓÖÃÑÍ [177]. ³ÒËÔÑÍ ÎËÕÇÓÂÕÖÓÞ…”

Section: ¶âêñäþì íñðõóâôõ¸çóðëíç°Aeunclassified

X-ray microscopy

Лидер¹

2017

Успехи физических наук

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±ÑÎÂÅÂâ sqap % l f m al coh (ÅAEÇ l coh ì ÒÑÒÇÓÇÚÐÂâ ÍÑÅÇ-ÓÇÐÕÐÑÔÕß ÒÖÚÍÂ) Ë ËÔÒÑÎßÊÖâ ×ÑÓÏÖÎÖ (3), ÒÓËÄÇAEÈÏ ÄÞÓÂÉÇÐËÇ (7) AEÎâ ³´²® Í ÔÎÇAEÖáÜÇÏÖ ÄËAEÖ: X-ray microscopy is a technique for obtaining real-space two-or three-dimensional images of an object using elements of the focusing optics. In this paper, various types of microscopes are reviewed and their applicability is examined; methods for obtaining image contrast are discussed, and directions for the further development of X-ray microscopy are outlined.

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Polarized X-ray scattering reveals non-crystalline orientational ordering in organic films

Cited by 281 publications

References 43 publications

Unraveling the chromophoric disorder of poly(3-hexylthiophene)

Unraveling the chromophoric disorder of poly(3-hexylthiophene)

Experimental evidence that short-range intermolecular aggregation is sufficient for efficient charge transport in conjugated polymers

X-ray microscopy

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