Designing pi-conjugated polymers for organic electronics
TL;DR: In this paper, a review of conjugated polymers with 1D and 2D topological structures is presented, and a design approach for the alternating donor-acceptor (D-A) copolymers is proposed.
About: This article is published in Progress in Polymer Science.The article was published on 2013-12-01. It has received 668 citations till now. The article focuses on the topics: Conductive polymer & Organic field-effect transistor.
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TL;DR: In this article, the authors discuss recent breakthroughs for organic materials with high thermoelectric figures of merit and indicate how these materials may be incorporated into new module designs that take advantage of their mechanical properties.
Abstract: Conjugated polymers and related processing techniques have been developed for organic electronic devices ranging from lightweight photovoltaics to flexible displays. These breakthroughs have recently been used to create organic thermoelectric materials, which have potential for wearable heating and cooling devices, and near-room-temperature energy generation. So far, the best thermoelectric materials have been inorganic compounds (such as Bi2Te3) that have relatively low Earth abundance and are fabricated through highly complex vacuum processing routes. Molecular materials and hybrid organic–inorganic materials now demonstrate figures of merit approaching those of these inorganic materials, while also exhibiting unique transport behaviours that are suggestive of optimization pathways and device geometries that were not previously possible. In this Review, we discuss recent breakthroughs for organic materials with high thermoelectric figures of merit and indicate how these materials may be incorporated into new module designs that take advantage of their mechanical and thermoelectric properties. Thermoelectrics can be used to harvest energy and control temperature. Organic semiconducting materials have thermoelectric performance comparable to many inorganic materials near room temperature. Better understanding of their performance will provide a pathway to new types of conformal thermoelectric modules.
860 citations
TL;DR: The results demonstrate that a fine and balanced modification/design of chemical structure can make significant performance differences and that the performance of solution-processed small-molecule-based solar cells can be comparable to or even surpass that of their polymer counterparts.
Abstract: A series of acceptor-donor-acceptor simple oligomer-like small molecules based on oligothiophenes, namely, DRCN4T-DRCN9T, were designed and synthesized. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated. Except for DRCN4T, excellent performances were obtained for DRCN5T-DRCN9T. The devices based on DRCN5T, DRCN7T, and DRCN9T with axisymmetric chemical structures exhibit much higher short-circuit current densities than those based on DRCN6T and DRCN8T with centrosymmetric chemical structures, which is attributed to their well-developed fibrillar network with a feature size less than 20 nm. The devices based on DRCN5T/PC71BM showed a notable certified power conversion efficiency (PCE) of 10.10% under AM 1.5G irradiation (100 mW cm(-2)) using a simple solution spin-coating fabrication process. This is the highest PCE for single-junction small-molecule-based organic photovoltaics (OPVs) reported to date. DRCN5T is a rather simpler molecule compared with all of the other high-performance molecules in OPVs to date, and this might highlight its advantage in the future possible commercialization of OPVs. These results demonstrate that a fine and balanced modification/design of chemical structure can make significant performance differences and that the performance of solution-processed small-molecule-based solar cells can be comparable to or even surpass that of their polymer counterparts.
766 citations
TL;DR: In this article, the authors summarize the latest developments in solution-processed interfacial layers that have contributed to the significantly improved performance of polymer and perovskite solar cells (PSCs and PVSCs).
Abstract: In this review, we summarize the latest developments in solution-processed interfacial layers that have contributed to the significantly improved performance of polymer and perovskite solar cells (PSCs and PVSCs). The solution-processed interfacial materials, including organic electrolytes, organic–inorganic hybrids, graphene oxides (GOs), transition metal oxides (TMOs), and self-assembled functional materials, along with their integration into efficient PSCs, polymer tandem cells (PTCs), and the emerging perovskite solar cells (PVSCs) are discussed. Regarding the rapid progress of PSCs and PVSCs, strategies and perspectives of further improving solution-processed interfacial materials are also discussed to help readers understand the challenges and opportunities in transitioning from scientific curiosity into technology translation for realizing low-cost, printable, and high-efficiency flexible solar cells to address the scalability issues facing solar energy.
696 citations
TL;DR: Overall, this Account correlates the molecular structures of the 2D-conjugated BDT-based polymers with their photovoltaic properties and can guide the molecular design of organic photvoltaic materials and the development of organic materials for other types of optoelectronic devices.
Abstract: ConspectusAs researchers continue to develop new organic materials for solar cells, benzo[1,2-b:4,5-b']dithiophene (BDT)-based polymers have come to the fore. To improve the photovoltaic properties of BDT-based polymers, researchers have developed and applied various strategies leading to the successful molecular design of highly efficient photovoltaic polymers. Novel polymer materials composed of two-dimensional conjugated BDT (2D-conjugated BDT) have boosted the power conversion efficiency of polymer solar cells (PSCs) to levels that exceed 9%.In this Account, we summarize recent progress related to the design and synthesis of 2D-conjugated BDT-based polymers and discuss their applications in highly efficient photovoltaic devices. We introduce the basic considerations for the construction of 2D-conjugated BDT-based polymers and systematic molecular design guidelines. For example, simply modifying an alkoxyl-substituted BDT to form an alkylthienyl-substituted BDT can improve the polymer hole mobilities s...
652 citations
TL;DR: This research presents a new generation of Bio-Inspired Smart Interfacial Science and Technology Materials and Devices for Multidisciplinary Science, developed by the team of Prof. J. Heeger and Prof. Y. Sun at Beihang University, Beijing.
Abstract: Prof. L. Huo, T. Liu, Prof. X. Sun, Y. Cai, Prof. Y. Sun Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education Beijing Key Laboratory of Bio-Inspired Energy Materials and Devices School of Chemistry and Environment Beihang University Beijing 100191 , P. R. China E-mail: sunym@buaa.edu.cn Prof. L. Huo, T. Liu, Prof. X. Sun, Y. Cai, Prof. A. J. Heeger, Prof. Y. Sun Heeger Beijing Research and Development Center International Research Institute for Multidisciplinary Science Beihang University Beijing 100191 , P. R. China
476 citations
References
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TL;DR: Monocrystalline graphitic films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands and they exhibit a strong ambipolar electric field effect.
Abstract: We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 10 13 per square centimeter and with room-temperature mobilities of ∼10,000 square centimeters per volt-second can be induced by applying gate voltage.
55,532 citations
TL;DR: The bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications.
Abstract: The remarkable mechanical properties of carbon nanotubes arise from the exceptional strength and stiffness of the atomically thin carbon sheets (graphene) from which they are formed. In contrast, bulk graphite, a polycrystalline material, has low fracture strength and tends to suffer failure either by delamination of graphene sheets or at grain boundaries between the crystals. Now Stankovich et al. have produced an inexpensive polymer-matrix composite by separating graphene sheets from graphite and chemically tuning them. The material contains dispersed graphene sheets and offers access to a broad range of useful thermal, electrical and mechanical properties. Individual sheets of graphene can be readily incorporated into a polymer matrix, giving rise to composite materials having potentially useful electronic properties. Graphene sheets—one-atom-thick two-dimensional layers of sp2-bonded carbon—are predicted to have a range of unusual properties. Their thermal conductivity and mechanical stiffness may rival the remarkable in-plane values for graphite (∼3,000 W m-1 K-1 and 1,060 GPa, respectively); their fracture strength should be comparable to that of carbon nanotubes for similar types of defects1,2,3; and recent studies have shown that individual graphene sheets have extraordinary electronic transport properties4,5,6,7,8. One possible route to harnessing these properties for applications would be to incorporate graphene sheets in a composite material. The manufacturing of such composites requires not only that graphene sheets be produced on a sufficient scale but that they also be incorporated, and homogeneously distributed, into various matrices. Graphite, inexpensive and available in large quantity, unfortunately does not readily exfoliate to yield individual graphene sheets. Here we present a general approach for the preparation of graphene-polymer composites via complete exfoliation of graphite9 and molecular-level dispersion of individual, chemically modified graphene sheets within polymer hosts. A polystyrene–graphene composite formed by this route exhibits a percolation threshold10 of ∼0.1 volume per cent for room-temperature electrical conductivity, the lowest reported value for any carbon-based composite except for those involving carbon nanotubes11; at only 1 volume per cent, this composite has a conductivity of ∼0.1 S m-1, sufficient for many electrical applications12. Our bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications.
11,866 citations
IBM1
TL;DR: In this article, the authors demonstrate that poly(p-phenylene vinylene), prepared by way of a solution-processable precursor, can be used as the active element in a large-area light-emitting diode.
Abstract: CONJUGATED polymers are organic semiconductors, the semiconducting behaviour being associated with the π molecular orbitals delocalized along the polymer chain. Their main advantage over non-polymeric organic semiconductors is the possibility of processing the polymer to form useful and robust structures. The response of the system to electronic excitation is nonlinear—the injection of an electron and a hole on the conjugated chain can lead to a self-localized excited state which can then decay radiatively, suggesting the possibility of using these materials in electroluminescent devices. We demonstrate here that poly(p-phenylene vinylene), prepared by way of a solution-processable precursor, can be used as the active element in a large-area light-emitting diode. The combination of good structural properties of this polymer, its ease of fabrication, and light emission in the green–yellow part of the spectrum with reasonably high efficiency, suggest that the polymer can be used for the development of large-area light-emitting displays.
10,463 citations
TL;DR: It is found that the energy gap scales inversely with the ribbon width, thus demonstrating the ability to engineer the band gap of graphene nanostructures by lithographic processes.
Abstract: We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge carriers creates an energy gap near the charge neutrality point. Individual graphene layers are contacted with metal electrodes and patterned into ribbons of varying widths and different crystallographic orientations. The temperature dependent conductance measurements show larger energy gaps opening for narrower ribbons. The sizes of these energy gaps are investigated by measuring the conductance in the nonlinear response regime at low temperatures. We find that the energy gap scales inversely with the ribbon width, thus demonstrating the ability to engineer the band gap of graphene nanostructures by lithographic processes.
4,969 citations
TL;DR: In this paper, a single epitaxial graphene layer at the silicon carbide interface is shown to reveal the Dirac nature of the charge carriers, and all-graphene electronically coherent devices and device architectures are envisaged.
Abstract: Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers. Patterned structures show quantum confinement of electrons and phase coherence lengths beyond 1 micrometer at 4 kelvin, with mobilities exceeding 2.5 square meters per volt-second. All-graphene electronically coherent devices and device architectures are envisaged.
4,848 citations