The development of organic semiconductors (OSCs) applicable to organic field-effect transistors (OFETs) is crucial to realizing printed and flexible electronics, such as flexible displays and ...low-priced identification tags. OSCs for printed and flexible electronics must meet several prerequisites: (1) high chemical stability for use without special care, (2) charge carrier mobility exceeding 10 cm2/Vs for several applications, (3) appropriate solubility in organic solvents for solution processes, (4) high thermal durability for device fabrications and applications, and (5) a simple synthetic route for large-scale production. Previously reported OSCs do not meet all the requirements simultaneously, which has motivated intensive development of OSCs for future printed and flexible electronics applications. The author and collaborators developed state-of-the-art OSCs based on bent-shaped π-electron cores (π-cores) that satisfy the requirements for printed semiconductor devices. In this focused review, the chemistry and device engineering are introduced with respect to sulfur-bridged V-shaped and N-shaped π-cores among a series of bent-shaped π-cores.The development of organic semiconductors (OSCs) applicable to organic field-effect transistors is crucial to printed and flexible electronics. OSCs must meet several prerequisites: 1) high chemical stability, 2) charge carrier mobility exceeding 10 cm2/Vs, 3) appropriate solubility, and 4) high thermal durability. The author and collaborators developed state-of-the-art OSCs based on bent-shaped π-electron cores (π-cores) that satisfy the requirements for printed semiconductor devices. In this focused review, the chemistry and device engineering are introduced with respect to sulfur-bridged V-shaped and N-shaped π-cores among a series of bent-shaped π-cores.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A highly conductive metallic gas that is quantum mechanically confined at a solid-state interface is an ideal platform to explore non-trivial electronic states that are otherwise inaccessible in bulk ...materials. Although two-dimensional electron gases have been realized in conventional semiconductor interfaces, examples of two-dimensional hole gases, the counterpart to the two-dimensional electron gas, are still limited. Here we report the observation of a two-dimensional hole gas in solution-processed organic semiconductors in conjunction with an electric double layer using ionic liquids. A molecularly flat single crystal of high-mobility organic semiconductors serves as a defect-free interface that facilitates two-dimensional confinement of high-density holes. A remarkably low sheet resistance of 6 kΩ and high hole-gas density of 1014 cm−2 result in a metal–insulator transition at ambient pressure. The measured degenerate holes in the organic semiconductors provide an opportunity to tailor low-dimensional electronic states using molecularly engineered heterointerfaces.A two-dimensional hole gas with high carrier density is confined at the interface between a solution-processed, single-crystalline organic semiconducting film and the electric double layer formed by an ion gel on top of the film.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
The efficiency with which polymeric semiconductors can be chemically doped-and the charge carrier densities that can thereby be achieved-is determined primarily by the electrochemical redox potential ...between the π-conjugated polymer and the dopant species
. Thus, matching the electron affinity of one with the ionization potential of the other can allow effective doping
. Here we describe a different process-which we term 'anion exchange'-that might offer improved doping levels. This process is mediated by an ionic liquid solvent and can be pictured as the effective instantaneous exchange of a conventional small p-type dopant anion with a second anion provided by an ionic liquid. The introduction of optimized ionic salt (the ionic liquid solvent) into a conventional binary donor-acceptor system can overcome the redox potential limitations described by Marcus theory
, and allows an anion-exchange efficiency of nearly 100 per cent. As a result, doping levels of up to almost one charge per monomer unit can be achieved. This demonstration of increased doping levels, increased stability and excellent transport properties shows that anion-exchange doping, which can use an almost infinite selection of ionic salts, could be a powerful tool for the realization of advanced molecular electronics.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In situ extinction spectroscopy and transient absorption spectroscopy of the femtosecond laser-induced fragmentation of 60 nm diameter aqueous gold nanoparticles were performed. The threshold laser ...fluences of fragmentation determined by in situ spectroscopy and transmission electron microscopy, (7.3 ± 1.5) mJ·cm−2 for excitation at 400 nm and (3.6 ± 0.5) mJ·cm−2 at 532 nm, agreed well with the values of 6.0−7.4 and 3.4−4.1 mJ·cm−2 calculated by our simulation based on the twotemperature and liquid drop models. The transient absorption study revealed that real-time observation of fragmentation is possible at picosecond time scales. When monitored at 490 nm, at which the effect of fast relaxation dynamics is minimal, excitation at 400 nm afforded a reduced extinction signal of the localized surface plasmon resonance (LSPR) band of gold nanoparticles at laser fluences greater than or equal to (6.1 ± 1) mJ·cm−2. The reduction can be ascribed to nanoparticle fragmentation because the intensity (I) of the LSPR band depends on particle radius (R), I ∝ R 3. The signal reduction occurred not instantaneously but gradually within 100 ps, suggesting separation of initial densely packed small clusters during the observation period. The onset of the size reduction was laser-fluence-dependent, and it occurred earlier at higher fluences. This fluence dependence was explained well within the framework of our model: fragmentation occurs for liquid rather than solid gold, and the onset suggests the initiation of particle melting. The present result demonstrated that femtosecond laser-induced fragmentation is dominated by the Coulomb explosion mechanism, discussed many times without experimental verification. We believe we can provide information long needed in the field.
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Coherent charge transport can occur in organic semiconductor crystals thanks to the highly periodic electrostatic potential--despite the weak van der Waals bonds. And as spin-orbit coupling is ...usually weak in organic materials, robust spin transport is expected, which is essential if they are to be exploited for spintronic applications. In such systems, momentum relaxation occurs via scattering events, which enables an intrinsic mobility to be defined for band-like charge transport, which is >10 cm2 V-1 s-1 . In contrast, there are relatively few experimental studies of the intrinsic spin relaxation for organic band-transport systems. Here, we demonstrate that the intrinsic spin relaxation in organic semiconductors is also caused by scattering events, with much less frequency than the momentum relaxation. Magnetotransport measurements and electron spin resonance spectroscopy consistently show a linear relationship between the two relaxation times over a wide temperature range, clearly manifesting the Elliott-Yafet type of spin relaxation mechanism. The coexistence of an ultra-long spin lifetime of milliseconds and the coherent band-like transport, resulting in a micrometre-scale spin diffusion length, constitutes a key step towards realizing spintronic devices based on organic single crystals.
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Abstract
We fabricated a hybrid plasmonic device using self-imaging effect between guided light and surface plasmon polaritons in the hybrid plasmonic waveguide. The hybrid plasmonic device was ...fabricated by evaporating gold on the part of the silicon waveguide. Self-imaging was generated at the gold-covered section in the waveguide. Self-imaging of guided light and surface plasmon polaritons in hybrid plasmonic waveguides affect the output intensity of the hybrid plasmonic waveguide. The length of the hybrid plasmonic waveguide changes self-imaging conditions. We confirmed that the output intensity was affected by the length of the hybrid plasmonic waveguide. These findings contribute to the development of hybrid plasmonic devices and potentially improve integration density of hybrid photonic integrated circuits.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Quercetin is the major flavonoid involved in vegetables and fruits. Quercetin is ingested from the daily diet, but in 1970s it was reported as mutagenic. Quercetin possesses a variety of ...pharmacological activities, and in order for further clinical application, it is important to evaluate its safety. In Ames test, quercetin is regarded as mutagenic. However, recent in vitro studies indicate that quercetin is protective against genotoxicants, and regarded as antimutagenic. Some in vivo studies including National Toxicology Program reported carcinogenic effect of quercetin in F344 rats. However, the method used in the study was unusual and the result was not reproduced. Most of the results of in vivo studies indicate that quercetin is not carcinogenic. Since 1969, the International Agency for Research on Cancer (IARC) has undertaken a program to evaluate the carcinogenic risk of chemicals. In 1999, IARC concluded that quercetin is not classified carcinogenic to humans. In the U.S. and Europe, supplements of quercetin is commercially available, and beneficial effects of quercetin supplements were reported in clinical trials. Overall, quercetin is genotoxic to salmonella, but its safety upon human application is approved.
Abstract
Transistors, the most important logic elements, are maintained under dynamic influence during circuit operations. Practically, circuit design protocols and frequency responsibility should ...stem from a perfect agreement between the static and dynamic properties. However, despite remarkable improvements in mobility for organic semiconductors, the correlation between the device performances achieved under static and dynamic circumstances is controversial. Particularly in the case of organic semiconductors, it remains unclear whether parasitic elements that relate to their unique molecular aggregates may violate the radiofrequency circuit model. Thus, we herein report the manufacture of micrometre-scale transistor arrays composed of solution-processed organic semiconductors, which achieve near very high-frequency band operations. Systematic investigations into the device geometrical factors revealed that the radiofrequency circuit model established on a solid-state continuous medium is extendable to organic single-crystal field-effect transistors. The validity of this radiofrequency circuit model allows a reliable prediction of the performances of organic radiofrequency devices.
Two-dimensional (2D) layered semiconductors are a novel class of functional materials that are an ideal platform for electronic applications, where the whole electronic states are directly modified ...by external stimuli adjacent to their electronic channels. Scale-up of the areal coverage while maintaining homogeneous single crystals has been the relevant challenge. We demonstrate that wafer-size single crystals composed of an organic semiconductor bimolecular layer with an excellent mobility of 10 cm
V
s
can be successfully formed via a simple one-shot solution process. The well-controlled process to achieve organic single crystals composed of minimum molecular units realizes unprecedented low contact resistance and results in high-speed transistor operation of 20 MHz, which is twice as high as the common frequency used in near-field wireless communication. The capability of the solution process for scale-up coverage of high-mobility organic semiconductors opens up the way for novel 2D nanomaterials to realize products with large-scale integrated circuits on film-based devices.
The hole-carrier transport of organic semiconductors is widely known to occur via intermolecular orbital overlaps of the highest occupied molecular orbitals (HOMO), though the effect of other ...occupied molecular orbitals on charge transport is rarely investigated. In this work, we first demonstrate evidence of a mixed-orbital charge transport concept in the high-performance N-shaped decyl-dinaphtho2,3-d:2′,3′-d′benzo1,2-b:4,5-b′dithiophene (C10–DNBDT–NW), where electronic couplings of the second HOMO (SHOMO) and third HOMO (THOMO) also contribute to the charge transport. We then present the molecular design of an N-shaped bis(naphtho2′,3′:4,5thieno)2,3-b:2′,3′-epyrazine (BNTP) π-electron system to induce more pronounced mixed-orbital charge transport by incorporating the pyrazine moiety. An effective synthetic strategy for the pyrazine-fused extended π-electron system is developed. With substituent engineering, the favorable two-dimensional herringbone assembly can be obtained with BNTP, and the decylphenyl-substituted BNTP (C10Ph–BNTP) demonstrates large electronic couplings involving the HOMO, SHOMO, and THOMO in the herringbone assembly. C10Ph–BNTP further shows enhanced mixed-orbital charge transport when the electronic couplings of all three occupied molecular orbitals are taken into consideration, which results in a high hole mobility up to 9.6 cm2 V–1 s–1 in single-crystal thin-film organic field-effect transistors. The present study provides insights into the contribution of HOMO, SHOMO, and THOMO to the mixed-orbital charge transport of organic semiconductors.
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