Organic semiconductors might enable new applications in low-cost, light-weight, flexible electronics. To build a solid foundation for these technologies, more fundamental studies of ...electro-mechanical properties of various types of organic semiconductors are necessary. Here we perform basic studies of charge transport in highly crystalline solution-processed organic semiconductors as a function of applied mechanical strain. As a test bed, we use small molecules crystallized on thin plastic sheets, resulting in high-performance flexible field-effect transistors. These devices can be bent multiple times without degradation to a radius as small as ~200 μm, demonstrating that crystalline solution-processed organic semiconductors are intrinsically highly flexible. This study of electro-mechanical properties suggests that solution-processable organic semiconductors are suitable for applications in flexible electronics, provided that integration with other important technological advances, such as device scalability and low-voltage operation, is achieved in the future.
The field of organic electronics is still lacking ubiquitous organic transistors with an efficient electron (n‐type) transport that are environmentally and electrically robust. Here, ...solution‐processed n‐type N,N′‐1H,1H‐perfluorobutyldicyanoperylene‐carboxydi‐imide organic field‐effect transistors (OFETs) are reported and it is demonstrated that they are highly stable while operating both in vacuum and in the air at least up to temperatures as high as ≈100 °C. In addition, these crystalline thin‐film transistors are found to be resilient to photooxidation under intense illumination in oxygen atmosphere. The performance of these environmentally stable n‐type OFETs is on par with the commercial amorphous Si transistors: the highest electron mobility obtained in this study is μmax ≈ 0.6 cm2 V−1 s−1, while the average reproducible mobility is ⟨μ⟩ = 0.4 cm2 V−1 s−1. Importantly, no parasitic gate voltage VG sweep rate dependence of the nominal mobility in these devices is observed. In addition, the charge carrier mobility has been found to be temperature independent in the range T ≈ 250–373 K. The observed great operational stability and resilience against photooxidation, as well as a temperature‐independent mobility in these solution‐processed n‐type OFETs are beneficial for furthering practical applications of organic semiconductor devices.
n‐type organic field‐effect transistors based on highly crystalline oriented N,N′‐1H,1H‐perfluorobutyldicyanoperylene‐carboxydi‐imide films grown from a solution are shown to have an excellent environmental and electrical stability, resistance to photooxidation, and the ability to withstand temperature cycling in a wide temperature range. The charge carrier mobility is found to be temperature independent in the practically relevant range between −25 and 100 °C.
Reversible control of charge transport and magnetic properties without degradation is a key for device applications of transition metal oxides. Chemical doping during the growth of transition metal ...oxides can result in large changes in physical properties, but in most of the cases irreversibility is an inevitable constraint. Here we report a reversible control of charge transport, metal-insulator crossover and magnetism in field-effect devices based on ionically gated archetypal oxide system - SrRuO₃. In these thin-film devices, the metal-insulator crossover temperature and the onset of magnetoresistance can be continuously and reversibly tuned in the range 90-250 K and 70-100 K, respectively, by application of a small gate voltage. We infer that a reversible diffusion of oxygen ions in the oxide lattice dominates the response of these materials to the gate electric field. These findings provide critical insights into both the understanding of ionically gated oxides and the development of novel applications.
Human skin undergoes distinct changes throughout the aging process, based on both intrinsic and extrinsic factors. In a process called photoaging, UVB irradiation leads to upregulation of matrix ...metalloproteinase-1, which then causes collagen degradation and premature aging. Mixtures of medicinal plants have traditionally been used as drugs in oriental medicine. Based on the previously reported antioxidant properties of Panax ginseng Meyer and Crataegus pinnatifida, we hypothesized that the mixture of P. ginseng Meyer and C. pinnatifida (GC) would have protective effects against skin aging.
Anti-aging activity was examined both in human dermal fibroblasts under UVB irradiation by using Western blot analysis and in healthy human skin by examining noninvasive measurements.
In vitro studies showed that GC improved procollagen type I expression and diminished matrix metalloproteinase-1 secretion. Based on noninvasive measurements, skin roughness values, including total roughness (R1), maximum roughness (R2), smoothness depth and average roughness (R3), and global photodamage scores were improved by GC application. Moreover, GC ameliorated the high values of smoothness depth (R4), which means that GC reduced loss of skin moisture.
These results suggest that GC can prevent aging by inhibiting wrinkle formation and increasing moisture in the human skin.
Utilizing the intrinsic mobility–strain relationship in semiconductors is critical for enabling strain engineering applications in high‐performance flexible electronics. Here, measurements of Hall ...effect and Raman spectra of an organic semiconductor as a function of uniaxial mechanical strain are reported. This study reveals a very strong, anisotropic, and reversible modulation of the intrinsic (trap‐free) charge carrier mobility of single‐crystal rubrene transistors with strain, showing that the effective mobility of organic circuits can be enhanced by up to 100% with only 1% of compressive strain. Consistently, Raman spectroscopy reveals a systematic shift of the low‐frequency Raman modes of rubrene to higher (lower) frequencies with compressive (tensile) strain, which is indicative of a reduction (enhancement) of thermal molecular disorder in the crystal with strain. This study lays the foundation of the strain engineering in organic electronics and advances the knowledge of the relationship between the carrier mobility, low‐frequency vibrational modes, strain, and molecular disorder in organic semiconductors.
This paper reports Hall effect and Raman measurements of organic semiconductors as a function of uniaxial mechanical strain. It reveals a strong, anisotropic modulation of the intrinsic charge carrier mobility of single‐crystal rubrene transistors with strain, showing that the performance of organic circuits can be enhanced by up to 100% with only 1% of compessive strain.
Doping is one of the most fundamental building blocks for semiconductor processing, and enables adaptation to both charge concentration and electrical conductivity. Despite attempts to investigate ...various doping and de-doping methods for organic semiconductors over many years, their use has been limited to date. Here, we present a method to precisely control the degree of doping in dopant-implanted thiophene-based polymeric conductors. A simple post annealing at a relatively low temperature of approximately 110 °C can significantly diminish the charge carrier concentration with precision, where the controllability is evaluated comprehensively using electron spin resonance and optical absorption techniques. At higher doping regimes, a band-like charge transport with an ideal Hall effect and weak localization is confirmed.
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•A simple method to control doping levels in conjugated polymers is demonstrated.•Molecular kinetics induced by thermal energy allows controllable de-doping.•Band-like transport is realized even at intermediate doping stages.
During the aging process, skin shows visible changes, characterized by a loss of elasticity and the appearance of wrinkles due to reduced collagen production and decreased elasticity of elastin ...fibers. Panax ginseng Meyer has been used as a traditional medicine for various diseases due to its wide range of biological activities including skin protective effects. Ginsenosides are the main components responsible for the biological activities of ginseng. However, the protective activities of an enzymatic preparation of red ginseng against human skin aging have not been investigated.
The efficacy of an enzyme-treated powder complex of red ginseng (BG11001) in preventing human skin aging was evaluated by oral administration to 78 randomized individuals. All patients were requested to take three daily capsules containing either 750 mg of BG11001 or a placebo vehicle for 24 wk; at the end of the testing period, skin roughness, elasticity, and skin water content were measured.
BG11001 significantly reduced the average roughness of eye wrinkles and the Global Photo Damage Score compared with the placebo, although there were no significant differences in arithmetic roughness average between the groups. In addition, gross elasticity and net elasticity values increased, and transepidermal water loss level decreased, indicating improved skin elasticity and moisture content.
In conclusion, enzyme-treated red ginseng extract significantly improved eye wrinkle roughness, skin elasticity, and moisture content. Moreover, enzyme-treated red ginseng extract would be useful substance as a bio-health skin care product.
Magnetic topological insulators are a fertile platform for studying the interplay between magnetism and topology. The unique electronic band structure can induce exotic transport and optical ...properties. However, a comprehensive optical study at both near-infrared and terahertz frequencies has been lacking. Here, we report magneto-optical effects from a heterostructure of a Cr-incorporated topological insulator, CBST. By measuring the magneto-optical Kerr effect, we observe a high temperature ferromagnetic transition (160 K) in the CBST film. We also use time-domain terahertz polarimetry to reveal a terahertz Faraday rotation of 1.5 mrad and a terahertz Kerr rotation of 3.6 mrad at 2 K. The calculated terahertz Hall conductance is 0.42 e2/h. Our work shows the optical responses of an artificially layered magnetic topological insulator, paving the way toward a high-temperature quantum anomalous Hall effect via heterostructure engineering.
Magnetic topological insulators are a fertile platform for studying the interplay between magnetism and topology. The unique electronic band structure can induce exotic transport and optical ...properties. However, a comprehensive optical study at both near-infrared and terahertz frequencies has been lacking. Here, we report magneto-optical effects from a heterostructure of a Cr-incorporated topological insulator, CBST. By measuring the magneto-optical Kerr effect, we observe a high temperature ferromagnetic transition (160 K) in the CBST film. We also use time-domain terahertz polarimetry to reveal a terahertz Faraday rotation of 1.5 mrad and a terahertz Kerr rotation of 3.6 mrad at 2 K. The calculated terahertz Hall conductance is 0.42 e2/h. Our work shows the optical responses of an artificially layered magnetic topological insulator, paving the way toward a high-temperature quantum anomalous Hall effect via heterostructure engineering.
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