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Although significant progress has been made in the development of light-emitting materials for organic light-emitting diodes along with the elucidation of emission mechanisms, the electron injection/transport mechanism remains unclear, and the materials used for electron injection/transport have been basically unchanged for more than 20 years. Here, we unravelled the electron injection/transport mechanism by tuning the work function near the cathode to about 2.0 eV using a superbase. This extremely low-work function cathode allows direct electron injection into various materials, and it was found that organic materials can transport electrons independently of their molecular structure. On the basis of these findings, we have realised a simply structured blue organic light-emitting diode with an operational lifetime of more than 1,000,000 hours. Unravelling the electron injection/transport mechanism, as reported in this paper, not only greatly increases the choice of materials to be used for devices, but also allows simple device structures. Understanding the role electron injection and transport in organic light-emitting diodes (OLED) is critical for optimizing device performance. Here, the authors elucidate the electron injection/transport mechanism in OLEDs and identify the cathode/emissive layer energy barrier as the key factor.

The realisation of a cathode with various work functions (WFs) is required to maximise the potential of organic semiconductors that have various electron affinities. However, the barrier-free contact for electrons could only be achieved by using reactive materials, which significantly reduce the environmental stability of organic devices. We show that a stable electrode with various WFs can be produced by utilising the coordination reaction between several phenanthroline derivatives and the electrode. Although the low WF of the electrode realised by using reactive materials is specific to the material, the WF of the phenanthroline-modified electrode is tunable depending on the amount of electron transfer associated with the coordination reaction. A phenanthroline-modified electrode that has a higher electron injection efficiency than lithium fluoride has been demonstrated. The observation of various WFs induced by the coordination reaction affords strategic perspectives on the development of stable cathodes unique to organic electronics. Despite recent studies aimed at realizing efficient charge injection and collection in organic electronics, developing stable organic injection materials remains a challenge. Here, the authors report phenanthroline derivative-based materials for improved charge injection in organic devices.

Although organic light‐emitting diodes (OLEDs) have been studied extensively for various applications, the effect of the electron behavior on the characteristics of OLEDs has rarely been discussed owing to the difficulty in investigating the actual energy levels. Understanding the correlation between energy levels and the characteristics of OLEDs is essential to improve the performances of blue OLEDs, since the materials with relatively large band gaps used in blue OLEDs make it difficult to deliver electrons from the cathode to the emitting layer (EML). Here, it is shown that the operating voltages of blue OLEDs strongly depend on the energy barrier between the cathode and the EML, which is clarified by investigating the energy‐level alignment in blue OLEDs. It is found that a blue OLED fabricated using a superbase as the electron injection layer exhibits a lower operating voltage than conventional blue OLEDs fabricated using Li compounds. Moreover, there is a clear energy barrier between the cathode and the EML in conventional blue OLEDs, whereas there is no energy barrier in blue OLEDs fabricated using a superbase. Minimization of the energy barrier between the cathode and the EML is demonstrated to be essential to obtain blue emission at low operating voltages. The operating voltage of blue organic light‐emitting diodes (OLEDs) is found to be highly dependent on the energy barrier between the cathode and the emitting layer. This could only be clarified by associating the differences in the electron injection layer/electron transport layer‐dependent characteristics of blue OLEDs with the exact energy levels in blue OLEDs.

Reversible and drastic modulation of the transport properties in vanadium dioxide (VO 2 ) nanowires by electric field-induced hydrogenation at room temperature was demonstrated using the nanogaps separated by humid air in field-effect transistors with planer-type gates (PG-FET). These PG-FETs allowed us to investigate behavior of revealed hydrogen intercalation and diffusion aspects with time and spatial evolutions in nanowires. These results show that air nanogaps can operate as an electrochemical reaction field, even in a gaseous atmosphere, and offer new directions to explore emerging functions for electronic and energy devices in oxides.

The human postural control function is determined by inputs from three senses, namely, vision, balance, and somatosensation. Many studies have attempted to induce body movements in arbitrary directions using external stimuli to maintain and improve postural control functions. Previous studies demonstrated that sensory information from the plantar region of the foot is involved in the understanding of front–back position and regulation of body movements. In the present study, we investigated a method to induce postural control and walking movements in an arbitrary direction by presenting matrix-shaped tactile stimuli (MSTS) to the plantar region of the foot. We developed a tactile stimulation device to investigate body sway when the MSTS was presented to the dorsal surface region of a foot in a standing posture. This device is envisioned to be used as a wearable guidance tool in the future. In addition, the measurement experiment used a high-speed camera and an accelerometer placed on the top of the subject’s head to track the subject’s movements in response to the MSTS presented by the device. In this paper, the relationship between the control parameters ( L , T ) of tactile stimulation MSTS and body sway and its direction was considered. The results showed that the introduction of MSTS on the sole of the foot could induce body sway. The results also suggest that it is possible to induce body sway in the respective expected directions by setting appropriate parameters ( L , T ).

Achieving both high electroluminescence (EL) efficiency and power conversion efficiency (PCE) in a single organic device has long been considered difficult, since the design principles optimising one often compromise the other. In this study, we present a strategy employing multiple-resonance thermally activated delayed fluorescence materials with strong absorption and high emission efficiency, enabling coexistence of high EL and photovoltaic (PV) efficiencies. By precisely controlling charge-transfer states at donor/acceptor interfaces, we successfully achieve full-spectrum visible EL while maintaining efficient charge generation essential for PV operation. The optimised multifunctional devices exhibit emission colours ranging from blue to red, as well as white, with the green- and orange-light-emitting devices achieving an external quantum efficiency of EL exceeding 8.5% and a PCE of about 0.5%. These findings not only mitigate conventional efficiency trade-offs in organic devices but also open future avenues for emerging applications, including self-powered displays and lighting, potentially advancing optoelectronic technologies.Achieving both high electroluminescence (EL) efficiency and power conversion efficiency (PCE) in a single organic device has long been considered difficult, since the design principles optimising one often compromise the other. In this study, we present a strategy employing multiple-resonance thermally activated delayed fluorescence materials with strong absorption and high emission efficiency, enabling coexistence of high EL and photovoltaic (PV) efficiencies. By precisely controlling charge-transfer states at donor/acceptor interfaces, we successfully achieve full-spectrum visible EL while maintaining efficient charge generation essential for PV operation. The optimised multifunctional devices exhibit emission colours ranging from blue to red, as well as white, with the green- and orange-light-emitting devices achieving an external quantum efficiency of EL exceeding 8.5% and a PCE of about 0.5%. These findings not only mitigate conventional efficiency trade-offs in organic devices but also open future avenues for emerging applications, including self-powered displays and lighting, potentially advancing optoelectronic technologies.

Shearing of fractures and faults is important because it can result in permeability change or even induce seismicity—both are keys for efficient and safe energy recovery and storage in Earth systems. Quantitative analysis of shearing of intersecting fractures and faults is challenging because it can involve dynamic frictional contacts that are complicated by deformation of the rock matrix. To predict the shearing of intersecting fractures/faults, we attempt to answer the question of how intersections impact the shearing of a fracture network and whether we can simplify the description as compared to classical discrete fracture network (DFN) models. To answer these questions, we conducted a series of numerical simulations on scenarios for variable numbers of intersecting fractures. All these examples yield consistent results: the results of using DFNs are consistent with those of using hypothetical major paths. This leads to a new model, which we name simplified discrete fracture network model, to analyze shearing of intersecting fractures/faults using major path(s). We found that the intersections of fractures do not fundamentally change the shearing of two intersecting fractures if the intersecting angles are small. Furthermore, increasing the number of fractures/faults may relax the stress as more fractures/faults become available for shearing and distributing the stress. The simplified DFN model, which can capture efficiently the shearing behavior of each major paths from a large number of intersecting fractures/faults, will be a promising conceptual model that is complementary to existing equivalent continuum and discrete fracture models to analyze shearing of intersecting fractures/faults.HighlightsA new model—simplified discrete fracture network (DFN) model—that analyzes the shearing of intersecting fractures/faults using major path(s) was proposed and verifiedA step-by-step calculation and benchmarking to test the hypothesis of simplifying DFNs with major pathsQuantitative understanding of how intersections affect shearing of intersecting fractures/faultsDemonstration of the possibility of stress relaxation by increasing the number of fractures/faults in the DFNDemonstration of the simplified DFN model as a new model complementary to existing models, i.e., the equivalent continuum and discrete fracture models

Blue Organic Light‐Emitting Diodes In article number 2201925, Tsubasa Sasaki and colleagues show a clear correlation of the operating voltage of blue organic light‐emitting diodes (OLEDs) with the energy barrier between the cathode and the emitting layer. Since there is almost zero energy barrier in blue OLEDs fabricated using a superbase as the electron injection layer, they exhibit lower operating voltages than conventional blue OLEDs fabricated using Li compounds.

Gas chromatography (GC) of cis-eicosenoic acid (20:1) positional isomers has been investigated on a capillary column of ionic liquid 1,9-di(3-vinyl-imidazolium)nonane bis(trifluoromethyl)sulfonylimidate stationary phase (SLB-IL100). A test mixture of isomeric 20:1 methyl esters was prepared from flathead flounder flesh lipids. On a 60-m column operated at 150-180 °C, six peaks appeared in the elution order of 20:ln-15 → 20:ln-13 → 20:ln-11 → 20:ln-9 → 20:ln-7 → 20:ln-5. These peaks were baseline resolved within 20 min at 180 °C. The 20:ln-13 and 20:ln-11 isomers, poorly resolved on conventional polar polysiloxane stationary phases, were completely separated from each other with separation factor α = 1.02 and peak resolution (Rs) ≥ 1.57. When equivalent chain length (ECL) values were compared between the SLB-IL100 and CP-Sil 88 (biscyanopropyl polysiloxane), those of 20:ln-15 and 20:ln-13 exceptionally tended to be lower on the SLB-IL100. The excellent separation of 20:1 isomers seems due to less retention of 20:ln-15 and 20:ln-13 on SLB-IL100 rather than simply due to its high polarity. Analysis of herring oil 20:1 revealed the occurrence of 20:ln-13 in the Pacific herring but not in the Atlantic herring. The ionic liquid stationary phase, SLB-IL100, is effective for analyzing 20:1 isomers occurring in fish and other natural oils.

We fabricated a miniature ascorbic acid fuel cells equipped with a microchannel for the circulation of ascorbic acid (AA) solution using micro electronic mechanical system techniques. The fuel cell was fabricated on a flexible polyimide substrate, and its porous carbon-coated aluminium (Al) electrodes of 2.8 mm in width and 11 mm in length were formed using photolithography and screen-printing techniques. The porous carbon was deposited by screen-printing of carbon-black ink on the Al electrode surfaces in order to increase the effective electrode surface area and to absorb more enzymes on the cathode surface. The microchannel with a depth of 200 μm was fabricated using a hot-embossing technique. A maximum power of 0.60 μW at 0.58 V that corresponds to a power density of 1.83 μW/cm2 was realized by introducing a 200 mM concentrated AA solution at room temperature.