Recently, research interest in brain‐inspired neuromorphic computing based on robust and intelligent artificial neural networks has surged owing to the ability of such technology to facilitate ...massive parallel, low‐power, highly adaptive, and event‐driven computing. Here, a photosynaptic device with a novel weight updating mechanism for high‐speed and low‐power optoelectronic spike processing is proposed, wherein a synaptic weight is controlled by a mixed spike consisting of voltage and light spikes; the light spike, in particular, boosts up the probability of electron detrapping from graphene oxide charge‐trapping layer to the photosensitive indium–gallium–zinc oxide charge‐transporting layer. Compared to electrically operating synaptic device, the magnitude of conductance change in the proposed photosynaptic device increases remarkably from 2.32 to 5.95 nS without degradation of the nonlinearity (potentiation/depression values are changed from 4.24/8 to 5/8). Owing to this enhancement of synaptic operation, the recognition rates for the Modified National Institute of Standards and Technology digit patterns improve from 36% and 49% to 50% and 62% in artificial neural networks using long‐term potentiation/depression characteristics with 20 and 100 weight states, respectively. The proposed photosynaptic device technology capable of optoelectronic spike processing is expected to play a crucial role in the implementation of neuromorphic computing in the future.
A photosynaptic device with a novel weight updating mechanism using a mixed (light + voltage) spike is proposed. The photosynaptic device shows a remarkable increase in the conductance change (∆G) from 2.32 to 5.95 nS in 100 weight states without degradation of the nonlinearity, resulting in the improvement of the recognition rates for the digit patterns from 49% to 62%.
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The unique properties of hybrid heterostructures have motivated the integration of two or more different types of nanomaterials into a single optoelectronic device structure. Despite the promising ...features of organic semiconductors, such as their acceptable optoelectronic properties, availability of low‐cost processes for their fabrication, and flexibility, further optimization of both material properties and device performances remains to be achieved. With the emergence of atomically thin 2D materials, they have been integrated with conventional organic semiconductors to form multidimensional heterostructures that overcome the present limitations and provide further opportunities in the field of optoelectronics. Herein, a comprehensive review of emerging 2D–organic heterostructures—from their synthesis and fabrication to their state‐of‐the‐art optoelectronic applications—is presented. Future challenges and opportunities associated with these heterostructures are highlighted.
The hybridization of 2D materials and organic materials represents a promising domain for the realization of improved or unprecedented features in comparison to those of semiconductor devices. This comprehensive review focuses on emerging 2D–organic heterostructures (from their synthesis and fabrication to their state‐of‐the‐art optoelectronic applications) and highlights the future challenges and opportunities associated with these heterostructures.
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Recently, MXenes, which are 2D early transition metal carbides and carbonitrides, have attracted wide attention because of their excellent conductivities. Here, the electrode applications of ...Ti2C(OH)xFy, one member of the MXene family, in WSe2 and MoS2 field effect transistors (FETs) are assessed. Kelvin probe force microscopy analysis is performed to determine its work function, which is estimated to be ≈4.98 eV. Devices based on WSe2/Ti2C(OH)xFy and MoS2/Ti2C(OH)xFy heterostructures are fabricated with the mechanical transfer method and their electronic performances evaluated. The temperature‐dependent current–voltage transfer characteristics of the devices are determined to extract their Schottky barrier heights. The hole barrier between WSe2 and Ti2C(OH)xFy is estimated to be ≈0.23 eV and the electron barrier between the MoS2 band and Ti2C(OH)xFy is ≈0.19 eV, which indicates that the pinning effect occurs at the MoS2/Ti2C(OH)xFy interface but not at the WSe2/Ti2C(OH)xFy interface; this difference arises because of the difference between the band structures of WSe2 and MoS2. A complementary metal–oxide–semiconductor inverter based on these electrode properties of Ti2C(OH)xFy with MoS2 (n‐channel) and WSe2 (p‐channel) is fabricated, which demonstrates that Ti2C(OH)xFy is a promising electrode for future nanoelectronics applications.
By using Ti2C(OH)xFy as an electrode for the integration of 2D p‐FET (WSe2) and n‐FET (MoS2), the heights of the hole barriers of WSe2/Ti2C(OH)xFy and MoS2/Ti2C(OH)xFy are determined to be 0.23 eV and 0.19 eV, respectively. A complementary metal–oxide–semiconductor inverter is fabricated, which demonstrates that Ti2C(OH)xFy is a promising electrode for future nanoelectronics applications.
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Osteoarthritis (OA) is the most common form of arthritis. It is characterized by progressive destruction of articular cartilage and the development of chronic pain and constitutes a considerable ...socioeconomic burden. Currently, pharmacological treatments mostly aim to relieve the OA symptoms associated with inflammation and pain. However, with increasing understanding of OA pathology, several potential therapeutic targets have been identified, enabling the development of disease-modifying OA drugs (DMOADs). By targeting inflammatory cytokines, matrix-degrading enzymes, the Wnt pathway, and OA-associated pain, DMOADs successfully modulate the degenerative changes in osteoarthritic cartilage. Moreover, regenerative approaches aim to counterbalance the loss of cartilage matrix by stimulating chondrogenesis in endogenous stem cells and matrix anabolism in chondrocytes. Emerging strategies include the development of senolytic drugs or RNA therapeutics to eliminate the cellular or molecular sources of factors driving OA. This review describes the current developmental status of DMOADs and the corresponding results from preclinical and clinical trials and discusses the potential of emerging therapeutic approaches to treat OA.
Optogenetics refers to a technique that uses light to modulate neuronal activity with a high spatiotemporal resolution, which enables the manipulation of learning and memory functions in the human ...brain. This strategy of controlling neuronal activity using light can be applied for the development of intelligent systems, including neuromorphic and in‐memory computing systems. Herein, a flexible van der Waals (vdW) optoelectronic synapse is reported, which is a core component of optogenetics‐inspired intelligent systems. This synapse is fabricated on 2D vdW layered rhenium disulfide (ReS2) that features an inherent photosensitive memory nature derived from the persistent photoconductivity (PPC) effect, successfully mimicking the dynamics of biological synapses. Based on first‐principles calculations, the PPC effect is identified to originate from sulfur vacancies in ReS2 that have an inherent tendency to form shallow defect states near the conduction band edges and under optical excitation lead to large lattice relaxation. Finally, the feasibility of applying the synapses in optogenetics‐inspired intelligent systems is demonstrated via training and inference tasks for the CIFAR‐10 dataset using a convolutional neural network composed of vdW optoelectronic synapse devices.
A flexible van der Waals (vdW) optoelectronic synapse fabricated on 2D vdW layered rhenium disulfide, which features an inherent photosensitive memory nature derived from the persistent photoconductivity effect, is proposed. Following in‐depth analysis including density functional theory calculations on rhenium disulfide, its feasibility for hardware neural networks with learning ability is demonstrated using a convolutional neural network composed of vdW optoelectronic synapses.
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A novel hybrid phototransistor consisting of molybdenum carbide (Mo2C) and molybdenum disulfide (MoS2) is proposed. By exploiting the interface properties of MoS2 and Mo2C, a highly sensitive and ...broad‐spectral response photodetector is fabricated. The underlying mechanism of the enhanced performance is the efficient hot carrier injection from Mo2C to MoS2. The strong coupling of MoS2 and Mo2C at the interface provides the significantly low Schottky barrier height (≈70 meV), which gives rise to the significantly efficient hot carrier transfer from Mo2C to MoS2. The grating of metallic Mo2C produces plasmonic resonance, which provides hot carriers to the MoS2 channel. By adjusting the grating period of Mo2C (400–1000 nm), the optimal photoresponse of light can be controlled, from visible to NIR. By integrating various Mo2C multigrating periods (400–1000 nm) with MoS2, a novel photodetector is demonstrated with high responsivity (R > 103 A W−1) and light‐to‐dark current ratio (>102) over a broad spectral range (405–1310 nm). The proposed novel hybrid photodetector, 2D semiconductors with multigrating 2D metallic stripes, exhibits high sensitivity and broad spectral detection of light and can overcome the inherent weakness of conventional 2D photodetectors, paving the way forward for next‐generation photoelectric devices.
A hybrid photodetector consisting of a 2D semiconductor (MoS2) integrated with multiple grating metallic stripes (Mo2C) demonstrates high sensitivity and broad spectral detection of light, overcoming the inherent weakness of conventional 2D photodetectors and opening up possibilities for next‐generation photoelectric device technology by providing new functionalities for high sensitivity and effective broad‐spectrum photodetection.
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Conventional stretchable electronics that adopt a wavy design, a neutral mechanical plane, and conformal contact between abiotic and biotic interfaces have exhibited diverse skin‐interfaced ...applications. Despite such remarkable progress, the evolution of intelligent skin prosthetics is challenged by the absence of the monolithic integration of neuromorphic constituents into individual sensing and actuating components. Herein, a bioinspired stretchable sensory‐neuromorphic system, comprising an artificial mechanoreceptor, artificial synapse, and epidermal photonic actuator is demonstrated; these three biomimetic functionalities correspond to a stretchable capacitive pressure sensor, a resistive random‐access memory, and a quantum dot light‐emitting diode, respectively. This system features a rigid‐island structure interconnected with a sinter‐free printable conductor, which is optimized by controlling the evaporation rate of solvent (≈160% stretchability and ≈18 550 S cm−1 conductivity). Devised design improves both areal density and structural reliability while avoiding the thermal degradation of heat‐sensitive stretchable electronic components. Moreover, even in the skin deformation range, the system accurately recognizes various patterned stimuli via an artificial neural network with training/inferencing functions. Therefore, the new bioinspired system is expected to be an important step toward implementing intelligent wearable electronics.
A novel form of stretchable integrated system, namely a bioinspired stretchable sensory‐neuromorphic system, is presented, which comprises an artificial mechanoreceptor, an artificial synapse, and an epidermal photonic actuator as three devices. This system features a bioinspired sensory‐neuromorphic system entailing tactile sensing, pattern learning/inferencing, and visualizing feedback information.
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An ultrahigh performance MoS2 photodetector with high photoresponsivity (1.94 × 106 A W–1) and detectivity (1.29 × 1012 Jones) under 520 nm and 4.63 pW laser exposure is demonstrated. This ...photodetector is based on a methyl‐ammonium lead halide perovskite/MoS2 hybrid structure with (3‐aminopropyl)triethoxysilane doping. The performance degradation caused by moisture is also minimized down to 20% by adopting a new encapsulation bilayer of octadecyltrichlorosilane/polymethyl methacrylate.
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The outstanding performance (sheet resistance of 5 Ω sq–1 at transmittance of 90%) and strongly adhesive (30.7 J m–2) silver nanowires (AgNWs) are fabricated using flash‐induced plasmonic welding ...(FPW) based on theoretical research of photothermal interactions. The FPW‐processed AgNWs are utilized as electrodes of a transparent flexible energy harvester, and this device exhibits excellent transmittance and high electric output performance. The FPW methodology provides a high‐tech solution for transparent flexible electronics.
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Abstract
It is important to understand the dynamical processes that cause heat waves at regional scales. This study examined the physical mechanism that was responsible for a heat wave in South Korea ...in August 2016. Unlike previous August heat waves over the Korean Peninsula, the intensity of the geopotential height over the Kamchatka Peninsula in August 2016 was the strongest since 1979, which acted as an atmospheric blocking in the downstream region of the Korean Peninsula. Therefore, the anomalous high geopotential height in Mongolia, where the surface temperature was quite high, was observed persistently in August 2016. This anomalous high in Mongolia induced northerly winds with warm temperatures onto the Korean Peninsula, which contributed to a heat wave in August 2016. We further showed that the anomalous high geopotential height over the Kamchatka Peninsula in August 2016 was triggered by strong convection in the western-to-central subtropical Pacific through atmospheric teleconnections, which was quite different from a typical heat wave over the Korean Peninsula, in which convective forcing around the South China Sea is strong. This implies that convective forcing in the subtropical Pacific should also be monitored to predict heat wave events in East Asia, including South Korea. On the other hand, the zonal wave train associated with the circumglobal teleconnection pattern is also associated with the anomalous high geopotential height around Mongolia and the Kamchatka Peninsula, which may have contributed to the heat wave in August 2016.
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