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Herein, a new concept of device architecture to fabricate fibrous light-emitting devices is demonstrated based on an electrochemiluminescence (ECL) material for an electronic textile system. A unique feature of this work is that instead of conventional semiconductor materials, such as organics, perovskites, and quantum dots for fibrous light emitting devices, a solid-state ECL electrolyte gel is employed as a light-emitting layer. The solid-state ECL gel is prepared from a precursor solution composed of matrix polymer, ionic liquid, and ECL luminophore. From this, we successfully realize light-emitting fibers through a simple and cost-effective single-step dip-coating method in ambient air, without complicated multistep vacuum processes. The resulting fiber devices reliably operated under applied AC bias of ±2.5 V and showed luminance of 47 cd m

Bi catalysts supported on GaN nanowires/Si photocathode induce favorable activity toward CO2 reduction to HCOOH.

Hybrid materials consisting of semiconductors and cocatalysts have been widely used for photoelectrochemical (PEC) conversion of CO2 gas to value-added chemicals such as formic acid (HCOOH). To date, however, the rational design of catalytic architecture enabling the reduction of real CO2 gas to chemical has remained a grand challenge. Here, we report a unique photocathode consisting of CuS-decorated GaN nanowires (NWs) integrated on planar silicon (Si) for the conversion of H2S-containing CO2 mixture gas to HCOOH. It was discovered that H2S impurity in the modeled industrial CO2 gas could lead to the spontaneous transformation of Cu to CuS NPs, which resulted in significantly increased faradaic efficiency of HCOOH generation. The CuS/GaN/Si photocathode exhibited superior faradaic efficiency of HCOOH = 70.2% and partial current density = 7.07 mA/cm2 at -1.0 VRHE under AM1.5G 1 sun illumination. To our knowledge, this is the first demonstration that impurity mixed in the CO2 gas can enhance, rather than degrade, the performance of the PEC CO2 reduction reaction.

We report a photorechargeable supercapacitor that can convert solar energy to chemical energy and store it. The supercapacitor is composed of indium tin oxide branched nanowires (ITO BRs) and poly(3-hexylthiophene) (P3HT) semiconducting polymers. ITO BRs showed electrical double layer capacitive characteristics that originated from the unique porous and self-connected network structure. The hybrid structure of ITO BR/P3HT exhibited spontaneous light harvesting, energy conversion, and charge storage. As a result, photocharging/discharging of ITO BR/P3HT showed an areal capacitance of 2.44 mF/cm2 at a current density of 0.02 mA/cm2. The proof-of-concept photorechargeable device, composed of ITO BRs, ITO BR/P3HT, and Na2SO4/polyvinyl acetate gel electrolyte, generated a photovoltage as high as 0.28 V and stored charge effectively for tens of seconds. The combination of dual functions in a single hybrid material may achieve breakthrough advances.

We investigated the relationship between grain boundary (GB) oxidation of Cu–Ag thin-film catalysts and selectivity of the (photo)electrochemical CO2 reduction reaction (CO2 RR). The change in the ...

Serial femtosecond crystallography (SFX) enables the determination of room-temperature crystal structures of macromolecules with minimized radiation damage and provides time-resolved molecular dynamics by pump–probe or mix-and-inject experiments. In SFX, a variety of sample delivery methods with unique advantages have been developed and applied. The combination of existing sample delivery methods can enable a new approach to SFX data collection that combines the advantages of the individual methods. This study introduces a combined inject-and-transfer system (BITS) method for sample delivery in SFX experiments: a hybrid injection and fixed-target scanning method. BITS allows for solution samples to be reliably deposited on ultraviolet ozone (UVO)-treated polyimide films, at a minimum flow rate of 0.5 nl min−1, in both vertical and horizontal scanning modes. To utilize BITS in SFX experiments, lysozyme crystal samples were embedded in a viscous lard medium and injected at flow rates of 50–100 nl min−1 through a syringe needle onto a UVO-treated polyimide film, which was mounted on a fixed-target scan stage. The crystal samples deposited on the film were raster scanned with an X-ray free electron laser using a motion stage in both horizontal and vertical directions. Using the BITS method, the room-temperature structure of lysozyme was successfully determined at a resolution of 2.1 Å, and thus BITS could be utilized in future SFX experiments.

The electrochemical carbon dioxide (CO2) reduction is a promising method for carbon recycling. Bimetallic catalysts have been extensively developed for the selective production of carbon monoxide (...

Serial femtosecond crystallography (SFX) enables the determination of the room-temperature crystal structure of macromolecules, as well as providing time-resolved molecular dynamics data in pump–probe experiments. Fixed-target SFX (FT-SFX) can minimize sample consumption and physical effects on crystals during sample delivery. In FT-SFX studies, having a sample holder that can stably fix crystal samples is one of the key elements required for efficient data collection. Hence, development of sample holders from new materials capable of supporting various crystal sizes and shapes may expand the applications of FT-SFX. Here, a viscous-media-based crystal support in a sample holder for FT-SFX is introduced. Crystal samples were embedded in viscous media, namely gelatin and agarose, which were enclosed in a polyimide film. In the vertically placed sample holder, 10–15%(w/v) viscous gelatin and 1–4%(w/v) agarose gel stably supported crystals between two polyimide films, thereby preventing the crystals from descending owing to gravity. Using this method, FT-SFX experiments were performed with glucose isomerase and lysozyme embedded in gelatin and agarose, respectively. The room-temperature crystal structures of glucose isomerase and lysozyme were successfully determined at 1.75 and 1.80 Å resolutions, respectively. The glucose isomerase and lysozyme diffraction analyses were not impeded by excessive background scattering from the viscous media. This method is useful for delivering crystal samples of various sizes and shapes in FT-SFX experiments.

We present a remarkable improvement in the efficiency of AlGaN deep-ultraviolet light-emitting diodes (LEDs) enabled by the coupling of localized surface plasmon resonance (LSPR) mediated by a high-density array of Al nanoparticles (NPs). The Al NPs with an average diameter of ∼40 nm were uniformly distributed near the Al

Three-dimensional (3D) plasmonic structures have attracted great attention because abnormal wetting behavior of plasmonic nanoparticles (NPs) on 3D nanostructure can enhance the localized surface plasmons (LSPs). However, previous 3D plasmonic nanostructures inherently had weak plasmonic light absorption, low electrical conductivity, and optical transmittance. Here, we fabricated a novel 3D plasmonic nanostructure composed of Ag NPs as the metal for strong LSPs and 3D nano-branched indium tin oxide (ITO BRs) as a transparent and conductive framework. The Ag NPs formed on the ITO BRs have a more dewetted behavior than those formed on the ITO films. We experimentally investigated the reasons for the dewetting behavior of Ag NPs concerning the geometry of ITO BRs. The spherical Ag NPs are spatially separated and have high density, thereby resulting in strong LSPs. Finite-domain time-difference simulation evidenced that spatially-separated, high-density and spherical Ag NPs formed on ITO BRs dramatically boost the localized electric field in the active layer of organic solar cells (OSCs). Photocurrent of PTB7:PCBM OSCs with the ITO BRs/Ag NPs increased by 14%.

The electrochemical CO2 reduction in aqueous media is a promising method for both the mitigation of climate changes and the generation of value-added fuels. Although many researchers have demonstra...

Electrochemical reduction of carbon dioxide (CO2) is a promising method toward carbon recycling. Highly selective bimetallic catalysts have been extensively demonstrated, while efforts to understan...

Subwavelength-scale nanorods were implemented on the hexagonal pyramid of photochemically etched light-emitting diodes (LEDs) to improve light extraction efficiency (LEE). Sequential processes of Ag deposition and inductively coupled plasma etching successfully produce nanorods on both locally unetched flat surface and sidewall of hexagonal pyramids. The subwavelength-scale structures on flat surface offer gradually changed refractive index, and the structures on side wall of hexagonal pyramid reduce backward reflection, thereby enhancing further enhancement of the light extraction efficiency. Consequently, the nanorods implemented LED shows a remarkable enhancement in the light output power by 14% compared with that of the photochemically etched LEDs which is known to exhibit the highest light output power. Theoretical calculations using a rigorous coupled wave analysis method reveal that the subwavelength-scale nanorods are very effective in the elimination of TIR as well as backward reflections, thereby further enhancing LEE of the LEDs.

A new one-dimensional fixed-target sample delivery method combined with a real-time visual servo scan system has been developed for serial femtosecond crystallography. The developed high-throughput microcrystal delivery system shows significant improvements for microcrystal delivery efficiency at an optimal crystal stability and significantly reduced sample consumption to reveal protein structures utilizing X-ray free-electron laser pulses., Microcrystal delivery methods are pivotal in the use of serial femtosecond crystallography (SFX) to resolve the macromolecular structures of proteins. Here, the development of a novel technique and instruments for efficiently delivering microcrystals for SFX are presented. The new method, which relies on a one-dimensional fixed-target system that includes a microcrystal container, consumes an extremely low amount of sample compared with conventional two-dimensional fixed-target techniques at ambient temperature. This novel system can deliver soluble microcrystals without highly viscous carrier media and, moreover, can be used as a microcrystal growth device for SFX. Diffraction data collection utilizing this advanced technique along with a real-time visual servo scan system has been successfully demonstrated for the structure determination of proteinase K microcrystals at 1.85 Å resolution.

We theoretically and experimentally demonstrate an RGB achromatic metalens that operates concurrently at three visible wavelengths ( λ = 450 , 532, and 700 nm) with a high numerical aperture of 0.87. The RGB metalens is designed by simple integration of metalens components with the spatial interleaving method. The simulated spatial interleaving metalens shows RGB achromatic operation with focusing efficiencies of 25.2%, 58.7%, and 66.4% at the wavelengths of 450, 532, and 700 nm, respectively. A 450 μm diameter metalens operating at three designated wavelengths is fabricated with low-loss hydrogenated amorphous silicon. The fabricated metalens has the measured focusing efficiencies of 5.9%, 11.3%, and 13.6% at λ = 450 , 532, and 700 nm, respectively. The Strehl ratios of 0.89, 0.88, and 0.82 are obtained at given wavelengths, which show a capability of diffraction-limited operation.

Red, green, and blue top-emission organic light-emitting diodes (RGB TOLEDs) suffer from white color change with viewing angle due to the microcavity effect, called white angular dependence (WAD). Great efforts are devoted by applying various kinds of hazy films, but they suffer from poor mechanical stability and optical transmittance. Herein, we introduce an air-gap-embedded hazy film (AEHF) to solve these problems and suppress WAD in RGB TOLEDs. The AEHF is designed with optical simulation to realize high haze with transparency. By tuning geometries of the air gap inside the polymer, the AEHF realizes high haze of more than 90% in all RGB colors while maintaining high transparency. To experimentally demonstrate the AEHF, the O2 plasma is treated on a polymer film with AgCl as an etching mask to fabricate microstructures with high aspect ratios. Afterward, PDMS is coated on the patterned surface; air gaps develop spontaneously in the valleys between microstructures during the coating process. Using these processes, an air gap with 1.2 μm size and 400 nm period is formed inside the film and ∼100% haze is achieved while maintaining a high transmittance of 88%; these results agree well with rigorous coupled wave analysis results. By utilizing the AEHF into TOLEDs, the WAD can be drastically suppressed by 95.2% compared with that of a device without AEHF.

Large-scale industrial application of flexible device has called for development of transfer methods that deliver high yield and stability. Here, we show an ultrafast and chemically stable transfer method by using a water-soluble NaCl sacrificial layer. Extremely thin (10 nm) and large-area (4 in. wafer) free-standing Au nanomembranes (NMs) prepared on silicon substrate were successfully transferred to flexible PDMS substrate by dissolving the NaCl sacrificial layer. This transfer method enables highly transparent and electrically conductive Au NMs on PDMS substrate. To transfer a multilayered optoelectronic device, we fabricated flexible hydrogenated amorphous silicon (a-Si:H) solar cell on a glass substrate and transferred it to a PDMS substrate. There was no degradation of the electrical characteristic of the solar cell after the transfer. This approach enables the integration of high-temperature-processed a-Si:H solar cell onto low-temperature tolerant flexible polymer substrate without chemical contamination or damage.

Efficient electrochemical reduction of CO2 to formate is demonstrated by fabricating Bi nanoflake with pulse electrodeposition. The effect of pulse voltage on morphology of the Bi nanoflake and electrochemical property was investigated. The pulse voltage of 80 mVAg/AgCl with six pulse cycles successfully produces ultrathin Bi nanoflakes. The finite-element-based simulation shows that the two-dimensional geometry with large lateral dimensions and ultrathin thickness can localize a strong electric field at the corner site of the flakes, resulting in facilitating efficient reduction of CO2 to formate. As a result, formate Faradaic efficiency of the Bi nanoflakes showed over 90% at − 0.8 VRHE. Also, the formate production rate reached 69 µmol/cm2/h at − 0.8 VRHE. The pulse electrodeposition provides highly dense and uniform and tailored nanostructures in the large area without the requirements of high vacuum or high temperatures process.

We investigated the relationship between grain boundary (GB) oxidation of Cu-Ag thin-film catalysts and selectivity of the (photo)electrochemical CO

Blocking the near-infrared region (NIR) is indispensable for saving energy consumed to maintain the interior temperature in buildings. However, simultaneously enhancing transmission in visible light and blocking in the NIR remains challenging. Here, we theoretically demonstrate a transparent all-dielectric metasurface selectively blocking the NIR by using TiO2 nanocylinders and an indium tin oxide (ITO) layer. The ITO layer is implemented as a back reflector because ITO is transparent in visible light, whereas the ITO becomes a reflective material in the long-wavelength region (λ > 1500 nm). The designed metasurface exhibits high average transmittance of 70% in visible light and high solar energy rejection (SER) of 90% in the NIR. Furthermore, the blocking capability in the NIR of the designed metasurface is maintained over a wide range of an incident angle and polarization angle of light. Therefore, the metasurface gives a guideline for designing energy-saving applications.

Cavity top emission organic light-emitting diodes (TOLEDs) suffer from an angular color shift due to the microcavity effect, called white angular dependence (WAD). The hazy films embedding air-gaps exhibit high transparency as well as enhanced scratch resistance. The haze was systemically controlled by changing the size of the air-gaps, determined by the size of the nanostructure and the viscosity of the coated resin. The optimized hazy film significantly reduced WAD about 92 % in a multi-color TOLED without complicated design for red, green and blue colors. Optical simulations using FDTD were conducted to interpret the effect of haze on WAD.

Bulk optics have been used for various optical instruments such as microscope or camera, but it has limitations in size and thickness because of accumulation of various lenses. Metalenses are an emerging field as one of the next-generation optical technology for miniaturization of optical system. Subwavelength thick nanostructures on metalens control the amplitude, phase, absorption, emission, and transmittance of incident light. Focal length can be control by adjusting phase shift from 0 to 2π according to the change of shape, size, and period of nanostructures. Many kinds of metalens such as GaN nanopillar, Si nanodisk, or TiO2 nanofin have been studied recently, but chromatic aberration correction problem remains as the limitation in metalenses. Some researches such as group delay dispersion have been conducted to correct chromatic aberration, low focusing efficiency ( ~ 10 %) is unresolved limitation. In this work, we suggested a new method to design achromatic metalens for 400, 600 and 800 nm wavelengths focusing. Spatial multiplexing method can correct chromatic aberration very simply. First, three metalenses are designed for each wavelengths. In the next step, meta-atoms of each metalenses are interleaved in one metalens. The coupling between three kinds of meta-atoms is small, therefore we can expect three wavelength focusing in one metalens. We used finite-difference time-domain (FDTD) simulation to investigate field distribution and focusing efficiency of each metalenses. By using this method, we demonstrated achromatic metalens with numerical aperture of 0.89, which focus light at 400, 600, and 800 nm to same focal spot. Focusing efficiency of achromatic metalens for 400, 600 and 800 nm are 38, 44 and 54%, respectively. This design method can attend significant role to demonstrate desired achromatic metalens.

The electrochemical CO

We report a way to make an air-gap-embedded flexible film to reduce the screen-door effect (SDE) in virtual reality (VR) displays. Oxygen plasma was treated with a polyethylene terephthalate substrate to produce wavelength-scale micropatterns. These micropatterns induce an effective haze, but it is easily destroyed by a very small external scratch. Such a problem could be solved by coating the patterns with poly(dimethylsiloxane) (PDMS). The viscosity of PDMS, controlled by the ratio of the base and curing agents, plays a key role in determining the size of air-gaps at the valleys of micropatterns. As the ratio of base agent increases to 40, the average haze abruptly increased from 0.9% to 88.6% in visible wavelengths, while the average total transmittance maintained was between 89.8 and 91.7%. The origin of air-gap-induced haze is confirmed by numerical simulations. The hazy film remarkably reduced the SDE of the VR display from 30.27% to 4.83% for red color, from 21.82% to 2.58% for green, and from 26.02% to 3.38% for blue, as the size of air-gaps increases from 0 to 406 ± 91 nm. No defects were found after 10 000 bending cycles with a bending radius of 3 mm.

We report solid-state fabric supercapacitors with polymer electrolyte composites (PEC). The fabric supercapacitors were comprised of a fiber-shape PEC and electrodes. The PEC was formulated by mixing a network-forming polymer, poly(vinylidene fluoride-co-hexafluoropropylene) and a room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. By using a simple electrospinning technique, we could successfully fabricate a free-standing fiber-shape PEC. The electrospun PEC showed high ionic conductivity of 0.48 mS/cm and mechanical strength of 2.4 MPa. The electrodes were produced by two-step processes consisting of electrospinning and spray coating. By using these spun electrolyte composites and electrodes, fabric supercapacitors with a sandwich structure were fabricated. The resulting device exhibited typical capacitive energy storage characteristics and the measured specific capacitance was 6.72 mF/cm2. Moreover, the device maintains its structure and electrochemical performance under repeated bending stress. This work can offer a new option for developing solid-state energy storage devices for smart textile and wearable electronic applications.

By virtue of their semiconducting and electrolytic characteristics, hybrid organic–inorganic perovskites have received intense research attention in various applications, which include energy, electronics, and display technologies. While research studies on the semiconducting or electronic properties of perovskite materials in solar cells and light-emitting diodes have been actively investigated, studies on their electrolytic or ionic behavior have rarely been conducted. To probe the electrolyte properties of the metal halide perovskite, we have fabricated solution-processed zinc oxide (ZnO) thin-film transistors using a methylammonium lead iodide (CH3NH3PbI3) perovskite thin film as a gate insulator material. The resulting perovskite film revealed ionic characteristics, with an ionic conductivity of about 10–8 S/cm. The perovskite-gated ZnO transistors exhibited typical n-type characteristics with an average field-effect mobility of 0.047 cm2/V s at a low applied voltage below 2 V because of the electric...

Improving the activity of Ag-based catalysts for oxygen reduction reaction (ORR) is a challenge for achieving economic alkaline-based fuel cells. Here, vertically-aligned nanoporous Ag nanowires (NWs) are developed as electrocatalysts for the ORR. Electrochemical reduction of vertically-aligned AgCl NWs eliminate Cl− ions from the NWs, and thereby reduces Ag+ cations to metallic Ag atoms, to yield nanoporous Ag NWs with a large amount of catalytic active Ag (110) surfaces. The gap between Ag NWs can be a pathway for the electrolyte and increase mass transport of dissolved oxygen to the electrode surface. Consequently, the Ag NWs have 36.4 times higher electrochemical surface area but less than 0.08 times as much charge-transfer resistance as Ag film. As a result, the Ag NWs achieve an ORR-onset potential of 0.97 VRHE and a good long-term stability with only 50 mV decrease in ORR-onset potential even after 30,000 cycles (480,000 s).

Sharpening of noble metal catalysts has been proven to enhance the performance of CO2 electrochemical reduction to CO. However, this approach has not been validated for non-precious metal catalysts such as Cu-based bimetallic catalysts. Moreover, the morphology of sharpened catalysts was relatively random and non-uniform, making it difficult to quantify the curvature of nanostructures. Here, we experimentally studied the relationship between sharpness of Sn/Cu catalysts with their activity through the fabrication of Sn/Cu foil, rods, and cones. The Sn/Cu catalysts were fabricated by template-based nanoimprint lithography, electroplating of Cu film, and electroless coating of Sn nanoparticles. The finite-element-based simulation provides evidence that the local electric field intensified as the curvature of catalysts increased. As a result, Sn/Cu cones exhibited much better faradaic efficiency of CO (FECO) = 82.7% and current density of CO (jCO) = 5.43 mA/cm2 than Sn/Cu foil (FECO = 41.3% and jCO = 2.29 mA/cm2) and Sn/Cu rods (FECO = 59.7% and jCO = 3.87 mA/cm2). This work reveals that the local electric field induced by the sharp tip plays a significant role in improving the FECO and lowering the onset potential of CO2 reduction reaction.

We present an innovative approach to fabricate an extremely flat (EF) metal film which was done by depositing metal on an extremely flat mother substrate, then detaching the metal from the substrate. The detached flexible metal films had a roughness that was within 2% of the roughness of the mother substrate, so EFs with Ra < 1 nm could be fabricated using the surface roughness transfer method. With quantitative analysis using in situ synchrotron XPS, it was concluded that the chemical reaction of oxygen atoms with the metal film played a critical role in designing a peel-off system to get extremely flat metal films from the mother substrate. The OLED was successfully implemented on the metal film. The OLED's luminance could be increased from 15 142 to 17 100 cd m−2 at 25 mA m−2 by replacing the glass substrate with an EF copper (Cu) substrate, due to the enhanced heat dissipation during the operation. This novel method can be very useful for mass production of large scale, low-cost and high quality metal films using roll-to-roll process.

For flexible organic light emitting diodes (OLEDs), roll-to-roll production enables low-cost fabrication and wide-ranging applications. Choosing an appropriate substrate material is one of the critical issues in the fabrication of flexible OLEDs. We demonstrated top-emitting OLEDs with a highly reflective distributed Bragg reflector (DBR) using a metal foil substrate. The DBR, made of seven pairs of SiO2/ZrO2, was formed by electron-beam evaporation on metal foil and showed high reflectivity of 90.5% at λ = 500 nm. The DBR served not only as the optical reflector, but also the substrate insulating layer which enabled the electrical isolation and prevented crosstalk. The OLEDs showed an operation voltage of 6.5 V at a current density of J = 10 mA cm−2 and maximum luminance of 17 400 cd m−2 at J = 225 mA cm−2. The electroluminescence property of the device could be maintained under the tensile bending condition.