Low Transmittance Research Articles

Improving the thermal performance of PVC windows with pultruded thermoplastic reinforcement

Today, composite profiles of constant cross section are widely used in advanced engineering structures. The use of composite profiles in window and door structures can reduce thermal bridging and reduce energy consumption for heating and cooling. This article focuses on the production of new, thermoplastic-based structural pultruded profiles and their application in a PVC (polyvinylchloride) window structure as a reinforcement. The heat transfer model was developed to determine die temperature and pulling speed for pultrusion of the 30 × 20 × 3.5 mm tube and a 31.5 × 25.0 × 3.5 mm channel from tapes. The microscopy results demonstrated full consolidation of all tapes in the material, thus confirming proper selection of pultrusion parameters. The mechanical tests results of the welded angle joint show that the window structure with composite reinforcement can be twice as strong as the steel reinforced one. This was achieved by welding the composite reinforcement simultaneously with welding of the PVC frame on a butt welding machine. The results of the hot box test show that the U-value of the window sash and frame with the composite reinforcement is 12% lower than that of a window with a steel reinforcement. The U-value of the window with composite reinforcement is 1.47 W/(m2·K), and that of the steel reinforced window is 1.55 W/(m2·K). Thus, the windows with composite reinforcement have low thermal transmittance complying with building regulations in various countries, and their use is permitted in northern climatic zones.

Effect of Photovoltaic Energy-Saving Window Factors on Building Heating Load Under Three Control Modes

Photovoltaic (PV) glazing is widely used in the building sector for its power generation advantages. However, its low transmittance reduces solar heat gain, limiting energy-saving effectiveness in heating regions. To address this, the present study proposes a novel PV energy-saving window that reduces heating load by separately controlling its components—PV glazing, insulated shutter, and clear glazing—through three control modes: Mode 1 controls insulated shutter, Mode 2 controls insulated shutter and PV glazing, and Mode 3 controls insulated shutter and clear glazing. First, the energy-saving benefits of the window were confirmed through in situ testing. Next, using a validated model, the correlation between key factors and heating load was analyzed under the above three modes. Finally, the impact of configurations on heating load under the three control modes was clarified. The main findings are as follows: (1) When PV glazing is controlled, clear glazing layers become the primary factor influencing the heating load. (2) In Modes 1 and 3, the configurations have a greater impact on heating load, reducing it by 34.62% and 39.60%, respectively, while Mode 2 shows a reduction of 17.93%. (3) Mode 2 is the optimal control mode, confirming the effectiveness of controlling PV glazing to reduce heating load.

Preparation of eco-friendly multifunctional lyocell fabric with flame retardant, antibacterial and UV resistant using glucose-derived NP compounds.

A biomass-based finishing agent (ArCP) rich in nitrogen and phosphorus was synthesized from glucose, arginine and phosphorous acid, which was then used for lyocell fabrics to prepare flame retardant, antibacterial and UV resistant properties lyocell fabrics (ArCP-lyocell). The elemental composition, surface morphology, combustion performance, antibacterial and UV resistant properties for the lyocell fabrics before and after modification were investigated. ArCP-lyocell fabrics showed excellent self-extinguishing properties with a limiting oxygen index (LOI) of 35.1% and maintained an LOI of 30.7% even after 30 laundering cycles (LCs). Antibacterial experiments confirmed the antibacterial effect of ArCP-lyocell against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with 99.9% and 92.8% inhibition rates, respectively. In addition, the modified fabrics exhibited excellent UV resistant properties with a UV production factor (UPF) of up to 184.54, and lower transmittance both UVA and UVB rays under 2%. This study provides a simple and efficient approach for developing eco-friendly multifunctional textiles.

Analysis of Digital Television Signal Reception in Combined Transmitter Antenna Systems

The Indonesian broadcasting sector has undergone significant transformation with the implementation of the Analogue Switch Off (ASO) program. By July 2023, approximately 97.23% of television stations in Indonesia had migrated to digital broadcasting. However, this figure does not reflect an equitable distribution of normal broadcasts. Data from Transmission Station X indicate that 6.77% of broadcasts are blank, 12.24% experience freezing, and only 80.99% are classified as normal for channel X in the Jabodetabek region. These statistics suggest that the primary objective of the ASO program—providing an enhanced television viewing experience—has not yet been universally achieved. Therefore, efforts are required to ensure the equitable distribution of normal broadcasts. Transitioning from a lower transmitter antenna system to a combined transmitter antenna system is proposed as a potential solution. This study evaluates the Modulation Error Ratio (MER) values in the Jabodetabek region when channel X uses a combined transmitter antenna system. Measurements, conducted using the drive test method, reveal that 99.703% of MER data are above the threshold (normal broadcasts), 0.042% are at the threshold (freeze broadcasts), and 0.255% are below the threshold (blank broadcasts). These results demonstrate that adopting a combined transmitter antenna system can help address the uneven distribution of normal broadcasts in the Jabodetabek region.

The design and technology development of the JUNO central detector

The Jiangmen Underground Neutrino Observatory (JUNO) is a large-scale neutrino experiment with multiple physics goals including determining the neutrino mass hierarchy, the accurate measurement of neutrino oscillation parameters, the neutrino detection from supernovae, the Sun, and the Earth, etc. JUNO puts forward physically and technologically stringent requirements for its central detector (CD), including a large volume and target mass (20 kt liquid scintillator, LS), a high-energy resolution (3% at 1 MeV), a high light transmittance, the largest possible photomultiplier (PMT) coverage, the lowest possible radioactive background, etc. The CD design, using a spherical acrylic vessel with a diameter of 35.4 m to contain the LS and a stainless steel structure to support the acrylic vessel and PMTs, was chosen and optimized. The acrylic vessel and the stainless steel structure will be immersed in pure water to shield the radioactive background and bear great buoyancy. The challenging requirements of the acrylic sphere have been achieved, such as a low intrinsic radioactivity and high transmittance of the manufactured acrylic panels, the tensile and compressive acrylic node design with embedded stainless steel pad, and one-time polymerization for multiple bonding lines. Moreover, several technical challenges of the stainless steel structure have been solved: the production of low radioactivity stainless steel material, the deformation and precision control during production and assembly, and the usage of high-strength stainless steel rivet bolt and of high friction efficient linkage plate. Finally, the design of the ancillary equipment such as the LS filling, overflowing, and circulating system was done.

Hybrid Frequency–Spatial Domain Learning for Image Restoration in Under-Display Camera Systems Using Augmented Virtual Big Data Generated by the Angular Spectrum Method

In the rapidly advancing realm of mobile technology, under-display camera (UDC) systems have emerged as a promising solution for achieving seamless full-screen displays. Despite their innovative potential, UDC systems face significant challenges, including low light transmittance and pronounced diffraction effects that degrade image quality. This study aims to address these issues by examining degradation phenomena through optical simulation and employing a deep neural network model incorporating hybrid frequency–spatial domain learning. To effectively train the model, we generated a substantial synthetic dataset that virtually simulates the unique image degradation characteristics of UDC systems, utilizing the angular spectrum method for optical simulation. This approach enabled the creation of a diverse and comprehensive dataset of virtual degraded images by accurately replicating the degradation process from pristine images. The augmented virtual data were combined with actual degraded images as training data, compensating for the limitations of real data availability. Through our proposed methods, we achieved a marked improvement in image quality, with the average structural similarity index measure (SSIM) value increasing from 0.8047 to 0.9608 and the peak signal-to-noise ratio (PSNR) improving from 26.383 dB to 36.046 dB on an experimentally degraded image dataset. These results highlight the potential of our integrated optics and AI-based methodology in addressing image restoration challenges within UDC systems and advancing the quality of display technology in smartphones.

Applications of Isosceles Triangular Coupling Structure in Optical Switching and Sensing.

In the case of waveguide-based devices, once they are fabricated, their optical properties are already determined and cannot be dynamically controlled, which limits their applications in practice. In this paper, an isosceles triangular-coupling structure which consists of an isosceles triangle coupled with a two-bus waveguide is proposed and researched numerically and theoretically. The coupled mode theory (CMT) is introduced to verify the correctness of the simulation results, which are based on the finite difference time domain (FDTD). Due to the existence of the side mode and angular mode, the transmission spectrum presents two high transmittance peaks and two low transmittance peaks. In addition, the four transmission peaks exhibit different variation trends when the dimensions of the isosceles triangle are changed. The liquid crystal (LC) materials comprise anisotropic uniaxial crystal and exhibit a remarkable birefringence effect under the action of the external field. When the isosceles triangle coupling structure is filled with LC, the refractive index of the liquid crystal can be changed by changing the applied voltage, thereby achieving the function of an optical switch. Within a certain range, a linear relationship between refractive index and applied voltage can be obtained. Moreover, the proposed structure can be applied to biochemical sensing to detect glucose concentrations, and the sensitivity reaches as high as 0.283 nm·L/g, which is significantly higher than other values reported in the literature. The triangular coupling structure has advantages such as simple structure and ease of manufacturing, making it an ideal choice for the design of high-performance integrated plasmonic devices.

Interlocking passive brick set: the design of interlocking building components with connecting air cavities for heat dissipation and as a complement to the Heating, Ventilation, and Air Conditioning (HVAC) system

This dissertation explores the design and implementation of the "Interlocking Passive Brick Set," a building component aimed at enhancing thermal efficiency and optimising the performance of Heating, Ventilation, and Air Conditioning (HVAC) systems. The bricks demonstrate thermal resistance and low thermal transmittance, reflecting their ability to manage heat flow and dissipation effectively. The research focuses on the interaction between the exterior and interior surfaces of the brick set, where the exterior is exposed to a hot environment, and the interior remains cooler. The design incorporates a central air cavity with lower thermal transmittance than solid surfaces. This cavity facilitates a heat dissipation cycle: hotter air rises and is expelled through the top compartment, while cooler air descends, cooling the space. This convective process enhances the overall thermal regulation within the structure. The data explain the discrepancy between predicted and measured thermal performance in interlocking brick systems and how the integrated air cavity addresses these issues. Heat-flux measurements were correlated in a general form to enable designers to account for convection at both the interior and exterior surfaces.

Analysis of Causes on High False Rejection Rate of Dark Tipping Paper Connector of ZJ118 Cigarette Machine

ZJ118 cigarette making and tipping machine combination is widely promoted in the industry because of its fast speed of production and stable operation. However, with the development of process requirements and the diversification of cigarette types, when producing cigarettes using dark tipping paper, the false rejection rate of tipping paper joint detection system is higher than the normal level. Given this situation, taking Black Middle cigarettes of a tobacco company as an example, the engineer spent 3 months to analyze its causes according to the characteristics of the detection system through on-site statistical investigation progressively, and finally concluded that the problem lay in the mismatch between the transmittance of tipping paper and the detection system. Dark tipping paper due to its low light transmittance, caused high false rejection rate. This article elaborates this in detail.

Recent Progress in Liquid Water Visualization of Polymer Electrolyte Fuel Cells Elucidated By Synchrotron X-Ray and Pulsed Neutron Sources

The formation, accumulation, evaporation, and elimination of water in polymer electrolyte fuel cells (PEFCs) is one of the key features for achieving high power density. The oxygen reduction reaction at the cathode catalyst surface produces water as a by-product. Some of the produced water is discharged from the PEFC through the gas flow channels, while the rest accumulates in the catalyst layer (CL) and gas diffusion layer (GDL). The accumulated water in the porous media inhibits the oxygen supply to the cathode catalyst surface, leading to an increase in the concentration overpotential. Therefore, we have developed water visualization techniques using synchrotron X-rays and pulsed neutrons [1–9]. The three-dimensional water transport behavior in GDLs has been reported by operando X-ray computed tomography (CT) [1]. The water condensation behavior in GDLs has been demonstrated by ex-situ X-ray micro-CT [2] and nano-CT [4]. The dynamic water behavior in GDLs induced by water injection has been studied by ex-situ X-ray high-speed time-resolved X-ray micro-CT [3]. The complementary use of operando X-ray and neutron radiography revealed the water drainage mechanism of large-sized PEFCs [5]. The water accumulation behavior in GDLs has been studied by operando X-ray radiography [6–8]. The water behavior in large-sized PEFCs during cold start has been clarified by the water/ice identification technique using operando pulsed neutron imaging [9].In this talk, we will briefly introduce our previous achievements and present a recent progress in new results: water visualization in Pt-based CLs and thawing behavior in large-sized PEFCs during cold start. In the first topic, water visualization imaging was performed using operando synchrotron X-ray radiography. In general, the strong X-ray absorption of Pt results in low transmittance, which limits water visualization in Pt-based CLs. To overcome this problem, we reviewed our cell configuration and developed a new in-house cell dedicated to the observation of water distribution in cathode CLs. In the second topic, water visualization imaging was performed using operando pulsed neutron radiography. We focused on the current recovery behavior observed during cold start in short stacks. The temperature condition in short stacks during cold start was reproduced in a single cell by rapid heating with an in-house external heater.Reference1) Y. Nagai, J. Eller, T. Hatanaka, S. Yamaguchi, S. Kato, A. Kato, F. Marone, H. Xu and F. N. Büchi, J. Power Sources, 435 (2019) 226809.2) S. Kato, S. Yamaguchi, W. Yoshimune, Y. Matsuoka, A. Kato, Y. Nagai and T. Suzuki, Electrochem. Commun., 111 (2020) 106644.3) S. Yamaguchi, S. Kato, A. Kato, Y. Matsuoka, Y. Nagai and T. Suzuki, Electrochem. Commun., 128 (2021) 107059.4) S. Yamaguchi, S. Kato, W. Yoshimune, D. Setoyama, A. Kato, Y. Nagai, T. Suzuki, A. Takeuchi and K. Uesugi, J. Synchrotron Radiat., 29 (2022) 1258-1264.5) A. Kato, S. Kato, S. Yamaguchi, T. Suzuki and Y. Nagai, J. Power Sources, 521 (2022) 230951.6) W. Yoshimune, Y. Higuchi, A. Kato, S. Hibi, S. Yamaguchi, Y. Matsumoto, H. Hayashida, H. Nozaki, T. Shinohara and S. Kato, ACS Energy Lett., 8 (2023) 3485.7) T. Suzuki, A. Kato, S. Yamaguchi, Y. Nagai, D. Hayashi and S. Kato, J. Power Sources Adv., 22 (2023) 100119.8) A. Kato, S. Kato, S. Yamaguchi, T. Suzuki and Y. Nagai, Int. J. Hydro. Energy, 50 (2024) 1218.9) Y. Higuchi, W. Yoshimune, S. Kato, S. Hibi, D. Setoyama, K. Isegawa, Y. Matsumoto, H. Hayashida, H. Nozaki, M. Harada, N. Fukaya, T. Suzuki, T. Shinohara and Y. Nagai, Commun. Eng., 3 (2024) 33.

Effect of Concentration and Addition Timing of Bromide Ion on Synthesis of Thin Silver Nanowires (AgNW)

Indium tin oxide (ITO), currently widely used as a transparent conductive material to OLED, solar cells and EC devices, has advantages such as low sheet resistance and high transmittance, but it has defects such as inflexibility, fragility and vacuum process production. Alternative transparent conductive materials are required to replace ITO. Silver nanowires (AgNW) have one of attractive attention because AgNW dispersed films show low sheet resistance and high transparency, and even more excellent flexibility, and solution process production. However, the current AgNW films have higher resistance than that of ITO because diameter of AgNW is sub mm order and poor formation of two-dimensional network of AgNW. Therefore, we aimed to reduce the resistance of AgNW film by thinning diameter of AgNW, which is expected to improve conductivity by increasing number of AgNW while maintaining transparency.Synthesis thinning diameter of AgNW was performed by a polyol reduction method using polyvinylpyrrolidone (PVP) and Br- ion as capping agents, and Ag+ ion was reduced to Ag metal by thermal decomposition of ethylene glycol. As PVP and Br- ion are selectively adsorbed on Ag(100) plane, Ag(111) plane grew, resulting in AgNW production. The reactant solution including NaCl, NaBr, PVP, and AgNO3 in ethylene glycol was heated to 130 ˚C to synthesize AgNW. Br- ion was first added before heating, and the synthesis was carried out at NaBr concentrations ranging from 0 µM to 59.8 µM. As a result, AgNW production was confirmed at the low NaBr concentrations below 53.1 µM, but thin AgNW was not observed. At the high NaBr concentration above 53.1 µM, no AgNW synthesis was observed because Br- ion inhibited the growth of AgNW.Next, we examined the timing of addition of Br- ion at the NaBr concentration of 53.1 µM. When excess Br- ion was added before heating, we supposed that it would inhibit the formation of AgCl nuclei and prevent AgNW growth. When Br- ion was added within 1 hour after the start of heating, the growth of AgNW was inhibited by Br- ion and the synthesis of AgNW could not be confirmed as same as the case of NaBr addition before heating. Addition of Br- ion over 1 hour after the start of heating did not also result in the formation of thin AgNW because the growth of thick AgNW had already been completed. By addition of Br- ion at 1 hour after the start of heating, the formation of thin AgNW was observed.The crude dispersed AgNW solution was diluted in ethanol and then stood for several hours to precipitate thick AgNW. The supernatant solution was pipetted and thin AgNW was precipitated by adding acetone to remove ethylene glycol. The purified thin AgNW were deposited on glass slides by the spray-coating method. Annealing of the deposited substrate at 130 ˚C was used to confirm the decrease in resistance. As a result of resistance measurement, a sheet resistance of 34.6 Ω/sq was achieved at 90% transmittance, and the transparent conductive material was successfully fabricated.

Growth of Diamond on Si, SiC, Mo and Diamond Substrates for Heat Spreader, Optical Window, and Surface Graphitized Devices

Introduction Diamond, owing to its exceptional impact resistance, high thermal conductivity, broad-spectrum optical transparency, elevated breakdown field strength, and superior carrier mobility, finds widespread application in diverse fields such as high-power laser windows, efficient heat spreader, and high-performance semiconductor devices. Experimental 1. Heteroepitaxial Growth of Polycrystalline Diamond on Si, SiC, and Mo Substrates:In this part, substrates employed include double-side polished 4H-polytype SiC, (100) single-side polished single-crystal Si wafers, and Mo substrates. Ultrasonic grinding of substrates using diamond powder ethanol suspension to promote the dispersion of nucleation seeds, followed by sequential ultrasonic cleaning in acetone, ethanol, and deionized water.Subsequently, MPCVD was used for diamond growth, using hydrogen, methane, oxygen, and a mixture of hydrogen and nitrogen as reaction gases. Using different processes to produce efficient heat sinks and high-power laser windows. 2. Homoepitaxial Growth of Single-Crystal Diamond on Diamond Substrates:In the homoepitaxial growth process, (100) double-side polished single-crystal diamond substrates are utilized. No need for ultrasonic grinding steps, cleaning steps are the same as above. Then use MPCVD for homogeneous epitaxial growth of single-crystal diamond. 3. Investigation of Graphitized Surface Devices on Diamond:This study also investigated the graphitization devices on diamond surfaces. A high-temperature metal-catalyzed method is employed to promote surface graphitization of diamond. Firstly, polish and clean the diamond. Subsequently, a 300 nm thick nickel layer is deposited on the diamond surface. Rapid thermal annealing is then performed at 1300°C to form a highly conductive graphite layer. This process successfully prepares capacitor samples with a graphite-diamond-graphite three-layer structure. Results and Discussion 1. High-Power Laser Window Plates:The fabricated laser window plates utilize Si, SiC and Mo substrates, employing an ultra-low nitrogen growth process with a growth rate of approximately 3.7 µm/h. After double-sided polishing, the thickness reaches 1 mm. At room temperature, the transmittance at 10.6 µm wavelength approaches the theoretical maximum, reaching 67.9%. The overall thermal conductivity exceeds 1950 W/mK, approximating that of single-crystal diamond.Raman spectroscopy and XRD results indicate that the primary component is polycrystalline diamond with a (110) crystallographic orientation. Laser testing results demonstrate that these window plates possess a high laser-induced damage threshold with a peak energy of 60 J/cm2 and a peak power of 12 MW/mm2, capable of withstanding high-power CO2 laser output. 2. Heat Spreader:This study involves depositing diamond on Si and SiC substrates, forming diamond-based composite materials. This significantly improves the heat dissipation efficiency of the devices, bringing their performance closer to theoretical limits. The deposition process employs a low-nitrogen technique to balance growth rate and defect density, achieving a growth rate of approximately 5 µm/h.Raman spectroscopy and XRD results indicate that the primary component is polycrystalline diamond with a (110) crystallographic orientation. Although the increased nitrogen content results in lower optical transmittance compared to optical window plates, the grain size can be increased from 124 nm to 22 μm through production process adjustments, thereby enhancing thermal conductivity.Test results demonstrate that the thermal conductivity of the Si-diamond composite material reaches 450 W/mK,3 times that of single-crystal Si. The SiC-diamond composite material achieves a thermal conductivity of 500 W/mK,3.5 times that of SiC. 3. Single-Crystal Diamond:The transmittance and thermal conductivity of single-crystal diamond grown by homoepitaxial growth are superior to those of polycrystalline diamond. However, limitations in size and growth conditions restrict its large-scale application in heat spreaders and optical windows. Single-crystal diamond is more suitable for manufacturing semiconductor devices such as diamond capacitors, Schottky diodes, and hydrogen-terminated MOSFETs.The author has conducted research on doping of single-crystal diamond. Characterization through Raman spectroscopy, XRD, and TEM confirms that the primary component is single-crystal diamond with a (100) crystallographic orientation. The dislocation density is below 103/cm2, meeting the stringent requirements for semiconductor devices. 4. Graphite-Diamond-Graphite Capacitors:Utilizing prepared diamond, graphite-diamond-graphite capacitors were fabricated. Measurements using a semiconductor parameter analyzer revealed a high capacitance value of 4 nF. TCAD simulation indicated a breakdown voltage as high as 1100 V. This research explores a novel method for diamond capacitor fabrication. Conclusions Diamond heteroepitaxial grown on Si, SiC, and Mo substrates has prepared high-power laser windows with 67.9% optical transmittance at 10.6 μm wavelength, and composite materials with thermal conductivity enhanced to 3-3.5 times that of the original materials. Homoepitaxially grown diamond on single-crystal diamond substrates exhibits a dislocation density below 10³/cm², meeting the requirements for semiconductor device substrates. Furthermore, this research has developed a novel diamond capacitor fabrication technique, yielding capacitors with a capacitance of 4 nF and a breakdown voltage of 1100 V.

Aqueous Solution-Based Switchable Silver Mirror Devices

Dimming glass using electrochromic materials that can control the amount of transmitted light by switching between the colored and transparent states. At the colored state, light is absorbed and is changed to heat resulting in increasing temperature. Meanwhile, a switchable metal mirror between mirror and transparent states, is expected not to absorb light but to reflect light. In the previous study, the switchable silver mirror based on reversible electroplating and electrodissolving on the ITO electrode has been realized. The ionic liquid has been used as a solvent for the silver plating bath. It’s unique solvent, which has the melting salt in room temperature, nonvolatility and ionic electrolyte whereas it’s expensive. Furthermore, aqueous solution is usually employed in the metal plating bath whereas toxic cyanide ion is containing in the bath for stabilizing metal ion. Therefore, in this study, we investigated switchable mirror characteristics using an aqueous solution-based Ag plating bath instead of ionic liquids and wihtout containing cyanide ions.First, an Ag plating bath was prepared by dissolving silver nitrate, sodium sulfate as an electrolyte, sodium citrate as an additive, and ammonia as ligand for silver ion in pure water. Using the Ag plating bath, Ag plating was performed on the ITO modified by a Pd catalyst by applying a constant current of -4 mA/cm2 for 20 sec and the formation of a mirror surface was confirmed. However, the average transmittance in the visible light region is high at about 10%, and the Ag surface looks whitish. This is thought to be due to light scattering caused by the presence of unevenness on the electroplated Ag surface. The surface irregularities would be caused by the lack of dense modification of Pd catalyst, which is the core of silver for smooth plating of silver, so that the conditions to make more highly dispersed Pd catalyst were investigated. Pd strike plating was performed by changing the current density at the same charge. When the current density increased from -5 to -40 mA/cm2, the grain size of Pd catalyst gradually decreased from 130 nm to 61.6 nm. The dispersibility of Pd catalyst also increased with decrease in particle size. When the Pd-modified ITO at the current density of -40 mA/cm2 was plated with Ag by applying a constant current of -4 mA/cm2, a mirror surface with a low transmittance of less than 1% was successfully formed.After Ag plating, Ag dissolution was also investigated by applying a constant current of +4.0 mA/cm2 under the potential of +0.25 V vs. Ag/Ag+ and then a constant potential of +0.25 V vs. Ag/Ag+ . However, black residue was remained on the ITO after dissolving the plated Ag on the Pd-modified ITO. Therefore, the catalyst was changed from Pd to platinum in order to complete Ag dissolution from the ITO. Pt has the advantage of catalytic property and electrochemical stability compared to Pd. Complete dissolution was achieved by plating and dissolution using Pt-modified ITO under the same conditions as those for Pd-modified ITO.The repeating cycle of Ag plating and dissolution was carried out on the Pt-modified ITO until three cycles. At the three cycles, the un-plated region appeared on the upper part of the mirror surface. In order to resolve this problem, we changed the configuration of the equipment to prevent the influence of the Ag plating bath interface, and succeeded in disappearing the un-plated region. Therefore, it is considered that the Ag plating is affected by the oxygen at the plating bath interface during Ag plating.Switchable silver mirror device will be fabricated using an aqueous Ag plating bath. The device shape would prevent the influence of atmospheric oxygen because of the closed system. The device will be repeatedly switched between the transparent and mirror states to evaluate the cycling characteristics of the aqueous solution-based switchable silver mirror device.

Optimizing Na2EDTA concentration for enhanced properties of SILAR - deposited CTS thin films

Abstract This study investigates the impact of varying Na2EDTA concentrations on the properties of copper tin sulfide (CTS) thin films deposited on soda lime glass substrates using the successive ionic layer adsorption and reaction (SILAR) method. The aim is to optimize CTS thin film growth for photovoltaic technology applications. CTS thin films were prepared using SILAR with Na2EDTA concentrations of 0.01 M, 0.04 M, and 0.07 M, resulting in samples CTS01, CTS04, and CTS07. Characterization techniques included XRD, SEM, EDAX, FTIR, I-V curves, transmittance spectra, and Tauc plots. The results reveal significant variations in film properties with changing Na2EDTA concentration. XRD patterns indicate polycrystalline films with an orthorhombic CTS phase. SEM images show smooth, dense films with localized clusters. FTIR spectra detect hydrocarbon chains, aromatic rings, and hydroxyl or ether groups. The I-V curves of three samples (CTS01, CTS04, and CTS07) show a voltage-dependent transition from semiconducting to ohmic behavior. The CTS01 exhibits superior conductivity (3.13 × 10−5/Ωm), while the samples’ resistance and conductivity values show an inverse relationship. Transmittance curves display low UV transmittance and high visible transmittance,suggests that the samples are highly absorptive in the UV range and become more transparent in the visible range, indicating potential applications in optical filtering and photovoltaic devices. Tauc plots estimate band gap energies of 3.66, 3.89, and 3.23 eV, indicating high band gap energies suitable for buffer layers in solar cells. The correlation between band gap energy and crystallite size as a function of Na2EDTA concentration is also observed. The study demonstrates the importance of optimizing Na2EDTA concentration for achieving high-quality CTS thin films with desirable properties for photovoltaic applications. The findings highlight the potential of CTS thin films for solar cells, optical filtering, and photonic devices.

Optical and Methanol Sensing Properties of Al-doped ZnO Thin Film

The study investigates the optical and electrical properties of undoped and aluminum (Al)-doped zinc oxide (ZnO) films, focusing on their performance as gas sensors and their potential applications. Optical analysis, conducted using UV-visible spectrophotometry, reveals that 1% Al-doped ZnO films exhibit the highest transmittance of 91%, indicating superior optical clarity and suitability for applications like solar cell electrodes. In contrast, 3% Al-doped ZnO films show significantly lower transmittance due to increased light scattering and photon absorption. The bandgap of ZnO films decreases with higher Al doping concentrations, from 3.3 eV for undoped ZnO to 3.15 eV for 3% Al-doped ZnO, suggesting enhanced electrical conductivity due to reduced bandgap. The extinction coefficient data demonstrate that 2% Al-doped ZnO has the highest extinction coefficient, reflecting improved light absorption and scattering properties. Electrical characterization through I-V curves indicates that 1% Al-doped ZnO films have higher current (121 µA) compared to undoped (431 µA) and higher doping concentrations, attributed to enhanced carrier concentration and mobility. Sensitivity tests show that 2.5% Al-doped ZnO films exhibit the highest sensitivity to methanol vapor, with a significant reduction in resistance compared to 0.5% Al-doped ZnO films. Resistance measurements with varying methanol volumes reveal a rapid decrease upon gas introduction, stabilizing and then increasing as the gas is removed. Sensitivity analysis indicates that 100 µL methanol provides the highest sensitivity (97%) at 60°C, while 2% Al-doped ZnO films show consistent sensitivity at 60 °C and 100 °C, but not at 80 °C.

Fine-Tuning Conformation of PEDOT Chains Enables Simultaneously Enhanced Conductivity, Work Function, Transmittance, and Waterproofness in PEDOT:PSS Interlayer for Highly Efficient and Stable Organic Photovoltaics.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely utilized as the hole transport layer (HTL) inorganic photovoltaics (OPVs) because of its low-temperature solution processing peculiarity, high optical transmittance, and excellent mechanical flexibility. However, the core-shell structure of PSS coated PEDOT results in relatively low conductivity, work function, transmittance and waterproofness of PEDOT:PSS interlayer, limiting the photovoltaic performance and stability of OPVs. Here, the conformation of PEDOT chains are regulated from helical benzoyl to linear quinone structure via incorporation of 2D Cd0.85PS3Li0.15H0.15dopant into the conventional PEDOT:PSS interlayer, promoting an interpenetrating network structure in PEDOT:PSS interlayer and forming an efficient hole transport channel from active layer to ITO electrode. Such features significantly improve the electrical conductivity, work function, and transmittance of PEDOT:PSS interlayer. In consequence, the maximum power conversion efficiency (PCE) of D18:L8-BO, PBDB-T:ITIC, as well as PTzBI-dF:L8-BO based OPVs ameliorated from 18.37%, 8.94%, and 15.80% to 19.26%, 10.00%, and 16.83%, respectively. The application of Cd0.85PS3Li0.15H0.15 doping PEDOT:PSS strategy demonstrates great potential for the development of strongly conductive, large-work-function, highly transparent, and excellent-waterproof PEDOT:PSS interlayer toward highly efficient and stable OPVs.

Enhanced Second‐Harmonic Generation in Quadratically Nonlinear Weyl Semimetal NbAs for Broadband Photodetection Applications

AbstractQuadratically nonlinear photodetectors (QNPDs) typically focus on 2D materials with high second‐order nonlinear polarizability, thereby severely disregarding bulk nonlinear optical (NLO) crystals as these rely on phase‐matching technology and achieving efficient bulk QNPDs remains a significant challenge. Weyl semimetal crystals have some signatures of inversion symmetry breaking, most notably second‐order NLO polarizability, while the inability to balance the low transmittance limits frequency conversion of the zero‐band gap absorption‐induced crystal. Herein, this study investigates an efficient QNPD based on bulk NbAs crystals designed with a strong second‐harmonic effect due to its large refractive index (≈5.0), resulting in an intense laser reflectivity of 50% on its surface, which creates a favorable environment for achieving second‐harmonic generation (SHG) without phase matching. The QNPD has a rectification ratio exceeding 107 with a dark current of 164 pA and an enhanced photoresponse in the 355‒1900 nm range, exhibiting a maximum responsivity of 4.1 mA W−1 with a detectivity of 0.8 × 1010 Jones at 355 nm. The responsivity improvement rate is 88% higher than that of linear NbAs (001) photodetector. This study opens new avenues for designing QNPDs by utilizing the second harmonic effect in bulk Weyl semimetal crystals.

Electrically Controlled Smart Window for Seasonally Adaptive Thermal Management in Buildings.

Smart windows offer a sustainable solution for energy-efficient buildings by adapting to various weather conditions. However, the challenge lies in achieving precise control over specific sunlight bands to effectively respond to complex weather changes and individual needs. Herein, a novel electrochromic smart window fabricated by integrating a self-assembled cellulose nanocrystals (CNCs) layer with an electrochromic poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) layer is reported, which exhibits high near-infrared transmittance, low solar reflectivity (26%), and infrared emissivity (20%) in winter, and low near-infrared transmittance, high solar reflectivity (91%), and infrared emissivity (≈94%) in summer. Interestingly, the material offers dynamic temperature control based on its photothermal properties, maintaining the internal temperature of buildings within a comfortable range of 20-25 °C from morning to night, particularly in winter with significant daily temperature fluctuations. Simulations show that the CNC-PED device demonstrates excellent energy-saving and CO2 emission reduction capacities across various global climate zones. This study presents a feasible pathway for constructing season-adaptive smart windows, making them suitable for energy-efficient buildings.

Hybrid Functional ITO/Silver Nanowire Transparent Conductive Electrodes for Enhanced Output Efficiency of Ultraviolet GaN-Based Light-Emitting Diodes.

We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 16.4 Ω/sq, while the reference ITO TCE exhibited a transmittance of 76.4% and a sheet resistance of 18.7 Ω/sq. Despite the 8.9% lower optical transmittance, the UVLEDs fabricated with HFTCEs achieved a 25% increase in output efficiency compared to reference UVLEDs. This improvement is attributed to the HFTCE's twofold longer current spreading length under operating forward voltages, and more significantly, the enhanced out-coupling of localized surface plasmon (LSP) resonance with the trapped wave-guided light modes.

Broadband metamaterial polarizers with high extinction ratio for high-precision terahertz spectroscopic polarimetry

The demand for precise polarizers is increasing to investigate the polarization characteristics of materials non-invasively in the terahertz region. Recently, to address the low extinction ratio and fragile nature of conventional wire-grid polarizers, plasmonic structures and metasurfaces have been proposed. However, the challenge of achieving low transmittance compared to a high extinction ratio, along with the bulky structure due to a thick substrate, remains to be addressed. Here, we present high-efficiency broadband metamaterial polarizers consisting of cross-aligned double-layers of subwavelength metallic slit arrays, leveraging the extraordinary optical transmission and funneling effects. We obtained extinction ratios exceeding 70 dB over a broad frequency range, from 0.2 to 2.5 THz, reaching a maximum extinction ratio of ∼90 dB at 0.7 THz. To investigate the influence of high extinction ratio polarizers on actual measurement results, we measured a non-Hermitian metasurface with asymmetric polarization conversion and analyzed them using the Jones matrix formalism. The results confirmed that the extinction ratio of the polarizer has a significant impact on precise polarization-dependent measurements, especially on cross-polarization measurements. The enhanced performance of our polarizers offers significant potential for sensitive THz systems, paving the way for advancements in polarization analysis of emerging materials and chiral sensing.