Dye-sensitized solar cells (DSSCs) suffer from efficiency limitations due to interfacial charge recombination at the TiO₂/dye/electrolyte interface. In this study, aminopropyltrimethoxysilane (APS) was introduced onto nanoporous TiO₂ photoelectrodes via a dip-coating process with controlled coating times to investigate the effect of silanization time on interfacial charge transport behavior. Unlike concentration-driven structural modification, this work focuses on the evolution of the APS-modified interface governed by reaction time. The DSSC with 30 min APS treatment exhibited the highest power conversion efficiency of 5.34%, representing a 19% enhancement compared to the untreated device (4.49%), mainly due to increased short-circuit current density and open-circuit voltage. However, prolonged coating times (2 h and 24 h) resulted in a significant decrease in photocurrent density, leading to reduced device performance despite partial improvement in recombination resistance. These results are attributed to the time-dependent evolution of the APS interfacial layer. At moderate coating time, APS provides effective surface functionalization, enhancing dye adsorption and suppressing interfacial recombination. In contrast, prolonged coating is expected to induce increased surface coverage and silane condensation, which can hinder electron injection and increase charge transport resistance. Therefore, the photovoltaic performance is governed by a trade-off between recombination suppression and charge injection efficiency, controlled by the silanization time. This study highlights the critical role of interfacial reaction kinetics in determining charge transport behavior and provides an effective strategy for optimizing DSSC performance through time-dependent interface engineering.

Dye adsorption is one of the most time-consuming processes in the fabrication of dye-sensitized solar cells (DSSCs), typically requiring approximately 24 h at room temperature. In this study, the effect of adsorption temperature and time on photovoltaic performance of DSSCs was investigated in order to reduce processing time and improve device productivity. Nanoporous TiO₂ photoelectrodes were immersed in N719 dye solution at 60°C for 3 h, 10 h, 17 h, and 24 h, and their performance was compared with that of cells sensitized at room temperature for 24 h. Photovoltaic characterization under AM 1.5 illumination showed that DSSCs sensitized at 60°C exhibited improved performance compared to those sensitized at room temperature. The device sensitized at 60°C for 3 h showed comparable or higher conversion efficiency than the reference cell sensitized for 24 h at room temperature. The improvement in device performance is attributed to enhanced dye adsorption kinetics resulting from increased reaction rate between the carboxyl groups of N719 dye molecules and hydroxyl groups on the TiO₂ surface. Electrochemical impedance spectroscopy analysis revealed reduced recombination resistance at the TiO₂/dye/electrolyte interface for cells sensitized at elevated temperature. UV–Vis absorption analysis confirmed increased dye loading on the TiO₂ surface for the 60°C condition. These results demonstrate that elevated temperature dye adsorption significantly reduces processing time while maintaining photovoltaic performance, providing an effective strategy for improving manufacturing efficiency of DSSCs.

The dielectric and piezoelectric properties of the ferroelectric BaTiO₃ were measured and analyzed using both strong and weak electric field conditions. To measure the electric field induced polarizations and strains, a high voltage source and the measuring circuit were used and the dielectric constants were measured with an impedance analyzer. The spontaneous polarization of BaTiO₃ at room temperature was calculated as 17 μC/cm² based on the lattice structure and internal ion location, which is in good agreement with the experimental results. The polarization and strain hysteresis curve according to the electric field were analyzed in terms of lattice structure and ion position. The magnitude of remanent polarization is proportional to the offset distance of Ti⁴⁺ ion from the lattice center. The magnitude of dielectric permittivity is proportional to the degree to which Ti⁴⁺ ion can move freely inside the lattice. The magnitude of piezoelectric constant d₃₃ is proportional to how much Ti⁴⁺ ion distorts the lattice as it moves inside the lattice.

Renewable energy harvesting technologies, which convert ambient resources such as wind into electrical energy, have attracted significant attention as sustainable power sources for self-powered systems. However, the long-term applicability of wind energy harvesters in remote or extreme environments has not yet been fully discussed, particularly in terms of structural robustness and environmental adaptability. In this study, we designed a double-clamped flutter-type triboelectric generator (DFTEG) for efficient wind energy harvesting and evaluated its output performance under various simulated outdoor conditions. The DFTEG features a modular acrylic frame with a magnet-based assembly for easy maintenance and film replacement, utilizing PTFE films and aluminum electrodes to maximize the charge density difference according to the triboelectric series. Structural optimization revealed that a single-film configuration with a length of 110 mm produced the most stable flutter vibration and a large effective contact area, achieving a maximum open-circuit voltage of 42.28 V and a short-circuit current of 2.89 μA. Furthermore, performance evaluations under various environmental variables, including relative humidity, temperature, and sand particles interference, confirmed consistent electrical output across diverse environmental conditions. These results demonstrate the potential of the proposed DFTEG as an environmentadaptive independent power source capable of stable operation under complex environmental factors.

Organic solar cells based on bulk heterojunction (BHJ) structures have attracted considerable attention because of their low fabrication cost, mechanical flexibility, and compatibility with solution-processing techniques. In BHJ organic photovoltaic devices, nanoscale morphology and crystallinity of the photoactive layer critically influence photovoltaic performance. In this study, the effects of solvent selection and thermal annealing on crystallization evolution and photovoltaic characteristics of P3HT:PCBM organic solar cells were systematically investigated. Three different solvents, including toluene, chlorobenzene (CB), and dichlorobenzene (DCB), were employed for active-layer fabrication, followed by post-thermal annealing treatment. UV–visible absorption spectroscopy revealed solvent-dependent differences in molecular ordering and intermolecular π–π interactions within the active layer. X-ray diffraction analysis confirmed that thermal annealing significantly enhanced crystallinity and lamellar ordering of P3HT domains, particularly for CB-processed films. Electrical characterization demonstrated that solvent evaporation behavior strongly affects photovoltaic performance. Among the investigated devices, the thermally annealed CB-processed device exhibited the highest power conversion efficiency of 1.83% with an enhanced short-circuit current density of 7.057 mA cm⁻². The improved device performance is attributed to optimized crystallization behavior and balanced nanoscale phase separation induced by the moderate evaporation characteristics of CB. In contrast, although DCB-assisted films exhibited relatively strong optical absorption and enhanced crystallinity, excessively slow solvent evaporation likely induced excessive aggregation and coarse phase separation, limiting efficient photovoltaic characteristics. These results demonstrate that solvent engineering combined with thermal annealing is an effective strategy for controlling morphology evolution and crystallization behavior in P3HT:PCBM bulk heterojunction solar cells.

This paper reviews the energy yield enhancement characteristics of bifacial photovoltaic systems combined with solar tracking, focusing on their performance relative to conventional monofacial fixed-tilt configurations. The fundamental mechanisms of yield improvement are summarized, highlighting the largely additive contributions of solar tracking, which increases front-side irradiance, and bifacial modules, which utilize rear-side reflected and diffuse radiation. Reported results from previous studies indicate that bifacial systems with single-axis tracking typically achieve 25–35% higher annual energy yield compared with standard monofacial fixed-tilt systems, with variations depending on environmental and design conditions. Key design and environmental considerations influencing system performance are discussed to provide practical insights for the application of bifacial tracking systems in utilityscale photovoltaic installations.

Polymer nanocomposites incorporating inorganic nanofillers have emerged as highly promising electromagnetic interference (EMI) shielding materials, combining mechanical compliance with robust conductive percolation networks. Carbon nanotubes (CNTs) are particularly attractive as conductive fillers because their high aspect ratio facilitates percolation at low loadings. Also, CNTs offer superior mechanical durability under deformation compared to rigid, fracture-prone metal nanowires. For EMI shielding, high electrical conductivity is critical as it enhances both reflection and absorption through efficient charge dissipation and conduction losses. However, achieving highly aligned conductive pathways without degrading the intrinsic electrical properties of CNTs remains a significant challenge. Here, we demonstrate a non-destructive magnetic surface-functionalization and alignment strategy. Using a polydopamine (PDA)-mediated route, pristine multiwalled CNTs are uniformly decorated with Fe₃O₄ nanoparticles (FMWCNTs). This enables highly effective magnetic field-driven alignment at fields as low as 10 mT, promoting the strategic formation of percolation networks. By optimizing the Fe₃O₄/MWCNT ratio for high saturation magnetization and uniform coverage, the aligned FMWCNTs exhibit significant electrical anisotropy, delivering a 10.7-fold higher electrical conductivity in the parallel configuration compared to the vertical configuration. These findings present a scalable, room-temperature platform for engineering directionally enhanced conductivity in polymer nanocomposites, with broad applicability in advanced EMI shielding, flexible electronics, and advanced packaging technologies.

There is an increasing demand for freeform stretchable display technologies capable of overcoming spatial limitations in next-generation platforms such as augmented reality (AR) and virtual reality (VR). To realize such stretchable displays, all constituent materials—including semiconductors, electrodes, insulators, and substrates—must exhibit sufficient mechanical elasticity. To date, stretchable gate insulators have primarily relied on organic polymers such as poly(4-vinylphenol-co-methyl methacrylate) (PVP-co-PMMA). However, their practical application is significantly limited by poor electrical properties, including low dielectric constant and instability. In this work, we propose a novel gate insulator structure that minimizes the use of solution-based processes, which often suffer from poor uniformity and may damage underlying layers during fabrication. The proposed structure integrates the advantages of both organic and inorganic materials by employing a hybrid configuration. Specifically, high-k HfO₂ thin films are deposited on both the top and bottom of an organic layer composed of PVP-co-PMMA, poly(melamine-co-formaldehyde) (PMF) as a crosslinking agent, and propylene glycol monomethyl ether acetate (PGMEA) as a solvent. This inorganic–organic–inorganic structure effectively compensates for the inherent electrical limitations of organic materials. As a result, the fabricated thin-film transistors (TFTs) exhibit improved electrical performance and reliability compared to devices employing a single organic gate insulator.

GaN nanowire (NW)-based hybrid structures have attracted attention for optoelectronic applications due to their high surface area and efficient carrier transport. However, the optical transparency of GaN NWs is often limited by unintended residual species accumulated on the surface and in the inter-wire regions, as well as defect-related absorption, leading to reduced light transmission. In this work, we demonstrate that thermal annealing significantly improves the optical transparency of GaN NWs grown on indium tin oxide (ITO)/glass substrates. The transmittance increased from 47.9% to 78.5% at 550 nm after rapid thermal annealing at 800^oC for 3 min, while a comparable value (~75.5%) was achieved at 600^oC for 5 min. PbBr₃ was deposited onto the GaN NWs to form hybrid structures, and temperature-dependent photoluminescence (TDPL) measurements revealed enhanced emission stability with suppressed peak shift and reduced spectral broadening. Arrhenius analysis based on a two-channel model revealed that the activation energy of the dominant non-radiative recombination pathway increased from 62 meV in the as-grown sample to 85 meV after thermal annealing, while its relative contribution remained nearly unchanged. In contrast, the shallow trap-assisted pathway exhibited a similar activation energy of approximately 6 meV in both samples, but its contribution decreased from 0.35 to 0.17 after annealing. As a result, the internal quantum efficiency (IQE) improved from 75.9% to 87.4%. These results show that thermal annealing improves optical transparency by removing residuals and suppresses defect-related recombination, leading to enhanced carrier dynamics and improved optical performance of PbBr₃-based hybrid structures.

This paper proposes a circular sequential lighting control method to reduce current imbalance and luminance deviation among multiple LED modules in AC-powered LED lighting systems. Conventional fixed-sequence lighting control repeatedly prioritizes the same LED modules in every rectified voltage cycle, which leads to unequal current distribution, luminance non-uniformity, and the accelerated degradation of specific modules during long-term operation. To address these limitations, a circular sequential lighting strategy is introduced, in which the lighting order is cyclically rotated at every rectified cycle, ensuring that all LED modules experience equal lighting opportunities. A prototype AC-LED lighting system consisting of four series-connected LED modules was implemented and experimentally evaluated. The results demonstrate that, while the conventional fixed-sequence method produces a maximum average current deviation of up to 1.6 mA among modules, the proposed method equalizes the average current across all modules to approximately 17.1 mA. Furthermore, the flicker index remains at 0.13, which is comparable to that of the conventional method, indicating that luminance uniformity is improved without degradation of optical performance. The proposed circular sequential lighting control effectively distributes electrical stress, enhances luminance uniformity, and improves long-term reliability, making it a practical and efficient solution for high-quality AC-LED lighting applications.

The rapid advancement of large-scale language models and artificial intelligence technologies has highlighted the importance of data processing efficiency. This study outlines a measurement optimization method for high-speed pulse equipment to accurately analyze the operating dynamics of ReRAM, a core hardware component for simulating neural networks. An optimized evaluation methodology combining connection compensation and a dual-channel configuration was established to minimize measurement errors caused by parasitic resistance and capacitance during pulse measurements using the Keithley 4200A-SCS and 4225-PMU modules, and to address HRS/LRS measurement errors caused by mismatches between the measurement range and source limits. The proposed precision measurement guidelines can be applied to the evaluation of semiconductor devices that require pulse measurements, such as transistors and DRAM.

The ability to manipulate and probe biomolecules at the single-molecule level has become an essential approach for understanding molecular interactions, conformational dynamics, and nanoscale transport phenomena. Advances in experimental techniques have enabled precise control of individual molecules with high spatial resolution and piconewton-level force sensitivity. These developments have significantly expanded the capability of studying biomolecular mechanics and dynamics beyond conventional ensemble measurements. A variety of physical strategies have been developed for single-molecule manipulation, including mechanical-force-based approaches, electric-field-driven methods, and nanoscale structural confinement techniques. Mechanical-force-based methods, such as optical tweezers, magnetic tweezers, and atomic force microscopy, enable direct measurement of molecular mechanical responses. Electric-field-based manipulation, represented by dielectrophoresis, allows noncontact control of particles and biomolecules through polarization effects in non-uniform electric fields. In addition, nanopore-based systems employ nanoscale confinement to regulate molecular transport and residence behavior. This review provides an overview of representative single-molecule manipulation techniques based on mechanical, electrical, and structural control and discusses their fundamental principles and implementation strategies.

Lead-free bismuth sodium titanate (BNT)-based ceramics have attracted strong attention as environmentally benign dielectric materials for high-efficiency electrostatic energy-storage capacitors. A key challenge is that pristine BNT typically exhibits large hysteresis, high remnant polarization, and limited dielectric reliability, which restrict recoverable energy storage and efficiency under practical electric fields. Here, we present a focused mini-review of recent studies to clarify how composition design, phase boundary tuning, defect chemistry, and microstructural control collectively enable slim or pinched polarization-electric field (P-E) behavior and improved energy-storage functionality in BNT-related bulk ceramics. The reviewed outcomes consistently show that stabilizing relaxor states governed by polar nanoregions (PNRs), often via solid-solution engineering and secondary relaxor/antiferroelectric-like incorporation, suppresses irreversible switching and reduces hysteresis loss, while densification and grain-size control enhance electrical homogeneity and breakdown strength. In addition, defect-mediated tuning of oxygen vacancy-related complexes is highlighted as an independent lever to control relaxor ergodicity and polarization reversibility, providing a complementary route to slim-loop optimization. These insights are expected to guide integrated design strategies that couple phase/relaxor-state engineering with defect and microstructure optimization, accelerating the development of reliable, temperature-robust, lead-free dielectric capacitors based on BNT-related ceramics.

The recent rapid adoption of electric vehicles (EVs) is creating new load characteristics in the distribution system, and in particular, the widespread use of single-phase charging methods is exacerbating phase load imbalances, leading to voltage unbalance issues. Such voltage imbalances can undermine the stability of the distribution system and may cause side effects such as reduced power quality and shortened equipment lifespan. This study proposes a smart distribution panel system that can detect voltage imbalance issues caused by uneven electric vehicle charging loads in real time and actively compensate for them. The proposed system aims to contribute to the stability and power quality improvement of the distribution network by integrating a load balancing algorithm with inter-phase voltage monitoring functionality.

MoS₂ has attracted significant attention as a next-generation semiconductor material to overcome the physical scaling limits of silicon-based devices due to its atomic thinness and excellent electrical properties. However, high contact resistance and the formation of Schottky barriers resulting from interface defects during the metal deposition process remain major bottlenecks that degrade overall device performance and reliability. In this study, we fabricated MoS₂ FETs by employing Sb₂Te₃, van der Waals (vdW) contacts. Minimized interface inhomogeneity was achieved through a hemispherical stamp-based dry transfer of h-BN for device encapsulation. h-BN encapsulation decreased the hysteresis window in the ±25 V gate voltage range from 17 V to 11.5 V compared to un-capped devices, confirming that charge trapping phenomena induced by external environmental factors were suppressed. Consequently, the dry transfer technique of h-BN using a hemispherical stamp demonstrated in this study provides a potential solution for securing the long-term reliability of MoS₂ devices with vdW contact by minimizing interface contamination.

The safety and stability concerns of liquid electrolytes in conventional lithium-ion batteries have accelerated the development of solid-state alternatives. NASICON type ceramics Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) offer promising properties, including high bulk ionic conductivity and good compatibility with lithium anodes. However, their practical application is hindered by grain boundary resistance and relatively low total ionic conductivity. This study investigates the effect of Ta₂O₅ doping on LATP to overcome these limitations. Doping with 5 wt% Ta₂O₅ improved the ionic conductivity to 2.95 × 10-4 S/cm by enhancing lattice structure, reducing grain boundary resistance, and suppressing the formation of secondary phase. Additionally, Ta₂O₅ positively influenced the sintering behavior, resulting in a denser, and more uniform microstructure. These enhancements suggest that Ta₂O₅-doped LATP is a strong candidate for next-generation all-solid-state lithium-ion batteries.

This review systematically examines the structural characteristics, compositional design strategies, and recent research trends of layered double hydroxides (LDHs), which are recognized as promising electrocatalyst materials in electrochemical nitrate-to-ammonia conversion. Despite the rapid growth in related research, achieving simultaneous high selectivity and efficiency remains a significant technical challenge due to the complex mechanisms of the nitrate reduction reaction (NitRR) and its inherent competition with the hydrogen evolution reaction (HER). In this study, we analyzed the structural contributions of LDH catalysts for maximizing nitrate reduction efficiency and systematically established key catalyst design indicators required to ensure optimal performance. Specifically, we provide a detailed investigation of the physicochemical mechanisms for enhancing NH₃ production by precisely regulating the adsorption energies of reaction intermediates and maximizing charge transfer efficiency through compositional control and defect engineering. Furthermore, we discuss advanced structural design strategies, such as core-shell tandem structures, MOF-derived architectures, and interlayer anion control, as effective methods for enhancing catalytic performance and optimizing mass transport processes. These insights offer a strategic roadmap for designing high-performance LDH catalysts and represent a critical step toward the practical implementation of sustainable green ammonia production systems, particularly for integration into high-efficiency membrane electrode assembly (MEA) technologies.

Breakdown strength is an essential parameter for evaluating the electrical performance and degradation behavior of cable insulation and IEC 60243 also emphasizes its importance for detecting changes in insulation characteristics due to aging. However, the current IEC standards are mainly limited to specifying electrode configurations and test voltage conditions for breakdown tests, while the influence of insulating oil, is not clearly addressed. In this study, the breakdown strength of a 66 kV wet-type submarine cable was experimentally evaluated using insulating oils with different kinematic viscosities of 10, 100, 500, and 1,000 cSt in order to achieve reliable and reproducible breakdown measurements. The experimental results show that the measured breakdown strength decreases by up to approximately 20% depending on the oil viscosity. This indicates that the viscosity of the insulating oil has a significant influence on the measured breakdown strength during breakdown test. Therefore, it is necessary to perform breakdown strength measurements under identical test conditions, including the physical properties of the insulating oil, to ensure reliable comparison and accurate assessment of insulation performance and degradation characteristics.

The increasing global demand for renewable energy has accelerated the deployment of offshore wind farms, thereby highlighting the need for advanced development and performance assessment techniques for dynamic submarine cables used in floating offshore wind systems. These cables are continuously subjected to combined thermal, electrical, and mechanical stresses, with mechanical loading playing a particularly dominant role. As a result, dynamic submarine cables exhibit degradation behaviors that differ significantly from those of conventional fixed submarine cables. This paper presents the design and implementation of a comprehensive evaluation system capable of applying combined thermal, electrical, and mechanical stresses to dynamic submarine cables. The system was validated using a 66 kV wet type submarine cable through commissioning tests and insulation performance measurements. Electrical stress of 72 kV, thermal stress exceeding 95°C, and mechanical stress corresponding to a bending radius of 20 times the cable diameter over 20 cycles were applied to verify system reliability. The subsequent insulation assessments quantitatively confirmed performance variations induced by the combined stresses. The results demonstrate that the proposed platform is the first system capable of simultaneously applying thermal, electrical, and mechanical stresses to dynamic submarine cables, and its operational performance has been successfully validated. This platform enables realistic reliability evaluation of dynamic cables used in floating offshore wind farms and is expected to improve the overall operational reliability of offshore wind power systems.

The rapid proliferation of artificial intelligence (AI) servers and high-performance computing systems has significantly elevated the technical and reliability requirements for multilayer ceramic capacitors (MLCCs). In such systems, MLCCs are critical passive components that must deliver high capacitance, fast transient response, and robust insulation performance under high temperature, voltage, and current density. This review examines the material, structural, and process innovations that underpin MLCC performance in AI applications. Key topics include the development of ultrathin dielectric layers (<0.5 μm), rare-earth doped BaTiO₃-based dielectrics with enhanced DC bias stability, and core-shell microstructures designed for temperature and field resilience. The paper also explores insulation degradation mechanisms―such as vacancydriven conduction and demixing―and advanced reliability assessment methodologies, including HALT, TSDC, and the tipping point framework. Comparisons with automotive-grade MLCCs highlight the unique requirements of AI systems, such as ultraminiaturization, high volumetric efficiency, and ppm-level field failure rates. Finally, the review discusses emerging trends in MLCC technology, including particle engineering, interface stabilization, and advanced lamination techniques, and provides insight into the future direction of capacitor development tailored to AI data center environments.

This study investigates the effect of mask material and thickness on the silicon etching profile using a high-density plasma (HDP) etching system, aiming to reduce optical loss in silicon-based optical waveguides. As the mask thickness increased, the etching sidewall angle became steeper. An etching profile angle of 87° was obtained when tetraethyl orthosilicate (TEOS) was used as the mask material, while 80° was obtained for photoresist (PR). This is attributed to electron charging on the mask surface in the plasma. The charged mask modifies the distribution and strength of the electric field depending on its thickness, thereby affecting the trajectory of positive ions accelerated toward the substrate by the bias voltage. Furthermore, Plasma diagnostics using optical emission spectroscopy (OES) and surface composition analysis using field emission Auger electron spectroscopy (FE-AES) revealed that changes in the mask material also alter the reaction pathways and formation characteristics of active species and silicon by-products in the plasma. These results suggest that the mask material influences the overall plasma characteristics, including electron density and ion energy, and plays a critical role in the precise control of silicon etching profiles for high-performance optical device fabrication.

The quench behavior of wires for superconducting fault current limiters at DC faults was simulated, with a focus on the effect of capacitor discharge on the quench. The behavior was also expressed in mathematical forms to facilitate a better understanding of the simulation results and for rough analytical estimations of the wire length suitable for the circuit voltage and capacitance. The quench resistance development behavior for various wire lengths and circuit capacitances was simulated using the model developed in the previous work. The quench behavior was expressed in mathematical forms, reflecting the concept of heat balance. During the quench, the wire temperature increased more slowly for longer wires, but was found to increase in a similar pattern. The wire length estimated by the mathematical formula was close to the one obtained by the simulation, with an error range of a few %. The calculations will be used to estimate effectively the length of wires needed to build superconducting fault current limiters for applications in DC power systems.

Cellulose nanofiber (CNF) has attracted significant attention as a next-generation insulating material due to its ecofriendly nature and outstanding functionalities. However, conventional kraft insulation paper suffers from limited dielectric breakdown strength and long-term reliability under high-voltage conditions, highlighting the need for alternative materials. In this study, kraft pulp was combined with five types of CNFs (A, B, C: wood-based / D, E: non-wood-based) to fabricate composite insulation papers, and their electrical and mechanical properties were systematically evaluated. The results showed that CNF incorporation generally enhanced density and tensile strength, while certain types contributed to lowering dielectric constant and improving breakdown strength. Among the wood-based CNFs, type C exhibited the most balanced performance in terms of dielectric stability and mechanical reinforcement. Among the non-wood-based CNFs, type E demonstrated notable improvements in structural compactness and tensile strength, suggesting favorable reliability. Therefore, this study identifies CNF C among wood-based types and CNF E among non-wood-based types as the most promising candidates for insulation performance enhancement, suggesting their applicability as next-generation insulating materials for power equipment and ecofriendly electronic devices.

Organic photovoltaics (OPVs) are attractive candidates for sustainable energy conversion due to their flexibility, lowcost processing, and compatibility with large-area fabrication. However, their efficiency is hindered by interfacial defects and vertical phase separation in the active layer, which induce charge imbalance and recombination losses. This work presents an interfacial engineering approach to overcome these limitations in P3HT:PC₇₀BM-based OPVs. Two key strategies were employed: (i) reducing the post-deposition annealing time of the active layer to suppress PC₇₀BM accumulation at the bottom electrode, and (ii) using a DCB:DCM mixed solvent system to regulate solvent evaporation, thereby promoting uniform film formation during PC₇₀BM overlay deposition. Devices fabricated with these optimizations exhibited notable enhancements, achieving short-circuit current density up to 15.83 mA/cm² and a 58.1% increase in power conversion efficiency compared to control devices. X-ray photoelectron spectroscopy confirmed reduced surface aggregation of PC₇₀BM, while X-ray diffraction indicated improved P3HT crystallinity and molecular ordering. These results highlight the critical role of interfacial and morphological control in enhancing charge separation and transport, offering a practical route toward efficient, reproducible, and stable OPVs.

Humidity monitoring of exhaled breath has emerged as a vital approach for noninvasive respiratory health assessment, underscoring the need for sensitive and reliable humidity sensors. Despite its high conductivity and hydrophilic functional groups, reduced graphene oxide (rGO) often undergoes irreversible moisture adsorption and gradual oxidation by residual water, resulting in sensitivity degradation and long-term instability during cycling. In this study, a montmorillonite/reduced graphene oxide (MMT/rGO) composite is developed as a room-temperature humidity-sensing material, exhibiting an optimized response of 115%, more than 14 times higher than that of pristine rGO. This superior performance originates from the synergistic interaction between the reversible MMT swelling and the conductive rGO network near the electrical percolation transition, which ensures excellent stability and repeatability under repeated humidity cycles. These findings suggest that the MMT/rGO composite provides a cost-effective and biocompatible platform for next-generation wearable humidity sensors capable of continuous respiratory monitoring.

The growing demand for thinner, lighter, and more energy-efficient electronic systems has driven the development of acoustic technologies toward compact and flexible sound generation platforms. Despite significant progress, conventional electromagnetic speakers remain limited by bulky structures, energy losses, and poor compatibility with modern ultrathin devices. In this review, recent advancements in piezoelectric acoustic systems are presented, demonstrating a new generation of speakers capable of producing high-fidelity sound from ultra-slim, lightweight, and mechanically compliant designs. Through refined structural configurations and efficient electromechanical coupling, these piezoelectric exciters achieve strong acoustic output, fast response, and wide frequency operation while drastically reducing component thickness. These exciters also show their suitability for seamless integration into flexible displays, wearable devices, and automotive panels, offering enhanced spatial audio practicality and multifunctional operation, including demonstrative output and sensing. This advancement marks a step toward the convergence of acoustic, haptic, and interactive technologies, for the realization of sustainable and immersive humanmachine interfaces in future electronic and automotive systems.

To ensure high-voltage stability and thermal resistance of insulation paper used in transformers, this study evaluated the structural and electrical properties of four types of insulation paper samples fabricated using unbleached kraft pulp (UKP). The samples were prepared under controlled conditions with different freeness levels (300-700 ml). Tensile strength, dielectric constant, breakdown strength (dry and oil), volume resistivity, water absorption, and oil absorption were quantitatively measured. The sample with a beating degree of 300 exhibited the highest breakdown strength (53.85 kV/mm) and volume resistivity (1.49×10¹⁶ Ω·cm), whereas the samples with higher beating intensity showed improved fiber bonding and densification. These findings demonstrate the practical applicability of UKP-based insulation paper as a high-performance, eco-friendly insulating material for transformer systems, providing a scientific foundation for process optimization in insulation paper design.

AlGaN/GaN High Electron Mobility Transistors (HEMTs) are emerging as next-generation semiconductors optimized for high-power and high-frequency applications, with their performance highly dependent on the surface and interface quality of the AlGaN/GaN structure. In particular, the 2-Dimensional Electron Gas (2DEG) formed in the AlGaN layer is susceptible to trapping by surface defects, which degrades electrical characteristics and makes the device vulnerable to degradation. In this study, we propose an approach to enhance device reliability and performance by forming a gallium oxynitride (GaON) interfacial layer through O₂ plasma treatment on the AlGaN surface. This method effectively suppresses interface defects, resulting in improved electrical properties such as reduced interface trap density (Dit), threshold voltage (Vth) shift, increased drain current density (Id), and enhanced transconductance density (gm). Furthermore, this surface treatment demonstrates the potential for process simplification by improving the electrical characteristics of power semiconductor devices without the need for complex deposition steps.

(La_1-xBi_xSr_0.3)FeO₃ ceramics exhibiting excellent magnetoresistance were synthesized via the conventional solid-state reaction method. The structural and electrical properties were investigated as a function of Bi³⁺ content to evaluate their potential application as temperature sensors. And the sintering temperature and time were 1,200℃ and 4 h, respectively. The structural and electrical properties were investigated as a function of Bi content. With increasing Bi substitution, a slight enhancement in both average grain size and relative sintered density was observed. In particular, the specimen with x = 0.3 exhibited an average grain size of approximately 0.82 μm. All samples demonstrated negative temperature coefficient of resistance (NTCR) behavior, and the electrical resistivity decreased with increasing Bi content. The resistivity of the (La_0.4Bi_0.3Sr_0.3)FeO₃ composition was 4.68 mΩ-cm at 25°C. Additionally, the temperature coefficient of resistance (TCR) and the B_25/75-value, which quantify the sensitivity of resistivity to temperature variations, were found to increase with Bi content. (La_0.4Bi_0.3Sr_0.3)FeO₃ sample exhibited a TCR of 0.43%/°C and a B_25/75-value of 1,096 K at room temperature. The electrical conduction mechanism of the (La_1-xBi_xSr_0.3)FeO₃ system was well described by the small polaron hopping model, wherein thermally activated charge carriers hop between localized Fe-O-Fe sites via electron-phonon interactions.

Perovskite light-emitting diodes (PELEDs) are emerging as promising candidates for next-generation displays, thanks to their narrow full width at half maximum and low-cost solution processing capabilities. Blue PeLEDs are essential for achieving a full-color gamut; however, efficiency and stability challenges limit their practical use. A primary bottleneck arises from interfacial issues between the perovskite emissive and charge transport layers. This review summarizes the key interfacial challenges hindering the performance of blue PeLEDs and highlights recent advances in interfacial engineering strategies. By focusing on interfacial engineering between the hole-transport layer and perovskite, this review compares different strategies and outlines future directions for developing high-performance blue light-emitting devices.