Owing to carbon materials’ diverse functionalization and versatility, the design and synthesis of carbon-based three-dimensional porous structures have become important foundational research topics across various fields. Among the various methods for producing porous carbon structures, laser-induced graphene (LIG) has garnered attention because of its large surface area, controllable structure, excellent electrical conductivity, scalability, and eco-friendly synthesis process. In addition, recent research results have reported more novel functionalities by advancing further from the unique characteristics of LIG through functionalization or compounding of LIG, making it an attractive material for various applications in electronic devices, sensing, catalysis, and energy storage. This review aims to update the research trends in LIG and its functionalization, providing insights to inspire more interesting studies on functional LIG to expand its potential applications ultimately. Starting with the synthesis method and material characteristics of LIG, we introduce the functionalization of LIG, which is classified into surface modification, heteroatom doping, and hybridization based on the interaction mechanism. Finally, we summarize and discuss the prospects of LIG and its functionalization.

Piezoelectric actuators, which utilize piezoelectric crystals or ceramics, are commonly used in precision positioning applications, offering high-speed response and precise control. However, the use of low-performance ceramics and expensive single crystals is limiting their versatile use in the actuator market, necessitating the development of both high-performance and cost-effective piezoelectric materials capable of delivering higher forces and displacements. The use of textured Pb (lead)-based piezoelectric ceramics formed by so-called templated grain growth method has been identified as a promising strategy to address the performance and cost issue. This review article provides insights into recent advances in texturing Pb-based piezoelectric ceramics for improved performance in actuation applications. We discussed the relevant issues in detail focusing on current challenges and emerging trends in the textured piezoelectric ceramics for their reliability and performance in actuator applications. We discussed in detail focusing on current challenges and emerging trends of textured piezoelectric ceramics for their reliability and performance in actuator applications. In conclusion, the article provides an outlook on the future direction of textured piezoelectric ceramics in actuator applications, highlighting the potential for further success in this field.

As a potential alternative to flash memory, HfO₂/Al₂O₃ stacks appear to be a viable option as charge capture layers in charge trapping memories. The paper undertakes a review of HfO₂/Al₂O₃ stacks as charge trapping layers, with a focus on comparing the number, thickness, and post-deposition heat treatment and γ-ray and white x-ray treatment of such stacks. Compared to a single HfO₂ layer, the memory window of the 5-layered stack increased by 152.4% after O₂ annealing at ±12 V. The memory window enlarged with the increase in number of layers in the stack and the increase in the Al/Hf content in the stack. Furthermore, our comparison of the treatment of HfO₂/Al₂O₃ stacks with varying annealing temperatures revealed that an increased annealing temperature resulted in a wider storage window. The samples treated with O₂ and subjected to various γ radiation intensities displayed superior resistance. and the memory window increased to 12.6 V at ±16 V for 100 kGy radiation intensity compared to the untreated samples. It has also been established that increasing doses of white x-rays induced a greater number of deep defects. The optimization of stacking layers along with post-deposition treatment condition can play significant role in extending the memory window.

p-type Tunnel Oxide Passivating Contacts (TOPCon) solar cell is fabricated with a poly-Si/SiO_x structure. It simultaneously achieves surface passivation and enhances the carriers’ selective collection, which is a promising technology for conventional solar cells. The quality of passivation is depended on the quality of the tunnel oxide layer at the interface with the c-Si wafer, which is affected by the bond of SiO formed during the subsequent annealing process. The highest cell efficiency reported to date for the laboratory scale has increased to 26.1%, fabricated by the Institute for Solar Energy Research. The cells used a p-type float zone silicon with an interdigitated back contact (IBC) structure that fabricates poly-Si and SiO_x layer achieves the highest implied open-circuit voltage (iV_oc) is 750 mV, and the highest level of edge passivation is 40%. This review presents an overview of p-type TOPCon technologies, including the ultra-thin silicon oxide layer (SiO_x) and poly-silicon layer (poly-Si), as well as the advancement of the SiO_x and poly-Si layers. Subsequently, the limitations of improving efficiency are discussed in detail. Consequently, it is expected to provide a basis for the simplification of industrial mass production.

The value of experimentally obtained data becomes highest when they are properly analyzed based on valid logics. Many physical and chemical properties such as electrical and magnetic properties, chemical reaction rates, etc. are known to be thermally activated; thus, a proper understanding of thermally-activated processes is of importance. However, there are still a number of papers published with falsely analyzed data. In this contribution, we would like to revisit the meaning of thermally-activated processes, and then reanalyze a data set published misinterpreted. By showing a step-by-step procedure for the reanalysis, we would like to help researchers who may come across such data in the future not to make mistakes in their analysis.

La_0.7-xCe_xSr_0.3MnO₃ specimens were fabricated by a solid state reaction method and structural and electrical properties with variation of Ce4+ contents were measured. All specimens exhibited a polycrystalline rhombohedral crystal structure, and the (110) peaks were shifted to low angle side with increasing the amount of Ce⁴⁺ contents. As Ce⁴⁺ ions with different ion radii and charges are substituted with La³⁺ ions, electrical properties are thought to be affected by changes in the double exchange interaction between Mn³⁺-Mn⁴⁺ ions due to distortion of the unit lattice, a decrease in oxygen vacancy concentration, and an increase in lattice defects. Resistivity gradually decrease as the amount of Ce⁴⁺ added increased, and negative temperature coefficient of resistance (NTCR) properties were shown in all specimens. In the La_0.5Ce_0.2Sr_0.3MnO₃ specimens, electrical resistivity, TCR and B-value were 31.8 Ω-cm, 0.55%/℃ and 605 K, respectively.

In order to spread LED lighting, LED lighting technology directly driven by alternating current (AC) commercial power has recently been introduced. Since current does not flow at a voltage lower than the threshold voltage of the LED, a nonconductive section occurs in the current waveform, and the higher the threshold voltage of the LED, the more discontinuous current waveforms are generated. In this paper, multi-LED modules are connected in series so that the threshold voltage can be adjusted according to the number of LED modules. A small number of LED modules are driven at a low instantaneous rectified voltage, and a large number of LED modules are driven at a high instantaneous rectified voltage to lengthen the overall lighting time of AC-LED lighting, thereby minimizing the luminance deviation of AC-LED lighting. In addition, the load current flowing through the LED module is adjusted to be the same as the design current even at the maximum rectified voltage higher than the design voltage, so that the light brightness of the LED module is kept constant. Therefore, even if the rectified voltage applied to the LED module changes, the AC-LED lighting in which the light brightness is constant and the luminance deviation is minimal has been realized.

In this paper, we analyzed the transformation of the power following by the angle of incidence of the solar, the angle of photovoltaic module and artificial solar changed from 30° to 90° and synchronously changed the distance from 0.1 m to 0.5 m. Setting the distance between the artificial solar and the luminometer from 0.1 m to 0.5 m and set the angles to 90°, 60°, 45°, and 30°, the angle was 90° and when the distance was 0.1 m, the maximum Illuminance was 19,580 lux, the light could be obtained more. If the angle of incidence between the Artificial solar and the photovoltaic module was 90° and the variable resistance was 1,000 Ω at a distance of 0.4 m, the maximum power reached 0.82 W. Provided that the angle of incidence between the artificial solar and the photovoltaic module was 90° and the distance was 0.2 m since the variable resistance had the maximum power of 500 Ω, the maximum power was 0.78 W. At 1,000 Ω, the maximum power is 0.80 W so the maximum power at the variable resistance 1,000 Ω could obtain higher power than the variable resistance 500 Ω. The variable resistance was 1,000 Ω and the angle of incidence between the Artificial solar and the photovoltaic module was 90° at a distance of 0.4 m, and the maximum power reached 0.82 W. The angle was 60° at 0.3 m and 0.4 m the maximum power reached 0.10 W. The angle was 45° at 0.2 m maximum power reached 0.020 W, the angle was 30° at 0.4 m, and the maximum power reached 0.004 W. In four results about maximum power depending on the angle of incidence between the artificial solar and the photovoltaic module, the luminous efficiency and maximum power can be got the best at an angle of 90°.

Recently, sterilization technology has received increasing interest due to the COVID-19 pandemic and required safety precautions. Particularly, sterilization devices using near ultraviolet (UV) with a 405 nm wavelength are also drawing attention. It has a UV-C wavelength and other sterilization effects. Its blue-colored light on the boundary between UV and visible light is used as a light-emitting diode (LED) lamp for 405 nm sterilization, owing to its longer wavelengths than UV rays. However, the 405 nm wavelength contains blue light that can damage the eyes and skin during prolonged exposures and affect the emotional and biological parts of the body. Currently, 405 nm sterilization LED light registers are circulating in the market. However, they have not undergone safety tests for blue-light hazards. Thus, with the active distribution of sterilization LED lights, solid safety standards and management systems are essential to protect users from blue-light hazards. Accordingly, in this study, we conducted spectral radiance and spectral radiative luminance tests on 405 nm sterilization LED registers available in the market by the measurement criteria of IEC 62471. Safety standards must be established to secure users' safety against blue light hazards at a time when 405nm sterilization LED lights are actively distributed due to COVID-19.

La_0.7Sr_0.3-xMg_xMnO₃ (LSMMO) (x=0.05~0.20) specimens are fabricated by a solid phase sintering method, and the sintering temperature and time are 1,300℃ and 2 hours, respectively. The dependence of the crystalline structure according to the amount of Mg²⁺ contents is not observed, and all specimens show a polycrystalline rhombohedral crystal structure, the X-ray diffraction (110) peaks move to the high angle side with increasing the amount of Mg²⁺ contents. LSMMO specimens exhibit a granule-shaped microstructure with an average grain size of 1 μm or less. Resistivity gradually decrease as the amount of Mg²⁺ contents increased. And in the La_0.7Sr_0.1Mg_0.2MnO₃ specimen, resistivity and B_25/65-value are 36.7 Ω-cm and 394 K at room temperature, respectively. LSMMO specimens show a variable-range hopping (VRH) electrical conduction mechanism, and the negative temperature of coefficient of resistance (NTCR) is approximately 0.37~0.38%/℃.

A breakdown voltage and breakdown electric field of the transformer insulating oil of liquid dielectric were studied in uniform electric field and non-uniform electric field and the transformer insulating oil was observed by the process reached breakdown. Insulation performance evaluation of the liquid dielectric was evaluated at the electrode spacing of 2.5 mm under the conditions of domestic and international standards (KS C IEC 60156), so a comparative review was conducted at the electrode spacing of 2.5 mm. When the electrode spacing is 2.5 mm, the average breakdown voltage is 38.5 kV for sphere-sphere electrodes, 26.6 kV for plate-plate electrodes, 22.9 kV for needle-needle electrodes, and 24.3 kV for sphere-needle electrodes. 23.7 kV for the sphere-plate electrode, and 20.7 kV for the needle-plate electrode. From these results, it can be seen that the average value of the breakdown voltage at the electrode spacing of 2.5 mm, in ascending order, is sphere-sphere, plate-plate, sphere-needle, sphere-plate, needle-needle and needle-plate. It was found that the breakdown voltage of the unequal field was lower than that of the equal field.

Perovskite materials are promising candidates for next-generation optoelectronic devices owing to their outstanding external quantum efficiency, high color purity, and ability to tune the light emission wavelength. However, conventional thermal annealing processes caused the degradation of perovskite, resulting in poor optoelectronic properties and a short lifetime. Herein, we propose a laser-induced recrystallization of perovskite thin film to enhance its light-emitting properties. Laser-induced recrystallization process was performed using rapid and instantaneous laser heating, which successfully induced grain growth of the perovskite material. The laser processing conditions were thoroughly optimized based on theoretical calculations and various material analyses such as x-ray diffraction, scanning electron microscope, and photoluminescence spectroscopy.

Triboelectric devices are attracting attention from researchers as self-powered electronic systems that can instantly convert mechanical input into electrical energy output. To improve triboelectric energy harvesting performance, increasing the number of contacts as well as the contact area has been carried out by numerous researchers. In this study, we design a shaker-type energy harvester which is called as maracas triboelectric generator (M-TEG), inspired by the structure of maracas, one of the musical percussion instruments. A tripod frame is inserted to the inside of a cylindrical case, which is a device with the electrodes of aluminum and copper. Then, the triboelectric energy harvesting characteristics between polypropylene (PP) balls and the electrodes are measured. The M-TEG with the frame generates the energy harvesting signals up to ~100 V and ~2.5 μA due to larger contact area and numbers, which enhances the voltage and current output by 250% and 610% compared to that without the frame, respectively. This study presents the feasibility of self-powered sensors and toys using improved triboelectric energy performance with a low-cost and simple manufacturing process in the interesting structure.

In this paper, we discussed the effect of field plate dielectric materials such as silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), and hafnium oxide (HfO₂) on the breakdown characteristics of β-Ga₂O₃ Schottky barrier diodes (SBDs). The breakdown voltage (BV) of the SBDs with a field plate was higher than that of SBDs without a field plate. The higher dielectric constant of HfO₂ contributed to the superior reduction in electric field concentration at the Schottky junction edge from 5.4 to 2.4 MV/cm. The SBDs with HfO₂ field plate showed the highest BV of 720 V, and constant specific on-resistance (R_on,sp) of 5.6 mΩ·㎠, resulting in the highest Baliga’s figure-of-merit (BFOM) of 92.0 MW/㎠. We also investigated the effect of dielectric thickness and field plate length on BV.