The direct utilization of steelmaking by-product gases in solid oxide fuel cells (SOFCs) offers a promising pathway to improve energy efficiency and reduce carbon emissions in the steel industry. In this study, a Sr-deficient and Ni-doped double perovskite oxide, Sr_1.95Fe_1.35Ni_0.15Mo_0.5O_6-δ (SFNM), was investigated as an anode material for direct Linz-Donawitz converter gas (LDG)-fueled SOFCs. A single-phase double perovskite structure was successfully obtained after calcination at 1,200°C for 12 h, while exsolved metallic Ni nanoparticles were generated on the SFNM surface after reduction at 800°C. Electrochemical performance was evaluated using H₂, simulated-LDG, and CO/CO₂ (85:15) fuels at 800°C. The maximum power densities achieved were 1.23, 0.70, and 0.40 W cm^-2 for H₂, simulated-LDG, and CO/CO₂ fuels, respectively. Although CO-containing fuels exhibited lower opencircuit voltages and power outputs than H₂, the SFNM anode maintained stable operation and appreciable performance under direct simulated-LDG utilization. Impedance analysis revealed that the increased polarization resistance in simulated-LDG and CO/CO₂ atmospheres was mainly associated with fuel adsorption/desorption and gas diffusion, while interfacial charge-transfer resistance remained relatively small. The superior performance obtained with simulated-LDG compared to the CO/CO₂ mixture was attributed to the presence of a small amount of H₂, which facilitated anode reaction kinetics. These results demonstrate that SFNM is a promising mixed ionic-electronic conductor anode for the direct electrochemical conversion of CO-rich steelmaking by-product gases into electricity.

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.

Metal halide perovskite materials have emerged as promising candidates for next-generation optoelectronic applications owing to their outstanding optical properties and tunable emission characteristics. However, their practical application is hindered by poor environmental stability, especially under conditions of heat, moisture, and UV exposure, necessitating effective encapsulation strategies. This review summarizes recent progress in enhancing the environmental stability of perovskite nanocrystals through polymer matrix embedding, inorganic oxide encapsulation, and compositionally matched core-shell structures using homogenous perovskite derivatives. We discuss how polymers enhance the environmental and moisture stability of perovskite nanocrystals, how oxide-based shells (e.g., SiO₂, TiO₂) contribute to thermal robustness and barrier protection, and how homostructural core-shells provide lattice-matched defect passivation with improved long-term durability. A comprehensive understanding of the advantages and limitations of each encapsulation strategy, along with their rational integration, can accelerate the commercialization of perovskite-based technologies in various applications such as highcolor- purity displays, color conversion filters, and flexible optoelectronic devices.

Perovskite, which follows the chemical formula ABX3 and exhibits an octahedral structure, is primarily a hybrid of organic and inorganic materials. It can be broadly categorized into three types based on dimensionality: 0D nanocrystals, quasi- 2D, and 3D bulk structures. As a result, it is gaining attention as a next-generation optoelectronic material for applications in light-emitting devices, solar cells, and sensors. This paper provides insights into dimension of perovskites, their respective synthesis methods, and current research trends, thereby offering prospects for advancements in the study of next-generation optoelectronic materials.

This review examines the use of halide perovskite materials in electronic devices, highlighting their exceptional optoelectronic properties and the challenges associated with them. Despite their potential for high-performance devices, practical applications are limited by sensitivity to environmental factors such as moisture and oxygen, etc. We discuss advances in enhancing stability and operational reliability, featuring innovative synthesis methods and device engineering strategies that help mitigate degradation. Furthermore, we explore the integration of perovskites in applications such as field-effect transistors and LEDs, emphasizing their transformative potential. This review also outlines future research directions, stressing the need for ongoing improvements in material stability and device integration to fully realize the commercial potential of perovskites.

In line with the development of electronic devices and technologies, the demand for improving ferroelectric materials’ performance is increasing. Since K_0.5Na_0.5NbO₃ (KNN), an eco-friendly ferroelectric material that does not use lead and has a high Curie temperature, it is attracting attention to its usability as a high-temperature dielectric, and various studies are being conducted to increase performance. In a KNN having a perovskite structure, there was a simulation result that the KNN has higher spontaneous polarization when the A-site in which sodium ions exist is replaced with lithium ions. If the simulation results can be proven experimentally, the application range of KNN-based ferroelectric materials will increase. To this end, we tried to manufacture a K_1-xLi_xNbO₃ (KLN) with high electrical characteristics by fabricating niobium-deficient and potassium-excessive compositions, which attempt was made to solve the stoichiometry problem by volatilization and suppress secondary phases. If KLN’s secondary phase suppression and relative permittivity improvement are successful, it will contribute to meeting the demand for developing electronic devices.

Intrinsically stretchable light-emitting diodes, composed of stretchable electrodes, charge transport layers, and luminescent materials, have garnered significant interest for enhancing human well-being and advancing the field of deformable electronics. Various luminescent materials, such as perovskites and organics, have been integrated with stretchable elastomers to function as the stretchable emissive layers in these intrinsically stretchable LEDs. Stretchable conductors including Ag nanowire based percolating structures and conducting polymers have been utilized as stretchable transparent electrode. Despite this progress, their performances in terms of efficiency and stability remain challenging compared to their structurally stretchable and rigid LED counterparts. This review offers a comprehensive overview of recent advancements in intrinsically stretchable LEDs, focusing on material innovations.

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.

Color conversion layer refers to a layer that converts the blue light emitted from the backlight into the red and green light. Heavy metal-free quantum dots and perovskite nanocrystals have attracted great attention as base materials for color conversion layers due to their outstanding optical characteristics. Here, we review recent advances in the development of color conversion layers based on quantum dots. First, we overview the representative optical characteristics of quantum dots and perovskite nanocrystals, and then introduce printing techniques for color converting layers including photolithography, inkjet printing, and nanoimprinting. Finally, we conclude this review with a brief perspective.

For the last decades, a research hotspot for the halide perovskites (HPs) is now showing great progress in terms of improving efficiency for numerous photovoltaic devices (PVDs). However, it still faces challenges in the case of long-term stability in the air atmosphere. Defect-free high-quality HP single crystals show their promising properties for the remarkable development of highly efficient and stable PVDs. Here, we summarize the growth processing routes for the stable HP single crystals as well as briefly discuss the pros and cons of those well-established synthesis routes. Furthermore, we briefly include the comparison note between the HP single crystals and polycrystalline perovskite films regarding their device applications. Based on the future progress, the review concludes subjective perspectives and current challenges for the development of HPs high-quality PVDs.

Field-effect transistors (FETs) are the key elements of conventional electronics; hence, have drawn a lot of research and commercial interests. In recent years, metal halide perovskite materials have achieved a remarkable efficiency of 29.15% in the field of photovoltaics, and have drawn the scientific community’s attention to promote their use in the field of optoelectronics, such as FETs and phototransistors. The MAPbI₃ (methylammonium lead iodide) perovskite TFT has achieved a record hole mobility of 21.41 ㎠/V-s in the year 2020. In this review, we will briefly discuss the physical structure of MAPbI₃ perovskite and the essential factors that stimulate these devices, together with the role of defects, the ion migration concept, and the implication of both dielectric and electrode materials on the device’s performance.

Inorganic-organic hybrid perovskite solar cells have demonstrated considerable improvements, reaching 25.5% of certified power conversion efficiency in 2020 from 3.8% in 2009. In normal structured perovskite solar cells, TiO₂ electrontransporting materials require heat treatment process at a high temperature over 450℃ to induce crystallinity. Inverted perovskite solar cells have also been studied to exclude the additional thermal process by using [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as a non-oxide electron-transporting layer. However, the drawback of the PCBM layer is a charge accumulation at the interface between PCBM and a metal electrode. The impact of bathocuproin (BCP) buffer layer on photovoltaic performance has been investigated herein to solve the problem of PCBM. 2-mM BCP-modified perovskite solar cells were observed to exhibit a maximum efficiency of 12.03% compared with BCP-free counterparts (5.82%) due to the suppression of the charge accumulation at the PCBM-Au interface and the resulting reduction of the charge recombination between perovskite and the PCBM layer.

Methylammonium lead iodide (MAPbI₃) thin films were grown at low temperatures on glass substrates via 3-zone chemical vapor deposition. Lead iodide (PbI₂) and lead bis (dipivaloylmethanate) [Pb(dpm)₂] precursors were used as lead sources. Due to the high sublimation temperature (~400℃) of the PbI₂ precursor, a low substrate temperature could not be constantly maintained. Therefore, MAPbI₃ thin films degraded into the PbI₂ phase. In contrast, for the Pb(dpm)₂ precursor, a substrate temperature of ~120℃ was maintained because the sublimation temperature of Pb(dpm)₂ is as low as 130℃ at a high vapor pressure. As a result, high-quality MAPbI3 thin films were successfully grown on glass substrates using Pb(dpm)₂. The rms (root-mean-square) roughness of MAPbI3 thin films formed from Pb(dpm)₂ was as low as ~19.2 nm, while it was ~22.7 nm for those formed using PbI₂. The grain size of the films formed from Pb(dpm)₂ was as large as approximately 350 nm.

Inorganic-organic hybrid perovskite solar cells have demonstrated a significant achievement by reaching a certified power conversion efficiency of 25.2% in 2019 as compared to that of 3.8% in 2009. However, organic hole conductors such as PTAA and spiro-OMeTAD are known to be expensive and unstable when they are exposed to operational conditions. In this study, the inorganic hole conductor CuSCN was used to overcome such concerns. The influence of dipropyl sulfide (DPS) and diethyl sulfide (DES) as CuSCN deposition solvents on the underlying perovskite active layer was investigated. DES solvent was observed to be advantageous in terms of CuSCN solubility and mild for the perovskite layer, thereby resulting in a power conversion efficiency of 16.9%.

Nanomaterials have considerable potential to solve several key challenges in various electrochemical devices, such as fuel cells. However, the use of nanoparticles in high-temperature devices like solid-oxide fuel cells (SOFCs) is considered problematic because the nanostructured surface typically prepared by deposition techniques may easily coarsen and thus deactivate, especially when used in high-temperature redox conditions. Herein we report the synthesis of a self-regenerated Pd metal nanoparticle on the perovskite oxide anode surface for SOFCs that exhibit self-recovery from their degradation in redox cycle and CH₄ fuel running. Using Pd-doped perovskite, La(Sr)Fe(Mn, Pd)O₃, as an anode, fairly high maximum power densities of 0.5 and 0.2 cm^-2 were achieved at 1,073 K in H₂ and CH₄ respectively, despite using thick electrolyte support-type cell. Long-term stability was also examined in CH₄ and the redox cycle, when the anode is exposed to air. The cell with Pd-doped perovskite anode had high tolerance against re-oxidation and recovered the behavior of anodic performance from catalytic degradation. This recovery of power density can be explained by the surface segregation of Pd nanoparticles, which are self-recovered via re-oxidation and reduction. In addition, self-recovery of the anode by oxidation treatment was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

The phase evolution, microstructure, and microwave dielectric properties of Ba(Mg_0.5-2xY_2xW_0.5-xTi_x)O₃ (x＝ 0.005~0.05) ceramics sintered at 1,700℃ for 1h were investigated. All compositions exhibited a 1:1 ordered cubic perovskite structure. The field emission scanning electron microscopy image revealed a dense microstructure in all the compositions. As the value of x increased, the lattice parameter, dielectric constant, and quality factor increased. The temperature coefficient of resonant frequency changed from -19.6 ppm/℃ to -5.9 ppm/℃ with increasing x value. The dielectric constant, quality factor, and temperature coefficient of resonant frequency of Ba(Mg_0.40Y_0.10W_0.45Ti_0.05)O₃ were 21.7, 132,685 GHz, and -5.9 ppm/℃, respectively.

Perovskite solar cells have received increasing attention in recent years because of their outstanding power conversion efficiency (exceeding 22%). However, they typically contain toxic Pb, which is a limiting factor for industrialization. We focused on preparing Pb-free perovskite films of Ag-Bi-I trivalent compounds. Perovskite thin films with improved optical properties were obtained by applying an anti-solvent (toluene) washing technique during the spin coating of perovskites. In addition, the surface condition of the perovskite film was optimized using a multi-step thermal annealing treatment. Using the optimized process parameters, AgBi₂I₇ perovskite films with good absorption and improved planar surface topography (root mean square roughness decreased from 80 to 26 nm) were obtained. This study is expected to open up new possibilities for the development of high performance AgBi₂I₇ perovskite solar cells for applications in Pb-free energy conversion devices.

In a Pb-included piezoelectric composition, Sr_yPb_1-y[(Zn_1/3Nb_2/3)_x-(Ni_1/3Nb_2/3)_0.2-(Zr_0.46Ti_0.54)_0.8-x]O₃ was selected in order to attain high piezoelectric properties. According to the PZN ratio (x) and the amount of Sr doping (y), the crystal structure, microstructure and piezoelectric properties were measured and evaluated. In the case of Sr 4 mol% doping, the piezoelectric properties were the highest for a PZN ratio of 0.1. In this condition, the grain size was larger and the intensity was higher. With the PZN ratio fixed and varying the Sr doping, the piezoelectric properties increased until 10 mol% doping and then decreased for over 12 mol% doping. In the case of x＝0.1 and y＝10 mol%, the best piezoelectric properties were obtained, i.e., d₃₃＝660 pC/N and k_p＝68.5%, and these values seem to be related to the grain size and crystal structure.

Pb(Zr, Ti)O₃ (PZT) is a piezoelectric material applied in a typical actuator and has been actively studied. However, in order to overcome the limitations of PZT, piezoelectric ceramics comprising mixed solid solutions of PZT with various relaxer electric materials have been studied. The Pb(Zn_1/3Nb_2/3)-Pb(Ni_1/3Nb_2/3)-Pb(Zr, Ti)O₃ (PZN-PNN-PZT) piezoelectric ceramic, known to have high piezoelectric constant and electromechanical coupling coefficient, was studied herein. The piezoelectric characteristics with various Zr contents (Zr/Ti ratios), PZN molar ratios, and sintering temperatures were compared. The piezoelectric properties of d₃₃＝580 pC/N and kP＝0.68 were obtained with the 0.1PZN-0.2PNN-0.7PbZr_0.46Ti_0.54O₃ composition sintered at 1,290℃.

Recently perovskite materials with much cheaper cost and marvellous optoelectronic properties have been studied for next generation LED display devices overseas. Technology development trends of inorganic CsPbX₃(X=halogen) based LEDs (PeLEDs) with assumed high stability were investigated on literature worldwide. It was found that syntheses methods of these nanocrystals (NCs, mainly quantum dots, QDs) made great progress. A new room temperature synthesis method showed outstanding PL (photoluminescence) properties such as high quantum yield (QY), narrow emission width, storage stability comparable with, or often exceeding those of conventional hot injection method and CdSe@ZnS type inorganic colloidal QDs. PeLEDs with shell layers might be more promising, indicating urgent real research start of this solution processing technology for small businesses in Korea.

We investigated the effect of Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) modification on the ferroelectric and electric-field-induced strain (EFIS) properties of lead-free 0.97Bi1/2(Na0.82K0.18)1/2TiO3-0.03LaFeO3 (BNKTLF) ceramics as a function of BNKT content (x= 0, 0.1, 0.2, 0.3, 0.5, and 1). BNKT-modified BNKTLF powders were synthesized using a conventional solid-state reaction method. As the BNKT content x increased from 0 to 1 the normalized electric-field-induced strain (S_{max}/E_{max}) was observed to increase at relatively low fields, i.e., below the poling field. Moreover, BNKTLF-30BNKT showed about 460 pm/V as low as at 3 kV/mm, which is a considerably high value among the lead-free systems reported so far. Consequently, it was confirmed that ceramic-ceramic composite, a mixture of an ergodic relaxor matrix and embedded ferroelectric seeds, is a salient way to make lead-free piezoelectrics practical with enhanced EFIS at low field as well as less hysterical.

The perovskite solid solutions of the Sr1-xMgxFe3+ 1-τFe4+ τO3-y system (x=0.0, 0.1, 0.2, and 0.3) were synthesized in N2 at 1,150℃. X-ray powder diffraction study assured that all the four samples had cubic symmetries(SM-0: 3.865 Å, SM-1: 3.849 Å, SM-2: 3.833 Å, and SM-3: 3.820 Å) and that the lattice volumes decreased steadily from 57.7 Å3 to 55.7 Å3 with x values. The nonstoichiometric chemical formulas were determined by Mohr salt analysis and with the increase of x values the amounts of Fe4+ ion and oxygen were decreased simultaneously. Thermal analysis showed that SM-0 started to lose its oxygen at 450℃ and SM-1, Sm-2, and SM-3 began to lose their oxygen at around 350～400℃. SM-0 showed almost reversible weight change in the cooling process. All the samples exhibited semiconducting behaviors in the temperature range of 10~400℃. Conductivities of the 4 samples were decreased in the order of SM-0, SM-1, SM-2, and SM-3 at constant temperature. The activation energies of the conductions were in the range of 0.176 eV～0.244 eV.

A marvellous solar cell technology system based on organometal halide perovskites has recently shown an unprecedented progress in power conversion efficiency (PCE); the certified one of 17.9% and unconfirmed of 19.3%, as well as the estimated electricity with a generating cost lower than the half of conventional methods based on fossil fuels. In this report the present status of stability with regards to moisture, ambient temperature, ultraviolet and lead toxicity as well as the key technological developments for the early commercialization are covered. Comprehensive understanding of material science for perovskitesis required, together with complete encapsulation technologies beyond those for OLEDs, in order to ensure a20-year-longer-than lifetime of PSCs (perovskite solar cells) and the stability according to the IEC 61646damp heat test standard, which will result in the replacement of silicon solar cells with PSCs.

We investigated the effect of excess CuO on the sintering behavior, ferroelectric, andpiezoelectric properties of lead-free Bi0.5(Na0.82K0.18)0.5TiO3 (BNKT) ceramics. The addition of excess CuOwas found to greatly contribute to the densification and grain growth, however, excess CuO over 3 mol%was precipitated at grain boundaries after sintering. BNKT with 1∼2 mol% CuO in excess sintered at975℃ showed piezoelectric properties comparable to those of unmodified BNKT sintered at 1,175℃. These results seem meaningful for its application to low cost multilayer actuators (MLAs) becauselow firing ceramics make it possible to apply less expensive base metals to the inner electrode ofMLAs.

In this study, lead-free Piezoelectric (Na0.47K0.47Sr0.03Ca0.03)(Nb0.94Ti0.06)O3-0.1 MnO2 ceramics werefabricated using mixed oxide method and the effects of various sintering temperature on the structural andelectrical properties were investigated. For the (Na0.47K0.47Sr0.03Ca0.03)(Nb0.94Ti0.06)O3-0.1 MnO2 (NKN-SCT-MnO2)ceramics sintered at temperatures of 1,025∼1,100℃. The results indicated that all specimens were perovskitesingle phase formation without any second phase. It has been shown that relative density is increased toincreasing sintering temperature. When the sintered temperature at 1,075℃, highest sintered density andmaximum value of 4.45 g/cm3. Average grain size is increased to increasing sintering temperature. Theelectromechanical coupling factor, dielectric constant, dielectric loss, d33 and curie temperature at the sinteringtemperature 1,075℃ of NKN-SCT-MnO2 specimens were 0.22, 511, 0.033, 103 and 380℃, respectively.

In the (La0.8Ca0.2)(Cr0.9Co0.1)O3 (LCCC), which has been using as interconnector materials in SOFC, Al ions were substituted for Co because ionic radius of Al is similar to that of Co. Because of the almost identical ionic radius of Al and Co, the substitution was not thought to be affect the tolerance factor of LCCC, and the densification behavior, high temperature electrical conductivity and thermal expansion coefficient were examined as a function of Al concentration. In the cases of the x= 0 and x= 0.02 in (La0.8Ca0.2)(Cr0.9Co0.1-xAlx)O3 (x= 0∼0.1), the samples showed the relative densities above ≥95% when those were sintered at ≥1,350℃. In the case of the x≥0.06 the sintered density deteriorated greatly at lower sintering temperatures. High temperature electrical conductivity of the samples decreased as the content of Al increased. Since the valence state of Al ion is unchangeable, while Cr or Co ions contribute to the electrical conduction by changing those valence states, Al substitution resulted in the decreased electrical conductivity. Al doping of LCCC was an effective way of decreasing the thermal expansion coefficient (TEC).