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Halide perovskites, fascinating memristive materials owing to mixed ionic-electronic conductivity, have been attracting great attention as artificial synapses recently. However, polycrystalline nature in thin film form and instability under ambient air hamper them to be implemented in demonstrating reliable neuromorphic devices. Here, we successfully fabricated vertically aligned 2D halide perovskite films (V-HPs) for active layers of artificial synapses, showing moisture stability for several months. Unlike random-oriented HPs, which exhibit negligible current hysteresis, the V-HPs possess multilevel analog memristive characteristics, programmable potentiation and depression with distinguished multi-states, long-short-term plasticity, paired-pulse facilitation, and even spike-timing-dependent plasticity. Furthermore, high classification accuracy is obtained with implementation in deep neural networks. These remarkable improvements are attributed to the vertically well-aligned lead iodide octahedra acting as the ion transport channel, confirmed by first-principles calculations. This study paves the way for understanding HPs nanophysics and demonstrating their potential utility in neuromorphic computing systems.

Waste energy harvesting can contribute to the increase of the efficiency of many industrial processes, which consume energy to produce valuable products. Among all the wasted energy, heat energy is the most abundant, existing in almost any situation. Thermoelectric devices have the capability to harvest and convert the thermal energy into electrical power via the Seebeck effect. With its simple operating principle, thermoelectric devices can be reliable even under the harshest environments, taking advantage of any type of heat source. As a result, various inorganic and organic materials are being explored as thermoelectric materials. Among the reported materials, carbon‐based materials are promising in terms of commericialization, due to their nontoxic and abundant nature, and solution processability. In particular, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), carbon nanotubes, and graphene are extensively studied as thermoelectric materials owing to their remarkable thermoelectric performance. Also, organic–inorganic hybrid halide perovskites show the potential to be used as future high‐performance thermoelectric materials. Here, the progess in carbon materials as thermoelectrics is reviewed in detail, focusing on four base materials (PEDOT:PSS, carbon nanotubes, graphene, and organic–inorganic hybrid halide perovskites). This review illuminates the potential of carbon‐based materials in the field of thermoelectrics and their application to next‐generation energy devices.

An atomic gradient passivation layer, (Ta,Mo)x(O,S)y, is designed to improve the charge transportation and photoelectrochemical activity of CuInS2-based photoelectrodes. We found that Mo spontaneously diffused to the a-TaOx layer during e-beam evaporation. This result indicates that the gradient profile of MoOx/TaOx is formed in the sublayer of (Ta,Mo)x(O,S)y. To understand the atomic-gradation effects of the (Ta,Mo)x(O,S)y passive layer, the composition and (photo)electrochemical properties have been characterized in detail. When this atomic gradient-passive layer is applied to CuInS2-based photocathodes, promising photocurrent and onset potential are seen without using Pt cocatalysts. This is one of the highest activities among reported CuInS2 photocathodes, which are not combined with noble metal cocatalysts. Excellent photoelectrochemical activity of the photoelectrode can be mainly achieved by (1) the electron transient time improved due to the conductive Mo-incorporated TaOx layer and (2) the boosted electrocatalytic activity by Mox(O,S)y formation.

Graphene quantum dots (GQDs) synthesized by single phase solution chemistry are embedded in metal halide perovskite (MHP) films because they can act as passivating defects that are present throughout the MHP film, not only at the interface but also throughout the bulk of the film. The perovskite photodetectors composed of indium-doped tin oxide/SnO2/MHP with embedded GQDs/poly triarylamine/Au have the reduced dark current, increased detectivity, and fasted response speed due to lower trap density throughout the bulk MHP layer.

Morphology and crystal grain size of inorganic CsPbBr3 metal halide perovskite (MHP) films are controllable through a diffusion-controlled anti-solvent dripping crystallization method using an anti-solvent mixture of toluene (Tol):isopropanol (IPA). The 8:2 (v:v) Tol:IPA anti-solvent enables the production of a pinhole-free CsPbBr3 MHP film with the smallest crystal grain size and the brightest photoluminescence (PL). Accordingly, the 8:2 CsPbBr3 MHP film reveals a very uniform and strong PL mapping image. As a result, the 8:2 CsPbBr3 MHP light emitting diode (LED) exhibits ∼12.8, ∼7.4, and ∼7.9 fold enhanced maximum electroluminescence (ELmax), current efficiency (CEmax), and external quantum efficiency (EQEmax) compared to the 10:0 pristine device. The optimized 8:2 MHP LED shows an ELmax of 22,298 cd/m2, CEmax of 36.65 cd/A and EQEmax of 9.64%, respectively. In addition, the 8:2 CsPbBr3 MHP LED with controlled morphology and grain size has better operating stability than the pristine device.

Enhancement in weak-light detection and other photodetection properties was observed for organic-inorganic halide perovskite photodetectors as a result of benzylammonium iodide (BzAI) treatment at the methylammonium lead triiodide (MAPbI3) and hole-transport layer (HTL) interface. After treatment, growth of the two-dimensional Ruddlesden-Popper perovskite phase was observed at the MAPbI3 surface, which shifted the overall surface work function upwards and thus effectively facilitated charge transfer across the MAPbI3/HTL interface. As a result, the fully fabricated device with 10 mg/mL (BzAI/isopropanol) treatment exhibited shorter rise time (trise) and decay time (tdecay) of 53 and 38 μs, respectively, compared to trise and tdecay of 214 and 120 μs, respectively, for the pristine MAPbI3 sample. In addition, the BzAI-treated device exhibited larger linearity compared to the pristine MAPbI3 sample, demonstrating a high and stable specific detectivity of 1.49 × 1013 to 2.14 × 1013 Jones under incident light intensity of 10-3 to 100 mW/cm2, respectively.

Developing intrinsically self-healable semiconducting polymers is particularly important for realizing stretchable electronic devices which can spontaneously recover their mechanical damage. We synthesized a series of conjugated donor polymers (PTO2-tm series) functionalized with a thymine group at the terminal of the side chain. Bulk heterojunction (BHJ) films of PTO2-tm polymers blended with an IT-4F acceptor achieved power conversion efficiencies up to 11.9% from the BHJ-based organic photovoltaics, which are comparable with that of unfunctionalized PTO2 and, however, exhibited much improved stretchability by virtue of stress dissipation in the BHJ films during mechanical deformation. More importantly, the corresponding BHJ film prepared with a melamine additive efficiently recovered their packing structures after being mechanically damaged by stretching. As a result, reversible multiple hydrogen bonding of the melamine molecule with thymine in PTO2-tm polymers showed much improved crack onset strain and maximum recoverable strain compared with PTO2.

Highlights MoP nanorod-array catalysts were directly synthesized on graphene passivated silicon photocathodes without secondary phase. Mo-O-C covalent bondings and energy band bending at heterointerfaces facilitate the electron transfer to the reaction sites. Numerous catalytic sites and drastically enhanced anti-reflectance of MoP nanorods contribute to the high solar energy conversion efficiency. Abstract Transition metal phosphides (TMPs) and transition metal dichalcogenides (TMDs) have been widely investigated as photoelectrochemical (PEC) catalysts for hydrogen evolution reaction (HER). Using high-temperature processes to get crystallized compounds with large-area uniformity, it is still challenging to directly synthesize these catalysts on silicon photocathodes due to chemical incompatibility at the heterointerface. Here, a graphene interlayer is applied between p-Si and MoP nanorods to enable fully engineered interfaces without forming a metallic secondary compound that absorbs a parasitic light and provides an inefficient electron path for hydrogen evolution. Furthermore, the graphene facilitates the photogenerated electrons to rapidly transfer by creating Mo-O-C covalent bondings and energetically favorable band bending. With a bridging role of graphene, numerous active sites and anti-reflectance of MoP nanorods lead to significantly improved PEC-HER performance with a high photocurrent density of 21.8 mA cm−2 at 0 V versus RHE and high stability. Besides, low dependence on pH and temperature is observed with MoP nanorods incorporated photocathodes, which is desirable for practical use as a part of PEC cells. These results indicate that the direct synthesis of TMPs and TMDs enabled by graphene interlayer is a new promising way to fabricate Si-based photocathodes with high-quality interfaces and superior HER performance. Graphic Abstract

Ni,Ti-co-doped MoO2 nanoparticles with excellent moisture stability and improved conductivity are synthesized via solvothermal cracking process for hole transporting material (HTM) in metal halide perovskite solar cells (MHP SCs). The Ni,Ti-doped MoO2 has similar oxidation state with pristine MoO2, but has better reduction stability than the MoO2 due to the weaker electronegativity of Ni and Ti than the Mo. Accordingly, the Ni,Ti-co-doped MoO2 HTM based MHP SC has 18.1% of power conversion efficiency at 1 sun (100 mW/cm2) condition. In addition, the un-encapsulated Ni,Ti-co-doped MoO2 HTM based MHP SC has 12–13% degradation after stability test under 85 °C/60% relative humidity for 20 days.

Summary Inorganic perovskite solar cells (PSCs) are promising for achieving long-term operational stability with good device performance. Here, we report the fabrication of inorganic CsPbI2Br-based perovskite thin films with a well-defined CsPbI3−xBrx composition gradient in the surface region by a scalable, orthogonal processable spray-coating approach. The graded structure broadens absorption wavelength range and increases carrier lifetime, but it also causes electrical field redistribution within a device stack for more efficient charge separation and collection. With this approach, we obtained a power conversion efficiency of 16.81% for a 0.096-cm2 PSC. We further demonstrated a monolithically integrated perovskite submodule based on the graded CsPbI3−xBrx by spray coating with an efficiency of 13.82% (112-cm2 aperture area) and ∼9% degradation over 1,000-h continuous 1-sun light soaking.

Coal as catalytic support is advantageous in many respects. The pore structure and surface composition are controllable, and the high thermal conductivity can increase the thermal efficiency of the reactor. It is stable in acidic or basic media and it is easy to recycle the catalyst after use. In this study, six different coals were evaluated as catalytic supports based on their ability to disperse of the metal and their catalytic performance. Nickel particles with an average diameter of

Post-processable CH3NH3PbX3 (MAPbX3, X = Cl, Br, I, and their mixtures) metal halide perovskite nanocrystals (MHP NCs) for thin solid-film were synthesized by modified ligand-assisted re-precipitation method adopting MAPbX3, N,N-dimethylformamide (DMF), toluene, and oleic acid and hexylamine as MHP, good solvent, poor solvent, and co-ligands, respectively. Through simple optimization of the amount of DMF good solvent, the full colored MAPbX3 MHP NC-solid-films were formable. The self-powered panchromatic photodetectors were fabricated by depositing the post-processable blue, green, and red colored MAPbX3 MHP NCs on a mesoporous TiO2 film and the effective panchromatic photon harvesting were possible in a single cell.

Biodegradable polymer polylactide (PLA) can form stereocomplex crystals through racemic blending between poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA). This stereocomplexation could lead to sub...

Understanding the effects of the chemical structures of donor polymers on the photovoltaic properties of their corresponding organic photovoltaic (OPV) devices under various light-intensity conditions is important for improving the performance of these devices. We synthesized a series of copolymers based on poly[(2,6-(4,8-bis(5-(2-thioethylhexyl)thiophen-2-yl)benzo[1,2

Large-sized α-MoO3 nanoplates with 10−100 μm were synthesized by introduction of titanium tetra isopropoxide as TiO2 precursor in hydrothermal solution chemistry. During the hydrothermal synthesis, the TiO2 can be selectively deposited on the (001) facets of h-MoO3 hexagonal rods and on the (001) and/or (010) facet of α-MoO3 re-growing crystals due to the small lattice mismatch between them. Owing to the TiO2 passivation of the surface of h-MoO3 rods, the h-MoO3 rods are changed to MoO3 tubes because the h-MoO3 are dissolved from the inner part of the TiO2 passivated h-MoO3 rods. The TiO2-passivated (001) facets of h-MoO3 rods act as templates for the re-growth of α-MoO3 and consequently produced rectangle-shaped α-MoO3 nanoplates. Simultaneously, the TiO2 passivated on the (001) and/or (010) facet of the re-growing α-MoO3 crystals inhibits the preferred crystal growth to [001] direction and promoted the crystal growth to [100] direction, thereby yielding plate-shaped α-MoO3. The small α-MoO3 nanoplates and rectangle-shaped ones are further grown to larger nanoplates by attachment process and/or continuous growth.

PbI2(DMSO) complex powder, which is essential to fabricate efficient metal halide perovskite solar cells (MHP SCs), was synthesized by liquid phase solvent extraction process irrespective of reaction volume scale. The isopropanol (IPA) solvent could selectively extract the DMSO from PbI2(DMSO)2 powder during extraction process so that compositionally uniform PbI2(DMSO) powder could be obtained in a large scale process, whereas the vacuum drying process could not produce uniform PbI2(DMSO) powder. Due to the compositional uniformity of PbI2(DMSO) powders prepared by solvent extraction process, the MHP SCs could be fabricated very reproducibly.

A void-free metal halide perovskite (MHP) layer on a mesoscopic TiO2 (m-TiO2) film was formed via the wetting-induced infiltration of MHP solution in the m-TiO2 film via a green ultrasonic spray coating process using a non-hazardous solvent. The systematic investigation of the behavior of ultrasonic-sprayed MHP micro-drops on the m-TiO2 film disclosed that the void-free MHP layer on the m-TiO2 film can be formed if the following conditions are satisfied: (1) the sprayed micro-drops are merged and wetted in the mesoscopic scaffold of the m-TiO2 film, (2) the MHP solution infiltrated into the m-TiO2 film by wetting is leveled to make a smooth wet MHP film, and (3) the smooth wet MHP film is promptly heat treated to eliminate dewetting and the coffee ring effect by convective flow in order to form a uniform void-free MHP layer. A void-free MHP layer on the m-TiO2 film was formed under optimal ultrasonic spray coating conditions of substrate temperature of ∼30 °C, spray flow rate of ∼11 mL h−1, nozzle to substrate distance of ∼8 cm, and MHP solution-concentration of ∼0.6 M under a fixed scan speed of 30 mm s−1 and purged N2 carrier gas pressure of 0.02 MPa. The mesoscopic MHP solar cells with an aperture area of 0.096, 1, 25, and 100 cm2 exhibited 17.14%, 16.03%, 12.93%, and 10.67% power conversion efficiency at 1 sun condition, respectively.

Structure engineering of trivalent metal halide perovskites (MHPs) such as A3Sb2X9 (A = a monovalent cation such as methyl ammonium (MA), cesium (Cs), and formamidinium (FA) and X = a halogen such as I, Br, and Cl) is of great interest because a two dimensional (2D) layer structure with direct bandgap has narrower bandgap energy than a zero dimensional (0D) dimer structure with indirect bandgap. Here, we demonstrated 2D layer structured FACs2Sb2I6Cl3 MHP by dual-site (A and X site) mixing. Thanks to the lattice-symmetry change by I–Cl mixed halide, the shortest ionic radius of Cs, and the lower solution energy due to dual-site mixing, the FACs2Sb2I6Cl3 MHP had 2D layer structure and thereby the MHP solar cells exhibited improved short-circuit current density.

Vertically aligned TiO2 nanorod (NR) electrodes with straight macropores enabled a metal halide perovskite (MHP) solution to be fully infiltrated within their structure and, as a result, formed void-free dense MHP films reproducibly during an electrospray-coating process, whereas conventional mesoporous TiO2 (m-TiO2) electrodes with three-dimensionally interconnected mesopores formed internal voids by imperfect infiltration of MHP solution. Hence, TiO2 NR-based MHP solar cells could be more reproducibly fabricated by an electrospray-coating process and exhibited smaller current density-voltage hysteresis with respect to the scan direction and scan rate than the m-TiO2-based MHP solar cells due to the short and straight electron pathway either by a one-dimensional TiO2 NR electrode or a densely formed MHP layer within the TiO2 NR electrode.

Organic-inorganic hybrid perovskites have recently attracted substantial attention as a top candidate for use as light-absorbing materials in high-efficiency, low-cost and solution-processable photovoltaic devices owing to their excellent optoelectronic properties. Here, we fabricated inverted planar perovskite solar cells by incorporating small amounts of ammonium halide NH4X (X = F, Cl, Br, I) additives into a CH3NH3PbI3 (MAPbI3) perovskite solution. A compact and uniform perovskite absorber layer with large perovskite crystalline grains is realized by simply incorporating small amounts of additives and by using an anti-solvent engineering technique to control the nucleation and crystal growth of perovskite. The enlarged perovskite grain size with a reduced density of the grain boundaries and improved crystallinity results in fewer charge carrier recombinations and a reduced defect density, leading to enhanced device efficiency (NH4F: 14.88 ± 0.33%, NH4Cl: 16.63 ± 0.21%, NH4Br: 16.64 ± 0.35%, and NH4I: 17.28 ± 0.15%) compared to that of a reference MAPbI3 device (Ref.: 12.95 ± 0.48%) and greater device stability. This simple technique involving the introduction of small amounts of ammonium halide additives to regulate the nucleation and crystal growth of perovskite films translates into highly reproducible enhanced device performance.

The quality of life is gradually improving with the development of medicine and the rising standard of living, but human beings are still faced with the risks of various diseases, accidents, aging, and industrial disasters. Accordingly, the importance of biocompatible materials for treating and recovering human tissues or functions is increasing. Furthermore, materials with various biological functions that interact with surrounding tissues and cells are being researched and developed, instead of materials that simply replace damaged tissues. This study analyzes the research and development trends of biocompatible materials and examines the latest status of technological developments. Biocompatible materials generally include metals, ceramics, polymers, gels, and composite materials. Polymer materials began to be widely used as biocompatible materials from the mid-20th century. Recently, polymer-extracellular matrix (ECM) composite technology using ECMs, which exist naturally in the human body, is drawing considerable attention. Thus, the ultimate objective of this study is to establish strategies to secure key patents in the field of polymer materials among various biocompatible materials. To this end, quantitative and qualitative analyses are conducted based on patents published in South Korea, the U.S., Japan, and Europe by country, keyword, applicant, and inventor. Based on the results of these analyses, this study examines recent patent application trends, and establishes directions for technology development and strategies for developing key technologies in this field. Consequently, four major strategies are established: technology development, purchasing patents, setting cross-licenses, and bypass technology development. Subsequently, concrete patent acquisition plans in line with each direction are conceived. In addition, four industries related to biocompatible materials (over-the-counter drugs, prescription drugs, medical materials, and cosmetics) are selected, the key patents in each industry are examined, and patent acquisition scenarios are suggested.

Highly efficient and thermally stable inorganic CsPbI2Br mesoscopic metal halide perovskite (MHP) solar cells with a poly-3-hexylthiophene (P3HT) hole transporting layer (HTL) are demonstrated by s...

We synthesized a donor polymer of bis(2-ethylhexyl)thiophene-substituted benzodithiophene (BDT-Th) and 1,3-bis(2-ethylhexyl)-5,7-di(thiophene-2-yl)benzo[1,2-c:4,5-c′]dithiophene-4,8-dione, for whic...

Low-temperature solution processable TiO2 nano-sol for electron transporting layer (ETL) of flexible perovskite solar cells is prepared by synthesizing TiO2 nano-sols by peptization in acidic aqueous solution and re-dispersing the TiO2 nanoparticles in H2O, ethanol (EtOH), dimethylsulfoxied (DMSO), and N,N-dimethylformamide (DMF). By considering dielectric constant, zeta potential, and surface tension of solvent media, we found that the DMF is the best to form uniform TiO2 ETL by spin-coating among them because it has low surface tension and high zeta potential. Accordingly, we could demonstrate 18.2% power conversion efficiency (PCE) for rigid glass substrate based perovskite solar cells and 15.8% PCE for flexible polymer substrate based devices by low-temperature solution process.

High-performance and hysteresis-less mesoscopic CsPbI2Br perovskite solar cells (PSCs) are demonstrated by adapting hole-transporting materials (HTMs) with controlled highest occupied molecular orb...

Here, we develop a method to prepare a dopant-free hole transporting material by blending an organic semiconductor and a conjugated polymer with 1,8-diiodooctane (DIO) additive. The normal-type solar cell based on the hole transporting material (HTM) blend with DIO + PCDTBT shows enhanced efficiency up to 18.0% compared to 14.7% for the device using the pristine small molecule. Incorporation of DIO results in increased crystallinity, while the conjugated polymer induces an intermolecular network for efficient charge transport with improved film morphology. Consequently, the HTM blend with DIO + PCDTBT shows a higher hole mobility and more efficient charge transfer at the perovskite/hole transporting layer interface compared with the pristine HTM. Furthermore, the solar cell introducing the HTM blend with DIO shows high mechanical and moisture stability; the compact and homogeneous film of high crystalline HTM shows more adhesive contact with perovskite and effectively prevents the penetration of moisture. The efficiency of the unencapsulated device using a small molecular HTM decreases to 60%, whereas the corresponding device with HTM blend maintains 80% performance after storage under 85% relative humidity and 85 °C.

The energy transfer and multiple photoluminescence of LuNbO4:Eu3+,Tb3+ powders were investigated. The photoluminescence spectra of the powders mainly consisted of green and red emission peaks. The green emission peaks (551 nm) were assigned to the 5D4 → 7F5 transition of Tb3+, and the strong red emission peaks (614 nm) originated from Eu3+ (5D0 → 7F2) via a Tb3+ → Eu3+ energy transfer. Tb3+–Eu3+ co-doping greatly enhanced the red emission under UV excitation that could rarely activate Eu3+ ions. The emission of the powders was tunable from green to red by adjusting the ratio of Eu3+/Tb3+, and thus warm white-light-emitting powders could be obtained. The Tb3+ → Eu3+ energy transfer mechanism was explained using the energy transfer efficiency, the critical distance for the Tb3+ → Eu3+ energy transfer, fluorescence decay curves, and multipolar interactions. The results demonstrate that LuNbO4:Eu3+,Tb3+ powders have a high potential for use in UV-pumped white-light-emitting diodes.

Under a 980-nm excitation, the up-conversion (UC) spectra of LuNbO4 :Yb3+ ,Tm3+ powders exhibited predominantly near-infrared bands (~805 nm) of Tm3+ through an energy transfer process from Yb3+ to Tm3+ . Regarding the down-conversion (DC) luminescence of the powders, the photoluminescence excitation spectra consisted of a broad charge transfer band (270 nm) due to [NbO4 ]3- and sharp band (360 nm) of Tm3+ , while the corresponding emission spectra exhibited a blue emission at 458 nm. Upon substitution of Ga3+ and Ta5+ for Lu3+ and Nb5+ , respectively, both UC and DC luminescence properties were significantly enhanced. For the Ga3+ substitution, the increased emission intensity could be explained by the crystal field asymmetry surrounding the Tm3+ ions induced by the large difference in ionic radius between Ga3+ and Lu3+ . For the Ta5+ substitution, we believe that an M'-LuTaO4 substructure was formed in the host, which led to the formation of a TaO6 octahedral coordination instead of a NbO4 tetrahedral coordination. Consequently, the crystal symmetry of the local structure was modified, and thus the UC and DC luminescence properties were enhanced. The dual-mode (UC and DC) luminescence demonstrates that LuNbO4 :Yb3+ ,Tm3+ has a great potential in the fields of temperature sensing probes, anti-counterfeiting, and bioapplications.

Tubular scaffolds have been commonly used for vascular stents, grafts, and replacement of the trachea. Common scaffolds are built from non-biodegradable synthetic polymers that have superior mechanical properties; these polymers include expanded poly(tetrafluoroethylene), poly(ethylene terephthalate), and poly(urethane). Unfortunately, biodegradable polymers are rarely used for vascular scaffolds due to their inferior mechanical properties. To overcome the current limitations of biodegradable tubular scaffolds, a novel polymer melt-tube drawing (MD) process that allows the fabrication of biodegradable vascular scaffolds with high compressive strength has been developed. The machine designed for the MD process uses a combination of melt extrusion and tube-drawing. In comparison to the scaffold prepared by conventional techniques, the poly(lactide) tubular scaffold fabricated using the MD process showed improved compressive strength and recovery ability as well as a smooth surface. Furthermore, the MD-tube displayed extensive chain orientation and increased crystallinity. As a result, this novel MD process has the potential to permit fabrication of biodegradable vascular scaffolds with excellent mechanical properties. It provides an opportunity to greatly expand the application of biodegradable polymeric tubes.

Polylactide (PLA) is among the most common biodegradable polymers, with applications in various fields, such as renewable and biomedical industries. PLA features poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) enantiomers, which form stereocomplex crystals through racemic blending. PLA emerged as a promising material owing to its sustainable, eco-friendly, and fully biodegradable properties. Nevertheless, PLA still has a low applicability for drug delivery as a carrier and scaffold. Stereocomplex PLA (sc-PLA) exhibits substantially improved mechanical and physical strength compared to the homopolymer, overcoming these limitations. Recently, numerous studies have reported the use of sc-PLA as a drug carrier through encapsulation of various drugs, proteins, and secondary molecules by various processes including micelle formation, self-assembly, emulsion, and inkjet printing. However, concerns such as low loading capacity, weak stability of hydrophilic contents, and non-sustainable release behavior remain. This review focuses on various strategies to overcome the current challenges of sc-PLA in drug delivery systems and biomedical applications in three critical fields, namely anti-cancer therapy, tissue engineering, and anti-microbial activity. Furthermore, the excellent potential of sc-PLA as a next-generation polymeric material is discussed.

As renewable energy source integration increases, P2G technology that can store surplus renewable power as methane is expected to expand. The development of a CO2 methanation catalyst, one of the core processes of the P2G concept, is being actively conducted. In this work, low-rank coal (LRC) was used as a catalyst support for CO2 methanation, as it can potentially enhance the diffusion and adsorption behavior by easily controlling the pore structure and composition. It can also improve the process efficiency owing to its simplicity (no pre-reduction step) and high thermal conductivity, compared to conventional metal oxide-supported catalysts. A screening of single metals (Ni, Co, Ru, Rh, and Pd) on LRC was performed, which showed that Ni was the most active. When Ni on the LRC catalyst was doped with a promoter (Ce and Mg), the CO2 conversion percentage increased by >10% compared to that of the single Ni catalyst. When the CO2 methanation activity was compared at 250–500 °C, the Ce-doped Ni/Eco and Mg-doped Ni/Eco catalysts showed similar or better activity than the commercial metal oxide-supported catalyst. In addition, the catalytic performance remained stable even after the test for an extended time (~200 h). The results of XRD, TEM, and TPR showed that highly efficient LRC-based CO2 methanation catalysts can be made when the metal dispersion and composition are modified.

The detection of hydrogen peroxide (H2O2) is essential in many research fields, including medical diagnosis, food safety, and environmental monitoring. In this context, Au-based bimetallic alloy nanomaterials have attracted increasing attention as an alternative to enzymes due to their superior catalytic activity. In this study, we report a coreduction synthesis of gold–copper (Au–Cu) alloy nanoparticles in aqueous phase. By controlling the amount of Au and Cu precursors, the Au/Cu molar ratio of the nanoparticles can be tuned from 1/0.1 to 1/2. The synthesized Au–Cu alloy nanoparticles show good peroxidase-like catalytic activity and high selectivity for the H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB, colorless) to TMB oxide (blue). The Au–Cu nanoparticles with an Au/Cu molar ratio of 1/2 exhibit high catalytic activity in the H2O2 colorimetric detection, with a limit of detection of 0.141 μM in the linear range of 1–10 μM and a correlation coefficient R2 = 0.991. Furthermore, the Au–Cu alloy nanoparticles can also efficiently detect glucose in the presence of glucose oxidase (GOx), and the detection limit is as low as 0.26 μM.

Adjustable speed drives use Pulse Width Modulation (PWM) to switch DC-bus voltage for the synthesis of three-phase voltages to provide power to the permanent magnet synchronous motor (PMSM). This switching action produces very short rise and fall times and Common Mode Voltage (CMV) in the motor winding, exciting the parasitic capacitances inherent to the motor geometry. These parasitic capacitances give rise to shaft voltage due to a voltage divider action. Therefore, in this paper, first, motor parasitic capacitances and voltage divider action is explained. Second, the Barium Titanate (BTO) layer is coated onto the rotor to enhance stator-to-rotor compound capacitance and a simulation is performed showing the dependence of the shaft voltage on the permittivity of the perovskite (BTO) layer. The rotor BTO layer reduces the bearing voltage ratio as well. Third, experimental results are presented showing effectiveness of the application of the BTO layer to rotor and reduction of shaft voltage of the motor in anticipation to mitigate the damaging electric discharge machining (EDM) bearing currents. Likewise, the experiment shows that the magnetic design of the motor is not affected by the BTO layer to rotor.

This study presents the comparison of frequency responses of the motor with bearing voltage reduction structures. Since the bearing fault due to the electrical stress is significant issue in the field, various bearing voltage reduction structures were proposed. The manufacturer needs to select the bearing protection strategy by regarding the harmonic characteristic of common mode voltage which is the source of the bearing voltage. Therefore, the frequency responses of the motor with each technique should be derived to accept the most proper structure. In this paper, the frequency responses for several bearing voltage reduction method by regarding electric equivalent circuit.

Summary Although many synthetic methods such as hot injection and anionic exchange can produce full-color perovskite nanocrystals (PNCs), their emission spectra are broadened by compositional non-uniformity. Here, we propose the synthetic method, hydrogen halide (HX; X = Cl, Br, and I)-mediated uniform halide anion exchange at mild temperatures, for high color-purity PNCs emitters across the full-color spectrum. The HX-mediated exchange reaction produces high-purity PNCs without metallic Pb impurities due to the use of volatile HX as the X source. The blue, green, and red PNCs show narrow emission spectra, with 16, 18, and 18.5 nm of full width at half-maximum, respectively. The red PNC emitter synthesized by the HX-mediated method has a single photoluminescent (PL) peak, with a narrow emission spectrum at low temperature due to compositional uniformity, whereas the PNCs produced by other methods have multiple PL peaks. Accordingly, the red/green/blue electroluminescent devices also have narrow emission spectra.

Organometallic and all-inorganic halide perovskites (HPs) have recently emerged as promising candidate materials for resistive switching (RS) nonvolatile memory due to their current-voltage hysteresis caused by fast ion migration. Lead-free and all-inorganic HPs have been researched for non-toxic and environmentally friendly RS memory devices. However, only HP-based devices with electrochemically active top electrode (TE) exhibit ultra-low operating voltages and high on/off ratio RS properties. The active TE easily reacts to halide ions in HP films, and the devices have a low device durability. Herein, RS memory devices based on an air-stable lead-free all-inorganic dual-phase HP (AgBi2 I7 -Cs3 Bi2 I9 ) are successfully fabricated with inert metal electrodes. The devices with Au TE show filamentary RS behavior by conducting-bridge involving Ag cations in HPs with ultra-low operating voltages ( 107 ), multilevel data storage, and long retention times (>5 × 104 s). The use of a closed-loop pulse switching method improves reversible RS properties up to 103 cycles with high on/off ratio above 106 . With an extremely small bending radius of 1 mm, the devices are operable with reasonable RS characteristics. This work provides a promising material strategy for lead-free all-inorganic HP-based nonvolatile memory devices for practical applications.

The cesium lead triiodide (CsPbI3) perovskite is a promising candidate for stable light absorbers and red-light-emitting sources due to its outstanding stability. Phase engineering is the most impo...

Large-sized α-MoO3 elongated nano-plates were synthesized by the introduction of multi-amines such as ethylene di-amine and diethylene tri-amine (DETA) in the conventional hydrothermal reaction. DETA made large hexagonal rods with an h-MoO3 intermediate phase containing H2O, NH4OH, and DETA ions. During the hydrothermal reaction, the hexagonal rods were transformed to elongated α-MoO3 nano-plates by the re-dissolution of h-MoO3 and re-growth to α-MoO3 because DETA retarded the preferred growth reaction of the MoO6 octahedra to the [001] direction and helped the MoO6 octahedra to grow in the [100] direction. In addition, DETA promoted α-MoO3 nano-belts to be assembled into elongated nano-plates by oriented attachment because the multi-ammonium groups in the DETA backbone could adhere to the α-MoO3 nano-belts due to attractive Coulomb interactions.

In this study, we measured the force of electrostatic interactions between poly(methyl methacrylate) (PMMA) particles dispersed in organic solvent mixtures of cyclohexyl bromide (CHB) and n-decane. Optical laser tweezers were employed to directly measure interactive forces between paired PMMA particles in a CHB medium that contained n-decane in various volume ratios. CHB, having a moderate dielectric constant, provided an environment with a high charge storage capacity. The addition of n-decane lowered the effective refractive index of the medium, which increased the optical trapping efficiency. We also fabricated microscope flow cells with a commonly used UV-curable adhesive and quantified the effects of dissolved adhesive compounds through interactive force measurements and nuclear magnetic resonance analysis. In addition, we studied the impact of CHB dissociation into H+ and Br- ions, which could screen electrostatic interactions.

Perovskite solar cells (PSCs) have attracted a great deal of attention due to their combined advantages of high efficiency and good flexibility (bendability). Here, we address the latest technology and future prospects of flexible hybrid PSCs. Flexible PSCs consist of a flexible substrate, transparent electrode, electron (or hole) conductor, perovskite, hole (or electron) conductor, and electrode layer. Among these layers, the flexible substrate and transparent electrode are critical bottlenecks for achieving high efficiency and super flexibility, since flexible polymer substrates exhibit lower transmittance than rigid glass substrates due to a higher overall refractive index and an inherently brittle transparent conducting oxide (TCO). Therefore, we mention the research background of flexible PSCs in the introduction and review their technological advancement with regard to flexible substrates and transparent electrodes in the main text. In addition, we briefly discuss the upscaling issues and the material costs of flexible PSCs for their commercialization.

A semitransparent flexible metal halide perovskite (MHP) solar cells were demonstrated by reproducible dry stamping transfer of a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS, PH1000) transparent flexible top electrode onto poly(ethylene terephthalate) (PET)/indium tin oxide (ITO)/PEDOT:PSS (AI4083)/MHP/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The reproducible transfer of the PEDOT:PSS top electrode was enabled by the modification of PEDOT:PSS with poly(ethylene imine) (PEI)/2-methoxyethanol (2-MEA) solution. In addition, the PEI/2-MEA modification to PEDOT:PSS resulted in improved conductivity and reduced work function of the top electrode. Therefore, we could fabricate highly efficient flexible semitransparent MHP solar cells with >13% (active area = 1 cm2) power conversion efficiency.

The effect of Al3+ substitution on the enhancement of the luminescence of Lu1–xAlxNbO4:Eu3+ and Lu1–xAlxNbO4:Tb3+ was investigated. X-ray diffraction patterns confirmed that the Eu3+, Tb3+, and Al3+ ions were fully incorporated into the Lu3+ sites. In the case of Lu1–xAlxNbO4:Eu3+, the predominant red emission (614 nm) was assigned to the 5D0 → 7F2 transition of Eu3+ and for x = 0–0.05, its intensity increased up to ~125 and 108% under 395 nm (7F0 → 5L6) and a charge transfer band excitation, respectively. For Lu1–xAlxNbO4:Tb3+, the strongest emission band peaking at 551 nm was attained in the green region among multiple emission bands corresponding to the 5D4 → 7FJ transitions of Tb3+. Increasing the x values from 0 to 0.05 increased the green emission significantly by ~137%. These phenomena were explained by the local structural distortions and crystal field asymmetry surrounding Eu3+ and Tb3+, which were attributed to a large difference in the ionic radii of Al3+ and Lu3+.

We investigated the color conversion characteristics of a quantum dot/organic light-emitting diode (QD/OLED) by altering blue emission using the microcavity effect. Compared to the ITO-based OLED, the WO3/Ag/WO3 (WAW)-based OLED has a narrow shape of resonance and high cavity enhancement factor. As a result, the peak emission intensity wavelength remarkably shifts as the thickness of the WO3 layer increases and the WAW-based OLED with inner WO3 thickness of 120 nm shows an additional emission peak at 420 nm due to the second resonance. As the thickness of the WO3 layer increases, the color coordinates of the hybrid QD/OLED with the ITO anode are nearly unchanged. However, hybrid WAW-based devices exhibit distinct color coordinates, such as nearly blue light, nearly green light and nearly white light with color coordinates of (0.31, 0.37).

Preserving the stability of Sn-based halide perovskites is a primary concern in developing photovoltaic light-absorbing materials for lead-free perovskite solar cells. Whereas the addition of SnX2 (X = F, Cl, Br) has been demonstrated to improve the photovoltaic performance of Sn halide perovskite solar cells, the mechanistic roles of SnX2 in the performance enhancement have not yet been studied appropriately. Here we perform a comparative study of CsSnI3 films and devices and examine how SnX2 additives affect their stability, and the results are corroborated by first-principles-based theoretical calculations. Unlike the conventional belief that the additives annihilate defects, we find that the additives effectively passivate the surface and stabilize the perovskite phase, promoting the stability of CsSnI3. Our mechanism suggests that SnBr2, which shows ca. 100 h of prolonged stability along with a high power conversion efficiency of 4.3%, is the best additive for enhancing the stability of CsSnI3.

Flexible Ti metal substrate-based efficient planar-type CH3NH3PbI3 (MAPbI3) organic–inorganic hybrid perovskite solar cells are fabricated by lamination of the flexible Ti metal substrate/dense TiO2 electron-transporting layer formed by anodization/MAPbI3/polytriarylamine and the graphene/polydimethylsiloxane (PDMS) transparent electrode substrate. By adjusting the anodization reaction time of the polished Ti metal substrate and the number of graphene layers in the graphene/PDMS electrode, we can demonstrate the planar-type MAPbI3 flexible solar cells with a power conversion efficiency of 15.0% (mask area = 1 cm2) under 1 sun condition.

Polylactide (PLA) is one of the most commonly used biodegradable polymers for various fields such as biomedical and renewable industries. This material must undergo molding processes to achieve the desired shape in the final manufactured product, which are typically thermal- or solvent-based. Unfortunately, the mechanical and thermal properties of PLA, such as the strength and crystallinity, are inevitably damaged during the molding process due to the slow crystallization rate. To overcome this limitation, a simple, novel, one-pot, self-accelerating method for the in situ self-nucleating (ISN) polymerization of l-lactide is developed. This strategy results in the simultaneous polymerization and self-nucleation of l-lactide crystallites upon addition of a self-nucleating agent. The results show that ISN-PLA experiences an acceleration effect on the crystallization with stereocomplex polylactide (sc-PLA) as the nucleating agent and has enhanced mechanical and thermal properties, despite repetitive thermal p...