Highly Crystalline Perovskite-Based Photovoltaics via Two-Dimensional Liquid Cage Annealing Strategy.

Rendering a high crystalline perovskite film is integral to achieve superior performance of perovskite solar cells (PSCs). Here, we established a two-dimensional liquid cage annealing system, a unique methodology for remarkable enhancement in perovskite crystallinity. During thermal annealing for crystallization, wet-perovskite films were suffocated by perfluorodecalin with distinctively low polarity, nontoxic, and chemically inert characteristics. This annealing strategy facilitated enlargement of perovskite grain and diminution in the number of trap states. The simulation results, annealing time, and temperature experiments supported that the prolonged diffusion length of precursor ions attributed to the increase of perovskite grains. Consequently, without any complicated handling, the performance of perovskite photovoltaics was remarkably improved, and the monolithic grains which directly connected the lower and upper electrode attenuated hysteresis.

Synthesis and Electroresponse Activity of Porous Polypyrrole/Silica-Titania Core/Shell Nanoparticles.

Inverted conducting polymer/metal oxide core/shell structured pPPy/SiO2-TiO2 nanoparticles were prepared as electrorheological (ER) materials using sequential experimental methods. The core was synthesized via the low-temperature self-assembly of PPy and SiO2 materials, and the outer TiO2 shell was easily coated onto the core part using a sol-gel method and a titanium isopropoxide precursor. Sonication-mediated etching and redeposition were employed to etch out SiO2 portions from the core part to blend with TiO2 shells. Each step in nanoparticle synthesis involved morphological and physical changes to the surface area and porosity, with subsequent changes in the intrinsic properties of the materials. Specifically, the electrical conductivity and dielectric properties were successfully altered. The final pPPy/SiO2-TiO2 nanoparticle configuration was optimized for ER applications, offering low electrical conductivity, high dielectric properties, and increased dispersion stability. pPPy/SiO2-TiO2 nanoparticles exhibited 24.7- and 2.7-fold enhancements in ER performance compared to that of PPy-SiO2 and PPy-SiO2/TiO2 precursor nanoparticles, respectively. The versatile method proposed in this study for the synthesis of inverted conducting polymer/metal oxide core/shell nanoparticles shows great potential for the development of custom-designed ER materials.

Paintable Carbon-Based Perovskite Solar Cells with Engineered Perovskite/Carbon Interface Using Carbon Nanotubes Dripping Method.

Paintable carbon electrode-based perovskite solar cells (PSCs) are of particular interest due to their material and fabrication process costs, as well as their moisture stability. However, printing the carbon paste on the perovskite layer limits the quality of the interface between the perovskite layer and carbon electrode. Herein, an attempt to enhance the performance of the paintable carbon-based PSCs is made using a modified solvent dripping method that involves dripping of the carbon nanotubes (CNTs), which is dispersed in chlorobenzene solution. This method allows CNTs to penetrate into both the perovskite film and carbon electrode, facilitating fast hole transport between the two layers. Furthermore, this method is results in increased open circuit voltage (Voc ) and fill factor (FF), providing better contact at the perovskite/carbon interfaces. The best devices made with CNT dripping show 13.57% power conversion efficiency and hysteresis-free performance.

Influence of Spark Plasma Sintering Conditions on the Optical and Mechanical Properties of Spinel.

The influence of spark plasma sintering (SPS) conditions on the optical and mechanical properties of MgAl2O4 spinel was investigated for application to infrared windows as parts of military systems. The thermal conditions of SPS, including the temperature and heating rate, have a significant impact on optical and mechanical properties. This study shows that the formation and growth of abnormal grains cause mechanical degradation with an increasing SPS temperature. In-line transmittance (Tin) was affected by the heating rate due to changes in oxygen vacancy and carbon contamination in SPSed samples. The fabricated spinel exhibited excellent flexural strength of 401 MPa and an average mid-infrared transmittance of 84.8% in the range of 3-5 µm.

Fluorine plasma treatment on carbon-based perovskite solar cells for rapid moisture protection layer formation and performance enhancement.

A fluorine plasma-treated carbon electrode is used in HTM-free perovskite solar cells for high efficiency and moisture resistance. The fluorine-treated device with a champion power conversion efficiency (PCE) of 14.86% is achieved with a highly enhanced FF (FF = 0.69), showing superior long-term stability and excellent moisture penetration suppression.

Current-induced domain wall nucleation and its pinning characteristics at a notch in a spin-valve nanowire.

The characteristics of domain wall (DW) pinning at a notch in a spin-valve nanowire were investigated when a DW was created by a current, flowing into a spin-valve nanowire. It was found that DW pinning at a notch is quite sensitive to the magnitude of the current and its polarity. The current-polarity dependence of DW pinning is likely due to the spin structure in the core of the DW, which is determined by an Oersted field from the current in a Cu layer. This indicates that the control of DW pinning at a notch in a nanowire can be achieved by a current acting on its own, which is an important advantage of this method, compared with field-induced DW control.

Fabrication of Uniform Wrinkled Silica Nanoparticles and Their Application to Abrasives in Chemical Mechanical Planarization.

A simple one-pot method is reported for the fabrication of uniform wrinkled silica nanoparticles (WSNs). Rapid cooling of reactants at the appropriate moment during synthesis allowed the separation of nucleation and growth stages, resulting in uniform particles. The factors affecting particle size and interwrinkle distance were also investigated. WSNs with particle sizes of 65-400 nm, interwrinkle distances of 10-33 nm, and surface areas up to 617 m2 g-1 were fabricated. Furthermore, our results demonstrate the advantages of WSNs over comparable nonporous silica nanospheres and fumed silica-based products as an abrasive material in chemical mechanical planarization processes.

Superfast Room-Temperature Activation of SnO2 Thin Films via Atmospheric Plasma Oxidation and their Application in Planar Perovskite Photovoltaics.

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has now exceeded 20%; thus, research focus has shifted to establishing the foundations for commercialization. One of the pivotal themes is to curtail the overall fabrication time, to reduce unit cost, and mass-produce PSCs. Additionally, energy dissipation during the thermal annealing (TA) stage must be minimized by realizing a genuine low-temperature (LT) process. Here, tin oxide (SnO2 ) thin films (TFs) are formulated at extremely high speed, within 5 min, under an almost room-temperature environment (<50 °C), using atmospheric Ar/O2 plasma energy (P-SnO2 ) and are applied as an electron transport layer of a "n-i-p"-type planar PSC. Compared with a thermally annealed SnO2 TF (T-SnO2 ), the P-SnO2 TF yields a more even surface but also outstanding electrical conductivity with higher electron mobility and a lower number of charge trap sites, consequently achieving a superior PCE of 19.56% in P-SnO2 -based PSCs. These findings motivate the use of a plasma strategy to fabricate various metal oxide TFs using the sol-gel route.

Enhanced efficiency and air-stability of NiOX-based perovskite solar cells via PCBM electron transport layer modification with Triton X-100.

We modified phenyl-C61-butyric acid methyl ester (PCBM) for use as a stable, efficient electron transport layer (ETL) in inverted perovskite solar cells (PSCs). PCBM containing a surfactant Triton X-100 acts as the ETL and NiOX nanocrystals act as a hole transport layer (HTL). Atomic force microscopy and scanning electron microscopy images showed that surfactant-modified PCBM (s-PCBM) forms a high-quality, uniform, and dense ETL on the rough perovskite layer. This layer effectively blocks holes and reduces interfacial recombination. Steady-state photoluminescence and electrochemical impedance spectroscopy analyses confirmed that Triton X-100 improved the electron extraction performance of PCBM. When the s-PCBM ETL was used, the average power conversion efficiency increased from 10.76% to 15.68%. This improvement was primarily caused by the increases in the open-circuit voltage and fill factor. s-PCBM-based PSCs also showed good air-stability, retaining 83.8% of their initial performance after 800 h under ambient conditions.

Enhanced Electrorheological Performance of Mixed Silica Nanomaterial Geometry.

The mixed geometrical effect on the electrorheological (ER) activity of bimodal ER fluids was investigated by mixing SiO2 spheres and rods of different dimensions. To gain an in-depth understanding of the mixed geometrical effect, 12 bimodal ER fluids were prepared from 4 sizes of SiO2 spheres (50, 100, 150, and 350 nm) and 3 types of SiO2 rods with different aspect ratios (L/D = 2, 3, and 5). Five concentrations of SiO2 spheres and rods were created for each bimodal ER fluid, resulting in a total of 60 sets of comprehensive ER measurements. Some bimodal ER fluids exhibited enhanced ER performance, as high as 23.0%, compared to single SiO2 rod-based ER fluids to reveal the mixed geometrical effect of bimodal ER fluids. This interesting experimental result is based on the structural reinforcement provided by spheres to fibrillated rod materials, demonstrating the mixed geometrical effect on ER activity.

Large Grain-Based Hole-Blocking Layer-Free Planar-Type Perovskite Solar Cell with Best Efficiency of 18.20.

There remains tremendous interest in perovskite solar cells (PSCs) in the solar energy field; the certified power conversion efficiency (PCE) now exceeds 20%. Along with research focused on enhancing PCE, studies are also underway concerning PSC commercialization. It is crucial to simplify the fabrication process and reduce the production cost to facilitate commercialization. Herein, we successfully fabricated highly efficient hole-blocking layer (HBL)-free PSCs through vigorously interrupting penetration of hole-transport material (HTM) into fluorine-doped tin oxide by a large grain based-CH3NH3PbI3 (MAPbI3) film, thereby obtaining a PCE of 18.20%. Our results advance the commercialization of PSCs via a simple fabrication system and a low-cost approach in respect of mass production and recyclability.

Insertion of a specular reflective and transmissive nano-oxide layer into giant magnetoresistance spin-valve structure.

We have studied the influence of the insertion of a nano-oxide layer (NOL) into a magnetic GMR spin-valve. It was found that the spin-valve with NOL has a higher GMR ratio than that of the normal spin-valve without NOL. Naturally formed NOL without vacuum break shows a uniform layer, which effectively suppresses the current shunt, resulting in the reduction of the sheet resistance of GMR. The NOL spin-valve also shows a lower interlayer coupling (Hin) than that of the optimal normal spin-valve, which is consistent with AFM measurement showing lower roughness of NOL formed CoFe surface. Based on the advantage of NOL, we succeeded in lowering Hin while maintaining GMR ratio by insertion of NOL inside the CoFe free layer, where the free layer consists of CoFe/NOL/CoFe/NOL/Capping layer.

Morphology-controlled mesoporous SiO2 nanorods for efficient scaffolds in organo-metal halide perovskite solar cells.

In meso-superstructured perovskite solar cells, the scaffolding layer, composed of insulating metal oxide nanoparticles, plays an important role in the loading efficiency of the perovskite layer. This communication describes 1D mesoporous silica nanoparticles that were successfully used as scaffolds to enhance the electron extraction from the perovskite absorber layer to the working electrode.

Hierarchical mesoporous silica nanoparticles as superb light scattering materials.

A novel approach to enhance the light scattering effect was explored by applying hierarchical silica nanoparticles in DSSCs as scattering layers. The WSN-incorporated cells showed a PCE value of 9.53% and a PCE enhancement of 30.19% compared with those of the reference cells.

A graphene quantum dots based fluorescent sensor for anthrax biomarker detection and its size dependence.

Graphene quantum dots (GQDs) with two different diameters were modified with a EuIII-macromolecule complex and applied in dual emission fluorescent sensors for detection of Bacillus anthracis spores. The Eu-GQD sensors exhibited a morphology of ultrafine particles, increased surface-to-volume ratio, enhanced dispersibility, and extraordinary sensitivity. The 3 nm Eu-GQDs showed three emission bands, which are ascribed to the emission from the blue GQDs (435 nm) and the red [(Eu)-(DPA)] complex (593 nm and 616 nm). Accordingly, incorporation of the GQDs as a non-interfering internal calibration makes it possible for use as a ratiometric sensor. The time dependent fluorescence response study revealed that the reaction was complete within 8 s, thus enabling rapid detection of B. anthracis spores. It is noteworthy that the Eu-GQD sensors exhibited an extraordinary limit of detection (LOD) of ca. 10 pM towards B. anthracis, which is six orders of magnitude smaller than the infectious dose of the spores (60 µM). Furthermore, the selectivity study indicates that Eu-GQD sensors have an outstanding selectivity of 103-fold for DPA over competing aromatic ligands.

Lead-free BaTiO3 nanowires-based flexible nanocomposite generator.

We have synthesized BaTiO3 nanowires (NWs) via a simple hydrothermal method at low temperature and developed a lead-free, flexible nanocomposite generator (NCG) device by a simple, low-cost, and scalable spin-coating method. The hydrothermally grown BaTiO3 NWs are mixed in a polymer matrix without a toxic dispersion enhancer to produce a piezoelectric nanocomposite (p-NC). During periodical and regular bending and unbending motions, the NCG device fabricated by utilizing a BaTiO3 NWs-polydimethylsiloxane (PDMS) composite successfully harvests the output voltage of ∼ 7.0 V and current signals of ∼ 360 nA, which are utilized to drive a liquid crystal display (LCD). We also characterized the instantaneous power (∼ 1.2 µW) of the NCG device by calculating the load voltage and current through the connected external resistance.

Characteristics of domain wall pinning and depinning in a three-terminal magnetic Y-junction.

The characteristics of domain wall (DW) pinning and propagation in a three-terminal magnetic Y-junction were investigated, where the junction consisted of two input and one output wires. The output switching depends strongly on the junction angle (α). Junctions with high angles of α>9.5° lead to DW pinning at the junction, whereas junctions with low angles of α<9.5° have no DW pinning effect. At the critical angle of α = 9.5°, the Y-junction showed a multimode DW propagation, which was ascribed to a moderate transverse field effect.