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This paper proposes some effective approaches to address the inherent issues of consequent-pole (CP) permanent magnet (PM) machines, such as saturation of the salient rotor core and unipolar PM leakage flux of the end region caused by asymmetric field. The effect of CP Halbach PM array with different magnetization direction and parameters that affect the saturation have been investigated for the CP PM machine with short pole pitch. By employing the CP Halbach array, the saturation issue can be solved and superior performance can be obtained without reducing the PM pole arc. In addition, unequal and multistep staggered rotors with magnetic barriers have been proposed to reduce the unipolar leakage flux in the end region. Compared with regular staggered rotors, not only better electromagnetic performance can be achieved, but also the end unipolar leakage flux can be reduced. Finally, a prototype is manufactured and the predictions have been validated by measurements.

The surface treatment method has a great influence on the structure and properties of applied materials for interface catalysis. In this study, we prepare Ni(OH)2·NiO/FeOOH by surface treatment in ...

Inorganic-organic hybrid perovskite (ABX3, A = organic cation, B = metal ion, X = halogen anion) combines the advantages of inorganic and organic materials. However, the properties and performance of mixed-halide CH3NH3PbBr2.5Cl0.5 (MAPbBr2.5Cl0.5) are still poorly understood. In this study, we synthetized MAPbBr2.5Cl0.5 single crystal and studied its structure, optical, thermal stability properties and optoelectronics applications for photodetector device. Compared with those of MAPbCl3, the interplanar distance of (100) crystal plane for MAPbBr2.5Cl0.5 becomes larger and the absorption spectrum of MAPbBr2.5Cl0.5 is extended to the visible region. The band gap of the MAPbBr2.5Cl0.5 single crystal is 2.28 eV. We find the device based on MAPbBr2.5Cl0.5 has high selectivity from 369 to 564 nm. The maximum ▴J (Jon– Joff) under 3.0 V bias voltage is about 1.2 µAcmr-2 at 454 nm visible light with 1 W mr-2 light intensity (1/1000 of the standard sunlight intensity), which proves the device has a high sensitivity. The linear relationship is established between the value of ▴J and light intensity and bias voltage. The fast current intensity transients (Fit) shows that the disappearance period of photocurrent density is 0.3 ms, which indicates the device is rapidly responsive photodetector. The highest value (1.7%) of external quantum efficiency (EQE) and the highest value of detectivities (D) both appear at 480 nm visible light at 4.0 V bias voltage when the irradiation power is 30 W m-2. Therefore, this simple and low-cost photoresponsive device is promising for industrial production of photodetector and photocatalysts device in the future.

The titanium alloy blade is a key part of an aero-engine, but its high surface efficiency and precision machining present technical problems. Belt grinding can effectively prolong the fatigue life of the blade and enhance the service performance of the aero-engine. However, the residual stress of the workpiece after belt grinding directly affects its service performance and life. The traditional single particle abrasive model simulation is limited in exploring the influence of grinding process parameters on surface residual stress. In this study, an ABAQUS simulation model of multi-particle belt grinding is established for titanium alloy material, a finite element (FE) simulation is conducted with different technological parameters, and the results are analysed. The critical belt grinding experiment is conducted on thin-walled titanium alloy parts, and the distribution characteristics of surface residual stress after grinding are studied to understand the influence of grinding parameters on the formation of surface residual stress. Comparing the results of the FE simulation and the grinding experiment, the common law of stress change and the prediction model are obtained. The results show that the multi-particle belt grinding simulation is consistent with the belt grinding experiment in terms of the influence of grinding parameters on residual stress. The simulation can serve as a guide in actual belt grinding to some extent. Directions for improving the multi-particle abrasive simulation model are discussed.

The structure, mobility and memristor properties of tetragonal CH3NH3PbBr3 single crystals (T-MAPbBr3 SC) are rarely reported. In this study, we synthesized T-MAPbBr3 SC with the P4/mmm (123) space group by the growing, dropping and growing (GDG) crystal seed method. A CH3NH3+ cation is a disordered state in T-MAPbBr3 SC. The mobility values of T-MAPbBr3 SC under light and dark conditions are 464.28 and −1685.3 cm2 V−1 s−1, respectively. The carrier types under light and dark conditions are holes and electrons, respectively. The memristor based on T-MAPbBr3 SC has a wide and low operating voltage window (0–0.9 V). The high and low resistances of the memristor based on T-MAPbBr3 SC achieve values of 41 and 0.35 GΩ, respectively. The values of high and low resistances are relatively stable for 100 cycles. Thus, the memristor device based on T-MAPbBr3 SC has good applications in the field of memristors.

Hybrid electrocatalysts derived from surface self-reconstruction during reaction processes can facilitate charge transfer between different phases and nanostructures by their unique interfaces. Herein, amorphous/crystalline hybrid iron disulfide obtained by self-reconstruction is developed for the first time for the oxygen evolution reaction (OER). The amorphous/crystalline hybrid FeS2 catalyst exhibited a high OER activity with an overpotential of only 189.5 mV (IR-corrected) to deliver 10 mA cm-2 in 1.0 M KOH, which was superior to that of the commercial RuO2. Notably, in the two-electrode system with the amorphous/crystalline hybrid FeS2 as the anode electrocatalyst and Pt/C as the cathode, the catalytic activity towards the overall water splitting was enhanced with a voltage of only 1.43 V at 10 mA cm-2. The phase, composition and surface structure were changed greatly before and after the reaction. All these surface reconstructions after the OER reaction may play significant roles in the high electronic catalytic efficiency. Therefore, the study of the surface reconstruction of catalysts during the reaction process is very important for the structure-performance relationship and the design of efficient hybrid electrocatalysts.

Vanadium carbide embedded in mesoporous carbon (VC–MC) is prepared using an in-situ synthesis method as hybrid electrode for supercapacitor. The electrochemical performance of the VC and VC–MC electrodes are analyzed and compared through a combination of cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy measurements in 1 M H2SO4 aqueous electrolyte. The introduced mesoporous structure of the hybrid electrode provides optimized conducting pathways for electrons and protons, thus improving the capacitive performance of VC–MC electrode compared to pristine VC electrode. The synthesized VC–MC electrode achieves a specific capacitance up to 191.2 F g−1, which is significantly higher than the pristine VC electrode (95.6 F g−1). Moreover, the VC–MC hybrid electrode exhibits an excellent cycle performance with 89.5% capacitance retention after 10,000 charge–discharge cycles, considerably higher than the pristine VC electrode. Apparently, the VC–MC hybrid electrode which shows desirable capacitive performance, excellent stability and enhanced electrochemical properties can be attributable to the combination of the advantages possessed by MC and VC. Moreover, VC–MC was applied as counter electrode in flexible dye-sensitized solar cell which generate power conversion efficiencies of 6.50%, much higher than those of the devices using VC and MC counter electrodes (4.14% and 5.28%).

While the CuBi2O4-based photocathode has emerged as an ideal candidate for photoelectrochemical water splitting, it is still far from its theoretical values due to poor charge carrier transport, poor electron–hole separation, and instability caused by self-photoelectric-corrosion with electrolytes. Establishing synthesis methods to produce a CuBi2O4 photocathode with sufficient cocatalyst sites would be highly beneficial for water splitting. Here, the platinum-enriched porous CuBi2O4 nanofiber (CuBi2O4/Pt) with uniform coverage and high surface area was prepared as a photocathode through an electrospinning and electrodeposition process for water splitting. The prepared photocathode material was composed of a CuBi2O4 nanofiber array, which has a freestanding porous structure, and the Pt nanoparticle is firmly embedded on the rough surface. The highly porous nanofiber structures allow the cocatalyst (Pt) better alignment on the surface of CuBi2O4, which can effectively suppress the electron–hole recombination at the electrolyte interface. The as-fabricated CuBi2O4 nanofiber has a tetragonal crystal structure, and its band gap was determined to be 1.8 eV. The self-supporting porous structure and electrocatalytic activity of Pt can effectively promote the separation of electron–hole pairs, thus obtaining high photocurrent density (0.21 mA/cm2 at 0.6 V vs. RHE) and incident photon-to-current conversion efficiency (IPCE, 4% at 380 nm). This work shows a new view for integrating an amount of Pt nanoparticles with CuBi2O4 nanofibers and demonstrates the synergistic effect of cocatalysts for future solar water splitting.

The performance of lead halogen perovskite is often closely related to its crystal structure. However, the chemical and optoelectronic properties of tetragonal phase single crystal MAPbCl3 (SC T-MAPbCl3) are rarely reported. In this study, we synthesized SC T-MAPbCl3 with the P4/mcc (124) space group by a modified inverse temperature crystallization (M-ITC) method. The twist angle of the Cl anion on the equatorial plane of the PbCl64- octahedron around the c-axis is 8.4°. The resistance (62 MΩ) of SC T-MAPbCl3 obviously decreased to 3 MΩ under 395 and 404 nm ultraviolet light. The photodetector based on SC T-MAPbCl3 under 3 V bias voltage exhibits high sensitivity (2.60 μA cm-2 under 1 W m-2 light intensity). The high selectivity of the device is in the ultraviolet region, rather than the visible region.

The control of surface elements and nanostructures is one of the effective ways to design and synthesize high performance catalysts. Herein, we, for the first time, prepare FeS2 crystal lattices on WS2 nanosheets (FeS2 CL@WS2 NS) by solvothermal methods for the oxygen evolution reaction (OER). The FeS2 CLs effectively prevent the oxidation and aggregation of WS2 nanosheets and increase the electrochemically active surface area. The abundant surface defect in the FeS2 CL@WS2 NS electrocatalyst reduces the stress between the crystal lattices of FeS2 and that of WS2. The overpotential (260 mV) of the FeS2 CL@WS2 NS electrocatalyst for the OER at a current density of 10 mA cm-2 is superior to those of WS2 NS/Ni foam (310 mV) and IrO2/Ni foam (300 mV) in 1.0 M KOH solution. An electrochemical-kinetic study shows that the Tafel slope of 54 mV per decade for the FeS2 CL@WS2 NS electrocatalyst is lower than those of WS2 NS (102 mV per decade) and IrO2/Ni foam (77 mV per decade). In addition, the charge transport resistor (2.3 Ω) of the FeS2 CL@WS2 NS electrocatalyst for the OER is smaller than that of WS2 NS. These faster kinetic properties, in turn, explain the high catalytic activity of the FeS2 CL@WS2 NS electrocatalyst for the OER. The XPS and HRTEM results of the post stability sample confirm that Fe2+ and W4+ are oxidized after durability measurement. Thus, we think that the FeS2 CL@WS2 NS electrocatalyst is a promising candidate for efficient, low-cost, and stable non-noble-metal-based OER electrocatalysts.

Photodetectors play a key role in the military, aerospace, communications, bio-imaging, etc. In this study, we fabricate photodetector devices based on (CH3NH3)2FeCuI4Cl2 (MA2FeCuI4Cl2) and (CH3NH3)2InCuI6 (MA2InCuI6) for the first time. We find that the device based on MA2InCuI6 is highly selective for ultraviolet light (880 nA mW-1) and shows high anti-interference for visible-light (20-50 nA mW-1). The electrochemical impedance results indicate that the value (480 ± 10 Ω) of the resistance based on the MA2InCuI6 photodetector device is much smaller than that (1 ± 0.001 MΩ) based on the MA2FeCuI4Cl2 photodetector device, which in turn proves the difference in photoelectric response.

Exploration of cost-efficient and high-performance photocatalyst for H2 evolution by using a facile approach is of great importance. In this manuscript, a facile one-pot method was employed to fabricate MoS2/CdS heterostructures with MoS2 intimately grown on the surface of CdS resulting in the formation of well-defined heterostructures. Screen experiment reveals the optimized photocatalytic H2 evolution performance of MoS2/CdS is far exceeding that of pristine CdS by a factor of more than 162. The outstanding performance can be ascribed to the formation of heterostructures which accelerate charge transportation and separation, and the MoS2 serving as a cocatalyst for the decrease of H2 overpotential. Moreover, the photocatalytic mechanism of the MoS2/CdS was carefully investigated, which contributes to the deep understanding of the photocatalytic process and the designation of other low-cost and high-efficient photocatalyst.

MoO 2 and MoO 3 with specific morphologies are synthesized on flexible carbon cloth through a facile hydrothermal method as supercapacitor electrodes. The prepared prismatic MoO 3 shows a specific capacitance of 54.7 F g −1 in 1 M LiOH electrolyte. Moreover, the prepared MoO 2 presents a spherical profile with hierarchical porous structure. Each MoO 2 sphere is stacked with several layers of MoO 2 “spindle” which is further built by amounts of MoO 2 nanoparticles. A high specific capacitance of 381.0 F g −1 is achieved for the MoO 2 sphere electrode, 7 times higher than that of MoO 3 .

The semi-transparent solar cells are promising to be applied in building integrated photovoltaic (BIPV) and tandem solar cells. In this study, we fabricate semi-transparent and stable solar cells for BIPV by utilizing a poly (ethylene oxide) electrolyte and controlling the size of TiO2 nanoparticles and the thickness of the TiO2 film. The power conversion efficiency of the semi-transparent (over 50% transmittance at 620-750 nm) and quasi-solid solar cells is 5.78% under standard AM1.5G, 100 mW cm-2. The higher conductivity and smaller diffusion resistance of the quasi-solid electrolyte inside the mesoporous TiO2 film indicate the confinement effects of the polymer electrolyte inside a mesoporous TiO2 film. The unsealed semi-transparent and quasi-solid solar cell retains its initial efficiency during 1000 h irradiation in humid air.

A novel kind of hollow carbon spheres with artificial surface openings is fabricated as highly effective supercapacitor electrode. This kind of carbon sphere possesses typical hierarchical mesoporous structure with surface area of 670.0 m2 g−1, much higher than that of the conventional hollow carbon spheres and solid carbon spheres. The electrochemical performance of the prepared hollow carbon spheres with surface openings, hollow carbon spheres and solid carbon spheres electrode are evaluated in acidic aqueous electrolyte. The hollow carbon sphere with surface openings electrode shows the optimal capacitive performance due to the specific surface openings and hierarchical mesoporous structure which can provide a large ion-accessible surface area and a loose channel for the electrolyte ions to diffuse into the internal of the spheres, making the internal charge storage sites work more effectively. The hollow carbon spheres with surface openings electrode achieves a remarkable specific capacitance of 272.2 F g−1, much higher than that of the hollow carbon spheres and solid carbon spheres. Besides, the hollow carbon spheres with surface openings preserves 96.9% of its initial capacitance after 10000 charge-discharge cycles, suggesting a perfect cycle life.

In this study, for the first time, self-driven photodetector based on cubic CH3NH3PbI3 large single crystal (C-MAPbI3 LSC) with adjustable positive-negative signal is fabricated. The preparation of MAPbI3 large single crystal (MAPbI3 LSC) is realized by the method of growth-drop-growth (GDG). The band gap of MAPbI3 single crystals with Pm-3m (221) space group (6.134×6.134×6.134 Å, 90.00 x 90.00 x 90.00) is 1.58 eV. CH3NH3+ cation is orientation-disorder within the perovskite cubo-octahedral cavity. The photocurrent density at 803 nm of the C-MAPbI3 LSC photodetector under different bias voltages is the highest under different wavelength. The responsivities (R), response time, external quantum efficiencies (EQE) and the detectivity (D) for C-MAPbI3 LSC photodetector at 803 nm wavelength with 1 W m-2, respectively, is 508.7 µA/mW, 0.1338 ms, 79.6% and 8.64*1011 Jones. Notably, the C-MAPbI3 LSC photodetector can be self-driven under 0 V bias voltage, in particular, the positive and negative values of the photocurrent can be adjusted. The proposed mechanism of poling inducing built-in potential is explained adjustable positive-negative signal in self-driven photodetector based on cubic CH3NH3PbI3 large single crystal.

Ion exchange of organic-inorganic hybrid perovskite plays an important role in controlling the performance of materials ant its devices. In this study, we found an interesting phenomenon that the precipitate in the in suspension (CH3NH3PbI3-xBrx in γ – butyrolactone) presented different colors at high and room temperature. The mechanism study shows that the phenomenon is controlled by temperature sensitive and reversible halide ion exchange in organic-inorganic hybrid CH3NH3PbI3-xBrx mixed-halide perovskite. The results of structure phase, element composition morphology and band gap indicate that high temperature 55 °C is beneficial to the increasing of I content in MAPbI3-xBrx and room temperature or lower is beneficial to increasing of Br content in MAPbI3-xBrx.measurement were carried out. Compared with MAPbI0.76Br2.24 precipitate obtained at room temperature, MAPbI1.17Br1.83 precipitate obtained at high temperature exhibit wider lattice spacing, better crystallinity, better morphology and narrower band gap. The results and findings in this study will arouse the interest of readers or experts in the field of organic-inorganic hybrid perovskite materials and related optoelectronic applications.

While bismuth vanadate (BiVO4) has emerged as a promising photoanode in solar water splitting, it still suffers from poor electron-hole separation and electron transport properties. Therefore, the development of BiVO4 nanomaterials that enable performing high charge transfer rate at the interface and lowering charge recombination is urgent needed. Herein, cobalt borate (Co-B) nanoparticle arrays anchored on electrospun W-doped BiVO4 porous nanotubes (BiV0.97W0.03O4) was prepared for photoelectrochemical (PEC) water oxidation. One-dimensional, free-standing and porousBiV0.97W0.03O4/Co-B nanotubes was synthesized through electrospun and electrodeposition process. BiV0.97W0.03O4/Co-B arrays exhibit a unique self-supporting core-shell structure with rough porous surface, providing abundant conductive cofactor (W) and electrochemically active sites (Co) exposed to the electrolyte. When applied to PEC water oxidation. BiV0.97W0.03O4/Co-B modified FTO electrode displays high incident photon-to-current conversion efficiency (IPCE) of 33% at 405 nm (at 1.23 V vs. RHE) and its photocurrent density is about 4 times to the pristine nanotube. The higher PEC water oxidation properties of BiV0.97W0.03O4/Co-B porous nanotubes may be attributed to the effectively suppress the electron-hole recombination at electrolyte interface due to its self-supporting core-shell structure, the high electrocatalytic activity of Co and the good electrical conductivity of BiV0.97W0.03O4 arrays. This work offers a simple preparation strategy for the integrated Co-B nanoparticle with BiV0.97W0.03O4 nanotube, demonstrating the synergistic effect of co-catalysts for PEC water oxidation.

In this study, all-inorganic copper halide salt K2Cu2Cl6 single-crystal and thin films were prepared. The single-crystal diffraction data belonged to the monoclinic K2Cu2Cl6 (space group = P2(1)/C, unit cell parameters of a = 4.0340 A, b = 13.7987 A, c = 8.7445 A, α = 90.000, β = 97.123, and γ = 90.000). As far as we know, this is the first study of the copper halide salt K2Cu2Cl6 for optoelectronic applications. The band gap of K2Cu2Cl6 is calculated to be approximately 1.85 eV. A low-cost photodetector based on the K2Cu2Cl6 thin film was efficient under different monochromatic light from 330 to 390 nm with different chopping frequencies (1.33–30 Hz). Density functional theory (DFT) computational results indicate that the valence bands (VBs) and conduction bands (CBs) are shifted up in energy using the orbital-dependent correction to the DFT energy. Partial density of states reveals that the VBs and narrow CBs are derived from the hybrid orbitals of Cu2+ 3d and Cl– p, respectively.

Organic-inorganic hybrid material is a recent hot topic in the scientific community. The best band gap for the entire solar absorption spectrum is about 1.1 eV. However, the lead perovskite band gap is about 1.5 eV. Therefore, developing organic-inorganic hybrid material toward the broader light harvesting of the solar spectrum is extremely urgent. In this study, we prepare three kinds of organic-inorganic hybrid palladium perovskite materials, including (CH3NH3)2PdCl4, (CH3NH3)2PdCl4-x Br x , and CH3NH3PdI3, for an optoelectronic response. The absorption cut offs of (CH3NH3)2PdCl4, (CH3NH3)2PdCl4-x Br x , and CH3NH3PdI3 are approximately 600, 700, and 1000 nm, respectively. The band gaps of (CH3NH3)2PdCl4, (CH3NH3)2PdCl4-x Br x , and CH3NH3PdI3 are determined to be approximately 2.15, 1.87, and 1.25 eV, respectively. To the best of our knowledge, this is the first study that discusses adsorption properties and photoelectric behavior of organic-inorganic hybrid palladium perovskite materials. Interestingly, the photoelectric response of the devices based on CH3NH3PdI3 reaches 950 nm. The results will attract attention in the fields of optical recorders, optical memory, security, light capture, and light treatment.

Splitting of water into hydrogen and oxygen has become a strategic research topic. In the two semi-reactions of water splitting, water oxidation is preferred to the four-electron-transfer process with a higher overpotential (η) and is the decisive step in water splitting. Therefore, efficient water oxidation catalysts must be developed. IrOx and RuOx catalysts are currently the most efficient catalysts in water oxidation. However, the limited reserve and high prices of precious metals, such as Ir and Ru, limit future large-scale industrial production of water oxidation catalysts. In this study, we tune inert Ni-foam into highly active NiOOH/FeOOH heterostructures as water oxidation catalysts via three-step strategy (surface acid-treating, electroplating, and electrooxidation). NiOOH/FeOOH heterostructures as water oxidation catalysts only require η of 257 mV to reach a current density of 10 mA cm–2, which is superior to that of IrO2/Ni-foam (280 mV). The high electrochemically active surface area (72.50 cm2) and roughness factor demonstrate abundant interfaces in NiOOH/FeOOH heterostructures, thus accelerating water oxidation activity. The small value (4.8 Ω cm2) of charge transfer resistance (Rct) indicate that fast electronic exchange occurs between NiOOH/FeOOH heterostructures catalyst and reaction of water oxidation. Hydrogen-to-oxygen volume ratios (approximately 2:1) indicate an almost overall water splitting by the double-electrode system. Faraday efficiency of H2 or O2 is close to 90% at 2:1 hydrogen-to-oxygen volume ratio. NiOOH/FeOOH heterostructures exhibit good stability. The results provide significance in fundamental research and practical applications in solar water splitting, artificial photoelectrochemical cells, and electrocatalysts.

In the process of conversion of solar energy into electricity and fuel, efficient electrocatalysts are indispensable. Rieske iron–sulfur protein and FeS catalysts play an important role in natural photosynthesis (NPS), and in artificial photoelectrochemical cells, respectively. Nano–micro composite catalysts (NMCCs) possess not only high catalytic activity but also fast electron transport. Herein, we prepared a nano–micro composite (NMC) of Fe1−xS nanoparticles decorated on sulfur-doped graphene oxide (S-GO) sheets (namely, Fe1−xS@S-GO–NMC) to be used as a cathode in dye-sensitized solar cells (DSCs). The GO effectively inhibit the aggregation of Fe1−xS nanoparticles. Notably, DSCs based on an Fe1−xS@S-GO–NMC cathode achieved a high solar-to-electrical conversion efficiency up to 7.23%. The conversion efficiency is, to our knowledge, one of the highest efficiencies for DSCs based on an FeS or FeS2 cathode. Although the Fe1−xS@S-GO–NMC exhibited a low thermodynamic possibility for redox reactions, it showed a higher kinetic rate than that of Pt for the charge transfer between the reaction medium and the cathode. This indicates that a fast electron exchange process occurs at the interface between the reaction and the cathode. The value of the time constant (τ) corresponding to the charge exchange resistance based on Fe1−xS@S-GO–NMC (0.0215 ms) was smaller than that obtained with Pt (0.261 ms). Therefore, we ascribed the superior performance of the photoelectrochemical device based on Fe1−xS@S-GO–NMC to its good electrocatalytic performance. The results are of great interest for fundamental research and for practical applications of FeS and FeS2 and their composites in the solar splitting of water, artificial photoelectrochemical cells, and electrocatalysts.

All-inorganic lead halide perovskite CsPbBr3 has important applications in photoelectronic devices such as photodetectors, LEDs and photovoltaic devices. However, preparing high-quality CsPbBr3 thin films has proven to be challenging. In this study, we prepared all-inorganic lead halide perovskite CsPbBr3 thin films with micron-grains (MG-CsPbBr3-TF) via a heat-spraying process (HSP) using a CsPbBr3-saturated solution (CsPbBr3-SS), and the films exhibited large area, low defects and high stability. The grain size of MG-CsPbBr3-TF was about 1–5 microns. The micron-sized grains in MG-CsPbBr3-TF enabled the absorption cutoff edge to be extended from 537 to 545 nm. In addition, the presence of fewer boundaries in MG-CsPbBr3-TF reduced the defects in MG-CsPbBr3-TF (the blue shift of luminescence). The response wavelengths of a low-cost and self-driven (zero-biased) photodetector based on MG-CsPbBr3-TF were from 330 to 600 nm. CsPbBr3 thin films having a large area (10 cm × 10 cm) and micron-sized grains were also prepared by HSP and exhibited excellent stability (1944 h) in air (T = 298 K, 40% humidity). To the best of our knowledge, this is the first study of high-quality CsPbBr3 thin films prepared by HSP. The results are of great interest for both fundamental research and practical applications of CsPbBr3 in photodetectors, LEDs and photovoltaic devices.

Organic–inorganic hybrid-based lead perovskites show inherent and unavoidable problems such as structural instability and toxicity. Therefore, developing low-cost and environment-friendly organic–inorganic hybrid materials is extremely urgent. In this study, we prepared earth-abundant and environment-friendly organic–inorganic hybrid tetrachloroferrate salt CH3NH3FeCl4 (MAFeCl4) for optoelectronic applications. The single crystal diffraction data are assigned to the orthorhombic MAFeCl4 (Pnma space group), with parameters a = 11.453 (5) A, b = 7.332 (3) A, c = 10.107 (5) A, α = 90.000, β = 90.000, and γ = 90.000. The band gap of MAFeCl4 is approximately 2.15 eV. Moreover, three-emission luminescence (398, 432 and 664 nm) was observed. To the best of our knowledge, this is the first study involving the investigation of the structure, adsorption properties and photoelectric behavior of MAFeCl4. A low cost photodetector based on the MAFeCl4 thin film is efficient under different monochromatic light from 330 nm to 410 nm with different chopping frequencies (1.33 Hz to 40 Hz). The photoelectric conversion efficiency based on FTO/TiO2/MAFeCl4/carbon electrode device reaches 0.054% (Voc = 319 mV, Jsc = 0.375 mA cm−2, and fill factor = 0.45) under AM1.5, 100 mW cm−2 simulated illumination. Our findings will attract attention from the magnetic, piezoelectric and photoelectronic research fields.

Minimizing the thermal cracks in mass concrete at an early age can be achieved by removing the hydration heat as quickly as possible within initial cooling period before the next lift is placed. Recognizing the time needed to remove hydration heat within initial cooling period helps to take an effective and efficient decision on temperature control plan in advance. Thermal properties of concrete, water cooling parameters and construction parameter are the most influencing factors involved in the process and the relationship between these parameters are non-linear in a pattern, complicated and not understood well. Some attempts had been made to understand and formulate the relationship taking account of thermal properties of concrete and cooling water parameters. Thus, in this study, an effort have been made to formulate the relationship for the same taking account of thermal properties of concrete, water cooling parameters and construction parameter, with the help of two soft computing techniques namely: Genetic programming (GP) software “Eureqa” and Artificial Neural Network (ANN). Relationships were developed from the data available from recently constructed high concrete double curvature arch dam. The value of R for the relationship between the predicted and real cooling time from GP and ANN model is 0.8822 and 0.9146 respectively. Relative impact on target parameter due to input parameters was evaluated through sensitivity analysis and the results reveal that, construction parameter influence the target parameter significantly. Furthermore, during the testing phase of proposed models with an independent set of data, the absolute and relative errors were significantly low, which indicates the prediction power of the employed soft computing techniques deemed satisfactory as compared to the measured data.

Two-dimensional tungsten sulfide is widely applied in electrocatalysis. However, WS2 possesses catalytic active sites located at the layer edge and an inert surface for catalysis. Therefore, increasing the exposure of active sites at the edge and effectively activating the inert sites on the surface is an important challenge. Here, an edge/defect-rich and oxygen-heteroatom-doped WS2 (ED-O-WS2 ) superstructure was synthesized. The power-conversion efficiency (PCE) of dye-sensitized solar cells (DSCs) based on an ED-O-WS2 counter electrode reached 10.36 % (under 1 sun, AM 1.5, 100 mW cm-2 ) and 11.19 % (under 40 mW cm-2 ). These values are, to our knowledge, the highest reported efficiency for DSCs based on Pt-free counter electrodes in I3- /I- electrolytes. Analysis of the micro/nano structure and the electrocatalytic mechanism indicate that ED-O-WS2 exhibits metallic properties in the electrolyte, and that abundant edges and defects as well as oxygen doping in ED-O-WS2 play an important role in improving the catalytic activity of WS2 . Moreover, ED-O-WS2 displays better catalytic reversibility for I3- /I- electrolytes than Pt.

A novel composite catalyst based on in situ synthesis of W1+49 nanorods on reduced graphene oxide sheets was successfully fabricated through a one-pot solvothermal route. The as-prepared W18O49–reduced graphene oxide (rGO) composite has been systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman microscopy, X-ray photoelectron spectra, and a rotating disk electrode. Compared to W18O49 nanorods or reduced graphene oxide alone, or their physical mixture, the composite catalyst exhibited unexpectedly high ORR activity with a more positive onset-potential (close to that of Pt/C) and a higher kinetic current density (JK), which is mainly attributed to the nanorod morphology, surface oxygen vacancies of W18O49, and strong coupling interaction between the W18O49 nanorods and reduced graphene oxide sheets. These results raise the possibility of developing low-cost and efficient ORR electrocatalysts.

As one type of organic–inorganic hybrid material, APbX3 organic–inorganic lead perovskite materials have attracted considerable attention in optoelectronic applications. Although organic–inorganic lead perovskites possess high solar-to-electrical conversion efficiency, the toxic Pb in organic–inorganic lead perovskites is expected to cause environmental pollution in future mass applications. Thus, exploiting Pb-free organic–inorganic hybrid materials is urgently needed. In this study, a lead-free and amorphous CH3NH3MnI3 (a-MAMnI3) thin film was prepared by spin coating a mixed MnI2 and MAI precursor solution on an electronic transport layer (ETL)-TiO2. A mesoscopic a-MAMnI3/TiO2 heterojunction was formed by filling the mesoporous TiO2 layer with MAMnI3. The architecture of the optoelectronic device is FTO/ETL-TiO2/a-MAMnI3/Spiro-MeOTAD/Ag. The photovoltage of the optoelectronic device based on the mesoscopic a-MAMnI3/TiO2 heterojunction reached 300 mV under AM1.5, 100 mW cm−2 simulated illumination. The evident photoresponse was observed at 530 nm green light. The test with 2000 s on/off cycling indicated the good stability and repeatability of the device. The findings pave a way for realizing Pb-free and amorphous organic–inorganic hybrid materials applied to optoelectronic logic devices, photodetectors, and optical memory devices.

Organic–inorganic lead perovskite materials show impressive performance in photovoltaics, photodetectors, light-emitting diodes, lasers, sensors, medical imaging devices, and other applications. Although organic–inorganic lead perovskites have shown good performance in numerous fields, they contain toxic Pb, which is expected to cause environmental pollution in future large-scale applications. Thus, the photoelectric properties of Pb-free organic–inorganic perovskite materials should be developed and studied. In this paper, we report on the photoresponse of Pb-free organic–inorganic hybrid manganese perovskite (CH3NH3)2MnCl4. To the best of our knowledge, this study demonstrates the first time that organic–inorganic hybrid manganese perovskites are used for this type of application. We found that the solution-processed MA2MnCl4 thin film tends to be oriented along the b-axis direction on the TiO2 surface. The evident photoresponse of the FTO/TiO2/MA2MnCl4/carbon electrode devices was observed under 10–30 ...

Developing a highly effective bifunctional electrode material is vital to the self-powered integrated electronics that combine the energy conversion unit of the dye-sensitized solar cell (DSC) and the energy storage unit of the supercapacitor. In this study, a nitrogen doped carbon sphere (NCS) is synthesized to promote the electrode activity as compared with that of the conventional solid carbon sphere (SCS) in both DSC and supercapacitor systems. In the DSC system, the rigid and flexible devices using NCS counter electrodes yield power conversion efficiencies of 8.64% and 6.73%, much higher than those of the devices using SCS counter electrodes (6.96% and 4.57%). As a supercapacitor working electrode, the NCS shows a remarkable specific capacitance of 224.6 F g−1, much higher than the counterpart value of the SCS electrode (124.9 F g−1) under the same conditions, which demonstrates capacitance improvement by 79.8%. Moreover, NCS preserves more than 90.0% of their initial capacitance after long term stability tests, suggesting a perfect cycle life. The enhanced activity of the NCS can be ascribed to the improved conductivity, charge transfer, and mass transport processes caused by nitrogen doping.

The ideal liquid–solid heterogeneous electrocatalysis should have not only high catalytic activity but also free electron transport. However, preparing a single catalyst that simultaneously possesses both advantages has proven to be challenging. Herein, we prepared nano–micro composite catalysts (NMCCs) composed of highly dispersed Fe3O4 nanoparticles fixed on reduced graphene oxide (RGO) sheets (namely Fe3O4@RGO-NMCC) as the counter electrode (CE) in dye-sensitized solar cells (DSCs). Compared with the Fe3O4 or RGO CE, the Fe3O4@RGO-NMCC CE exhibited improved activity and reversibility for the catalytic reduction of triiodide ions (I3−) to iodide ions (I−). Notably, DSCs using rigid and flexible Fe3O4@RGO-NMCC CEs achieved high PCEs up to 9% and 8% on fluorine-doped tin oxide (FTO)/glass substrates and flexible polymer substrates, respectively. These values are, to our knowledge, some of the highest reported efficiencies for DSCs based on a flexible Pt-free CE. We ascribed the superior catalytic performance of Fe3O4@RGO-NMCC to faster electron hopping between Fe2+ and Fe3+ and free electron transport by broad RGO sheets. Finally, Fe3O4@RGO-NMCC exhibited good stability in the practical application of DSCs because Fe3O4 nanoparticles were chemically bonded to the surface of RGO. Our work here will be of great interest for fundamental research and practical applications of Fe3O4 in lithium batteries, splitting water and magnetic fields.

Carbon-based ZnO/CH3NH3PbI3/C planar heterojunction perovskite solar cells (PHJ-PSCs) were prepared at low-temperature without using organic hole conductor and metal electrode. When measured via reverse bias scan, rigid and flexible PHJ-PSCs achieved power conversion efficiencies (PCEs) up to 8% and 4% on fluorine-doped tin oxide (FTO)/glass substrates and flexible polymer substrates, respectively. The flexible devices were capable of maintaining 80% of their initial PCEs after 1000 times of bending.

Low cost, high efficiency, and stability are straightforward research challenges in the development of organic-inorganic perovskite solar cells. Organolead halide is unstable at high temperatures or in some solvents. The direct preparation of a carbon layer on top becomes difficult. In this study, we successfully prepared full solution-processed low-cost TiO2/CH3NH3PbI3 heterojunction (HJ) solar cells based on a low-temperature carbon electrode. Power conversion efficiency of mesoporous (M-)TiO2/CH3NH3PbI3/C HJ solar cells based on a low-temperature-processed carbon electrode achieved 9%. The devices of M-TiO2/CH3NH3PbI3/C HJ solar cells without encapsulation exhibited advantageous stability (over 2000 h) in air in the dark. The ability to process low-cost carbon electrodes at low temperature on top of the CH3NH3PbI3 layer without destroying its structure reduces the cost and simplifies the fabrication process of perovskite HJ solar cells. This ability also provides higher flexibility to choose and optimize the device, as well as investigate the underlying active layers.

Sufficient contact, high catalytic activity, free electron transport and ionic diffusion are desired for liquid–solid heterogeneous electrocatalysis. However, preparing catalysts that simultaneously possess all of these four advantages has proven challenging. Nanostructures originating from anisotropic growth always exhibit specific structural advantages and unique physical, chemical or catalytic properties. Herein, via a facile and template-free solvothermal approach, we synthesized W18O49 nanofibers (NFs) and nanofiber bundles (NFBs), as well as hierarchical spheres (HSs). As catalyst for the counter electrode (CE) of dye-sensitized solar cells (DSCs), W18O49 NFs demonstrated remarkable electrocatalytic activity because: (i) abundant oxygen vacancies offered sufficient active sites for reduction of I3− into I−; (ii) the one dimensional NFs were more beneficial to electron transport; (iii) the two phases, the liquid electrolyte and the solid NFs, could fully contact each other, and meanwhile ions could diffuse freely among the networks constructed by the interlaced NFs. Notably, DSCs using the NF-based semitransparent CE achieved high photoelectric conversion efficiencies (PCEs) up to 8.58%, superior to those based on NFBs or HSs, and comparable to that of 8.78% using Pt as the CE. Furthermore, it was proven that both the electrolytic activity and the PCE deteriorated drastically when the NFs were destroyed. Our work here will be of great interest for both fundamental research and practical applications of W18O49 nanomaterials in other fields.

Hafnium oxygen nitride binary/ternary nanocomposites were prepared by combining Hf7O8N4, HfO2, and amorphous carbon through a simple chemical synthesis. The obtained HfO2 (Hf-R0-U), HfO2–C (Hf-R5-B), and Hf7O8N4–HfO2–C (Hf-R12-T) were characterized by XRD, SEM, FESEM, and electrochemical measurements. Dye-sensitized solar cells (DSCs) with binary Hf-R5-B and ternary Hf-R12-T composites as counter electrode (CE) showed superior electrocatalytic activity for I3− reduction and high power conversion efficiencies (PCE) of 6.71% and 7.85%, respectively, matching the performance of DSCs with Pt CE (7.19%). The design strategy demonstrated is promising for fabricating highly efficient and low-cost composite CE catalysts for DSCs.

The scarcity and noble indium and platinum (Pt) are important elements in photoelectric nanomaterials. Therefore, development of low cost alternative materials to meet different practical applications is an urgent need. Two-dimensional (2D) layered graphene (GE) with unique physical, mechanical, and electrical properties has recently drawn a great deal of attention in various optoelectronic fields. Herein, the large scale (21 cm × 15 cm) high-quality single layer graphene (SLG) and multilayer graphene on a flexible plastic substrate PET were controllably prepared through layer-by-layer (LBL) transfer using the thermal release adhesive transfer method (TRA-TM). Transmission and antibending performance based on PET/GE were superior to traditional PET/ITO. The square resistance of a nine-layer graphene electrode reached approximately 58 Ω. Combined with our newly developed and highly effective Fe3O4@RGO (reduced graphene oxide) catalyst, the power conversion efficiency of the dye-sensitized solar cell (DSC) using flexible PET/GE conductive substrate was comparable to that of the DSC using the PET/ITO substrate. The desirable performance of PET/GE/Fe3O4@RGO counter electrodes (low-cost indium- and platinum-free counter electrodes) is attributed to the interfacial compatibility between 2D graphene composite catalyst (Fe3O4@RGO) and 2D PET/GE conductive substrate. In addition, DSCs that use only PET/GE (without Fe3O4@RGO catalyst) as counter electrodes can also achieve a photocurrent density of 6.30 mA cm(-2). This work is beneficial for fundamental research and practical applications of graphene and graphene composite in photovoltaics, photocatalytic water splitting, supercapacitors.

A Multiple I-V Ramp Test is designed to stress low-k SiCOH-based dielectrics that have absorbed moisture. Two conduction regimes are found based on the total injected fluence into the dielectric films and the concentration of water in the dielectric. The dielectric under stress is either characterized by electron trapping, or the generation of traps and/or interface states. A mechanism for moisture-related breakdown is proposed that is consistent with results from previous works on water-diffused silicon dioxide films.

Three-dimensional (3D) graphene composites have drawn increasing attention in energy storage/conversion applications due to their unique structures and properties. Herein, we synthesized 3D honeycomb-like Ni 3 S 2 @graphene oxide composite (3D honeycomb-like Ni 3 S 2 @GO) by a one-pot hydrothermal method. We found that positive charges of Ni 2+ and negative charges of NO 3 − in Ni(NO 3 ) 2 induced a transformation of graphene oxide with smooth surface into graphene oxide with wrinkled surface (w-GO). The w-GO in the mixing solution of Ni(NO 3 ) 2 /thioacetamide/H 2 O evolved into 3D honeycomb-like Ni 3 S 2 @GO in solvothermal process. The GO effectively inhibited the aggregation of Ni 3 S 2 nanoparticles. Photoelectrochemical cells based on 3D Ni 3 S 2 @GO synthesized at 60 mM l −1 Ni(NO 3 ) 2 exhibited the best energy conversion efficiency. 3D Ni 3 S 2 @GO had smaller charge transfer resistance and larger exchange current density than pure Ni 3 S 2 for iodine reduction reaction. The cyclic stability of 3D honeycomb-like Ni 3 S 2 @GO was good in the iodine electrolyte. Results are of great interest for fundamental research and practical applications of 3D GO and its composites in solar water-splitting, artificial photoelectrochemical cells, electrocatalysts and Li-S or Na-S batteries.

This paper presents an advanced lumped parameter network (LPN) to predict thermal behavior of a fault-tolerant permanent-magnet (FTPM) motor. The key thermal parameters of the motor, such as equivalent thermal conductivity and convection heat transfer coefficients, have been analyzed and identified. Additionally, the thermal radiation of the motor is considered due to its high temperature gradient from frame surface to ambient medium. Last, the LPN results are compared with finite element method ones, verifying the effectiveness of the development LPN method.

A composite catalyst of rosin carbon/Fe3O4 with marvellous morphology was synthesized and applied as a counter electrode (CE) in dye-sensitized solar cells (DSCs), demonstrating notable electrocatalytic activity for the reduction of I3(-). Based on this CE, a high power conversion efficiency of 8.11% was achieved, comparable to that of the traditional Pt CE.

Low-cost bendable photoanodes and counter electrodes (CEs), as well as gel electrolytes, are potentially desired for the mass production of completely flexible dye-sensitized solar cells (DSSCs). In this work, via printing at low temperature, we fabricated titanium carbide (TiC)-functionalized conductive-carbon (CC) on flexible polyimide (PI) films to replace traditional and expensive Pt/ITO/PEN CEs. Morphology characterization revealed this composite CE was highly porous and homogeneous. Electrochemical investigations demonstrated that this Pt-and-ITO free flexible CE exhibited a high electro-catalytic activity. Finally, the conversion efficiencies of the all flexible quasi-solid DSSCs using this low-cost TiC-CC/PI CE achieved 86% of that based on a Pt/CC/PI CE. Thus, the facile fabrication process of this novel CE, along with its notable performance, are quite promising for the future roll-to-roll production of completely flexible DSSCs.