Structural and Electrical Investigation of Cobalt-Doped NiOx/Perovskite Interface for Efficient Inverted Solar Cells

Inorganic hole-transporting materials (HTMs) for stable and cheap inverted perovskite-based solar cells are highly desired. In this context, NiOx, with low synthesis temperature, has been employed. However, the low conductivity and the large number of defects limit the boost of the efficiency. An approach to improve the conductivity is metal doping. In this work, we have synthesized cobalt-doped NiOx nanoparticles containing 0.75, 1, 1.25, 2.5, and 5 mol% cobalt (Co) ions to be used for the inverted planar perovskite solar cells. The best efficiency of the devices utilizing the low temperature-deposited Co-doped NiOx HTM obtained a champion photoconversion efficiency of 16.42%, with 0.75 mol% of doping. Interestingly, we demonstrated that the improvement is not from an increase of the conductivity of the NiOx film, but due to the improvement of the perovskite layer morphology. We observe that the Co-doping raises the interfacial recombination of the device but more importantly improves the perovskite morphology, enlarging grain size and reducing the density of bulk defects and the bulk recombination. In the case of 0.75 mol% of doping, the beneficial effects do not just compensate for the deleterious one but increase performance further. Therefore, 0.75 mol% Co doping results in a significant improvement in the performance of NiOx-based inverted planar perovskite solar cells, and represents a good compromise to synthesize, and deposit, the inorganic material at low temperature, without losing the performance, due to the strong impact on the structural properties of the perovskite. This work highlights the importance of the interface from two different points of view, electrical and structural, recognizing the role of a low doping Co concentration, as a key to improve the inverted perovskite-based solar cells’ performance

Sustainable and photoresponse triboelectric nanogenerators based on 2D-gC3N4 and agricultural wastes

Two bio-friendly and photoactive triboelectric nanogenerators (TENG) are introduced, employing sustainable and biocompatible materials as functional components. The TENGs utilize corn husk and coconut coir fibers as the positive layers and incorporate two-dimensional graphitic carbon nitride (g-C3N4) nanosheets as negative layers. Upon simple biomechanical forces, the optimized devices fabricated from corn husk and coconut fibers produce a maximum output voltage of 630 V and 581 V, respectively. Under short-circuit conditions, the measured current was approximately 0.79 mA for corn husk-TENG and 11.47 mA for coconut fibers-TENG. Also, the maximum output power of 131 mW and 1980 mW were achieved over a 2 × 2 cm2 area of corn husk-TENG and coconut fibers-TENG. The TENGs were also tested under blue commercial lights and UV light, and an increase of approximately 1.5 times was observed in the output voltages of both TENGs under UV light. These g-C3N4-based TENGs perform superior under UV illumination and can be used as nanogenerators and active photosensors. This paper proposes two eco-environmentally friendly and robust electronic devices for energy harvesting and photo-sensing applications based on two agricultural wastes, corn husk, and coconut coir fibers

Development of a triboelectric nanogenerator for joining of silver nanorods

On account of their excellent properties, 2D nanostructures beyond graphene, such as MoS2, have extensive applications. Given their quantum confinement effects, MoS2 monolayers could efficiently trap electrons as an intermediate layer between friction and electrode in triboelectric nanogenerators (TENGs) and successfully hinder their recombination and air breakdown, increasing their output. With the help of this phenomenon, a TENG called PS+PS/MoS2-AHSG (PPMA) TENG is fabricated with an open-circuit voltage of ≈1200V and a short-circuit current of 0.74mA, and a maximum power of 11.27mW. PPMA TENG consists of transparent polystyrene (PS) and PS/MoS2 as negative contact and storage layers. Also, the positive layer is a novel Alyssum homolocarpum seed gum (AHSG) layer, which is a natural polymer. This TENG could successfully light up 115 commercial light-emitting diodes. PPMA TENG exhibits exceptional mechanical robustness so that after a decrease in its outputs, heating would activate the self-healing mechanism, and the surface charge density could reach from 0.428 to 0.874 µC m−2, which is 82% of the initial value. To demonstrate the practical applications of PPMA TENG as a high-voltage sustainable power source, it is successfully employed to perform a dielectrophoretic assisted welding of silver nanorods

Study on the Effect of Laser Welding Parameters on the Microstructure and Mechanical Properties of Ultrafine Grained 304L Stainless Steel

In the present study, an ultrafine grained (UFG) 304L stainless steel with the average grain size of 300 nm was produced by a combination of cold rolling and annealing. Weldability of the UFG sample was studied by Nd: YAG laser welding under different welding conditions. Taguchi experimental design was used to optimize the effect of frequency, welding time, laser current and laser pulse duration on the resultant microstructure and mechanical properties. X-ray Diffraction (XRD), Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), microhardness measurements and tension tests were conducted to characterize the sample after thermomechanical processing and laser welding. The results showed that the ultrafine grained steel had the yield strength of 1000 Mpa and the total elongation of 48%, which were almost three times higher than those of the as-received sample. The microstructure of the weld zone was shown to be a mixture of austenite and delta ferrite. The microhardness of the optimized welded sample (315 HV0.5) was found to be close to the UFG base metal (350 HV). It was also observed that the hardness of the heat affected zone (HAZ) was  lower than that of the weld zone, which was related to the HAZ grain growth during laser welding. The results of optimization also showed that the welding time was the most important parameter affecting the weld strength. Overall, the study showed that laser welding could be an appropriate and alternative welding technique for the joining of UFG steels

Green Flexible Triboelectric Nanogenerators Based on Edible Proteins for Electrophoretic Deposition

Abstract The next generation of wearable electronics for internet of things (IoT) systems, and green energy harvesting require electrically conductive materials with high flexibility, conductivity, and being environmentally friendly. In this study, three biopolymers, cow's milk, soy milk, and egg white liquid, are investigated and compared as spin‐coated positive layers in triboelectric nanogenerators (TENGs). Superior results are obtained using egg white liquid as a novel liquid conductor with comparable conductivity and high transparency. After investigating various disposable polymers as substrates, sandpaper is used to improve the output performance of the proposed egg white liquid based TENG (EW‐TENG). The maximum output power density, voltage, and current of the EW‐TENG are 328.84 mW cm−2, 1720 V, and 16.05 mA, respectively. The fabricated EW‐TENG, with an area of 4 × 4 cm2, can directly illuminate 55 high‐power blue LEDs and can adequately perform an electrophoretic deposition of ZnO nanoparticles on copper layers without microcracks. The potential distribution of the EW‐TENG obtained by COMSOL Multiphysics software is consistent with the experimental results. Herein, an eco‐environmentally friendly, flexible, and lightweight electronic device for energy harvesting and electrophoretic deposition applications is proposed

Influence of zirconium addition on the microstructure, thermodynamic stability, thermal stability and mechanical properties of mechanical alloyed spark plasma sintered (MA-SPS) FeCoCrNi high entropy alloy

© 2018, © 2018 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute. Equiatomic FeCoCrNi (Zr0) and non-equiatomic FeCoCrNiZr0.4 (Zr0.4) high-entropy alloys (HEAs) were synthesised by mechanical alloying and spark plasma sintering. XRD analysis verified the formation of FCC and BCC solid solution phases in both alloys after 30 h of ball milling. While the SPS FeCoCrNi alloy contains both FCC and BCC solid solution phases, the FeCoCrNiZr0.4 presents an FCC solid solution. The thermodynamic analysis showed that FeCoCrNiZr0.4 is more stable with respect to the FeCoCrNi alloy. The phase stability of FeCoCrNiZr0.4 was revealed up to ∼800°C. The shear strength and hardness of the FeCoCrNi HEA improved with Zr addition. Failure analysis of the shear punch tested samples revealed a ductile fracture with dimple structure for FeCoCrNi and a brittle fracture with a smooth featureless surface for FeCoCrNiZr0.4.status: publishe

Microstructure and Mechanical Properties of Nanostructured CoCrFeMoTi High-Entropy Alloy Fabricated by Mechanical Alloying and Spark Plasma Sintering

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Insights into the Photocatalytic Bacterial Inactivation by Flower-Like Bi2WO6 under Solar or Visible Light, Through in Situ Monitoring and Determination of Reactive Oxygen Species (ROS)

This study addresses the visible light-induced bacterial inactivation kinetics over a Bi2WO6 synthesized catalyst. The systematic investigation was undertaken with Bi2WO6 prepared by the complexation of Bi with acetic acid (carboxylate) leading to a flower-like morphology. The characterization of the as-prepared Bi2WO6 was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), specific surface area (SSA), and photoluminescence (PL). Under low intensity solar light (<48 mW/cm(2)), complete bacterial inactivation was achieved within two hours in the presence of the flower-like Bi2WO6, while under visible light, the synthesized catalyst performed better than commercial TiO2. The in situ interfacial charge transfer and local pH changes between Bi2WO6 and bacteria were monitored during the bacterial inactivation. Furthermore, the reactive oxygen species (ROS) were identified during Escherichia coli inactivation mediated by appropriate scavengers. The ROS tests alongside the morphological characteristics allowed the proposition of the mechanism for bacterial inactivation. Finally, recycling of the catalyst confirmed the stable nature of the catalyst presented in this study

Effect of graphene oxide and friction stir processing on microstructure and mechanical properties of Al5083 matrix composite

In this study, the surface nanocomposite containing graphene oxide was produced on the Al5083 alloy surface, using Friction Stir Processing (FSP) in liquid cooled condition, in order to improve the microstructure and mechanical properties. For this purpose, FSP was carried out up to 3 passes on a base alloy with and without reinforcing particles. Microstructural features and mechanical properties of the obtained surface nanocomposite, FSPed Al 5083 and base alloy were investigated. In order to study the microstructure, Electron Back Scatter Diffraction (EBSD) was used. It was revealed that the grain size nanocomposite was about 1 μm after the process. This was while the grain size of the specimen with no reinforcement, after the process was 6 ± 1.1 μm and the size of the base alloy was 23 ± 2.3 μm. The substantial effect of the reinforcing particles in preventing the grains growth in the nanocomposite specimen was the main reason for this difference. Study of mechanical properties of base alloy, FSPed specimen, and the nanocomposite revealed that the simultaneous use of cooling environment and performing the process, increased the hardness of stir zone compared to the base alloy. This increase was raised in the presence of graphene oxide particles and reached to 123 ± 1.7 HV. It was also observed that the nanocomposite had a better tensile behavior than the base alloy and the FSPed specimen. SEM images of the fracture surfaces indicated the existence of dimples and voids at the surface of the base alloy specimens and the FSPed specimen which showed their ductile fracture, but at the nanocomposite surface, in addition to the ductile fracture, a brittle fracture was occurred