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Electronic and plasmonic phenomena at nonstoichiometric grain boundaries in metallic SrNbO <sub/>3</sub>
摘要： Grain boundaries could exhibit exceptional electronic structure and exotic properties, which are determined by a local atomic configuration and stoichiometry that differs from the bulk. However, optical and plasmonic properties at the grain boundaries in metallic oxides have rarely been discussed before. Here, we show that non-stoichiometric grain boundaries in the newly discovered metallic SrNbO3 photocatalyst show exotic electronic, optical and plasmonic phenomena in comparison to bulk. Aberration-corrected scanning transmission electron microscopy and first-principles calculations reveal that a Nb-rich grain boundary exhibits an increased carrier concentration with quasi-1D metallic conductivity, and newly induced electronic states contributing to the broad energy range of optical absorption. More importantly, dielectric function calculations reveal extended and enhanced plasmonic excitations compared with bulk SrNbO3. Our results show that non-stoichiometric grain boundaries might be utilized to control the electronic and plasmonic properties in oxide photocatalysis.
关键词： plasmonic properties,SrNbO3,grain boundaries,photocatalysis,metallic oxides
更新于2025-09-23 15:19:57
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Grain orientation and crystallographic texture governed gradient oxidation in laser peening
摘要： This study examined the microstructural/crystallographic textural changes within a laser peened circular spot on Al-Li alloy 2060-T8 and their correlation with gradient oxidation. These changes were looked at the center and edge regions of the circular spot peened at 8 J and 13 J pulse energies. At the pulse energy of 13 J, grain orientation profoundly changed from h0 0 1i (base region) to h1 1 0i (laser spot) with reduced low coincidence site lattice boundaries at the edge of the laser spot. Ideal fibre texture was transformed into strong Cube {0 0 1} h1 0 0i and Goss {0 1 1} h1 0 0i textures respectively at 8 J and 13 J. Dense atomic structured h1 1 0i and h1 1 1i grain orientations and transformed strong Goss texture are observed to promote the oxidation significantly at the edge of laser spot for 13 J. Reasons for gradient oxidation within the laser peened spot were explained from the view point of microstructural/crystallographic textural changes.
关键词： Al-Li alloy,Oxidation,Grain boundaries,Texture,Laser peening
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Growth Evolution of Polycrystalline CdTe/CdS with Atomic Scale Resolution via Molecular Dynamics
摘要： A new method to study polycrystalline growth of CdTe layers has been developed using Molecular Dynamics (MD). The results show the creation of polycrystalline CdTe/CdS structures that closely recreate the morphology of experimental polycrystalline growth. The growth shows the nucleation and coalescence of grains at early stages for CdS on amorphous CdS and CdTe on polycrystalline CdS.
关键词： grain boundaries,grain growth evolution,polycrystalline structures,molecular dynamics
更新于2025-09-19 17:13:59
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Controlled Growth of Single‐Crystal Graphene Films
摘要： Grain boundaries produced during material synthesis affect both the intrinsic properties of materials and their potential for high-end applications. This effect is commonly observed in graphene film grown using chemical vapor deposition and therefore caused intense interest in controlled growth of grain-boundary-free graphene single crystals in the past ten years. The main methods for enlarging graphene domain size and reducing graphene grain boundary density are classified into single-seed and multiseed approaches, wherein reduction of nucleation density and alignment of nucleation orientation are respectively realized in the nucleation stage. On this basis, detailed synthesis strategies, corresponding mechanisms, and key parameters in the representative methods of these two approaches are separately reviewed, with the aim of providing comprehensive knowledge and a snapshot of the latest status of controlled growth of single-crystal graphene films. Finally, perspectives on opportunities and challenges in synthesizing large-area single-crystal graphene films are discussed.
关键词： single-crystal,graphene,grain boundaries,growth,chemical vapor deposition,nucleation
更新于2025-09-19 17:13:59
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A Review on Reducing Grain Boundaries and Morphological Improvement of Perovskite Solar Cells from Methodology and Material‐Based Perspectives
摘要： Perovskite solar cells (PSCs) have achieved 25.2% of their certified efficiency and emerged as up-and-coming energy-harvesting candidates owing to their superior properties. However, perovskite films are mainly polycrystalline films, and thus, the formation of grain boundaries (GBs) is inevitable. Since GBs have numerous defect sites that provide a channel for ion migration, reducing GBs is highly significant for achieving high efficiency and long-term stability of PSCs. To this end, researchers have made efforts to produce a large crystal-based perovskite film with reduced GBs. In this study, various methods that decrease GBs and enhance the morphology of perovskites are summarized and categorized into methodology- and material-based approaches. Furthermore, a future research direction to produce high-quality and large grain-based perovskite film is also proposed.
关键词： perovskite solar cells,morphology,deposition methods,additive engineering,grain boundaries
更新于2025-09-19 17:13:59
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Interactions of plasmonic silver nanoparticles with high energy sites on multi‐faceted rutile TiO? photoanodes
摘要： The plasmonic interactions between silver nanoparticles and various rutile TiO2 facets are studied by correlating Advanced Electron Microscopy and Electrochemical Impedance Spectroscopy (EIS) to help design a route towards an optimised polycrystalline film fabrication. By using an Electron Backscatter Diffraction (EBSD) detector, it was determined that using HF as directing agent during the hydrothermal growth of TiO2 promotes the formation of high-angle grain boundaries. Silver photodeposition occurs preferentially at these boundaries, consistent with the presence of high energy sites on the (100)-oriented rutile TiO2 nanorods. Further EIS study showed an increase in the photoelectrochemical activity in the visible range of the solar spectrum for the samples consisting of silver nanoparticles deposited on these grain boundaries.
关键词： Water Splitting,Photoelectrochemistry,Plasmonic enhancement,Electron Microscopy,Grain Boundaries
更新于2025-09-19 17:13:59
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Interfacial and structural modifications in perovskite solar cells
摘要： The rapid and continuous progress in perovskite solar cells (PSCs) has drawn lots of attention from the photovoltaic research community and urges them to apply perovskite in other electronic devices such as photo detectors, light-emitting diodes, and batteries. Thanks to the diversity of the device configuration, optimization of the film deposition and exploration of material system, the power conversion efficiency (PCE) of PSCs has boosted to a certified 25.2%, making this solar cell to date the fastest advancing technology. As demonstrated by worldwide researchers, controlling the morphology and defects of the perovskite film is essential for attaining high performance of PSCs. In this regard, interface engineering has proven a very efficient way to address these issues, obtaining better charge collection efficiency and reducing recombination losses. In this review, the interfacial modification between perovskite films and charge-transport layers (CTLs) as well as CTLs and electrodes of PSCs has been widely summarized. Grain boundary (GB) engineering and stress engineering are also included since these are closely related with the improvement of device performance and stability.
关键词： grain boundaries,stress engineering,perovskite solar cell,structural,Interfacial,defects
更新于2025-09-19 17:13:59
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Heavy Alkali Treatment of Cu(In,Ga)Se <sub/>2</sub> Solar Cells: Surface versus Bulk Effects
摘要： Chalcopyrite solar cells achieve efficiencies above 23%. The latest improvements are due to post-deposition treatments (PDT) with heavy alkalis. This study provides a comprehensive description of the effect of PDT on the chemical and electronic structure of surface and bulk of Cu(In,Ga)Se2. Chemical changes at the surface appear similar, independent of absorber or alkali. However, the effect on the surface electronic structure differs with absorber or type of treatment, although the improvement of the solar cell efficiency is the same. Thus, changes at the surface cannot be the only effect of the PDT treatment. The main effect of PDT with heavy alkalis concerns bulk recombination. The reduction in bulk recombination goes along with a reduced density of electronic tail states. Improvements in open-circuit voltage appear together with reduced band bending at grain boundaries. Heavy alkalis accumulate at grain boundaries and are not detected in the grains. This behavior is understood by the energetics of the formation of single-phase Cu-alkali compounds. Thus, the efficiency improvement with heavy alkali PDT can be attributed to reduced band bending at grain boundaries, which reduces tail states and nonradiative recombination and is caused by accumulation of heavy alkalis at grain boundaries.
关键词： grain boundaries,alkali treatment,recombination,bulk,surface,chalcopyrite solar cells
更新于2025-09-16 10:30:52
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Microstructural characterization of Inconel 718 alloy after pulsed laser surface treatment at different powers
摘要： An annealed Inconel 718 alloy was surface-treated by pulsed laser at three different powers (100, 50 and 25 W). Microstructural changes induced by the laser treatments were characterized by use of electron backscatter diffraction and electron channeling contrast imaging techniques. Results show that both annealing twins and strengthening precipitates profusely existing in the as-received specimen are dissolved at elevated temperatures during the laser irradiation. Meanwhile, in the melting zone (MZ), densities of low angle boundaries (LABs) are greatly increased with a large number of Laves phases preferentially distributed along such LABs. For different specimens, widths and depths of their MZs are found to be gradually reduced with decreasing the laser powers. Orientation analyses reveal that the columnar grains in the MZ of the 100 W specimen could inherit orientations existing in the matrix while lower laser powers promote the formation of more nuclei with scattered orientations to grow to be granular grains in the MZ. Hardness tests reveal that the MZs of all laser-treated specimens are softer than the matrix probably due to both precipitate dissolution and grain coarsening.
关键词： pulsed laser surface treatment,hardness,grain boundaries,Inconel 718 alloy,electron backscatter diffraction
更新于2025-09-16 10:30:52
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Beneficial effects of potassium iodide incorporation on grain boundaries and interfaces of perovskite solar cells
摘要： Grain boundaries and interfacial impurities are the main factors that limit the further development of polycrystalline perovskite solar cells because their existence severely deteriorates the device performance. In order to optimize the efficiency of perovskite solar cells, it is essential to eliminate these defects. In the present work, potassium iodide (KI) is incorporated into the perovskite absorber. KI incorporation improves the crystallinity of the perovskite, increases the grain size, and decreases the contact potential distribution at the grain boundary, which are verified by X-ray diffraction, scanning electronic microscopy and Kelvin probe force microscopy. Besides, the activation energy of the recombination, estimated from the temperature dependent current–voltage of perovskite solar cells, is larger than the bandgap calculated from the temperature coefficient. These suggest that KI incorporation effectively passivates the grain boundaries and interfacial defects. As a result, charge trapping in the absorber as well as the bimolecular and trap-assisted recombination of the device are significantly suppressed. Consequently, the open circuit voltage and fill factor of the incorporated devices are greatly improved, enabling an optimized power conversion efficiency of 19.5%, in comparison with that of 17.3% for the control one. Our work provides an effective strategy of defect passivation in perovskite solar cells by KI incorporation and clarifies the mechanism of the performance optimization of KI incorporated devices.
关键词： potassium iodide,perovskite solar cells,defect passivation,grain boundaries,power conversion efficiency
更新于2025-09-11 14:15:04