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Surface morphology evolution during pulsed selective laser melting: Numerical and experimental investigations
摘要： A novel physical model for the selective laser melting (SLM) was proposed, providing insights into the surface morphology evolution in the pulsed SLM process. Both Marangoni effect and recoil pressure, which were the prevailing driving forces for the melt flow, were incorporated in the model. It was found that the melt track was characterized by regular fish scale patterns in pulsed remelting process, due to the periodic variation of the molten pool, while the melt track exhibited with a smooth surface under a continuous laser mode. The effect of the exposure time on the surface morphology was also investigated during pulsed SLM process. It was shown that the longer exposure time could produce greater recoil pressure and sufficient molten liquid, leading to a more congested fish scale patterns. The surface defects such as distortions and breakups were strongly associated with the distribution characteristics of the powders. The partially melted particles which attached to the melt flow were the main reasons to the formation of distortions. And the formation the breakups could be attributed to the local lacking of the powders. The simulated results were in good agreement with the experimental results.
关键词： Surface morphology,Surface defects,Pulsed selective laser melting,Exposure time,Molten pool evolution
更新于2025-09-16 10:30:52
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Passivating Surface Defects of <i>n</i> a??SnO <sub/>2</sub> Electron Transporting Layer by InP/ZnS Quantum Dots: Toward Efficient and Stable Organic Solar Cells
摘要： N-type tin oxide (n-SnO2) nanoparticle film has shown great potential as an electron transport layer (ETL) in fabricating highly efficient organic solar cells (OSCs) due to its low-temperature preparation and high electrical conductivity. However, surface defects on the n-SnO2 nanoparticles generated by the solution-processed approach seriously limit the performance of the OSCs with n-SnO2 ETL. InP/ZnS quantum dots (QDs) are employed to passivate the surface defects of n-SnO2 ETL, and an inverted OSC using PM6:Y6 as active layer achieves a power conversion efficiency (PCE) of 15.22%, much higher than that of a device based on pure n-SnO2 ETL (13.86%). The synergistic enhancement of the device open-circuit voltage (Voc) and fill factor (FF) is attributed to the improved morphologies of PM6:Y6 layer on the QDs/ETL, increased charge extraction and collection efficiency, and decreased monomolecular recombination caused by the defect-trapped charge carriers in the solar cell. Moreover, the inverted device with n-SnO2/InP/ZnS QDs ETL show a much higher stability than that of the conventional PEDOT:PSS based one. This work presents a promising QDs passivation strategy on n-SnO2 ETL to develop efficient and stable OSCs.
关键词： organic solar cells,surface defects,quantum dots
更新于2025-09-16 10:30:52
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Modelling the influence of laser drilled recast layer thickness on the fatigue performance of CMSX-4
摘要： This paper introduces a novel approach to fatigue life prediction modelling considering the laser drilling effect on film cooling holes of turbine vanes. The methodology proposed is based on a stress-life model such as the Basquin law and the introduction of manufacturing damage effect. The proposed empirical model gives a unique versatility compared to other stress-life models by considering surface damage such as the recast layer produced by the laser drilling process. The proposed empirical model has been thoroughly tested and validated using existing fatigue data. The statistical analysis shows that the proposed model is adequate for estimating the fatigue life of laser drilled specimens considering the recast layer thicknesses effect. The proposed model also can estimate the life of untested specimens even when only a small sample of fatigue data is available, thereby reducing the required testing data.
关键词： Fatigue life,recast layer,laser drilling,surface defects
更新于2025-09-12 10:27:22
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Alkali metal ions passivation to decrease interface defects of perovskite solar cells
摘要： Charge carrier recombination occurring in the interface has become a major hindrance impairing the efficiency and stability of perovskite solar cells (PSCs). Passivation of electronic defects at the surface and grain boundaries is one of the most important strategies to suppress charge recombination and improve crystallization in PSCs. Herein, sodium sulfate (Na2SO4) passivation layer was incorporated into the TiO2/perovskite interface to improve charge transfer. Compared to the devices without Na2SO4, the device with the optimized concentration of Na2SO4 solution exhibits an increased short-circuit current density of 22.83 mA/cm2 and an enhanced fill factor of 73.68%, yielding an increased power conversion efficiency from 15.20% to 18.75%. The efficiency improvement is attributed to the decreased defects and traps as well as the enhanced film crystallization quality.
关键词： Perovskite solar cells,Passivation layer,Surface defects,Charge recombination
更新于2025-09-12 10:27:22
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High-Performance Perovskite Light-Emitting Diode with Enhanced Operational Stability Using Lithium Halide Passivation
摘要： Defect passivation has been demonstrated to be effective in improving the radiative recombination of charge carriers in perovskites, and consequently device performance of the resultant perovskite light-emitting diodes (LEDs). State-of-the-art useful passivation agents in perovskite LEDs are mostly organic chelating molecules, which, however, simultaneously sacrifice the charge transport properties and thermal stability of the resultant perovskite emissive layers, deteriorating the performance especially the operational stability of the devices. In this work, we demonstrate that lithium halides can efficiently passivate defects of halide vacancies and reduce trap state density, suppressing ion migration in perovskite films. Efficient green perovskite LEDs based on all inorganic CsPbBr3 perovskite with a peak external quantum efficiency of 16.2% as well as a high maximum brightness of 50278 cd m-2 are achieved. In addtion, the device shows decent stability even under a brightness of 104 cd m-2. We highlight the universal applicability of defect passivation using lithium halides, which enable us to improve the efficiency and stability of blue and red perovskite LEDs.
关键词： passivation,lithium halide,surface defects,stability,non-radiative
更新于2025-09-12 10:27:22
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Removing Defects in WSe <sub/>2</sub> via Surface Oxidation and Etching to Improve Solar Conversion Performance
摘要： Layered metal dichalcogenide materials (MX2) have great potential for solar energy conversion. However, as-grown MX2 materials often contain edge and terrace defects that degrade semiconducting properties and hinder their solar performance. Herein, we demonstrate a simple approach to removing surface defects and improving the solar performance by using UV-generated ozone to oxidize the surface of WSe2 nanoplates and single crystals, followed by a simple soak in aqueous solutions to remove the oxide. Structural characterizations reveal that defective edges and basal plane defect sites are selectively oxidized and subsequently etched, and the ratio of the non-stoichiometric WSex species is reduced. After this treatment, p-type WSe2 single crystals show increased electron accumulation on the surface and significantly enhanced photoelectrochemical solar conversion efficiency. These results and insights will be useful in the improvement and utilization of layered MX2 materials based on both Se and S for solar energy conversion and other device applications.
关键词： surface defects,oxidation,layered metal dichalcogenide,WSe2,UV-generated ozone,etching,solar conversion
更新于2025-09-10 09:29:36
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Facial construction of defected NiO/TiO2 with Z-scheme charge transfer for enhanced photocatalytic performance
摘要： Here we report a defected NiO/TiO2 composite (NiO/TiO2-OV) fabricated by a two-step hydrothermal method with the followed one-step calcination, which induced the in situ generation of Ti3+ and oxygen vacancies, coupled with the construction of a direct Z-scheme band structure. The NiO/TiO2-OV catalyst exhibited a substantially improved performance in the photodegradation of organic pollutant and photocatalytic hydrogen evolution reaction (HER). The sensitization by narrow bandgap semiconductor of NiO enhanced the light response of catalysts. More importantly, the intrinsic defects, the Ti3+ and oxygen vacancies, acted as the mid-gap state in TiO2, and resulted in the direct Z-scheme charge transfer between the Ti3+/oxygen vacancies state and the valance band (VB) of NiO to suppress the recombination of photogenerated electrons and holes. Meanwhile, the realignment of band structure caused by constructing NiO/TiO2 heterojunction made the photogenerated carries more active in the photocatalytic reduction and oxidation reactions.
关键词： Z-scheme charge transfer,NiO/TiO2 hybrid,Photocatalysis,Surface defects,Self-doping of Ti3+
更新于2025-09-09 09:28:46