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LD end-pumped single-ended bonding Tm:LuAG laser
摘要： A diode end-pumped Tm:LuAG laser at room temperature was reported. The thermal lens effect of Tm:LuAG crystal was analyzed, the distribution of the light field and thermal field in the crystal was simulated moreover. In this paper, by using plane-concave resonator, the continuous 2 μm laser output with maximum output power of 10.8 W is obtained. The slope efficiency is 19.56% and the optical-to-optical conversion efficiency is 25.71%. The beam quality factors M2 are 1.24 and 1.28 in the x and y directions respectively.
关键词： Single-ended bonding,Laser diode pumped,Tm:LuAG crystal,2 μm
更新于2025-09-16 10:30:52
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Increasing of ENF Bonded Joints Performance by Design of Laser Surface Texturing
摘要： The quality of a bonded joint is strongly linked to the surface treatment used for the adherends. Recently, many studies have showed the opportunity to use a CO2 laser for enhancing the mechanical properties of bonded joints in FRP. Nowadays, to optimize their process parameters and texturing represent a necessary step for the growth in this technology. In this work, an experimental and numerical study of the effect of laser texturing on end notched flexure (ENF) joints realized in CFRP has been developed. The laser texturing showed an important effect on the mechanical resistance of ENF joints, with an increase of at least 76% respect untreated ones. The numerical results showed a good agreement with the experimental ones. Therefore, it is possible to design of the laser texturing for optimizing the mechanical response of bonded joints.
关键词： finite element analysis,Adhesive bonding,laser treatment
更新于2025-09-16 10:30:52
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The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling
摘要： The light-harvesting in photosynthetic purple bacteria can be tuned in response to the light conditions during cell growth. One of the used strategies is to change the energy of the excitons in the major light-harvesting complex, commonly known as LH2. In the present study we report the first systematic investigation of the microscopic origin of the exciton tuning using three complexes, namely the common (high-light) and the low-light forms of LH2 from Rps. acidophila plus a third complex analogous to the PucD complex from Rps. palustris. The study is based on the combination of classical molecular dynamics of each complex in a lipid membrane and excitonic calculations based on a multiscale quantum mechanics/molecular mechanics approach including a polarizable embedding. From the comparative analysis, it comes out that the mechanisms that govern the adaptation of the light conditions use the different H-bonding environment around the bacteriochlorophyll pigments to dynamically control both internal and inter-pigment degrees of freedom. While the former have a large effect on the site energies, the latter significantly change the electronic couplings, but only the combination of the two effects can fully reproduce the tuning of the final excitons and explain the observed spectroscopic differences.
关键词： purple bacteria,H-bonding environment,multiscale modeling,light-harvesting complexes,excitonic tuning
更新于2025-09-16 10:30:52
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Stress mitigation for adhesively bonded photovoltaics with fibre reinforced polymer composites in load carrying applications
摘要： Structural loads, especially in-plane compression, may cause local buckling and debonding of the photovoltaic (PV) cells that are mechanically integrated with structural members and this may lead to degradation in their electrical performance. This paper proposes an approach to mitigate the strains transferred from structural members to PV cells through the partial composite action provided by low-modulus adhesives. Specimens were fabricated by bonding amorphous silicon (a-Si) PV cells to glass fibre reinforced polymer (GFRP) structural components by an adhesive layer of 0.5- or 2.0-mm thickness. Two types of adhesives were used including a two-part rigid epoxy adhesive and a low-modulus silicone adhesive. These integrations were then submitted to in-plane compressive loadings. PV cells bonded by the silicone adhesive showed no damages during loading. While for PV cells bonded by epoxy adhesives, obvious electrical performance degradations were observed, when the strain reached 0.62% or 0.23% for specimens bonded by epoxy with a layer thickness of 0.5 mm or 2.0 mm respectively. Debonding and local-buckling of the PV cells were also witnessed. Theoretical analysis was conducted to understand the strain mitigation of the adhesive as a result of the induced partial composite action. Results demonstrate that such strain differences between the GFRP and the bonded PV cell are dominated by the shear modulus and thickness of the adhesive layer as well as elastic modulus, thickness and length of the PV cell. The theoretical analysis was validated by finite element (FE) modelling and design suggestions are provided accordingly.
关键词： Building integrated photovoltaics (BIPV),Solar cell,Compression,Bonding,Adhesive,Composite action,Fibre reinforced polymer composites
更新于2025-09-16 10:30:52
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Enhancing charge mobilities in self-assembled Na?ˉI halogen bonded organic semiconductors: A design approach based on experimental and computational perspectives
摘要： Charge transport in pyridine-ethynyliodophenyl supramolecules that involve intermolecular halogen bonding is studied by a combined experimental and computational approach. Selective fluorination of the molecules determines their crystallization pattern and is found to potentially increase the charge mobilities in the crystal. We report the synthesis of the molecules, full chemical characterization and resolved crystal structures. Computational analysis of the charge transport is provided to understand at the molecular level the structure-function relationships determining the charge mobilities. Combination of selective fluorination, halogen bonding motif and increased π system is highlighted as bearing the potential to achieve both enhanced hole and electron mobilities.
关键词： Selective fluorination and phenylation,Hole and electron mobility,Halogen bonding,Organic semiconductors,Charge transport,Density functional theory
更新于2025-09-16 10:30:52
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Freestanding and supported processing of sub-70 μm kerfless epitaxial Si and thinned Cz/FZ Si foils into solar cells: An overview of recent progress and challenges
摘要： Utilisation of expensive silicon (Si) material in crystalline Si modules has come down to 4 g Si per watt-peak in 2018, mainly as a result of reduction in wafer thickness and kerf losses as well as increase in module efficiencies. With continued progress in conventional multi-wire sawing of ingots, wafers as thin as 100 μm could eventually be produced. Beyond this, kerfless lift-off technologies are being investigated which enable wafer thicknesses well below 100 μm with negligible Si kerf waste. Such thin Si wafers and foils would be much lighter in weight than today's standard 165-180 μm-thick wafers and would exhibit considerable flexibility and fragility. This necessitates a rethink about how to handle and process thin Si into solar devices in a manufacturing line with high mechanical yield and high throughput. This paper gives a broad overview of the different approaches for fabricating solar cells on thin Si foils. In particular, three routes are discussed in detail, namely (1) freestanding processing of thin Si, (2) processing of thin Si supported mechanically on a conductive low-cost Si substrate (“wafer-equivalent” approach) and (3) processing of thin Si bonded to a transparent glass superstrate. In each case, the main challenges are explained and the recent progress in addressing them are summarised. Kerfless 50 μm-thick epitaxial Si foils lifted-off using porous Si and thinned-down Si wafers (below 70 μm) are used as model substrates for this work.
关键词： Fragility,Layer transfer,Breakage,Lift-off,Glass superstrate,Thin silicon foils,Supported processing,Epitaxial silicon,Bonding,Adhesive,Wafer-equivalent,Low-cost silicon substrate,Flexibility,Kerfless,Freestanding
更新于2025-09-16 10:30:52
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Laser radiation as a robust tool for the surface pre-treatment of FRP prior to adhesive bonding
摘要： Within the research project “ProPhoMuLA“, funded by the Federal Ministry of Education and Research (BMBF), fundamentals for innovative laser pre-treatment processes for fiber reinforced plastics (FRP) are elaborated in order to improve the adhesive joining properties of multi-material joints, e.g. FRP-FRP or FRP-metal-joints. The increasing application of material mixture results in a growing importance of the adhesive bonding technology as the most promising joining technique for multi-material joints. Until now, the use of adhesive bonding for multi-material joints is, however, connected with high process-technical expenditure. In addition, despite the successful implementation in individual applications, the methods have not yet been sufficiently developed for automotive large-scale manufacturing. One of the most important challenges is the provision of robust surface pre-treatment methods in order to ensure efficient and durable adhesively bonded joints. The possibility of in-line application is an advantage of the laser pre-treatment compared to other surface pre-treatment technologies such as sand blasting or grinding. Therefore, the application of laser pre-treatment technologies based on photonic production methods is predestined for this task. Numerical simulations are performed to analyze the influence of laser surface pre-treatment on automotive product developments. Suitable simulation methods are identified and validated regarding the functionality of the considered approach. The results of empirical investigations show that the laser pre-treatment is suitable, especially for the pre-treatment of thermoplastic FRP, where an increase of peel resistance to the factor of four in comparison to conventional pre-treatment techniques can be achieved.
关键词： photonic production methods,FRP,adhesive bonding,laser pre-treatment,surface pre-treatment
更新于2025-09-16 10:30:52
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Photodetector Based on Spontaneously Grown Strongly Coupled MAPbBr3/N-rGO Hybrids Showing an Enhanced Performance
摘要： Recently, metal-halide perovskites have emerged as a candidate for optoelectronic applications such as photodetectors. However, the poor device performance and instability have limited their future commercialization. We herein report the spontaneous growth of perovskite/N-rGO hybrid structures using a facile solution method and their application for photodetectors. In the hybrid structures, perovskites were homogeneously wrapped by N-rGO sheets through strong hydrogen bonding. The strongly coupled N-rGOs facilitate the charge carrier transportation across the perovskite crystals, but also distort the surface lattice of the perovskite creating potential barrier for charge transfer. We optimize the addition of N-rGO in the hybrid structures to balance the interfacial structural distortion and the inter-crystal conductivity. A high-performance photodetection up to 3 × 104 A/W, external quantum efficiency (EQE) exceeding 105 % and detectivity up to 1012 Jones were achieved in the optimal device with the weight ratio between perovskites and N-rGO to be 8:1.5. The underlying mechanism behind the optimal N-rGO addition ratio in the hybrids has also been rationalized via time-resolved spectroscopic studies as a reference for future application.
关键词： hydrogen bonding,perovskite/N-rGO,hybrid material,photodetector,time-resolved spectroscopy
更新于2025-09-12 10:27:22
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Influence of temperature and clamping force on the strength of the joint over different composite-metal combinations joined by laser
摘要： Vehicle weight in automobile industry is a strict limitation which can be overcome with novel material combinations. Laser conduction joining is an arising alternative but it still poses challenges for joining dissimilar metal-composite materials. Up to now, main research lines have been developed using constant process parameters (laser power and clamping force), so, the behavior of these composite-metal joints under different process parameters, and the control of the process itself, are unknown areas of investigation so far. This paper is focused on the implementation of closed-loop control systems for temperature and clamping force. Tests at different set-points have been carried out for different composite-metal combinations, and the strength of the joints has been assessed by single lap shear tests. The optimal joining process parameters have been found for each material combination.
关键词： Quality assurance,Laser joining,Metal-composite joining,Laser bonding,Process control
更新于2025-09-12 10:27:22
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Fluorescence coupled with electrochemical approach at the bulk and the interface region of hydrogen-bonding self assemblies of urea derivatives with DDP dye in aqueous solution
摘要： Photophysical and electrochemical techniques were employed to hydrogen-bonding self assemblies forming solutes (Urea, Dimethylurea and Tetramethylurea) in the presence of 4-dicyanomethylene 2, 6-dimethyl-4H-pyran (DDP) dye. Addition of urea derivatives to DDP dye (Intramolecular Charge Transfer (ICT)) results in a fluorescence enhancement accompanied with a significant shift. Fluorescence lifetime behavior exhibits a tri-exponential decay with a large variation in the fluorescence lifetime and relative amplitude distribution. The co-existence of three different fluorescence lifetime components of DDP with urea derivatives signifies the existence of heterogeneous micro environment. The dye is surrounded by varying proportion of solute and water molecules are established from fluorescence lifetime studies. Urea derivatives govern the excited state characteristics of DDP dye resulting in the formation and promotion of different microenvironment which are clearly distinguishable. The existence of multi environment attributed to urea-water structural behaviour is authenticated by electrochemical impedance spectral studies (EIS). A large variation in the contour pattern, shape and intensity in 3D fluorescence contour spectra of dye with urea validate the existence of dye in a heterogeneous micro environment. The hydrophobicity of urea derivatives along with the hydrogen-bonding properties of urea-water and urea-urea influence the photophysical and electrochemical nature of dye is emphasized.
关键词： Hydrogen-bonding,Urea derivatives,Fluorescence lifetime,Electrochemical impedance spectra,Fluorescence emission,DDP dye
更新于2025-09-12 10:27:22