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aSi:H/i-aSi:H/p+aSiGe:H Graded Band Gap Single Junction Solar Cell
摘要： In this paper, we present a single junction graded band gap thin film solar cell using heavily phosphorous doped amorphous silicon, intrinsic amorphous silicon and heavily boron doped amorphous silicon germanium. The first part of the work presents a rigorous analysis of J-V characteristics of recommended photovoltaic structure under short circuit (SC), open circuit (OC), dark and AM 1.5G illumination standard. Further, optimisation of thickness of active layers of the suggested n+aSi:H/i aSi:H/p+aSiGe:H solar cell structure is done using SCAPS1D solar simulator. The active layer thickness of the proposed solar cell is 430 nm only. Low active layer thickness and absence of multiple junctions reduces the material requirement, complexity and cost of the proposed solar cell. Furthermore, fabrication of individual layers and overall summary of their characterisation have been done. Finally, the proposed structure has been fabricated and validated its J-V characteristics. The fabricated solar cell has short circuit current density (Jsc) of 11.67 mA/cm2, open circuit voltage (Voc) of 1.18 V, fill factor (FF) of 0.857 and conversion efficiency (η) of 11.80 % which is on par with other announced single junction amorphous silicon solar cells. Here, we are reporting a single junction graded band gap solar cell using combination of aSi:H and aSiGe:H alloys with varying doping levels for the first time, which is better in conversion efficiency while compact and light.
关键词： SCAPS1D,graded bandgap,amorphous silicon germanium,J-V characteristics,PECVD,Amorphous Silicon Alloys
更新于2025-09-19 17:13:59
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Mapping the geometry of Ti-6Al-4V: From martensite decomposition to localized spheroidization during selective laser melting
摘要： The influence that complex component geometries can have on microstructure formation is investigated in a rocket engine impeller fabricated of a Ti-6Al-4V alloy by selective laser melting (SLM). The SLM melt pool monitoring, indicative of the component’s thermal history during processing, is linked to the bulk mapping of martensite decomposition obtained by high energy synchrotron X-ray diffraction. In addition to the martensitic and lamellar microstructures typically obtained during SLM of Ti-6Al-4V, spheroidization is identified to take place in the component’s down-skin regions. Grain boundary migration may contribute to the latter effect. Small recrystallized grains form along grain boundaries.
关键词： Titanium alloys,X-ray diffraction,Microstructure,Selective laser melting,Synchrotron radiation
更新于2025-09-19 17:13:59
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Development and calibration of a CFD-based model of the bed fusion SLM additive manufacturing process aimed at optimising laser parameters
摘要： The main concern deriving from the Selective Laser Melting technique is attaining a fully dense part out of the interconnected tracks. The right choice of process parameters is of fundamental importance to get a porosity free component. In this work a model has been developed simulating the printing process with the aim of creating a simple numerical tool for designing processing windows suitable to metal alloys of any composition. The applied simplified approach makes the model use as much practical as possible, while keeping the physical description representative. The model has been calibrated fitting experimental measures of track width, depth and cross sectional area taken from three literature sources, referring to: Ti6Al4V, Inconel 625 and Al7050. Effective liquid pool thermal conductivity, laser absorptivity and depth of application of laser energy are the fitting parameters. Laser absorptivity and depth of application of laser energy result to rise almost linearly with increasing specific energy; the slopes of the three analyzed alloys result very close to each other. The obtained results give confidence about the possibility of using the model as a predicting tool after further calibration on a wider range of metal alloys.
关键词： laser parameters,numerical model,processing window,SLM,additive manufacturing,metal alloys
更新于2025-09-19 17:13:59
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Simulation and partial prototyping of an eight‐junction holographic spectrum‐splitting photovoltaic module
摘要： Spectrum‐splitting photovoltaics incorporate optical elements to separate sunlight into frequency bands, which can be targeted at solar cells with bandgaps optimized for each sub‐band. Here, we present the design of a holographic diffraction grating‐based spectrum‐splitting photovoltaic module integrating eight III‐V compound semiconductor cells as four dual‐junction tandems. Four stacks of simple sinusoidal volume phase holographic diffraction gratings each simultaneously split and concentrate sunlight onto cells with bandgaps spanning the solar spectrum. The high‐efficiency cells get an additional performance boost from concentration incorporated using a single or a compound trough concentrator, providing up to 380X total concentration. Cell bandgap optimization incorporated an experimentally derived bandgap‐dependent external radiative efficiency function. Simulations show 33.2% module conversion efficiency is achievable. One grating stack is experimentally fabricated and characterized.
关键词： III‐V alloys,holographic optical elements,solar energy,multijunction,photovoltaic,spectrum splitting photovoltaics
更新于2025-09-19 17:13:59
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Investigation of Laser Polishing of Four Selective Laser Melting Alloy Samples
摘要： Selective laser melting (SLM) is a layer by layer process of melting and solidifying of metal powders. The surface quality of the previous layer directly affects the uniformity of the next layer. If the surface roughness value of the previous layer is large, there is the possibility of not being able to complete the layering process such that the entire process has to be abandoned. At least, it may result in long term durability problem and the inhomogeneity, may even make the processed structure not be able to be predicted. In the present study, the ability of a fiber laser to in-situ polish the rough surfaces of four typical additive-manufactured alloys, namely, Ti6Al4V, AlSi10Mg, 316L and IN718 was demonstrated. The results revealed that the surface roughness of the as-received alloys could be reduced to about 3 μm through the application of the laser-polishing process, and the initial surfaces had roughness values of 8.80–16.64 μm. Meanwhile, for a given energy density, a higher laser power produced a laser-polishing effect that was often more obvious, with the surface roughness decreasing with an increase in the laser power. Further, the polishing strategy will be optimized by simulation in our following study.
关键词： laser polishing,additive manufacturing,selective laser melting,typical alloys,surface roughness
更新于2025-09-19 17:13:59
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High Power Fiber Laser Welding with Filler Material
摘要： Industry today is continually challenged to improve quality, reliability, reduced cycle times, and improve the overall manufacturing efficiency. This is driving manufacturers across various market sectors to consider fiber laser welding and the possibility to automate their welding processes to improve consistency and part quality. Another driver is the changing workforce dynamics. It is hard to find or train skilled workers who can consistently and reliably weld aluminum, titanium, and high-strength nickel alloys. This is particularly true when welding with filler material where the base materials are subject to porosity and cracking during the welding process.
关键词： Fiber Laser Welding,Titanium,Filler Material,Nickel Alloys,Aluminium,Laser Welding
更新于2025-09-19 17:13:59
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Phase and Structural Transformations in Heat Resistant Alloys during Direct Laser Deposition
摘要： DLD, also known as Direct Laser Deposition, is an approached manufacturing technology. It is used to build full density metal parts directly from CAD files without using any modules or tools. A close look over the chemical composition and the microstructure of nickel based alloys will be shown in this paper.
关键词： X-Ray analysis,heat treatment,heat resistant alloys,cracking,Direct laser fabrication,nickel based alloys,direct laser deposition
更新于2025-09-16 10:30:52
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Improved optoelectronic properties in CdSexTe1?x through controlled composition and short-range order
摘要： We employ ?rst principles methods based on density functional theory and beyond to study CdSexTe1?x alloys in the zincblende and wurtzite structures. From the cluster expansion formalism, we provide a detailed phase diagram showing a consolute temperature of 325 K, above which miscibility may be achieved. In the random solid solution, a zincblende-to-wurtzite phase boundary is found to range from Se concentrations of x = 0.5–0.6, in agreement with experiment, owing to increasing ionic character of the Cd-anion bonds. Disordered CdSexTe1?x con?gurations are modeled using special quasirandom structures, for which optoelectronic properties are computed with the hybrid HSE06 functional. Alloying is shown to cause strong bowing e?ects in the band gap and e?ective electron/hole masses, which we attribute to local structural distortions as illustrated by analysis of bond length distributions. Downward bowing in the band gap and e?ective hole mass of the zincblende structure is highlighted for its potential bene?ts in photovoltaics through increased net photocurrent. Absorption coe?cients and re?ectivity are also reported, showing promising results in zincblende CdSexTe1?x as indicated by substantial optical absorption throughout all Se concentrations. Lastly, we identify the presence of short-range order in CdSexTe1?x characterized by clustering among like atoms in order to minimize strain. The degree of clustering, which may be tuned by temperature, also controls the magnitude of the band gap. Therefore, we propose both composition and short-range order as e?ective tools to be utilized in the design and synthesis of improved solar cell absorber layer materials.
关键词： Phase diagram,Optical properties,Bandgap-bowing,Short range order,CdSexTe1?x alloys
更新于2025-09-16 10:30:52
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Analysis of Thin-film Direct Band-gap SiGeSn alloy based Heterostructure Solar Cell Featuring SiGe Absorber Layer
摘要： Ternary alloy Si1-x-yGexSny or GexSn1-x made up of group IV elements has been receiving attention from researchers in recent years due to its direct band gap nature. In this work, we investigate the performance of solar cells made with this alloy. We have proposed a n+ Si1-x-yGexSny (emitter)/p- Si1-xGex (absorber)/p- Si1-x-yGexSny (base) /p+ Si1-x-yGexSny (back surface field layer: BSF) based solar cell grown on Si1-x-yGexSny substrate. The calculated values are compared with the values for existing Si1-xGex solar cells and comparatively improved performances are obtained for the proposed structure. The effects of different absorber layer thickness, doping concentrations of the absorber and BSF layers, Ge concentration in Si1-xGex and Sn concentration in Si1-x-yGexSny are also studied for the proposed structure. Conversion efficiency as high as 19.9% for substrate thickness as low as 10 μm has been obtained for the proposed structure. The low value of substrate thickness and high efficiency make the proposed structure attractive as a low-cost device for applications in spacecraft and satellites.
关键词： conversion efficiency,TCAD simulation,single junction solar cell,Si1-x-yGexSny alloys
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 - Fibre laser trepanning drilling of metals and alloys
摘要： Laser drilling of metals and alloys is extensively used in modern manufacturing industries to produce holes of various sizes and shapes. Currently, most aerospace laser drilling is performed using Nd:YAG laser and over the years many attempts have been made to increase the productivity of Nd:YAG lasers drilling process, but with little success. This paper investigates the use of recently developed millisecond-pulsed-Quasi-CW-fibre-laser for trepanning drilling of aerospace grade nickel super-alloy. The main investigation concentrates on understanding the effects of Quasi-CW-fibre-laser parameters on trepanning laser drilled hole quality. The principal findings are based on reducing the recast and oxide layer. Results show that the high average power of the Quasi-CW-fibre-lasers can be effectively used to achieve increased trepanning drilling speed without undermining the drilling quality, which is not feasible with a free-space Nd:YAG laser. Low peak power and high average power can be effectively used to produce better laser drilled hole than the high peak power and low frequency, which is observed with the traditional millisecond Nd:YAG drilling process.
关键词： alloys,Fibre laser,nickel super-alloy,trepanning drilling,oxide layer,aerospace,recast layer,metals
更新于2025-09-16 10:30:52