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Coupling and Trapping of Light in Thin-Film Solar Cells Using Modulated Interface Textures
摘要： Increasing the e?ciency of solar cells relies on light management. This becomes increasingly important for thin-?lm technologies, but it is also relevant for poorly absorbing semiconductors like silicon. Exemplarily, the performance of a-Si:H/μc-Si:H tandem solar cells strongly depends on the texture of the front and rear contact surfaces. The rear contact interface texture usually results from the front surface texture and the subsequent absorber growth. A well-textured front contact facilitates light-coupling to the solar cell and light-trapping within the device. A variety of di?erently textured ZnO:Al front contacts were sputter deposited and subsequently texture etched. The optical performance of a-Si:H/μc-Si:H tandem solar cells were evaluated regarding the two e?ects: light-coupling and light-trapping. A connection between the front contact texture and the two optical e?ects is demonstrated, speci?cally, it is shown that both are induced by di?erent texture properties. These ?ndings can be transferred to any solar cell technologies, like copper indium gallium selenide (CIGS) or perovskites, where light management and modi?cations of surface textures by subsequent ?lm growth have to be considered. A modulated surface texture of the ZnO:Al front contact was realized using two etching steps. Improved light-coupling and light-trapping in silicon thin-?lm solar cells lead to 12.5% e?ciency.
关键词： thin-?lm solar cell,light-trapping,ZnO:Al,front contact,light-scattering,surface texture,light-coupling
更新于2025-09-16 10:30:52
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Damage Diagnosis of Reactive Powder Concrete under Fatigue Loading Using 3D Laser Scanning Technology
摘要： Damage mechanisms of Reactive Powder Concrete (RPC) under fatigue loading are investigated using the 3D laser scanning technology. An independently configured 3D laser scanning system is used to monitor the damaging procedure. Texture analysis technique is also applied to enhance the understanding of the damage mechanisms of RPC under fatigue loading. In order to obtain the characteristic parameters of point cloud data, a point clouds projection algorithm is proposed. Damage evolution is described by the change of point cloud data of the damage in the 2D plane and 3D space during fatigue loading. The Gray Level Co-occurrence Matrix (GLCM) method is used to extract the characteristic parameters to evaluate the statue of the structural. Angular Second Moment and Cluster Shadow of typical sensitive characteristic indexes is screened by using the Digital Feature Screening. The reliability of the damage index was verified by image texture analysis and data expansion. Indexes extracted in this paper can be used as a new structural health monitoring indicator to assess health condition.
关键词： damage monitoring,texture analysis,feature extraction,gray level co-occurrence matrix,image processing,3D laser scanning
更新于2025-09-16 10:30:52
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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) - Improved Photoabsorption in Thin Gallium Arsenide Solar Cells using Light Trapping Techniques
摘要： Thin absorbers for space photovoltaics can achieve higher radiation tolerance, however, they suffer from reduced photoabsorption as the active region is thinned. In this work, increasing the photoabsorption in thin single junction n-i-p GaAs solar cells have been investigated by applying different light trapping structures at the rear of the cell. The main focus has been to develop a random surface texture that varies in three dimensions to increase light scattering and the effective optical path length. From the EQE, the random back surface reflector was successfully applied to a 1.1 μm thick GaAs solar cell which resulted in a notable 38% increase in current output, when compared to the GaAs baseline cell on its substrate without a BSR. The random texture has shown the capability to maintain the current output in the 1.1 μm thick GaAs absorber and shows promise for enhancing the photoabsorption in thin GaAs absorbers that approach the sub-μm thickness regime.
关键词： photoabsorption,thin GaAs solar cells,light trapping,random maskless texture,radiation tolerance
更新于2025-09-16 10:30:52
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Microstructurea??Texturea??Mechanical Property Relationship in Alloys Produced by Additive Manufacturing Following Selective Laser Melting (SLM) Technique
摘要： Additively manufactured alloys produced by selective laser melting (SLM) exhibit different microstructure, texture and mechanical properties compared to their conventionally processed counterparts. The reason for this difference has been attributed to unique conditions that are met during processing through SLM. The differences are specific to the alloy system. Most influencing variable of SLM processing has been found to be the scanning strategy which comprises interlayer hatch rotation, build orientation, printing pattern (unidirectional, meander or checker board), etc. These variants lead to alteration of microstructure and crystallographic texture. Among the properties, yield strength of SLM-processed alloys has been found to be higher compared to their conventionally processed counterparts, which has been attributed to the finer microstructure and high defect density resulting from the process. On the other hand, ductility is on the lower side due to voids and porosity. The texture of SLM-processed materials shows characteristic features, which is dependent on materials and processing strategies. This further influences the properties. This paper deals with the evolution of microstructure, texture and mechanical properties for selected alloy systems, namely the alloys of iron, aluminium, and titanium, which have been most extensively studied after SLM processing.
关键词： Mechanical properties,Crystallographic texture,Additive manufacturing,Microstructure,Selective laser melting
更新于2025-09-16 10:30:52
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Effect of Laser Processing Parameters on Surface Texture of Ti6Al4V Alloy
摘要： Surface micro-machining was performed on Ti6Al4V alloy sample by nanosecond laser. The micro-morphology, the depth of texture and the chemical composition of melt deposits were analyzed through different techniques including Ultra-Depth Microscopy, SEM and EDS. The single factor method was applied to investigate the influence of different laser parameters on the depth of texture and micro-morphology. The result showed that the depth of texture increased first and decreased with the increase of average power (11-20.9W), the texture depth decreases sharply when the scanning speed increased from 10mm/s to 40mm/s, and the repetition frequency had little effect on the depth of texture. It was possible to select an optimum combination of laser processing parameters that obtain different depths of texture without decreasing the surface quality of texture.
关键词： laser processing parameters,micro-morphology,Ti6Al4V alloy,depth of texture,surface texture
更新于2025-09-12 10:27:22
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Effects of laser additive manufacturing on microstructure and crystallographic texture of austenitic and martensitic stainless steels
摘要： Powder-fed laser additive manufacturing (LAM) based on directed energy deposition (DED) technology is used to produce S316-L austenitic, and S410-L martensitic stainless steel structures by 3D-printing through a layer-upon-layer fashion. The microstructural features and crystallographic textural components are studied via electron backscattering diffraction (EBSD) analysis, hardness indentation and tensile testing. The results are compared with commercial rolled sheets of austenitic and martensitic stainless steels. A well-developed <100> direction solidification texture (with a J-index of ~11.5) is observed for the austenitic structure produced by the LAM process, compared to a J-index of ~2.0 for the commercial austenitic rolled sheet. Such a texture in the LAM process is caused by equiaxed grain formation in the middle of each layer followed by columnar growth during layer-upon-layer deposition. A quite strong preferred orientation (J-index of 17.5) is noticed for martensitic steel developed by LAM. Large laths of martensite exhibit a dominant textural component of <011>//{111} in the α-phase, which is mainly controlled by transformation during layer-by-layer deposition. On the other hand, the martensitic commercial sheet consists of equiaxed grains without any preferred orientation or completely random orientations. In the case of the austenitic steel, mechanical properties such as tensile strength, hardness and ductility were severely deteriorated during the LAM deposition. A ductility loss of about 50% is recorded compared to the commercially rolled sheets that is attributed to the cast/solidified structure. However, LAM manufacturing of martensitic stainless steel structures leads to a considerably enhanced mechanical strength (more than double) at the expense of reduced ductility, because of martensitic phase transformations under higher cooling rates.
关键词： Directed energy deposition (DED),Laser additive manufacturing (LAM),Crystallographic texture,S316-L austenitic stainless steel,S410-L martensitic stainless steel
更新于2025-09-12 10:27:22
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Accuracy and biases in predicting the chemical and physical traits of many types of cheeses using different visible and near-infrared spectroscopic techniques and spectrum intervals
摘要： Near-infrared spectroscopy (NIRS) has been widely used to determine various composition traits of many dairy products in the industry. In the last few years, near-infrared (NIR) instruments have become more and more accessible, and now, portable devices can be easily used in the field, allowing the direct measurement of important quality traits. However, the comparison of the predictive performances of different NIR instruments is not simple, and the literature is lacking. These instruments may use different wavelength intervals and calibration procedures, making it difficult to establish whether differences are due to the spectral interval, the chemometric approach, or the instrument’s technology. Hence, the aims of this study were (1) to evaluate the prediction accuracy of chemical contents (5 traits), pH, texture (2 traits), and color (5 traits) of 37 categories of cheese; (2) to compare 3 instruments [2 benchtop, working in reflectance (R) and transmittance (T) mode (NIRS-R and NIRS-T, respectively) and 1 portable device (VisNIRS-R)], using their entire spectral ranges (1100–2498, 850–1048, and 350–1830 nm, respectively, for NIRS-R, NIRS-T and VisNIRS-R); (3) to examine different wavelength intervals of the spectrum within instrument, comparing also the common intervals among the 3 instruments; and (4) to determine the presence of bias in predicted traits for specific cheese categories. A Bayesian approach was used to develop 8 calibration models for each of 13 traits. This study confirmed that NIR spectroscopy can be used to predict the chemical composition of a large number of different cheeses, whereas pH and texture traits were poorly predicted. Color showed variable predictability, according to the trait considered, the instrument used, and, within instrument, according to the wavelength intervals. The predictive performance of the VisNIRS-R portable device was generally better than the 2 laboratory NIRS instruments, whether with the entire spectrum or selected intervals. The VisNIRS-R was found suitable for analyzing chemical composition in real time, without the need for sample uptake and processing. Our results also indicated that instrument technology is much more important than the NIR spectral range for accurate prediction equations, but the visible range is useful when predicting color traits, other than lightness. Specifically for certain categories (i.e., caprine, moldy, and fresh cheeses), dedicated calibrations seem to be needed to obtain unbiased and more accurate results.
关键词： chemometric,texture trait,cheese quality,water-soluble protein,Bayesian calibration
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - St. Petersburg, Russia (2019.10.17-2019.10.18)] 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Radiomics: Extracting more Features using Endoscopic Imaging
摘要： Cancer is the leading cause of death in the world and delayed detection being the cause of the most significant factor for its high mortality rate. Computers can help radiologists in analyzing medical images and detection of cancer. Radiomics refers to the computerized extraction of information from medical images and provides the potential for making cancer screening with high rapid and more accurate using machine learning algorithms. Endoscopic imaging and X-ray imaging (Computed tomography) are two common methods used in medical imaging. In this paper, the advantages and limitations of endoscopic and CT scan images discussed. Then the features that can be extracted from endoscopic and CT scans are discussed and finally these two imaging methods are considered and compared to use for computer-aided detection systems.
关键词： feature extraction,Computed tomography (CT) scan,Endoscopic image,Radiomics,texture features
更新于2025-09-12 10:27:22
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High energy femtosecond laser peening of 2024 aluminum alloy
摘要： A femtosecond laser with a pulse energy of up to 100 mJ is used to investigate the feasibility of laser peening of a 2024 aluminum alloy that is widely used in aerospace industry. Laser beam directly irradiates the as-received aluminum sample surface in air without any protective coating for laser absorption and transparent overlay for plasma confinement. The effects of pulse energy, pulse duration and beam spot size on peening performance are studied. Optical microscope and SEM are used to examine the surface morphology of laser peened samples. Vickers hardness test is used to determine the microhardness on the surface. Residual stresses on the surface and at selected depths are measured using x-ray diffraction method. It is found that femtosecond laser can impart compressive residual stresses to a depth of more than 100 μm for this material, but the surface stress condition is not altered significantly.
关键词： residual stress,aluminum alloy,hardness,femtosecond laser,surface texture,laser peening
更新于2025-09-12 10:27:22
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Nd3+:YAG laser surface processing of moly-chrome film at 1064 nm, 532 nm and 355 nm wavelengths
摘要： A nanosecond pulsed Nd3+:YAG laser was used to generate grooves as well as dimples on the surface of the moly-chrome film. Interaction of laser, operating at the laser wavelengths of 1064 nm, 532 nm and 355 nm, respectively on the target material were investigated. The principal finding is based on the geometrical parameters such as width, depth and recast layer in the case of the groove. Various roughness parameters inside the grooves were studied. Whereas in the case of the dimple, various parameters like dimple diameter, depth and recast laser were analyzed. A study to find the optical reflectivity of the moly-chrome material at different laser wavelengths was conducted. The groove and dimple formed with the laser wavelength of 1064 nm showed a high material removal and re-cast layer compared to 532 nm and 355 nm. The roughness Ra inside the groove formed with the laser wavelength of 1064 nm and 355 nm exhibited a percentage increase of around 68% and 20% compared to the 532 nm.
关键词： Groove,Wavelength,Surface texture,Dimple,Laser
更新于2025-09-12 10:27:22