A review of automated solar photovoltaic defect detection systems : approaches, challenges, and future orientations

The development of Photovoltaic (PV) technology has paved the path to the exponential growth of solar cell deployment worldwide. Nevertheless, the energy efficiency of solar cells is often limited by resulting defects that can reduce their performance and lifespan. Therefore, it is crucial to identify a set of defect detection approaches for predictive maintenance and condition monitoring of PV modules. This paper presents a comprehensive review of different data analysis methods for defect detection of PV systems with a high categorisation granularity in terms of types and approaches for each technique. Such approaches, introduced in the literature, were categorised into Imaging-Based Techniques (IBTs) and Electrical Testing Techniques (ETTs). Although several review papers have investigated recent solar cell defect detection techniques, they do not provide a comprehensive investigation including IBTs and ETTs with a greater granularity of the different types of each for PV defect detection systems. Types of IBTs were categorised into Infrared Thermography (IRT), Electroluminescence (EL) imaging, and Light Beam Induced Current (LBIC). On the other hand, ETTs were categorised into Current-Voltage (I-V) characteristics analysis, Earth Capacitance Measurements (ECM), Time Domain Reflectometry (TDR), Power Losses Analysis (PLA), and Voltage and Current Measurements (VCM). Approaches based on digital/signal processing and Machine Learning (ML) models for each method are included where relevant. Moreover, the paper critically analyses the advantages and disadvantages of each of the adopted techniques, which can be referred to by future studies to identify the most suitable method considering the use-case’s requirements and setting. The adoption of each of the reviewed techniques depends on several factors, including the deployment scale, the targeted defects for detection, and the required location of defect analysis in the PV system, which are expanded further in the presented analysis. From a high-level perspective, while IBTs provide a high-resolution visual representation of the module surface, allowing for the detection and diagnosis of small structural defects that may be missed by other techniques, ETTs can detect electrical faults beyond the PV module’s surface. On the IBT level, the most notable adopted techniques in the literature are IRT- and EL-based. While IRT techniques are more practical for large-scale applications than EL imaging, the latter is considered a non-intrusive technique that is highly efficient in localising defects of solar cells. The paper also discusses challenges observed in the state-of-the-art related to data availability, real-time monitoring, accurate measurements, computational efficiency, and dataset distribution, and reviews data pre-processing and augmentation approaches that can address some of these challenges. Furthermore, potential future orientations are identified, addressing the limitations of PV defect detection systems

Fabrication, characterization of high-entropy alloys and deep learning-based inspection in metal additive manufacturing

Alloying has been used to confer desirable properties to materials. It typically involves the addition of small amounts of secondary elements to a primary element. In the past decade, however, a new alloying strategy that involves the combination of multiple principal elements in high concentrations to create new materials called high- entropy alloys (HEAs) has been in vogue. In the first part, the investigation focused on the fabrication process and property assessment of the additive manufactured HEA to broaden its engineering applications. Additive manufacturing (AM) is based on manufacturing philosophy through the layer-by-layer method and accomplish the near net-shaped components fabrication. Attempt was made to coat AlCoCrFeNi HEA on an AISI 304 stainless steel substrate to integrate their properties, however, it failed due to the cracks at the interface. The implementation of an intermediate layer improved the bond and eliminated the cracks. Next, an AlCoCrFeNiTi0.5 HEA coating was fabricated on the Ti6Al4V substrate, and its isothermal oxidation behavior was studied. The HEA coating effectively improved the Ti6Al4V substrate\u27s oxidation resistance due to the formation of continuous protective oxides. In the second part, research efforts were made on the deep learning-based quality inspection of additive manufactured products. The traditional inspection process has relied on manual recognition, which could suffer from low efficiency and potential bias. A neural-network approach was developed toward robust real-world AM anomaly detection. The results indicate the promising application of the neural network in the AM industry --Abstract, page iv

Correlating X-ray microanalysis and cathodoluminescence data from III-nitride semiconductors

Research in group III- nitride semiconductors has seen major developments during the last couple of decades. One of the materials that satisfy requirements for optoelectronic devices in the ultra-violet (UV) spectral range and high power, high frequency electronic devices is the AlGaN. Performance and reliability of these devices will strongly depend on the electronic properties of epitaxial layers which are critically affected by structural defects and unintentional and intentional doped impurities. This thesis presents research on III- nitride semiconductors, in particular AlGaN and GaN materials. It is focused on characterization of AlGaN materials and the effects of n- and p-type doping, AlN content, occurrence of defects and crystal orientation on its quality. Different electron microscopy techniques are used to investigate luminescence, composition and doping properties of semiconductor structures and their correlation with surface features. The main techniques used for the characterization consisted of cathodoluminescence spectroscopy (CL) for the probing of luminescence properties, secondary electron (SE) and backscattered electron (BSE) imaging for investigation of the sample morphology and wavelength dispersive X-ray (WDX) spectroscopy for compositional analysis. The type of growth method and choice of substrate have a great influence on the surface morphology and luminescence homogeneity of the AlGaN layer, with compositional inhomogeneity of the MBE samples confirmed only on sub μm level but having lower emission intensity compared to MOCVD samples. The thesis presents detailed steps of a procedure to quantify trace elements and investigates the associated challenges. The whole process of measurement optimization for Mg and Si dopants is described and final recipe on how to measure the concentration of major (alloy) and minor Si/Mg (dopant) elements is presented. A systematic study of polar and semipolar n-type doped AlGaN/AlN layers grown on sapphire by (MOCVD) with varied Si/group-III ratios in the gas phase was accomplished. The AlN incorporation was higher in the polar samples and the highest values of Si incorporations were observed for the polar samples with the highest Si/III ratios, while saturation of Si incorporation was seen for the semipolar samples at higher Si/III ratios. CL point spectra showed how changes in the relative intensity of the NBE peaks and impurity transitions depend strongly on the growth conditions and surface orientations. The semipolar samples showed better compositional homogeneity. A study was also performed on AlGaN:Mg samples to study the impurity transitions and luminescence properties of non LED epilayer samples grown on MOCVD AlN/sapphire templates and more complicated LED structures with different numbers of MBE-grown layers. MBE samples showed superior quality to other combinations of MBE and MOCVD structures, mainly due to problems associated with the transfer of sample between different reactors and the introduction of impurities that will form different defects within the material. Finally, some proposals for future work are presented.Research in group III- nitride semiconductors has seen major developments during the last couple of decades. One of the materials that satisfy requirements for optoelectronic devices in the ultra-violet (UV) spectral range and high power, high frequency electronic devices is the AlGaN. Performance and reliability of these devices will strongly depend on the electronic properties of epitaxial layers which are critically affected by structural defects and unintentional and intentional doped impurities. This thesis presents research on III- nitride semiconductors, in particular AlGaN and GaN materials. It is focused on characterization of AlGaN materials and the effects of n- and p-type doping, AlN content, occurrence of defects and crystal orientation on its quality. Different electron microscopy techniques are used to investigate luminescence, composition and doping properties of semiconductor structures and their correlation with surface features. The main techniques used for the characterization consisted of cathodoluminescence spectroscopy (CL) for the probing of luminescence properties, secondary electron (SE) and backscattered electron (BSE) imaging for investigation of the sample morphology and wavelength dispersive X-ray (WDX) spectroscopy for compositional analysis. The type of growth method and choice of substrate have a great influence on the surface morphology and luminescence homogeneity of the AlGaN layer, with compositional inhomogeneity of the MBE samples confirmed only on sub μm level but having lower emission intensity compared to MOCVD samples. The thesis presents detailed steps of a procedure to quantify trace elements and investigates the associated challenges. The whole process of measurement optimization for Mg and Si dopants is described and final recipe on how to measure the concentration of major (alloy) and minor Si/Mg (dopant) elements is presented. A systematic study of polar and semipolar n-type doped AlGaN/AlN layers grown on sapphire by (MOCVD) with varied Si/group-III ratios in the gas phase was accomplished. The AlN incorporation was higher in the polar samples and the highest values of Si incorporations were observed for the polar samples with the highest Si/III ratios, while saturation of Si incorporation was seen for the semipolar samples at higher Si/III ratios. CL point spectra showed how changes in the relative intensity of the NBE peaks and impurity transitions depend strongly on the growth conditions and surface orientations. The semipolar samples showed better compositional homogeneity. A study was also performed on AlGaN:Mg samples to study the impurity transitions and luminescence properties of non LED epilayer samples grown on MOCVD AlN/sapphire templates and more complicated LED structures with different numbers of MBE-grown layers. MBE samples showed superior quality to other combinations of MBE and MOCVD structures, mainly due to problems associated with the transfer of sample between different reactors and the introduction of impurities that will form different defects within the material. Finally, some proposals for future work are presented

Institute of Ion Beam Physics and Materials Research; Annual Report 1999

Summary of the Scientific Activities of the Institute in 1999: Highlight Reports / Short Contributions / Statistic

Advanced Photonic Sciences

The new emerging field of photonics has significantly attracted the interest of many societies, professionals and researchers around the world. The great importance of this field is due to its applicability and possible utilization in almost all scientific and industrial areas. This book presents some advanced research topics in photonics. It consists of 16 chapters organized into three sections: Integrated Photonics, Photonic Materials and Photonic Applications. It can be said that this book is a good contribution for paving the way for further innovations in photonic technology. The chapters have been written and reviewed by well-experienced researchers in their fields. In their contributions they demonstrated the most profound knowledge and expertise for interested individuals in this expanding field. The book will be a good reference for experienced professionals, academics and researchers as well as young researchers only starting their carrier in this field

Integration of Indium Gallium Nitride with Nanostructures on Silicon Substrates for Potential Photovoltaic Applications

Ph.DDOCTOR OF PHILOSOPH

Interface Studies for Microcrystalline Silicon Thin-Film Solar Cells deposited on TCO-coated planar and textured glass superstrates

Ph.DDOCTOR OF PHILOSOPH

Properties and Applications of Graphene and Its Derivatives

Graphene is a two-dimensional, one-atom-thick material made entirely of carbon atoms, arranged in a honeycomb lattice. Because of its distinctive mechanical (e.g., high strength and flexibility) and electronic (great electrical and thermal conductivities) properties, graphene is an ideal candidate in myriad applications. Thus, it has just begun to be engineered in electronics, photonics, biomedicine, and polymer-based composites, to name a few. The broad family of graphene nanomaterials (including graphene nanoplatelets, graphene oxide, graphene quantum dots, and many more) go beyond and aim higher than mere single-layer (‘pristine’) graphene, and thus, their potential has sparked the current Special Issue. In it, 18 contributions (comprising 14 research articles and 4 reviews) have portrayed probably the most interesting lines as regards future and tangible uses of graphene derivatives. Ultimately, understanding the properties of the graphene family of nanomaterials is crucial for developing advanced applications to solve important challenges in critical areas such as energy and health