1,086 research outputs found

    Correlative X-ray Microscopy Studies of CuIn1−xGaxSe2 Solar Cells

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    abstract: It is well known that the overall performance of a solar cell is limited by the worst performing areas of the device. These areas are usually micro and nano-scale defects inhomogenously distributed throughout the material. Mitigating and/or engineering these effects is necessary to provide a path towards increasing the efficiency of state-of-the-art solar cells. The first big challenge is to identify the nature, origin and impact of such defects across length scales that span multiple orders of magnitude, and dimensions (time, temperature etc.). In this work, I present a framework based on correlative X-ray microscopy and big data analytics to identify micro and nanoscale defects and their impact on material properties in CuIn1-xGaxSe2 (CIGS) solar cells. Synchrotron based X-ray Fluorescence (XRF) and X-ray Beam Induced Current (XBIC) are used to study the effect that compositional variations, between grains and at grain boundaries, have on CIGS device properties. An experimental approach is presented to correcting XRF and XBIC quantification of CIGS thin film solar cells. When applying XRF and XBIC to study low and high gallium CIGS devices, it was determined that increased copper and gallium at grain boundaries leads to increased collection efficiency at grain boundaries in low gallium absorbers. However, composition variations were not correlated with changes in collection efficiency in high gallium absorbers, despite the decreased collection efficiency observed at grain boundaries. Understanding the nature and impact of these defects is only half the battle; controlling or mitigating their impact is the next challenge. This requires a thorough understanding of the origin of these defects and their kinetics. For such a study, a temperature and atmosphere controlled in situ stage was developed. The stage was utilized to study CIGS films during a rapid thermal growth process. Comparing composition variations across different acquisition times and growth temperatures required the implementation of machine learning techniques, including clustering and classification algorithms. From the analysis, copper was determined to segregate the faster than indium and gallium, and clustering techniques showed consistent elemental segregation into copper rich and copper poor regions. Ways to improve the current framework and new applications are also discussed.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

    Optically switched magnetism in photovoltaic perovskite CH3_3NH3_3(Mn:Pb)I3_3

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    The demand for ever-increasing density of information storage and speed of manipulation boosts an intense search for new magnetic materials and novel ways of controlling the magnetic bit. Here, we report the synthesis of a ferromagnetic photovoltaic CH3_3NH3_3(Mn:Pb)I3_3 material in which the photo-excited electrons rapidly melt the local magnetic order through the Ruderman-Kittel-Kasuya-Yosida interactions without heating up the spin system. Our finding offers an alternative, very simple and efficient way of optical spin control, and opens an avenue for applications in low power, light controlling magnetic devices

    Anomaly detection and automatic labeling for solar cell quality inspection based on Generative Adversarial Network

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    Quality inspection applications in industry are required to move towards a zero-defect manufacturing scenario, withnon-destructive inspection and traceability of 100 % of produced parts. Developing robust fault detection and classification modelsfrom the start-up of the lines is challenging due to the difficulty in getting enough representative samples of the faulty patternsand the need to manually label them. This work presents a methodology to develop a robust inspection system, targeting thesepeculiarities, in the context of solar cell manufacturing. The methodology is divided into two phases: In the first phase, an anomalydetection model based on a Generative Adversarial Network (GAN) is employed. This model enables the detection and localizationof anomalous patterns within the solar cells from the beginning, using only non-defective samples for training and without anymanual labeling involved. In a second stage, as defective samples arise, the detected anomalies will be used as automaticallygenerated annotations for the supervised training of a Fully Convolutional Network that is capable of detecting multiple types offaults. The experimental results using 1873 EL images of monocrystalline cells show that (a) the anomaly detection scheme can beused to start detecting features with very little available data, (b) the anomaly detection may serve as automatic labeling in order totrain a supervised model, and (c) segmentation and classification results of supervised models trained with automatic labels arecomparable to the ones obtained from the models trained with manual labels.Comment: 20 pages, 10 figures, 6 tables. This article is part of the special issue "Condition Monitoring, Field Inspection and Fault Diagnostic Methods for Photovoltaic Systems" Published in MDPI - Sensors: see https://www.mdpi.com/journal/sensors/special_issues/Condition_Monitoring_Field_Inspection_and_Fault_Diagnostic_Methods_for_Photovoltaic_System

    Characterization of Spintronic Systems using Soft X-ray spectroscopy

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    The subject of this dissertation revolves around soft x-ray spectroscopy of materials doped with 3d transition metals . More specifically, investigating the effects of synthesis techniques and the phenomena associated with subtle changes in synthesis technique resulting in key chemical changes. These materials have the potential to bring a new frontier of opportunity within electronic devices and enable critical new technologies. This investigation is done using two main techniques. Experimentally, spectra are mea- sured using high resolution synchrotron-based techniques, and these spectra are then com- pared to theoretical calculations to bring insights into the electronic structure, precise location of defect states, and band gap of promising materials for future devices. Using these techniques, a system based on the semiconductor In2O3 is examined first. With the same host material, and varying the 3d transition metal additions (Fe, Ni, Co, Mn), this allows the systematic study of a single synthesis technique with the major variable being the dopant atom. Results here show the successful substitution of iron into the host In2O3 lattice, with varying secondary states seen with the other three dopants. Notably, oxygen vacancies are found with iron substituting for indium within the structure, prompting a further investigation into these specific lattice defects. A system based on the semiconductor SnO2 is examined, now keeping two consistent codopant atoms, but varying the concentration of the Zn and Co additives. Through this, the effects of not only the concentration of the dopants can be seen, but using two atoms creates two distinct defect sites within the material. The ability to shift the location of oxygen vacancies within the material via annealing cycles during synthesis is displayed. Furthermore the dependency of ferromagnetic properties on oxygen vacancies adjacent to cobalt atoms substituting for tin within the lattice is found

    Solar cells micro crack detection technique using state-of-the-art electroluminescence imaging

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    In this article, we present the development of a novel technique that is used to enhance the detection of micro cracks in solar cells. Initially, the output image of a conventional electroluminescence (EL) system is determined and reprocessed using the binary and discreet Fourier transform (DFT) image processing models. The binary image is used to enhance the detection of the cracks size, position and orientation, principally using the geometric properties of the EL image. On the other hand, the DFT has been used to analyse the EL image in a two-dimensional spectrum. The output image of the DFT consists of structures of all required frequencies, thus improving the detection of possible cracks present in the solar cell. As a result, the developed technique improves the detection of micro cracks in solar cells compared to conventional EL output images

    Cubic phase gallium nitride photonics integrated on silicon(100) for next-generation solid state lighting

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    Semiconductors made of gallium nitride (GaN) and its compounds (AlInGaN) have transformed the visible light emitting diode (LED) industry thanks to their direct bandgap across the entire visible and ultraviolet spectra. Despite its success, the conventional hexagonal-phase GaN has fundamental disadvantages in performance and cost that hinder market adoption. These include: internal polarization field ( MV/cm2), high acceptor activation energy (260 meV), low hole mobility (20 cm2/V), and expensive substrates (Al2O3, SiC). Gallium nitride also crystallizes in the cubic crystal that has a higher degree of symmetry. This leads to some advantageous properties for light emitting applications: polarization-free, lower acceptor energy (200 meV), and higher hole mobility (150 cm2/V). These advantages are critical for the development of the next-generation solid state lighting. Difficulty in its synthesis stemming from the large crystal lattice mismatch, chemical incompatibility, and phase metastability has prohibited the growth of high quality semiconductor crystals that are device-worthy. This thesis explores a method of synthesizing phase-pure, high-quality cubic GaN crystals on nanopatterned Si(100) substrates via hexagonal-to-cubic phase transition, and the thesis presents a comprehensive material characterization of the crystals. Crystal growth geometry modeling of GaN on nanopatterned Si(100) substrates is used to estimate the necessary patterning parameters to facilitate complete phase transition. The cubic GaN material is then studied using structural characterization techniques including scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. The carrier recombination properties are studied using photoluminescence, Raman spectroscopy, and cathodoluminescence. The cubic GaN synthesized using the phase transition method on carefully patterned Si(100) substrates is shown to be phase-pure, defect-free, and optically superior. Material properties such as internal quantum efficiency, Varshni coefficients, and defect levels are extracted from the experiments. Other work on hexagonal GaN light emitters on silicon substrates, chamber conditioning for metalorganic chemical vapor deposition of III-nitrides, and space-based laser instruments for NASA missions is also discussed. Class lab module development and outreach activities are included

    Ion Beam Techniques and Applications

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    A wide variety of ion beam techniques are being used in several versatile applications ranging from environmental science, nuclear physics, microdevice fabrication to materials science. In addition, new applications of ion beam techniques across a broad range of disciplines and fields are also being discovered frequently. In this book, the latest research and development on progress in ion beam techniques has been compiled and an overview of ion beam irradiation-induced applications in nanomaterial-focused ion beam applications, ion beam analysis techniques, as well as ion implantation application in cells is provided. Moreover, simulations of ion beam-induced damage to structural materials of nuclear fusion reactors are also presented in this book

    Ultrafast High-Resolution Solar Cell Cracks Detection Process

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    This article presents the advancement of an ultrafast high-resolution cracks detection in solar cells manufacturing system. The aim of the developed process is to: first, improve the quality of the calibrated image taken by a low-cost conventional electroluminescence (EL) imaging setup; second, propose a novel methodology to enhance the speed of the detection of the solar cell cracks, and finally develop a proper procedure to decide whether to accept or reject the solar cell due to the existence of the cracks. The proposed detection process has been validated on various cracked/free-crack solar cell samples, evidently it was found that the cracks type, size, and orientation are more visible using the proposes method, while the speed of calibrating the EL images are in the range of 0.1–0.3 s, excluding the EL imaging time

    Advanced photonic and electronic systems WILGA 2018

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    WILGA annual symposium on advanced photonic and electronic systems has been organized by young scientist for young scientists since two decades. It traditionally gathers around 400 young researchers and their tutors. Ph.D students and graduates present their recent achievements during well attended oral sessions. Wilga is a very good digest of Ph.D. works carried out at technical universities in electronics and photonics, as well as information sciences throughout Poland and some neighboring countries. Publishing patronage over Wilga keep Elektronika technical journal by SEP, IJET and Proceedings of SPIE. The latter world editorial series publishes annually more than 200 papers from Wilga. Wilga 2018 was the XLII edition of this meeting. The following topical tracks were distinguished: photonics, electronics, information technologies and system research. The article is a digest of some chosen works presented during Wilga 2018 symposium. WILGA 2017 works were published in Proc. SPIE vol.10445. WILGA 2018 works were published in Proc. SPIE vol.10808
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