ABSTRACT: The solar energy, or photovoltaic (PV) industry, driven by economic competition with traditional fossil energy sources, strives to produce solar panels of the highest conversion efficiency and best reliability at the lowest production cost. Solar cells based on crystalline silicon are currently the dominant commercial PV technology by a large margin, and they are likely to remain dominant for at least one decade. The problem of improvement mechanical stability of silicon wafers and finished solar cell is one of the most critical for entire PV industry. Mechanical defects in wafer and cells in the form of periphery or internal cracks can be initiated at various steps of the manufacturing process and becomes the trigger for the fracture. There are a limited number of characterization methods for crack detection but only a few of those are able to satisfy PV industry needs in sensitivity of the crack detection incorporated with the analysis time. The most promising are a Resonance Ultrasonic Vibrations (RUV) technique and Photoluminescence (PL) imaging. The RUV method was further developed in this thesis project for fast non-destructive crack detection in full-size silicon wafers and solar cells. The RUV methodology relies on deviations of the resonance frequency response curve measured on a wafer with peripheral or bulk millimeter-length crack when it is compared with identical non-cracked wafers. It was observed that statistical variations of the RUV parameters on a similarly processed silicon wafers/cells with the same geometry lead to false positive events reducing accuracy of the RUV method. A new statistical approach using three independent RUV crack detection criteria was developed and applied to resolve this issue. This approach was validated experimentally. Crack detection using RUV technique was applied to a set of production-grade Cz-Si wafers and finished solar cells from the Isofoton's S.A. (Spain) production line. Cracked solar cells rejected by the RUV method using the statistical approach were imaged with room temperature PL mapping and independently controlled with Scanning Acoustic Microscopy (SAM). A comparison of three independent techniques for crack detection, RUV, PL and SAM, was performed on selected samples. A high accuracy and selectivity of the RUV method to identify mm-size cracks in wafers and cells was confirmed.

ABSTRACT: This thesis is about detection of cracks in single-crystalline silicon wafers by using a vibration method in the form of an impact test. The goal to detect cracks from vibration measurements introduced by striking the silicon wafer with an impact hammer. Such a method would reduce costs in the production of solar cells. It is an inexpensive, relatively simple method which if commercialized could be used as an efficient in-line production quality test. A hammer is used as the actuator and a microphone as the response sensor. A signal analyzer is used to collect the data and to compute frequency response. Parameters of interest are audible natural frequencies, peak magnitudes, damping ratio and coherence. The data reveals that there are differences in frequency between the cracked silicon wafers and the non-cracked silicon wafers. The resonant peaks in the defective wafers were not as sharp (i.e., lightly damped) and occurred at lower frequencies (i.e., lower stiffness) with a lower magnitude and a higher damping ratio. These differences could be used to detect damaged product in a solar cell production line.

Defects in silicon wafers affect their mechanical stability considerably during their processing and handling. In the new generation of thin silicon wafers, in addition to subsurface defects, cracks are also one of the most important defects that need to be evaluated. A comprehensive review of literature suggests the use of different techniques for non destructive evaluation (NDE) of silicon wafers. Among the few NDE techniques that can be used for both sub-surface and crack detection, Shearography has the advantage of being a whole field technique that can be utilized as a non-contact method for online inspection. Although, recently shearography has been used for sub-surface defect detection in silicon wafers, the capability of this technique to identify and detect cracks has not been investigated yet. In this work, a shearography system has been developed for nondestructive evaluation of silicon wafers. The optical set-up was arranged and several experiments were carried out to optimize its performance. Batch of perfect wafers, wafers with sub-surface defects and cracked wafers of 500?m thickness were qualitatively evaluated using the developed system. Two different loading mechanisms were used to stress the silicon wafer and the advantage of uniform thermal loading over concentrated force loading for crack and sub-surface defect detection has been discussed. In addition to crack detection, the unique potential of the developed system for detection of crack propagation has been discussed.

This book disseminates the current knowledge of semiconductor physics and its applications across the scientific community. It is based on a biennial workshop that provides the participating research groups with a stimulating platform for interaction and collaboration with colleagues from the same scientific community. The book discusses the latest developments in the field of III-nitrides; materials & devices, compound semiconductors, VLSI technology, optoelectronics, sensors, photovoltaics, crystal growth, epitaxy and characterization, graphene and other 2D materials and organic semiconductors.

The utilization of sun light is one of the hottest topics in sustainable energy research. To efficiently convert sun power into a reliable energy – electricity – for consumption and storage, silicon and its derivatives have been widely studied and applied in solar cell systems. This handbook covers the photovoltaics of silicon materials and devices, providing a comprehensive summary of the state of the art of photovoltaic silicon sciences and technologies. This work is divided into various areas including but not limited to fundamental principles, design methodologies, wafering techniques/fabrications, characterizations, applications, current research trends and challenges. It offers the most updated and self-explanatory reference to all levels of students and acts as a quick reference to the experts from the fields of chemistry, material science, physics, chemical engineering, electrical engineering, solar energy, etc..

Silicon, as a single-crystal semiconductor, has sparked a revolution in the field of electronics and touched nearly every field of science and technology. Though available abundantly as silica and in various other forms in nature, silicon is difficult to separate from its chemical compounds because of its reactivity. As a solid, silicon is chemically inert and stable, but growing it as a single crystal creates many technological challenges. Crystal Growth and Evaluation of Silicon for VLSI and ULSI is one of the first books to cover the systematic growth of silicon single crystals and the complete evaluation of silicon, from sand to useful wafers for device fabrication. Written for engineers and researchers working in semiconductor fabrication industries, this practical text: Describes different techniques used to grow silicon single crystals Explains how grown single-crystal ingots become a complete silicon wafer for integrated-circuit fabrication Reviews different methods to evaluate silicon wafers to determine suitability for device applications Analyzes silicon wafers in terms of resistivity and impurity concentration mapping Examines the effect of intentional and unintentional impurities Explores the defects found in regular silicon-crystal lattice Discusses silicon wafer preparation for VLSI and ULSI processing Crystal Growth and Evaluation of Silicon for VLSI and ULSI is an essential reference for different approaches to the selection of the basic silicon-containing compound, separation of silicon as metallurgical-grade pure silicon, subsequent purification, single-crystal growth, and defects and evaluation of the deviations within the grown crystals.

Enormous leaps forward in the efficiency and the economy of solar cells are being made at a furious pace. New materials and manufacturing processes have opened up new realms of possibility for the application of solar cells. Crystalline silicon cells are increasingly making way for thin film cells, which are spawning experimentation with third-generation high-efficiency multijunction cells, carbon-nanotube based cells, UV light for voltage enhancement, and the use of the infrared spectrum for night-time operation, to name only a few recent advances. This thoroughly updated new edition of Markvart and Castaner's Solar Cells, extracted from their industry standard Practical Handbook of Photovoltaics, is the definitive reference covering the science and operation, materials and manufacture of solar cells. It is essential reading for engineers, installers, designers, and policy-makers who need to understand the science behind the solar cells of today, and tomorrow, in order to take solar energy to the next level. A thorough update to the definitive reference to solar cells, created by a cast of international experts from industry and academia to ensure the highest quality information from multiple perspectives Covers the whole spectrum of solar cell information, from basic scientific background, to the latest advances in materials, to manufacturing issues, to testing and calibration. Case studies, practical examples and reports on the latest advances take the new edition of this amazing resource beyond a simple amalgamation of a vast amount of knowledge, into the realm of real world applications