Laureate
Professor Dr. Thorsten Trupke, The University of New South Wales & BT Imaging Pty Ltd., Australien, Dr. Robert Bardos, BT Imaging Pty Ltd., Australia
Subject
"Laser Based Luminescence Imaging of Silicon Bricks, Wafers and Solar Cells"
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Clear blue sky, bright shining sun and a white beach. A picture of a perfect paradise and the ingredients to generate clean electrical power to help save valuable resources and to protect the environment. But it’s a long way from a shovel of sand to solar panels on the roof. A number of complex processing techniques influence the efficiency that determines the competitiveness of this regenerative energy. | |
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| Dr. Robert Bardos and Prof. Dr. Thorsten Trupke |
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Measuring the important material properties after each processing step can reveal valuable information about their influence on degrading or improving efficiency. If these measurements are fast enough, they can also be used to monitor the quality of each single solar cell in mass production. Sounding perfect to scientists, developers and production managers, such measurement systems have in fact not been available for a long time. Of course, there are techniques and devices to determine the charge carrier lifetime in silicon wafers or the local electrical resistance on finished solar cells. But collecting the data for the complete surface of a wafer or a solar cell takes up to an hour. The cycle time for processing solar cells in state-of-the-art production lines amounts to a second. Even worse, some special measurement techniques can only be used on samples as they destroy the probes by scratching, e.g. through physical contact.
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| Solar cells in measurement system. |
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| | A fast, precise and nondestructive alternative measuring technique has been developed by Professor Thorsten Trupke and Dr. Robert Bardos at the University of New South Wales (UNSW) in Sydney, Australia. Its principle is to measure photo-induced light. Most material emits characteristic light when illuminated. A detailed analysis of this photoluminescence can reveal important material properties. |
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It is an established technology in scientific applications. Unfortunately it has been considered impractical or too slow to be used with silicon thus far. Because of its very poor photoluminescence, it has not seemed feasible to reach sufficiently fast measurements.
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| Inspection system of BT Imaging for solar cells. |
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| | During his research with silicon at the Centre of Excellence for Advanced Silicon Photovoltaics at the UNSW Thorsten Trupke finally realized the potential for an imaging technique that could even be easily used in industry. The key is application of the right laser technology. By illuminating the probes with high-power diode lasers and using optical filters in the measurement system for the weak photoluminescence signals, even whole areas can be measured with high spatial resolution in a short time. Ideal for the photovoltaic industry.
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Thorsten Trupke moved from Germany to Australia in 2001, he has lived and done his research in Sydney ever since. When he became Associate Professor in 2004, the Australian Robert Bardos joined his research group. Step by step they developed the specific measurement technology, built initial devices and tested them at the university’s solar cell production facilities. Eventually they founded their own company BT Imaging close to Sydney with venture capital. The company offers manual and automated measurement systems for the complete processing chain in photovoltaic industry from the suppliers of silicon blocks and wafers up to the manufacturers of solar cells.
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