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| Book/Dissertation / PhD Thesis | FZJ-2018-06976 |
2018
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-363-1
Please use a persistent id in citations: http://hdl.handle.net/2128/20281 urn:nbn:de:0001-2018120731
Abstract: Solar energy has the potential to provide clean and sustainable energy to all of human kind and during the past years the amount of operating solar power plants constantly increased. The increasing installation and production volumes call for powerful measuring techniques for the process control of solar cell production lines, but also for the monitoring of modules operating in solar power plants. Luminescence imaging of solar cells and modules is such a measuring technique. By observing the radiative recombination that is emitted by a solar cell, just like the light emission of LEDs, luminescence imaging provides spatially resolved information about a solar cells electrical and optical properties. Therefore, luminescence imaging has the ability to locate and rate defects and inhomogeneities insolar cells. This thesis focuses on the use of luminescence imaging for quantitative evaluations. Hence, it is not only looked at the ability of luminescence imaging to locate abnormalities in solar cells or modules but also on possibilities to use luminescence imaging as a way to quantify the strength of a defect or to estimate the inuence of a defect on the photovoltaic performance of a whole device. During this work it was made use of two model solar cell technologies. Crystalline silicon solar cells are currently the most successful solar cell technology for which luminescence imaging is already a well established tool. This technology isprimarily used in this thesis to test newly developed imaging methods. However, the focus of this thesis lies on the analysis of the so called CIGS solar cells and modules, which belong to the thin-lm technologies. Although the market share of the thin-lm technologies was only 5 % of the produced solar cells in 2016 their production volumes are constantly increasing. To allow for a quantitative evaluation of luminescence images of CIGS solarcells it is first essential to understand the inuence of metastable effects in this technology. Metastable effects alter the properties of CIGS solar cells, including the luminescence signal, during the exciation with illumination or the application of bias. An in depth analysis of the metastable effects at different applied currents and temperatures showed that the metastable effects lead in most cases to a reduction of the series resistance and dark recombination current in CIGS solar cells. The changes vary in magnitude for the different conditions and may happen within a matter of seconds. However, a stabilization of the solar cells can only be reached after a constant excitation of several hours. This knowledge is essential for an accurate quantitative evaluation of luminescence images. In this work, an influence of metastable effects on the results were avoided by automation and combining image data only with electrical data measured simultaneously.
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