Abstract
Renewable energy sources such as photovoltaic (PV) technologies are considered to be key drivers towards climate neutrality. Thin-film PVs, and particularly copper indium gallium selenide (CIGS) technologies, will play a crucial role in the turnaround in energy policy due to their high efficiencies, high product flexibility, light weight, easy installation, lower labour-intensiveness, and lower carbon footprint when compared to silicon solar cells. Nonetheless, challenges regarding the CIGS fabrication process such as moderate reproducibility and process tolerance are still hindering a broad market penetration. Therefore, cost-efficient and easily implementable in-line process control methods are demanded that allow for identification and elimination of non-conformal cells at an early production step. As part of this work, a practical approach towards industrial in-line photoluminescence (PL) imaging as a contact-free quality inspection tool is presented. Performance parameters of 10 CIGS samples with 32 individually contacted cells each were correlated with results from PL imaging using green and red excitation light sources. The data analysis was fully automated using Python-based image processing, object detection, and non-linear regression modelling. Using the red excitation light source, the presented PL imaging and data processing approach allows for a quantitative assessment of the cell performance.
Highlights
While PV plants employing silicon solar cells have established themselves as an important element in the global energy mix, thin-film processed PV cells have become progressively important for the renewable energy market, as indicated by an expected continuous annual growth rate of over 19% by 2023 [2]
The sample set contained 10 copper indium gallium selenide (CIGS) samples, each consisting of 32 separate cells
The band gap of the CdS buffer layer is in the range of 2.4 eV [30], corresponding to a wavelength of 516 nm, which leads to superimposition of the PL signal originating from the CIGS layer in the case of the green excitation light
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In the European Union, more than 75% of greenhouse gas emissions are caused by the generation and consumption of energy [1]. The European green deal was established with the pronounced goal to no longer emit any net greenhouse gases by 2050. Renewable energy sources such as photovoltaic (PV) technologies will be a main driver towards the targeted climate neutrality. While PV plants employing silicon solar cells have established themselves as an important element in the global energy mix, thin-film processed PV cells have become progressively important for the renewable energy market, as indicated by an expected continuous annual growth rate of over 19% by 2023 [2]
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