J. Denafas “Photovoltaic device manufacturing environmental impact reduction by silicon recycling and technological process modification of industrial c-si solar cells” doctoral dissertation defence

Thesis Defense

Author, Institution: Julius Denafas, Kaunas University of Technology

Science area, field of science: Technological Sciences, Environmental Engineering, T004

Scientific supervisor: Prof. Dr. Jolita Kruopienė (Kaunas University of Technology, Technological Sciences, Environmental Engineering, T004)

Dissertation Defence Board of Materials Engineering Science Field:
Prof. Dr. Žaneta Stasiškienė (Kaunas University of Technology, Technological Sciences, Environmental Engineering, T004) – chairwoman
Prof. Dr. Jolanta Dvarionienė (Kaunas University of Technology, Technological Sciences, Environmental Engineering, T004)
Prof. Dr. Kerstin Kuchta (Hamburg University of Technoloy, Technological Sciences, Environmental Engineering, T004)
Dr. Joris Libal (ISC Konstanz, Technological Sciences, Environmental Engineering, T004)
Prof. Dr Egidijus Šarauskis (Vytautas Magnus University, Technological Sciences, Environmental Engineering, T004)

The dissertation defence takes place in hybrid form, for online mode join here.

The doctoral dissertation is available  at the library of Kaunas University of Technology (K. Donelaičio g. 20, Kaunas).


The circular economy in solar energy has recently become an important research topic, with a special focus on the end of life phase of photovoltaic equipment. This area of ​​research has become particularly relevant as global accumulated photovoltaic waste is estimated to exceed one million tons by 2030 and Europe alone will be responsible for around 60% of this volume. Equally important is an optimization of waste generation not only at the end of life, but also at the production stage, where extraction of high-purity silicon, which is used for the production of solar cells, is the most energy-intensive stage in the entire solar energy value chain. Such situation demonstrates an importance and practical value of implementing the principles of sustainable production and eco-design at manufacturing stage of solar cells. In this thesis, two innovations were investigated and applied on industrial level – silicon recycling and process modification. Silicon recycling technology enables the solar cell manufacturer to return a large part of its production scrap for reuse and thus reduce the negative impact on the environment. The second innovation makes it possible to shorten the production process by eliminating the PSG cleaning step, as the additional SiOx layer formed during a modified diffusion process step no longer needs to be removed, which is required alternatively. As a result, consumption of raw materials, electricity and generation of waste is reduced. The results achieved in this thesis can increase the competitive advantage of European photovoltaic equipment manufacturers and enable them to offer products with significantly lower negative impact on the environment while still maintaining the necessary level of product cost and quality.

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