Environmental fate of Perovskite photovoltaics

• Umweltschicksal von Perowskit-Solarzellen

Schmidt, Felix; Schäffer, Andreas (Thesis advisor); Hugi, Christoph (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

Third-generation solar cells based on so-called perovskite absorber materials could become a major driver in green, renewable energy generation. High-efficiency perovskite solar cells, to date, rely on the use of lead (Pb) at concentrations of 0.5 g / m2, which is a potential environmental and safety concern. In this thesis, potential environmental impacts from (Pb in) perovskite solar cells are addressed across the life cycle of the technology. When designing novel solar cell devices, emphasis should be put on efficiency and stability, but the availability and supply of the employed materials need to be considered as well. The use of critical raw materials in emerging solar cell technologies is discussed and strategies to reduce, re-use or recycle critical raw materials are evaluated. A potential new failure mechanism of plastic-based solar cells that is induced by the presence of biological matter (so-called biodeterioration) is discussed. This biologically-induced degradation could affect both solar cell lifetime (when parts of the solar cell are subjected to biodeterioration) and efficiency (from the colonisation of biofilms). Environmental impacts from perovskite solar cell constituents (such as Pb) can mainly arise in the case of damage. Therefore, experimental investigations were carried out to address the fate of perovskite solar cell-derived metals in environmentally relevant systems. Soil-water systems were simulated in microcosm experiments and used to address mobility and availability of perovskite metal species. Soil was demonstrated to be a potent matrix for metal immobilisation under worst-case conditions that strongly limits metal (bio)availability. A novel setup was developed to investigate leaching kinetics of Pb from flexible perovskite solar cells. Critical damage could induce substantial Pb release in mildly acidic conditions. Still, proper encapsulation strategies can provide a straightforward way to mitigate risks from Pb leaching. A unique outdoor installation was constructed and used to determine metal concentrations from perovskite solar cells in rainwater under natural conditions. Both, laboratory and outdoor tests enabled modelling of Pb emissions and predict environmental concentrations in relevant scenarios. Lastly, a novel recycling process was developed to recover and re-use Pb from spent perovskite solar cells. The process uses only water and heat and demonstrated good applicability to a variety of different perovskite solar cell materials. Overall, novel insights into the potential environmental risks from perovskite solar cell constituents are presented. This could form part of the critical body of evidence required to enable perovskite solar cells to fulfil their potential and enable a transition towards climate neutrality.