Accelerated transfer of the next generation of solar cells to mass production - Future technology tandem solar cells (Zeitenwende)

Circular recycling for a sustainable raw materials cycle

Perovskite-silicon tandem solar cells face particular challenges in circular recycling. On the one hand, instead of one solar cell technology, two technologies have to be recycled at the same time. On the other hand, highly efficient perovskite solar cells contain lead in a soluble form. Today's module architectures solve these challenges with a "design for eternity" approach. Here, modules are integrated monolithically as far as possible. This monolithic integration means that the materials can no longer be separated from each other in an economically or energetically sensible way. As a result, the current recycling process consists of shredding modules and incinerating polymer components. Although this approach enables a recycling rate of over 95%, this recycling is not circular: a large proportion of the recovered materials can only be used for inferior purposes and are not available for the raw material cycle.

HI ERN is contributing its expertise in the field of materials science at this point. The aim of the "Cradle-to-Cradle Circularity" part of the project is to fundamentally change the design of solar cells: Away from a design for eternity towards a "design for recycling". In future, the principles of "green engineering" will form the basis for creating solar cells with improved circular recycling properties.

The solar experts at HI ERN are pursuing the following approaches in particular:

1. Improving the separation of the layer stack: The interfaces of all functional layers of the tandem should be designed in such a way that they can be chemically and mechanically separated from each other with high efficiency. For example, different solubility and different mechanical properties of the materials should be utilized. Where possible, solvents should be used that can be used directly in solar cell production.
   
2. Improving the purification of the materials used in the perovskite stack: After separation, elemental and phase impurities are present in the recovered materials. Purification processes are to be developed that function efficiently in terms of time and energy.
   
3. Proof of a complete cycle for lead: Due to its toxicity, lead is the most problematic element in perovskite solar cells. The project aims to develop processes that allow 100% of the lead present to be recovered from the solar cell. In addition, approaches will be investigated to convert any lead that cannot be recovered into a non-soluble form.

Project background

A massive expansion of photovoltaics and wind energy is necessary in order to strengthen sovereignty in the energy supply and simultaneously achieve the goal of climate neutrality. This is also being vigorously pursued as part of the current strategic policy goals of the German government and the European Union.

The necessary expansion of photovoltaics can only succeed with a new generation of photovoltaics: With an efficiency of over 30% and competitive costs, innovative tandem technology offers the potential to make solar energy more efficient and cost-effective. This technology must be developed to market maturity in the next 5 years in order to enable a climate-neutral circular economy.

In the "Zeitenwende" project, the Helmholtz-Zentrum Berlin (HZB), the Helmholtz Institute Erlangen-Nürnberg for Renewable Energies (HI ERN), part of Forschungszentrum Jülich, and the Karlsruhe Institute of Technology (KIT) are working on adapting existing silicon cell processes for optimal and effective tandem integration. Furthermore, industrially scalable deposition processes for highly efficient and large-area perovskite silicon tandem solar cells are to be developed. The stability of large-area tandem solar cells will also be investigated. In addition, analytics will be expanded to enable a better and faster understanding of solar cell properties. A further goal is the development of tandem solar cells with improved circular recycling properties. The project is coordinated by the HZB.

Project partners

Coordinated by Helmholtz-Zentrum Berlin (HZB), Forschungszentrum Jülich (FZJ) and the Karlsruhe Institute of Technology (KIT) are working closely with partners from industry.

Project period

October 1, 2022 – September 30, 2025

Funding

The Federal Ministry of Education and Research (BMBF) has provided funding of €6.25 million for the project.

Contact

Dr. Ian Marius Peters

Gruppenleiter "Hoch­durch­satz Cha­rakter­isierung und Modell­ierung für die PV"

Building HIERN-Immerwahrstr /
Room 2.3

+49 9131-12538303

E-Mail

Verwandte Inhalte

Sustainable Photovoltaics

Research Group

High Throughput Characterization and Modelling for PV