CIGSe thin-film solar cells: EU Sharc25 project increases efficiency

Research on the EU project Sharc25 also took place in the EMIL laboratory, where thin films and materials can be analysed with X-rays from BESSY II.

Research on the EU project Sharc25 also took place in the EMIL laboratory, where thin films and materials can be analysed with X-rays from BESSY II. © Ingo Kniest/HZB

Thin-film solar cells made of copper, indium, gallium, and selenium (CIGSe) are cost-effective to produce and now achieve efficiencies of significantly more than 20 percent. This level of performance was achieved through post-processing with alkali elements, and the procedures are suitable for industrial-scale production. Insights into the beneficial effect of these alkali treatments from the EU Sharc25 project have now been collected in an article published in Advanced Energy Materials.

Producing thin-film solar modules requires much less energy than conventional wafer-based Si PV modules, and therefore their energy payback time is much shorter. Chalcopyrite-structured compounds of copper, indium, gallium, and selenium (CIGSe) are an important class of materials for thin-film PV, because CIGSe absorbs incident light much better than silicon, and so a very thin layer grown on a substrate via coevaporation suffices to convert light into electrical energy efficiently.

Efficiency up to 22,6 percent

The European Sharc25 research project approached the challenge of optimizing the conversion efficiency of CIGSe thin film technology from multiple angles, combining theoretical modelling, experimental characterization, and sharing of technological expertise between several leading research groups throughout Europe. During the project, the efficiency of CIGSe solar cells produced within the consortium rose from 21.7 to 22.6 percent.

One focus of the project was to understand the positive effects of post-processing with the alkali elements potassium, rubidium, and cesium. This post-processing changes the chemical and electronic surface properties of the CIGSe absorber. In addition, the alkali atoms migrate from the surface into the grain boundaries between the CIGSe grains, which improves the electronic properties of the thin film. The recombination of charge carriers in the bulk CIGSe is reduced, among other effects. This beneficial effect is observed for CIGSe layers prepared at various temperatures and on different substrates.

Know-how for european industries

Eleven research institutions from eight countries, including an HZB team headed by Prof. Marcus Bär, collaborated on the EU Sharc25 project. An important goal was to secure Europe‘s pioneering role in the field of thin-film PV. “It is certainly a competitive advantage to be able to address questions related to applied materials research and to the development of industry-oriented devices using advanced research tools. To do so efficiently, we learn in such large EU projects. This represents a significant advantage and preserves the crucial edge in knowledge and know-how“, says Bär.

Partners: EMPA (CH), the Universities of Luxembourg (LU), Rouen (F), Parma (I), and Aalto (FIN), IMEC (B), HZB (D), INL (P), Flisom AG (CH), and Manz CIGS Technology GmbH (D). The Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) coordinated the project.

 

The study has been published in Adv. Energy Materials (2020): Heavy alkali treatment of Cu(In,Ga)Se2 solar cells: Surface versus bulk effects

DOI: 10.1002/aenm.201903752

http://sharc25.eu/ has received funding from the European Union’s Horizon 2020 Framework Programme for Research and Innovation under grant agreement No 64100.

red.


You might also be interested in

  • Best Innovator Award 2023 for Artem Musiienko
    News
    22.03.2024
    Best Innovator Award 2023 for Artem Musiienko
    Dr. Artem Musiienko has been awarded a special prize for his groundbreaking new method for characterising semiconductors. At the recent annual conference of the Marie Curie Alumni Association (MCAA) in Milan, Italy, he received the MCAA Award for the best innovation. Since 2023, Musiienko has been carrying out his research project with a postdoctoral fellowship from the Marie Sklodowska Curie Actions in Antonio Abate's department, Novel Materials and Interfaces for Photovoltaic Solar Cells (SE-AMIP).
  • Neutron experiment at BER II reveals new spin phase in quantum materials
    Science Highlight
    18.03.2024
    Neutron experiment at BER II reveals new spin phase in quantum materials
    New states of order can arise in quantum magnetic materials under magnetic fields. An international team has now gained new insights into these special states of matter through experiments at the Berlin neutron source BER II and its High-Field Magnet. BER II served science until the end of 2019 and has since been shut down. Results from data at BER II are still being published.

  • Where quantum computers can score
    Science Highlight
    15.03.2024
    Where quantum computers can score
    The travelling salesman problem is considered a prime example of a combinatorial optimisation problem. Now a Berlin team led by theoretical physicist Prof. Dr. Jens Eisert of Freie Universität Berlin and HZB has shown that a certain class of such problems can actually be solved better and much faster with quantum computers than with conventional methods.