COMET
The COMET project aims to increase the sustainability of PV module production by developing efficient copper metallization processes for p-type and n-type solar cells. A copper electroplating process for PERC and TOPCon cells will be demonstrated, which enables the metallization of front and back sides without ghost plating. In addition, innovative connections with conductive adhesives are developed and the physical phenomena of poly-Si/Cu contact formation are investigated.
Project partners
- JOANNEUM Research Forschungsgesellschaft mbH, Coordinator
- Polymer Competence Center Leoben GmbH
- CSEM - Centre Suisse d’Electronique et de Microtechnique SA
- EPFL - École Polytechnique Fédérale de Lausanne
- Kalyon PV
- SALD BV
Motivation and Goals
PV energy is now undisputedly the most important pillar of the EU's future low-carbon energy system.
energy system. However, as PV enters the TW era, with 8.8 TW of PV panels expected to be installed in the EU by 2035, concerns are being raised about the overall sustainability of the PV industry and a potential shortage of materials. sustainability of the PV industry and a potential shortage of materials. Ensuring the sustainability of PV energy at TW level requires reduce material intensity, i.e. improve PV energy production per amount of raw materials used in PV systems. This can be achieved be achieved through 3 approaches:
- Improving the power conversion efficiency (PCE) of PV systems.
- Significant reduction and ideally complete elimination of critical and hazardous raw materials in PV systems to eliminate supply shortages and reduce environmental impact. Eliminate supply bottlenecks and reduce the environmental footprint.
- Improve energy production during the lifetime of the PV system, i.e. provide PV products with longer lifetime (better reliability) and higher energy yield.
The COMET project aims to improve the overall sustainability of PV energy through the development of
copper metallization processes for current p-type and future n-type solar cells and modules. COMET will
demonstrate an efficient copper electroplating process for PERC and TOPCon solar cells, which enables the simultaneous metallization of the front and back sides up to M6 wafer format without ghost plating. Innovative and reliable connections based on electrically conductive adhesives will also be demonstrated. Furthermore
In addition, COMET will uncover the physical phenomena that determine poly-Si/Cu contact formation, including the barrier layers between poly-Si and copper, and identify the materials and process parameters that provide the lowest contact resistance without damaging surface passivation. Finally, COMET will demonstrate the reliability and cost-effectiveness of Cu-metallized solar cells down to mini-modules and perform both standard degradation tests as well as accelerated outdoor aging to determine the main failure modes to improve the validation and viability of Cu metallization as a sustainable replacement for Ag.
Main Goals
- Reduction of opto-electrical losses in modern n-type solar cells with charge carrier selective passivated contacts (CSPC) through the use of high-quality n-type wafers and improved contacts, with the aim of achieving a PCE of over 26 %.
- Replacing Ag metallization with Cu and using thinner wafers with the aim of reducing the material intensity of PV devices by 50% without sacrificing PCE.
- Monitoring Ag-free p-type and n-type PV modules in harsh climatic conditions to evaluate their actual energy yield and identify their main failure modes.
Objectives and Approach
The COMET project pursues several goals to improve the sustainability and efficiency of Cu-metallized solar cells. Key aspects include:
- Cu electroplating: CSEM is developing a Cu electroplating process with only three steps (printing of seed grids, dielectric application, plating). The process is intended to enable cost-effective and efficient metallization, with a focus on the simultaneous metallization of the front and rear sides of cells.
- Poly-Si/Cu contact formation: Advanced characterizations (e.g. XRD, SEM, TEM) will be used to improve the understanding of poly-Si/Cu contact formation. The aim is to optimize processes to achieve low contact resistance without damaging the passivation layer. Alternative Cu coating methods are being investigated in order to improve contact quality.
- Self-reducing Cu inks: Hybrid Cu inks are being developed that use Cu formate and microparticles to minimize oxidation and optimize conductivity. These inks should enable more cost-effective sintering under normal atmospheric conditions.
- Connection with ECAs: Development and improvement of copper connections through ECA and the investigation of their reliability
- These measures are intended to establish copper as a sustainable replacement for Ag in solar cells.
„ The COMET project supports the optimization of existing PV technologies in order to conserve resources and make the PV industry more sustainable.“
Funding Body
The research project is funded by the Climate and Energy Fund (Energieforschung 7. Ausschreibung, Solar Cofund 2 Additional Joint Call 2021) represented by the FFG (project number FO999897446) as funding body.
