The SALLI project, funded under the grant code 03EE1044B and running from 1 October 2019 to 31 March 2023, aimed to develop substrate‑conserving metallisation techniques that combine pressure‑based and galvanic processes for high‑efficiency silicon solar cells. The Fraunhofer Institute for Solar Energy Systems (ISE) led the technical work package 03EE1044B, coordinating the overall effort and delivering the key scientific results. The consortium comprised Benecke‑Kaliko AG, Notion Systems GmbH, ICB GmbH, with PV Nano Cell Ltd. and AZUR SPACE Solar Power GmbH as associated partners. The project was organised into seven work packages covering project coordination, material development, plant development, pressure‑process development, galvanic processing on structured back surfaces, process integration, and techno‑economic assessment.

In the material development phase, Fraunhofer ISE produced particle‑free inkjet inks and nanosilver‑containing formulations suitable for high‑resolution printing on silicon wafers. A custom n.jet lab PV inkjet printer was assembled, featuring a substrate table that could process four industrial solar‑cell wafers simultaneously. The inkjet process was scaled to demonstrate uniform deposition of conductive layers, while the flexographic printing collaboration with Benecke‑Kaliko and PV Nano Cell yielded high‑throughput, low‑cost deposition of metal layers on large‑area substrates. Electrolytes for electrochemical flexodr printing were co‑developed with ICB and subsequently tested by Benecke‑Kaliko, confirming stable ion transport and efficient metal deposition.

The galvanic work package introduced a mask‑and‑plate method that integrates a pressure‑based deposition step with a subsequent galvanic filling of micro‑structured back‑surface fields. This hybrid approach preserves the silicon substrate while achieving a dense, low‑resistance metal network. The process was successfully applied to structured back‑surface field (Al‑BSF) cells, enabling the fabrication of passivated‑contact cells that approach the theoretical efficiency ceiling of 25 %. The project’s performance data show that the developed metallisation routes do not impose the typical 25 % efficiency limit seen in conventional Al‑BSF, PERC, or passivated‑contact cells, thereby opening a pathway to higher conversion efficiencies.

Process integration studies demonstrated that the new metallisation sequence can be incorporated into existing silicon cell production lines with minimal re‑tooling. A techno‑economic assessment, completed in the final work package, quantified the cost savings from reduced material consumption and simplified processing steps, indicating a favourable return on investment for commercial deployment. The project also produced a cost‑neutral extension, approved by the funding agency, allowing the continuation of pilot‑scale demonstrations.

Collaboration was structured around regular project meetings—seven in total, four held online and two onsite at Fraunhofer ISE—where partners presented progress, negotiated milestones, and defined next steps. Bilateral and trilateral video conferences supplemented these gatherings, ensuring continuous communication between Fraunhofer ISE, Benecke‑Kaliko, Notion Systems, and ICB. The scientific leadership of the Fraunhofer ISE sub‑project transitioned from Swetlana Weit to Dr. Jörg Schube on 3 December 2020, while Dr. Roman Keding remained the principal responsible scientist throughout the project.

In summary, the SALLI project delivered a suite of substrate‑conserving metallisation technologies that combine inkjet and flexographic printing with pressure‑based and galvanic deposition. These innovations enable high‑efficiency silicon solar cells that surpass the conventional 25 % efficiency ceiling, while offering a scalable, cost‑effective manufacturing route. The collaborative effort of the consortium, supported by the 03EE1044B grant, has laid the groundwork for future industrial adoption of these advanced metallisation processes.