During the first project phase, C2C-PV achieved several key scientific and technological milestones:
1. Establishing a common material pool.
A database of photovoltaic materials was created to evaluate their suitability for circular use. The concept is based on integrating PV materials into a broader industrial ecosystem, so that glass, metals, and polymers used in solar modules can also circulate through other product cycles. The accompanying analysis, published as “Cradle-to-cradle recycling in terawatt photovoltaics: A vision of perpetual utility” (Peters et al., Joule 2024), demonstrated that the PV industry will soon become a major consumer of several essential materials such as glass, aluminum, and silver. This finding highlights the necessity of circular recycling to sustain global deployment. Current work extends this model to perovskite solar technologies and identifies materials that can be reused across product generations.
2. Developing interfaces for separability.
Reconciling durability with ease of disassembly emerged as the core scientific challenge. C2C-PV developed a bio-based sacrificial edge seal combined with a gel-type encapsulant, allowing modules to be opened and resealed without damage—an innovation now protected by patent. At the device level, the team demonstrated the first fully recyclable perovskite solar cell, where each layer can be selectively dissolved using orthogonal solvents. The results, published in “Closing the loop: recycling of MAPbI₃ perovskite solar cells” (Wu et al., Energy & Environmental Science 2024), achieved 99.97 % mass recovery with identical efficiency after reuse—proof of concept for rapid, clean closed-loop recycling.
3. Creating a unified design framework.
The conceptual and quantitative design space for recyclable solar cells was formalized in “The Ideal Recyclable Solar Cell” (Peters & Brabec, Nature Reviews Chemistry 2025). This work introduces measurable parameters—intra-layer bonding, inter-layer bonding, bonding contrast, and locked-in entropy—to describe the trade-offs between performance, stability, and recyclability. It provides the first theoretical framework for assessing recyclability in photovoltaic materials and has since been adopted by other research groups in the field.
4. Prototyping recyclable module envelopes.
Modules built with the new edge-seal design were shown to be reusable: after separation, the glass package could be resealed, maintaining full moisture protection and mechanical integrity. Devices encapsulated in this reusable structure exhibited the same operational stability as conventional references, confirming the practical feasibility of circular module construction.
5. Economic and environmental validation.
Techno-economic models demonstrated that recycling substrates and solvents can reduce material costs by more than 60 % at both laboratory and industrial scale. Life-cycle assessments showed a 70 % reduction in energy payback time and greenhouse-gas emissions compared with conventional fabrication. These findings confirm that C2C design is not only environmentally beneficial but also economically attractive.
6. Outreach and recognition.
The project’s results have been featured in major media outlets, science podcasts, and a German television documentary on recycling. Two patents were filed, and the PI and team have been invited to multiple international conferences, including EU PVSEC, IEEE PVSC, and MRS, establishing C2C-PV as a reference initiative in circular photovoltaics.
