Periodic Reporting for period 1 - EFESO (Exploiting Flexible pErovskites Solar technOlogies)
Période du rapport: 2023-06-26 au 2025-03-25
The transition to renewable energy sources is one of the most pressing challenges of our time. In this context, solar photovoltaics (PV) have emerged as a central pillar of the global energy strategy. However, current mainstream PV technologies are largely rigid, heavy, and dependent on energy-intensive fabrication processes that limit their integration in next-generation applications such as building-integrated photovoltaics (BIPV), portable electronics, and the Internet of Things (IoT). To unlock the full potential of solar energy in these emerging sectors, there is an urgent need for lightweight, flexible, and scalable photovoltaic technologies that combine high performance with environmental sustainability.
EFESO – Exploiting Flexible pErovskite Solar technOlogies – addresses this need by focusing on the development of robust, efficient, and scalable flexible perovskite solar modules (FPSMs). Perovskites are solution-processable materials that have shown remarkable power conversion efficiencies in recent years, rivalling and even surpassing those of conventional silicon-based cells. Their compatibility with low-temperature, ambient processing makes them ideal candidates for integration into flexible substrates. However, challenges remain: flexible perovskite devices still face significant issues related to mechanical fragility, environmental instability, scalability, and concerns about lead (Pb) toxicity.
The EFESO project is conceived to tackle these challenges through a multidisciplinary research program that combines materials engineering, device physics, environmental science, and industrial process design. The overarching objective is to develop flexible perovskite solar modules that are not only highly efficient and durable, but also environmentally responsible and scalable to commercial formats. The project achieves this by integrating additive engineering, interface design, mechanical durability testing, and encapsulation strategies into a single coherent framework.
Over the course of the project, the following six specific objectives are pursued:
1) Assess and optimize materials for flexible perovskite solar cells, focusing on solvents, additives, and interfacial layers to enhance film formation and reduce toxicity.
2) Fabricate high-efficiency small-area flexible devices, targeting over 23% power conversion efficiency while ensuring environmental and mechanical stability.
3) Upscale devices to module-level areas and conduct a Life Cycle Assessment (LCA) to evaluate environmental impacts and readiness for circular economy integration.
4) Develop advanced encapsulation techniques that provide robust protection against mechanical stress and mitigate lead leakage under real-world conditions.
5) Foster the researcher's scientific independence and transferable skill development through training, mentoring, and international collaboration.
6) Disseminate project results across academic, industrial, and public audiences to ensure widespread impact and knowledge transfer.
EFESO operates within the broader strategic priorities of the European Green Deal, contributing to the decarbonization of the energy sector and supporting Europe’s goal of becoming the first climate-neutral continent. The project also aligns with EU objectives in areas such as digital transformation, sustainable innovation, and industrial competitiveness, by delivering energy solutions tailored for smart devices and flexible electronics.
The project’s impact is expected to be significant: by advancing flexible solar technology toward commercial maturity, EFESO contributes to making solar energy more accessible, customizable, and sustainable. Its scientific and technological outputs, including new testing protocols and environmentally conscious processing workflows, are already influencing best practices and standardization efforts across the photovoltaics community. In doing so, EFESO sets a strong foundation for long-term innovation in renewable energy and supports Europe’s leadership in clean-tech solutions for the future.
EFESO – Exploiting Flexible pErovskite Solar technOlogies – addresses this need by focusing on the development of robust, efficient, and scalable flexible perovskite solar modules (FPSMs). Perovskites are solution-processable materials that have shown remarkable power conversion efficiencies in recent years, rivalling and even surpassing those of conventional silicon-based cells. Their compatibility with low-temperature, ambient processing makes them ideal candidates for integration into flexible substrates. However, challenges remain: flexible perovskite devices still face significant issues related to mechanical fragility, environmental instability, scalability, and concerns about lead (Pb) toxicity.
The EFESO project is conceived to tackle these challenges through a multidisciplinary research program that combines materials engineering, device physics, environmental science, and industrial process design. The overarching objective is to develop flexible perovskite solar modules that are not only highly efficient and durable, but also environmentally responsible and scalable to commercial formats. The project achieves this by integrating additive engineering, interface design, mechanical durability testing, and encapsulation strategies into a single coherent framework.
Over the course of the project, the following six specific objectives are pursued:
1) Assess and optimize materials for flexible perovskite solar cells, focusing on solvents, additives, and interfacial layers to enhance film formation and reduce toxicity.
2) Fabricate high-efficiency small-area flexible devices, targeting over 23% power conversion efficiency while ensuring environmental and mechanical stability.
3) Upscale devices to module-level areas and conduct a Life Cycle Assessment (LCA) to evaluate environmental impacts and readiness for circular economy integration.
4) Develop advanced encapsulation techniques that provide robust protection against mechanical stress and mitigate lead leakage under real-world conditions.
5) Foster the researcher's scientific independence and transferable skill development through training, mentoring, and international collaboration.
6) Disseminate project results across academic, industrial, and public audiences to ensure widespread impact and knowledge transfer.
EFESO operates within the broader strategic priorities of the European Green Deal, contributing to the decarbonization of the energy sector and supporting Europe’s goal of becoming the first climate-neutral continent. The project also aligns with EU objectives in areas such as digital transformation, sustainable innovation, and industrial competitiveness, by delivering energy solutions tailored for smart devices and flexible electronics.
The project’s impact is expected to be significant: by advancing flexible solar technology toward commercial maturity, EFESO contributes to making solar energy more accessible, customizable, and sustainable. Its scientific and technological outputs, including new testing protocols and environmentally conscious processing workflows, are already influencing best practices and standardization efforts across the photovoltaics community. In doing so, EFESO sets a strong foundation for long-term innovation in renewable energy and supports Europe’s leadership in clean-tech solutions for the future.
Since the beginning of the EFESO project, substantial progress has been made in developing flexible perovskite solar modules that are efficient, scalable, and environmentally robust. The technical work has proceeded through a structured pathway, corresponding to the scientific work packages defined in the project’s Grant Agreement. Each phase has contributed to advancing the state of the art in flexible photovoltaics and addressing core challenges in mechanical stability, process scalability, and environmental compliance.
The first phase focused on material assessment and interface engineering. A comprehensive screening of solvents, additives, and interfacial modifiers was carried out to optimize film formation on flexible substrates. Anisole was identified as a safer and more effective alternative to conventional solvents like toluene, improving the wettability and uniformity of hole transport layers (HTLs) such as PTAA. In parallel, benzamide-based additives were introduced as multifunctional interfacial agents, improving electronic contact and offering a strategy for lead immobilization under stress conditions. These findings laid a solid foundation for device fabrication.
The second phase addressed the fabrication and optimization of small-area flexible perovskite solar cells. Devices were produced using scalable techniques such as blade and slot-die coating in ambient or near-ambient conditions. The best-performing devices on a flexible substrate achieved stabilized power conversion efficiencies exceeding 22%. Early aging studies under continuous 1 Sun illumination revealed T80 values ranging from 160 to 690 hours, depending on encapsulation and device structure.
In the third phase, the project transitioned to module upscaling and environmental evaluation. Mini-modules with areas up to 10.5 cm² were fabricated using the previously optimized protocols. Laser scribing techniques (P1) were validated for accurate interconnect definition, and data collection for Life Cycle Assessment (LCA) was initiated. Environmental metrics related to material consumption, energy use, and waste generation were compiled, with support from industrial partners in preparation for the upcoming non-academic placement. In parallel, design considerations for low-light indoor and IoT-specific modules were developed in coordination with Saule Technologies.
The fourth technical phase focused on encapsulation strategies. Initial testing was performed using kapton tape and resin-based barriers, with additional investigations on polymer-based and semi-liquid encapsulants now underway. Preliminary ISOS testing showed that encapsulation plays a key role in stability retention and lead containment, and work is ongoing to finalize an encapsulation protocol that can be implemented across both small-area and module-scale devices.
From a scientific perspective, EFESO has already produced several high-impact contributions. These include the development of a new mechanical stability testing method tailored to flexible devices, and the introduction of a new figure of merit, the fatigue factor, for quantifying mechanical degradation under cyclic strain. These methodological innovations have begun to influence emerging standards in the field. Moreover, ongoing work on elastomeric interlayers and cross-linking molecules is clarifying the role of mechanical mismatch in device failure and helping identify materials that enable long-term durability.
The first phase focused on material assessment and interface engineering. A comprehensive screening of solvents, additives, and interfacial modifiers was carried out to optimize film formation on flexible substrates. Anisole was identified as a safer and more effective alternative to conventional solvents like toluene, improving the wettability and uniformity of hole transport layers (HTLs) such as PTAA. In parallel, benzamide-based additives were introduced as multifunctional interfacial agents, improving electronic contact and offering a strategy for lead immobilization under stress conditions. These findings laid a solid foundation for device fabrication.
The second phase addressed the fabrication and optimization of small-area flexible perovskite solar cells. Devices were produced using scalable techniques such as blade and slot-die coating in ambient or near-ambient conditions. The best-performing devices on a flexible substrate achieved stabilized power conversion efficiencies exceeding 22%. Early aging studies under continuous 1 Sun illumination revealed T80 values ranging from 160 to 690 hours, depending on encapsulation and device structure.
In the third phase, the project transitioned to module upscaling and environmental evaluation. Mini-modules with areas up to 10.5 cm² were fabricated using the previously optimized protocols. Laser scribing techniques (P1) were validated for accurate interconnect definition, and data collection for Life Cycle Assessment (LCA) was initiated. Environmental metrics related to material consumption, energy use, and waste generation were compiled, with support from industrial partners in preparation for the upcoming non-academic placement. In parallel, design considerations for low-light indoor and IoT-specific modules were developed in coordination with Saule Technologies.
The fourth technical phase focused on encapsulation strategies. Initial testing was performed using kapton tape and resin-based barriers, with additional investigations on polymer-based and semi-liquid encapsulants now underway. Preliminary ISOS testing showed that encapsulation plays a key role in stability retention and lead containment, and work is ongoing to finalize an encapsulation protocol that can be implemented across both small-area and module-scale devices.
From a scientific perspective, EFESO has already produced several high-impact contributions. These include the development of a new mechanical stability testing method tailored to flexible devices, and the introduction of a new figure of merit, the fatigue factor, for quantifying mechanical degradation under cyclic strain. These methodological innovations have begun to influence emerging standards in the field. Moreover, ongoing work on elastomeric interlayers and cross-linking molecules is clarifying the role of mechanical mismatch in device failure and helping identify materials that enable long-term durability.
EFESO has delivered several results that go beyond the current state of the art in flexible perovskite photovoltaics by addressing key limitations related to mechanical stability, scalability, environmental safety, and standardization.
A major innovation of the project is the development of a new mechanical stability testing method tailored for flexible devices, which accounts for degradation under bending. This also led to the introduction of a new figure of merit, the fatigue factor, providing a reproducible benchmark for durability. These results are contributing to the foundation of emerging testing standards for flexible PV technologies.
EFESO also introduced benzamide-based interfacial molecules and elastomeric interlayers to improve mechanical compliance and mitigate interface failure, offering clear design rules for device architecture. Additionally, the project identified anisole as a safer, high-performing alternative to traditional solvents for HTL deposition, promoting greener processing approaches.
Scalable fabrication using blade and slot-die coating was successfully implemented to produce modules under ambient conditions. These methods are compatible with industrial processes.
The expected impact includes enabling the next generation of lightweight, portable, and wearable PV systems, with applications in IoT, building-integrated photovoltaics (BIPV), and off-grid energy. EFESO's advances in process design, durability testing, and environmental safety offer practical solutions for commercial adoption.
A major innovation of the project is the development of a new mechanical stability testing method tailored for flexible devices, which accounts for degradation under bending. This also led to the introduction of a new figure of merit, the fatigue factor, providing a reproducible benchmark for durability. These results are contributing to the foundation of emerging testing standards for flexible PV technologies.
EFESO also introduced benzamide-based interfacial molecules and elastomeric interlayers to improve mechanical compliance and mitigate interface failure, offering clear design rules for device architecture. Additionally, the project identified anisole as a safer, high-performing alternative to traditional solvents for HTL deposition, promoting greener processing approaches.
Scalable fabrication using blade and slot-die coating was successfully implemented to produce modules under ambient conditions. These methods are compatible with industrial processes.
The expected impact includes enabling the next generation of lightweight, portable, and wearable PV systems, with applications in IoT, building-integrated photovoltaics (BIPV), and off-grid energy. EFESO's advances in process design, durability testing, and environmental safety offer practical solutions for commercial adoption.