Perovskites are one of the most intriguing technologies around. There is particular interest in perovskite solar cells, which have the potential of reaching efficiencies of more than 25%.

With that in mind, the European Commission recently issued a call for funding “Novel Thin Film Technologies Targeting High Efficiencies” (HORIZON-CL5-2022-D3-03-05) as part of its Horizon Europe research framework program with a proposal on flexible perovskite solar cells.

The project caught the eye of a consortium of 10 partners from eight different countries throughout the perovskite photovoltaics manufacturing value chain. And with that, the PEARL Project was formed.

“The PEARL project was formed among the partners to respond to the European Commission’s call for funding,” said Dr. Riikka Suhonen from VTT Technical Research Centre of Finland Ltd, the PEARL project coordinator. “The consortium already knew each other well. We had already collaborated on a project proposal with similar topic and consortium once before, but  this first proposal didn’t receive funding. Our new project proposal, PEARL, was evaluated positively and so we were able to start the project on Oct. 1, 2023.” The project will run for 36 months.

“With PEARL, we are not just developing a new technology; we are setting the foundation for the next generation of solar power,” said Dr. Christian May, business development manager in Fraunhofer Institute for Electron Beam and Plasma Technology FEP and dissemination manager for PEARL. “Our innovative approach with carbon electrodes will not only enhance the efficiency and stability of perovskite solar cells but will also ensure that these benefits are accessible and sustainable on a global scale.”

“The primary objective of PEARL is to realize flexible perovskite solar cells processed with industrially viable, scalable and environmentally sound methods, showing long term operational stability surpassing the IEC standards, efficiency of > 25%, lowered production costs below 0.3 EUR/Wp and minimal emissions < 0.01 kg CO2eq/kWh,” said Dr. Suhonen.

“To reach these objectives, PEARL is focusing on the development of planar, conventional n-i-p, and further n-i-c, device architectures utilizing low-temperature carbon pastes as the top electrodes aiming to the emerging markets of building integrated photovoltaics (BIPV), vehicle integrated photovoltaics (VIPV) and internet of things (IoT),” added Dr. Suhonen.

As noted above, the PEARL consortium consists of 10 partners from eight different countries, throughout the perovskite photovoltaics manufacturing value chain. The partners represent two universities (University of Rome Tor Vergata and University of Applied Sciences Northwestern Switzerland); five research and technology organizations (RTO) VTT, Netherlands Organisation for Applied Scientific Research TNO, Helmholtz Centre for Materials and Energy, HZB,  Fraunhofer FEP and Institute of Chemical Research of Catalonia (ICIQ-CERCA); two small and medium-sized enterprises (SME) Dycotec Materials Ltd.  and Saule Spółka Akcyjna (SAU); and one large enterprise (LE) Eni S.p.A..

Dr. Suhonen noted that each of the partners has key roles in the project. From the universities, University of Rome Tor Vergata will develop the high efficiency flexible cells and modules with small area deposition techniques. These tasks will benefit from the collaboration with Fraunhofer FEP (substrate optimization), ICIQ (small molecules for charge transport layers) and HZB (efficient and stable perovskite layer).

University of Rome Tor Vergata will also optimize the module design to reduce the cell-to-module losses. Another university partner, FHNW, will perform the Life Cycle Analysis (LCA) and develop recycling scenarios for the PV devices and materials.

From the RTOs, HZB is responsible on the development of stable, high performance perovskite cells and will study their degradation mechanisms in detail whereas ICIQ will design and synthesize stable charge transport materials to be applied in the highly efficient devices.

The perovskite materials and cell architectures will be processed into modules by the upscaling partners TNO and VTT on functional substrates provided by Fraunhofer FEP. TNO and VTT will use their unique pilot-scale infrastructures (Solliance, PrintoCent) to fabricate the perovskite solar cells and modules with high-throughput, roll-to-roll techniques and Fraunhofer FEP will utilize their R2R vacuum-based coating infrastructure in fabrication of flexible, transparent electrodes and barrier foils.

HZB, FHNW, TNO and ENI will also use their facilities to perform thorough stability testing under both indoor and outdoor conditions.

From the SMEs, Dycotec Materials is a material supplier providing and developing the carbon inks, barrier adhesives for the encapsulation and antireflection coatings. Dycotec Materials has existing collaborations with Saule, who is a European flexible perovskite PV supplier with a strong interest to expand production with the high-throughput deposition methods developed in PEARL.

As an energy company, Eni will use its facilities to study the module power production. Both indoor and outdoor test facilities will be utilized for the energy yield assessment of PEARL flexible perovskite modules.

Perovskites and Solar Cells

Dr. Suhonen observed that in the last decade, perovskite solar cells have shown an extremely rapid increase in efficiency from basic research. 

“For a new generation solar cell technology, such an increase has never been seen before, which gives great hope for highly efficient perovskite solar cells in the future,” Dr. Suhonen added. “The tunable bandgap of perovskite enables optimization for various light conditions, improving the solar cell’s performance. The use of low-cost materials in their composition reduces manufacturing expenses, while their roll-to-roll based processing on flexible substrates facilitates simpler and potentially cheaper production techniques.

“Perovskites demonstrate excellent charge transport properties, resulting in higher efficiency in converting sunlight to electricity,” added Dr. Suhonen. “Collectively, these factors contribute to the growing efficiency and decreasing costs of perovskite-based solar cells.”

The question is how the development of carbon electrodes will further the potential of these solar cells.

Dr. Suhonen pointed out that carbon-based perovskite solar cells are a cell concept that has been introduced to sort the issues of instability, manufacturing complexity and high costs faced by record-breaking metal/hole-selective layer-based PSCs.

“The hydrophobic nature of carbon promotes lower in-take of moisture into the cell, making it possible to improve the cell lifetime,” said Dr. Suhonen. “Carbon electrodes will also substantially reduce the environmental impact of the flexible PSCs due to the abundant raw material. The possibility to formulate carbon into printing inks that can be processed via scalable roll-to-roll processing techniques thus lowers the environmental impact of flexible PSCs even further.”

Dr. Suhonen reported that there are plenty of benefits to flexible perovskite solar cells. These include their versatility, as these cells can be integrated into various surfaces in arbitrary size and shape. In addition, these cells are lightweight and cost-effective, as they can utilize industrially viable roll-to-roll printing techniques.

“This will further expand the commercialization potential of PSCs into a variety of applications such as mobile electronic devices, vehicle- and building integrated PVs, building applied PV and the emerging applications within the Internet of Things (IoT) market,” added Dr. Suhonen.

As for challenges, Dr. Suhonen said that the greatest hurdle in such a research project is to integrate the outstanding research results of the individual partners into a single process where, ideally, all the objectives of the project would be fulfilled.

“In PEARL, our ambition is to close the efficiency gap between the laboratory-scale processed PSCs and the PSCs processed utilizing scalable, industrially relevant deposition techniques,” added Dr. Suhonen. “The main challenges here arise from the requirement to use industrially and environmentally acceptable materials and processing environments.”

Dr. Suhonen sees plenty of potential for flexible perovskite solar cells.

“The flexible perovskite solar technology developed in PEARL is to be implemented to the European PV and global market first in the emerging application segments of building integrated photovoltaics (BIPV) and Internet of Things (IoT) and later in the electrification infrastructure and other integrated PV markets such as vehicle integrated PV (VIPV), building applied PV (BAPV) and mobile electronic devices,” Dr. Suhonen concluded.