Flexible perovskite solar cell roll-to-roll processing at VTTs pilot line
Image: VTT Oy

An EU-funded research program consisting of ten European research organizations has fabricated a flexible perovskite solar cell on bendable substrates with an efficiency of 21.6%. 

The PEARL – Flexible Perovskite Solar Cells with Carbon Electrodes program is now more than halfway through its three-year research period, as it works towards a target of 25% efficient, low-cost flexible perovskite solar cells with carbon electrodes.

Spanish research institute ICIQ achieved the 21.6% efficiency through special surface treatments consisting of molecular surface passivation with fullerene and silane self-assembled materials.

Other notable achievements under the project to date include the University of Rome Tor Vergata's 17.03% efficiency for greener perovskite solvents and optimized blade-coating protocols. 

Elsewhere, Finnish research organization VTT has developed a lab-scale champion cell via a printing process that combines gravure-printed perovskite with dimethyl sulfoxide-based ink that achieved a power conversion efficiency of 14.8%. Meanwhile, Dutch research institute TNO has achieved a 9.1% power conversion efficiency with a fully roll-to-roll slot-die coated perovskite stack.

VTT and TNO have both scaled up their roll-to-roll coating and patterning to larger formats and developed flexible mini-modules with an area of 36 cm² and a power conversion efficiency of 4.5%.

The consortium has also developed protective encapsulation that keeps the solar cells stable for over 2,000 hours under damp-heat conditions, of 85 C temperature and 85% humidity, which they say proves the cells' durability for real-world applications.

Riika Suhonen, Pearl Project Coordinator at VTT, commented that the project’s work to date brings the 25% efficiency target “firmly within reach”.

The consortium has also conducted initial life cycle assessments that have found the use of carbon electrodes, recycled PET and green energy can reduce the carbon footprint by more than 50%. Processes have also been developed to recover materials, including lead and cesium from production waste.

During the second phase of the project, the consortium plans to further optimize its roll-to-roll manufacturing processes, test modules for outdoor use and publish the results of its life cycle assessments. It is also aiming to bring flexible cells to market in applications including building-integrated photovoltaics.

The Pearl project commenced at the start of October 2023 and receives funding from the European Union’s Horizon Europe research and innovation programme. Work has also been financed by the UK Research and Innovation’s Horizon Europe funding guarantee and the Swiss State Secretariat for Education, Research and Innovation.