To achieve PISCO’s objectives, we designed, synthesised, and characterised a new generation of dyes incorporating photochromic units. The project began with theoretical studies to verify that the proposed dyes met the optoelectronic criteria required for use as sensitizers in dye-sensitized solar cells (DSSCs). Modelling and simulations identified the most promising molecular structures and predicted their absorption properties. Based on these insights, we developed innovative synthetic routes, successfully obtaining several families of dyes adapted for solar cells, two of which were patented. These dyes exhibited excellent reversibility, high fatigue resistance, and strong photo-colourability, and their optical and electronic properties were studied using advanced characterisation techniques developed for the project.
The dyes were incorporated into DSSCs to evaluate photochromic behaviour and photovoltaic performance. Fabrication parameters were optimised, and electrical characterisation under different lighting conditions provided new insights into the interaction between photochromic and photovoltaic properties. This work significantly advanced our understanding of photochromic materials, revealing new relationships between molecular structure and device performance.
For the first time, we demonstrated fully reversible photochromic solar cells that change colour in response to light intensity. DSSCs with our dyes adapted their visible light transmission to daylight while simultaneously generating electricity, with fully coloured cells producing higher photocurrents and power conversion efficiencies (Nature Energy 2020, DOI: 10.1038/s41560-020-0624-7).
Building on this new knowledge, molecular engineering produced dyes with faster colouration and decolouration kinetics, lower recombination losses, improved efficiency, higher stability, and in some cases excellent colour rendering in semi-transparent devices. Data-driven and machine-learning approaches were also developed to accelerate the design of new electrolytes tailored to this class of dyes.
To demonstrate technological potential, minimodules up to 25 cm² were fabricated with Solaronix (Switzerland). Large-area photochromic modules of 600 cm² were produced with the University of Tor Vergata (Italy), confirming scalability and robustness. Manufacturing and recycling methods were also developed to reduce carbon footprint and costs, opening new industrial collaboration opportunities.
PISCO’s work has resulted in over 20 publications in high-impact journals, including Nature Energy, Advanced Energy Materials, Advanced Materials, Chemical Science, and Materials Horizons. The project also led to a patent, more than 30 invited presentations, and several awards, notably the Materials Horizons Prize (RSC, 2025). It has received extensive media coverage on specialised scientific platforms and in national newspapers and magazines, highlighting its technological and societal relevance.
