Photochromic Dyes for Semi-Transparent Solar Cells and Solar Mini-Modules with Light-Adjustable Transmittance and High Colour Rendering Index

Among the emerging photovoltaic technologies, dye-sensitised solar cells (DSSCs) have recently achieved power conversion efficiencies (PCE) above 15% and have demonstrated good stability, with lifetimes exceeding 12 years in real-world conditions. These devices can be coloured and semi-transparent, making them very attractive for both building-integrated photovoltaics (BIPV) and agrivoltaics (Agri-PV). However, to integrate these cells into windows for use in buildings or greenhouses, it is often necessary to find the right compromise between transparency and efficiency.<br/>In this talk, we will present our recent work aimed at developing new photochromic dyes specifically designed for use in photovoltaic devices.^[1] We will present the synthetic routes to these photochromic photosensitizers and detail their optoelectronic and photochromic properties. We will show that by modifying the substitution of dyes from the diphenylnaphthopyran family, it is possible to modulate their absorption range in the visible, to control their discoloration kinetics and to reduce the recombination processes in solar cells. ^{[2] [3]}<br/>We will then show that these dyes can be used to fabricate a new generation of semi-transparent solar cells and solar modules capable of self-regulating their optical transparency and energy conversion efficiency as a function of light intensity.<br/>Thanks to the molecular engineering of these photosensitizers and the development of novel formulations for the electrolytes, we will show that solar modules with a transmittance varying between 50 and 65% as a function of light exposure and a color rendering index above 95 can be obtained. ^[4]<br/><br/>References :<br/>[1] Huaulmé et al., <i>Nature Energy, </i>2020<i>, </i>5, 468-477.<br/>[2] Mwalukuku et al., <i>Adv. Energy Mater</i>., 2023, 13, 2203651.<br/>[3] Riquelme et al., <i>ACS Appl. Energy Mater.</i> 2021, 4, 9, 8941–8952.<br/>[4] Fauvel et al., <i>Chem. Sci.</i>, 2023, 14, 8497-8506.