A CEA team, in collaboration with the Pablo de Olavide University and the Swiss company Solaronix, has developed a new family of photochromic dyes specially designed for photovoltaic energy. The result of this work paves the way for solar glass whose transparency intelligently adapts to light.

The world of smart windows now has an additional “ally”. It’s about new photochromic photovoltaic panels created by the Interdisciplinary Research Institute of Grenoble (of the French CEA), in collaboration with the Spanish University Pablo de Olavide and the Swiss company Solaronix.

The team has developed some shades that can change color depending on the incidence of light and act as an active layer on solar cells. A quality that makes them valuable elements for energy-producing windows.

One of the most sought-after technologies in this field is semi-transparent photovoltaics: solar cells make it possible to capture energy without completely blocking the passage of light. However, there is a problem, as scientists explain:

Semi-transparent photovoltaics allow solar cells to be produced with fixed optical transmission during their manufacture, thanks to a fixed compromise between transparency and efficiency. However, for integration into buildings, the units must generate electricity, ideally offering users the ability to self-adjust light transmission according to the light intensity during the day.

The group was able to achieve this objective with the new photochromic photovoltaic panels based on diphenyl-naphthopyran dye. As with photochromic glasses, the devices made by the researchers darken in strong light and light up again as soon as the sun’s intensity decreases. The turning point is that they have succeeded in reconciling photochromatism and the photovoltaic effect.

The system is simple: in the dark, the tint is almost transparent and inactive; Under light, it changes from yellow to orange, red or dark green, starting to generate electricity.

For the development of smart photovoltaic windows and their integration into buildings, the variable and self-adapting optical properties would be very valuable. The ultimate goal is to create cells that are able to regulate their absorption under more intense light to produce energy without any external manipulation.

The prototype has an active area of ​​14 square centimeters and, after reaching full coloring, has a 32.5 mW power and an efficiency of up to 4.17%. The values ​​are still very low, but the study is only just beginning and organic photovoltaics continues to be an interesting bet thanks to significantly low production costs.

Even the first results in terms of stability are very encouraging (at least 50 days without encapsulation, that is to say without any protection in the cell). Therefore, the stability of these cells and the transition rates between low and high light should be optimized.

More information: www.nature.com