# Push-pull photochromic dyes for use in semi-transparent solar cells with dynamic optical properties

S. Fauvel, A. J. Riquelme, J. Liotier, J.-M. Andres Castán, V. M. Mwalukuku, Y. Kervella, C. Aumaître, S. Narbey, P. Maldivi, Renaud Demadrille

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S. Fauvel, A. J. Riquelme, J. Liotier, J.-M. Andres Castán, V. M. Mwalukuku, et al., Push-pull photochromic dyes for use in semi-transparent solar cells with dynamic optical properties. Photo-sciences 2024 - Réunion des sociétés françaises de photobiologie, photochimie, photophysique et des photosciences., May 2024, Grenoble, France. hal-04754727

HAL Id: hal-04754727

https://hal.science/hal-04754727v1

Submitted on 26 Oct 2024

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# Push-pull photochromic dyes for use in semi-transparent solar cells
with dynamic optical properties

S. Fauvel<fnref n="1" />, A. J. Riquelme<fnref n="1" />, J. Liotier<fnref n="1" />, J.-M. Andres Castán<fnref n="1" />, V. M. Mwalukuku<fnref n="1" />, Y. Kervella<fnref n="1" />, C. Aumaître<fnref n="1" />, S. Narbey<fnref n="2" />, P. Maldivi<fnref n="1" />, R. Demadrille<fnref n="1" />*

Email: renaud.demadrille@cea.fr

Photochromic solar cells are a new type of photovoltaic device with dynamic optical properties that could potentially be used in glazing and buildings in the future. These solar cells exhibit changes in colour, transparency and photovoltaic performance in response to sunlight conditions.

In 2020, we have shown that the design of push-pull photochromic photosensitizers of the diphenyl-
naphthopyran series and their use in a dye-sensitised solar cell configuration is an effective strategy for
achieving solar cells with light-driven optical properties. This approach resulted in excellent reversibility
of the colouring and decolouring process, as well as efficiencies of the order of 4% for the solar cells. We
have also shown that these dyes can be used to fabricate semi-transparent mini-modules with a
maximum power output of the order of 35mW. [1]

Recently, we have sought to develop push-pull photochromic dyes with faster bleaching kinetics and better optical properties. In this work, we will outline the synthetic routes used to prepare these photochromic dyes and detail their optoelectronic properties and structure-property relationships [2-3]. In particular, we will show that by appropriate molecular design, it is possible to obtain molecules that exhibit a better photochromic behaviour in devices [4]. We will also present the synthesis and characterisation of new dyes that show a better tuning of their spectra to the photopic response of the human eye allowing producing semi-transparent mini-module with an average visible transmittance varying between 66% and 50% and a colour-rendering index of around 95 in both the uncoloured and coloured states. [5]

<figure><img src="image_1.png" /></figure>

**Figure:** Image of a semi-transparent mini-module based on a push-pull photochromic dye.

## Acknowledgements

This work was funded under the European Union's Horizon 2020 research and innovation programme (grant agreement number 832606; project PISCO).

## References

1. Q. Huaulmé et al. *Nature Energy*. **2020**, *5*, 468-477

2. J. Liotier et al., *Solar RRL*. **2021**, *2100929*

3. J.M. Andres-Castán., *Mater. Chem. Front.*, **2022**, *6*, 2994-3005

4. V. M. Mwalukuku et al. *Adv. Energy Mater.*, **2023**, 2203651

5. S. Fauvel et al. *Chem. Sci.*, **2023**, 14, 8497–8506.

<footnote n="1">¹ Univ. Grenoble Alpes, CEA, CNRS, Grenoble INP, IRIG, SyMMES, Grenoble, France</footnote>

<footnote n="2">² Solaronix SA, Aubonne, Vaud, Switzerland</footnote>