Push-pull photochromic dyes for use in semitransparent solar cells with dynamic optical properties.
Renaud DEMADRILLE a, Samuel FAUVEL a, Johan LIOTIER a, José-Maria ANDRES CASTAN a, Antonio J. RIQUELME a, Valid M. MWALUKUKU a, Stéphanie NARBEY b, Pascale MALDIVI a, Juan ANTA c
a Grenoble Alpes University, CNRS, CEA, INP, IRIG/SYMMES, F38000 Grenoble, France
b Solaronix SA, Rue de l’Ouriette 129, Aubonne, 1170, Switzerland
c Área de Química Física, Universidad Pablo de Olavide, E-41013 Seville, Spain
Invited Speaker Session, Renaud DEMADRILLE, presentation 027
Publication date: 6th February 2024

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 diphenylnaphthopyran 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 produce semi-transparent mini-modules with a maximum power output of the order of 35mW [1].

However, the first generation of dyes, once incorporated into devices, resulted in semi-transparent solar cells with very slow decoration kinetics and poor colour rendering index, below 70 in the coloured state. To overcome these problems, we have sought to develop donor-acceptor photochromic dyes with faster decoloration kinetics and better optical properties. In this talk, 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 using an appropriate molecular design for the photochromic naphthopyran dyes, it is possible to obtain molecules that exhibit 6 times faster decolouration kinetics in devices [4]. We will also present the synthesis and characterisation of new dyes containing carbazole moieties as electron donors. These dyes allow a hypsochromic shift of the absorption of the coloured isomers in the visible region compared to the first generation of dyes, and a better tuning of their spectra to the photopic response of the human eye. Using one of these dyes (SF4) we have achieved a PCE of up to 3% in cells. Additionally, a semi-transparent mini-module has been produced 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]

R.D. acknowledges the European Research Council (ERC) for funding. This work was funded under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 832606; project PISCO).

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