Dye-sensitized solar cells (DSSCs) are devices easy to manufacture that have attractive characteristics for building integrated photovoltaics (BIPV). In recent years, many organic dyes have been developed for this application and some of them have demonstrated promising performances, allowing the fabrication of solar cells and modules combining high efficiency, transparency and stability. [1-2] Photochromic dyes are molecules that possess unique optical properties that can be controlled by light absorption. So far, they have been exploited in various fields, including optics, biomedicine and optoelectronics but rarely in photovoltaics. Recently, we have undertaken the task to develop pushpull photochromic dyes for using them as photosensitizers in DSSCs. These dyes have a donor-piacceptor structure incorporating a central photochromic unit such as diphenyl-naphthopyran, spiroindoline-naphthoxazine or -naphthopyran. Their optical, photochromic and acidochromic properties have been thoroughly studied and structureproperty relationships have been established before evaluating their potential as photoactive materials in solar cells. In this paper, we will disclose the synthesis strategies to access these molecules and their optoelectronic properties. We will demonstrate that these photochromic dyes can act as effective photosensitizers in DSSCs. [3-4-5-6] We will show that the solar cells embedding them are capable of varying their colour, can adapt their visible light transmission depending on illumination conditions and simultaneously convert light into electricity. We will also present the fabrication of photochromic semi-transparent mini-modules. Our work opens new application perspectives for photochromic dyes, and provides new research directions for designing solar cells with dynamic optical properties.

Dye-sensitized solar cells (DSSCs) are devices easy to manufacture that have attractive characteristics for building integrated photovoltaics (BIPV). In recent years, many organic dyes have been developed for this application and some of them have demonstrated promising performances, allowing the fabrication of solar cells and modules combining high efficiency, transparency and stability. [1-2] Photochromic dyes are molecules that possess unique optical properties that can be controlled by light absorption. So far, they have been exploited in various fields, including optics, biomedicine and optoelectronics but rarely in photovoltaics. Recently, we have undertaken the task to develop pushpull photochromic dyes for using them as photosensitizers in DSSCs. These dyes have a donor-piacceptor structure incorporating a central photochromic unit such as diphenyl-naphthopyran, spiroindoline-naphthoxazine or -naphthopyran. Their optical, photochromic and acidochromic properties have been thoroughly studied and structureproperty relationships have been established before evaluating their potential as photoactive materials in solar cells. In this paper, we will disclose the synthesis strategies to access these molecules and their optoelectronic properties. We will demonstrate that these photochromic dyes can act as effective photosensitizers in DSSCs. [3-4-5-6] We will show that the solar cells embedding them are capable of varying their colour, can adapt their visible light transmission depending on illumination conditions and simultaneously convert light into electricity. We will also present the fabrication of photochromic semi-transparent mini-modules. Our work opens new application perspectives for photochromic dyes, and provides new research directions for designing solar cells with dynamic optical properties.