Three new thiazolo[5,4-d]thiazole-based organic dyes have been designed and synthesized for employment as DSSC sensitizers. Alternation of the electron poor thiazolothiazole unit with two propylenedioxythiophene (ProDOT) groups ensured very intense light absorption in the visible region (ε up to 9.41 × 10⁴ M⁻¹ cm⁻¹ in THF solution). The dyes were particularly suitable for application in transparent and opaque thin-layer DSSCs (TiO₂ thickness: 5.5–6.5 μm, efficiencies up to 7.71%), thus being good candidates for production of solar cells under simple fabrication conditions.

Organic photosensitizers especially designed for producing semitransparent dye-sensitized solar cells (DSSCs) for greenhouse integration were prepared by introduction of different heterocyclic moieties into the thiazolo[5,4-d]thiazole- molecular scaffold. The aim was that of improving their light absorption capability in the green part of the visible spectrum while maintaining a good transparency in the blue and red regions, where the photosynthetic response is maximized. A short and efficient synthetic approach, featuring two consecutive C-H activation reactions in a one-pot procedure as key steps, was used. Based on their spectroscopic and electrochemical characterization, two of dyes prepared appeared especially suitable for greenhouse-integrated photovoltaics. The corresponding semitransparent DSSCs yielded 5.6-6.1% power conversion efficiencies, which were largely superior to those provided by other organic dyes previously proposed for the same application.

In this paper, we present the design and synthesis of three organic dyes specially developed for the fabrication of dye-sensitized solar cells for application in greenhouses cladding. The dyes (BTD-DTP1–3) are based on a benzothiadiazole (BTD)–dithienopyrrole (DTP) scaffold, and were assembled by using direct arylation reactions, allowing significant reduction of the number of synthetic and purification steps compared to classic cross-coupling procedures. Thanks to their structural design, the dyes absorb light in the green part of the visible spectrum while allowing good transmittance in the red and blue regions, thus ensuring high compatibility with light absorption by plants. Dye-sensitized solar cells built with the three dyes provided energy conversion efficiencies (ECEs) comparable or even superior to those obtained with the reference Ru-based dye N719, especially when using a thin and semitransparent TiO₂ layer (up to 8.77%). The photovoltaic performances are discussed considering the need to reach the best compromise between good ECE values and high levels of weighed transparency against the main plant photoreceptors.