Thiazolo[5,4-d]thiazole-based organic sensitizers with strong visible light absorption for transparent, efficient and stable dye-sensitized solar cells

A small set of thiazolo[5,4-d]thiazole-based D–π–A organic dyes, endowed with bis-pentylpropylenedioxythiophene (ProDOT) moieties in the π-spacer, was designed with the aid of computational analysis, synthesized and characterized. The presence of bulky and electronrich ProDOT groups beside the electron poor thiazolothiazole unit induced optimal physico-chemical properties, including broad and intense visible light absorption. As a consequence, the dyes were particularly suitable for application in thin layer dye-sensitized solar cells (TiO2 thickness: 3.0–6.5 μm). Small-scale (0.25 cm2) devices prepared using standard materials and fabrication techniques gave power conversion efficiencies up to 7.71%, surpassing those obtained with two different reference dyes. These results make this new family of organic sensitizers promising candidates for successful application in the production of efficient and stable transparent DSSCs for building-integrated photovoltaics.