Molecular Engineering of Potent Sensitizers for Very Efficient Light Harvesting in Thin-Film Solid-State Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have shown significant potential for indoor and building-integrated photovoltaic applications. Herein we present three new D–A−π–A organic sensitizers, <b>XY1</b>, <b>XY2</b>, and <b>XY3</b>, that exhibit high molar extinction coefficients and a broad absorption range. Molecular modifications of these dyes, featuring a benzothiadiazole (BTZ) auxiliary acceptor, were achieved by introducing a thiophene heterocycle as well as by shifting the position of BTZ on the conjugated bridge. The ensuing high molar absorption coefficients enabled the fabrication of highly efficient thin-film solid-state DSSCs with only 1.3 μm mesoporous TiO₂ layer. <b>XY2</b> with a molar extinction coefficient of 6.66 × 10⁴ M^–1 cm^–1 at 578 nm led to the best photovoltaic performance of 7.51%