Impact of fluorine-induced effects on co-sensitization systems in dye-sensitized solar cells

Effective molecular engineering strategies are crucial for developing photosensitizers. In this study, we designed three triazatruxene (TAT)-based donor-π-bridge-acceptor (D-π-A) photosensitizers, denoted JM202, JM203, and JM204. JM203 and JM204, which have fluorine atoms at different positions, were assembled into single-dye-adsorbed and cosensitized dye-sensitized solar cells with JM202. Then, the effect of fluorine substitution on the photophysical properties and cosensitization was investigated. When the fluorine atom was near the electron acceptor (JM204), the molar extinction coefficient of the dye was enhanced, and charge transport was improved. JM204 also facilitated the adsorption of JM202, leading to higher dye loading and significantly enhanced short-circuit photocurrent density. Furthermore, the co-adsorption of JM202 reduced electronic recombination, resulting in a higher open-circuit voltage. Consequently, the JM202-JM204 cosensitized device achieved an optimal photoelectric conversion efficiency of 11.7%. The results of this study offer a new perspective for developing cosensitized dye-sensitized solar cells.