The effect of the number, position, and shape of methoxy groups in triphenylamine donors on the performance of dye-sensitized solar cells

Four new organic photosensitizers (SH-11∼14) that introduced methoxy groups as an additional donor were synthesized, and used in dye-sensitized solar cells. The dyes were designed in order to investigate the effects on the dye photophysical properties and the cell photovoltaic performance, by the number, position, and shape of methoxy groups introduced at the para-/ortho- and para-/meta- and para-(open or closed ring shape) positions on the triphenylamine donor. The introduction of methoxy groups led to bathochromic shift of the absorption spectrum, and enhancement of the molar extinction coefficient of the dyes. Their introduction decreased the amount of dye adsorbed on TiO₂surface, due to the increased steric hindrance. As their number increased, an open-circuit voltage value decreased. All things considered, the dye (SH-14) with closed ring shape shows the best conversion efficiency of 6.01% under AM 1.5G conditions (N719 dye's 7.59% under the same conditions).