Influence of thiophene and benzene unit in triphenylamine dyes on the performance of dye-sensitized solar cells

Five triphenylamine dyes (WR1-5) featuring thiophene and benzene unit as the π-conjugated spacers or the substitutes attached to the triphenylamine core were synthesized for investigating the influence of thiophene and benzene unit on the performance of dye-sensitized solar cells (DSSCs). Apart from the alteration of the thiophene and benzene, the position of thiophene or benzene in triphenylamine dyes also has a major impact on some important electro-optical properties such as molar extinction coefficient, maximum absorption peaks and the ground-state oxidation behavior of these dyes. How the thiophene and benzene unit affect the charge recombination is discussed in terms of dye surface blocking and intermolecular interactions between dyes and electrolyte acceptor species. Among these dyes, WR2 containing thiophene unit as the π-conjugated spacer and thiophene donor group attached to the triphenylamine core yield the best photovoltaic performance: a short-circuit photocurrent density (JSC) of 10.8 mA cm−2, an open-circuit photovoltage (VOC) of 860 mV, and a fill factor (FF) of 0.66, corresponding to an overall conversion efficiency of 6.13% under standard global AM1.5 solar light conditions.