The effect of coupling and di-anchoring group in the performance of triphenylamine-based dyes for dye-sensitized solar cells

The effect of di-anchoring group was studied using 9,9-dioctyl-9H-fluorene as bridge which was formed by coupling two triphenylamine-based dyes. Two octyl chains were introduced into the core of di-anchoring dye to avoid its aggregation and minimize its TiO2/electrolyte recombination reactions. The photophysical, electrochemical and photovoltaic parameters of both mono- and di-anchoring sensitizers were compared, herein referred to as KS-18 and KS-20, respectively. Computational results indicated that the two anchoring groups adsorbed to the TiO2 in KS-20 were thermodynamically stable as compared to only one anchoring group. The results show that KS-20 produced a 7% increase in its photovoltaic conversion efficiency mainly due to an increase in the short-circuit current density. This increase was brought by the red-shifting and widening of its absorption spectra thereby increasing its light harvesting efficiency.