Influence of the conditions of sensitization on the characteristics of p-DSCs sensitized with asymmetric squaraines
The effect of the conditions of sensitization on the photoelectrochemical performance of p-type dye-sensitized solar cells (p-DSCs)
with screen-printed nickel oxide (NiO) photocathodes is analyzed. The dye-sensitizers employed in the present study are asymmetric
squaraines. The conditions of sensitization differ for the relative concentration of the anti-aggregating agentCDCA(chenideoxycholic
acid) with respect to the concentration of the dye-sensitizer. The co-adsorption of CDCA onto NiO electrode brings about a decrease
in the surface concentration of the anchored dye as well as a blueshift of the characteristic wavelengths of optical absorption of
the asymmetric squaraines considered here. Beside this, the employment of CDCA as co-adsorbent reduces the overall conversion
performance of the resulting squaraine-sensitized p-DSCs with consequent diminution of the short-circuit current density. This result
is ascribed to the acid action of CDCA toward the amminic nitrogen of the squaraines. Quantum efficiency spectra show that CDCA
acts as a quencher of the intrinsic photoelectrochemical activity of NiO. Moreover, CDCA does not interfere with the mechanism of
charge injection effectuated by the photoexcited squaraines. The photoelectrochemical impedance spectra was analyzed employing
a model of equivalent circuit developed for semiconducting nanostructure electrodes.