In spite of having color
To estimate the electrochemical properties of the sensitizers KNS1 and KNS2, CV was employed using a three-electrode cell with 0.1 M tetrabutylammonium hexafluorophosphate in the DMF as the supporting electrolyte. CV was performed in three electrode assembly using Pt wire as working electrode, Pt-foil as counter electrode and saturated calomel electrode (SCE) as the reference electrode at 20 mV/s scan rate. The potential in CV at X-axis was then converted to potential verses standard hydrogen electrode (SHE) adding 0.24 V (potential of SCE vs. SHE). To test the accuracy of the system and measurement, most commonly used ferrocene was used standard redox system. The inset of Fig. 4 represents the CV of ferrocene exhibiting GF 109203X peak at 0.63 V associated with Fe/Fe+ redox couple which can be translated in to −5.07 eV considering the potential of SHE to be −4.44 eV against the vacuum level. A perusal of Fig. 4 reveals that dyes KNS1 and KNS2 exhibit their oxidation at the potentials of 1.04 V and 1.09 V vs. SHE, respectively. Sensitizing dyes KNS1 and KNS2 apart from structural similarity with respect to donor and π-bridge, they vary only in terms of different anchoring group viz. cyanoacrylic acid verses rhodanine acetic acid moieties, respectively. Slightly higher electron withdrawing tendency of rhodanine moiety could be attributed to relatively higher observed oxidation poptential. It is interesting to note that both of the dyes exhibit higher oxidation potentials (deeper HOMO energy level) as compared to I−/I3− redox couple (0.5 V vs. SHE) indicating that during the DSSC operation, dye cation formed after the photoexcitation, can be thermodyanamically regenerated.