The EIS under illumination exhibits three semicircles, as shown in Figure 6. The high-frequency range
represents the charge transfer at the Pt counter electrode (Rct,pt), the middle-frequency range is related to the charge
transport (Rt)/recombination (Rct) at the TiO2/electrolyte interface, and the low-frequency range is assigned to the
ionic diffusion in the electrolyte. The EIS can be fitted with an equivalent circuit on the basis of the transmission
line model [7], [17], [18]. Lower resistance causes higher electron transfer, i.e. high Ș, in DSSC. The ohmic serial
resistance (Rs) (intersection of high-frequency circle and x-axis) is mainly associated with the sheet resistance of the
FTO substrate. The DSSC using ILE shows the smallest semicircles representing Rct2 and Rdiff, and the interfacial
resistances were general lower for DSSC using ILE as electrolyte. While the DSSC containing nanoparticles
exhibits the higher Rct2 and Rdiff, corresponding to their DSSC efficiency.