Figure 3. Photocurrent-voltage (I–V) curves (a) and electrochemical impedance spectra (b) of DSCs fabricated with the three types Pt nanocrystals as counter electrodes, where the lines express fit results for corresponding EIS data, and the insert gives the equivalent circuit.

R_s: series resistance; R_ct(solid): charge-transfer resistance of TiO₂-FTO or Pt-FTO interface; C_(solid): capacitance of TiO₂-FTO or Pt-FTO interface; R_ct(TiO2): charge-transfer resistance of dye-sensitized TiO₂ layer; C_dl(TiO2): double layer capacitance of dye-sensitized TiO₂/electrolyte interface; R_ct(Pt): charge-transfer resistance at the CE/electrolyte interface; C_dl(Pt): double layer capacitance of CEs; W_(sol): Warburg parameter describing the diffusion of I₃⁻ in the electrolyte.