Figure 2 Electrochemical characters. Nyquist plots (a) and Tafel polarization curves (b) of DSSCs based on PEDOT/FTO CE, TiO2-PEDOT:PSS/PEDOT:PSS/glass CE, and Pt/FTO CE. Table 1 Electrochemical impedance spectra (EIS) parameters of PEDOT/FTO CE, TiO 2 -PEDOT:PSS/PEDOT:PSS/glass CE, and Pt/FTO CE Counter electrode R s (Ω
cm2) R ct (Ω cm2) Z W1 (Ω cm2) PEDOT:PSS/FTO 4.22 4.47 11.28 TiO2-PEDOT:PSS/PEDOT:PSS/glass 23.26 1.51 4.02 Pt/FTO 4.91 5.73 – Furthermore, Tafel polarization curves ZD1839 in vitro were carried out on the same dummy cells used in EIS measurement to investigate the interfacial charge transfer properties of CE/see more electrolyte, and the corresponding results are shown in Figure 2b. The exchange current (J 0) = 0.58 mA, calculated from the intersection of the linear cathodic and anodic Tafel polarization curves [16, 21], was derived from the TiO2-PEDOT:PSS/PEDOT:PSS/glass composite film and higher than that of PEDOT:PSS/FTO film (0.14 mA). Correspondingly, the catalytic activity of TiO2-PEDOT:PSS/PEDOT:PSS/glass composite CE is much higher than that of PEDOT:PSS/glass CE, which demonstrates that the big surface area of TiO2 nanoparticles enhances the reduction of I3 − to I− remarkably. Though the J 0 of TiO2-PEDOT:PSS/PEDOT:PSS/glass composite CE is smaller than that of buy PS-341 Pt/FTO CE (1.2 mA), the former still exhibits superior catalytic activity and has great
potential to act as CE for DSSC. Figure 3 presents the photocurrent density-voltage (J-V)
curves of DSSCs using PEDOT:PSS/FTO CE, TiO2-PEDOT:PSS/PEDOT:PSS/glass CE, and Pt/FTO CE, TCL respectively, and the related photovolatic parameters are shown in Table 2. There is little difference in V oc values of these three cells. The FF of the DSSC with PEDOT:PSS/FTO CE is just 0.43 because of the poor catalytic activity of PEDOT:PSS solution. After modified by the TiO2 nanoparticles, the DSSC with TiO2-PEDOT:PSS/PEDOT:PSS/glass CE has obtained higher FF of 0.51 and thus higher η = 4.67% (increasing 22% compared with 3.64% for the DSSC with PEDOT:PSS/FTO CE). This is mainly due to the reduced charge transfer resistance and porous diffusion impedance because of the large electrochemical surface area in the porous TiO2-PEDOT:PSS layer. Compared with DSSC based on Pt/FTO CE, the one with TiO2-PEDOT:PSS/PEDOT:PSS/glass CE has lower FF, but its overall efficiency has already reached 91.39% of the one with Pt/FTO CE. It is noticeable that the performance of TiO2-PEDOT:PSS/PEDOT:PSS layers can befurther enhanced by optimazation of their weight ratio and the film thicknesses, referring to the previous studies using TiO2-PEDOT:PSS/FTO CE [22]. With such an excellent performance, the TiO2-PEDOT:PSS/PEDOT:PSS/glass CE has great potential to be a substitute for Pt- and FTO-based CEs which are very expensive and account for a large part of the cost.