Figure 5 Relationship between J SC and dye loading as a function of dye adsorption time. ZnO film thickness is 26 μm. To determine parameters related to electron transport and recombination, this study used EIS to analyze cells based on 26-μm-thick films. The experimental impedance data, given by the Nyquist plots in Figure 6b, were fitted to an equivalent circuit based on the diffusion-recombination model [42–44] (Figure 6a). The circuit elements related to the ZnO photoelectrode include the electron transport resistance within the ZnO mesoporous film Emricasan clinical trial (R w) (R w = r w L, where L = film thickness), the charge eFT508 in vitro transfer resistance

(R k) (R k = r k/L), which is related to the recombination of electrons at the ZnO/electrolyte interface, and the chemical capacitance of the ZnO electrode (C μ) (C μ = cμ L). Additional circuit elements were introduced to modify the equivalent circuit model, as described in the following. The series resistance (R S) represents total transport resistance of the FTO substrates and external circuits. Z N is the impedance of the diffusion of I3 − in the electrolyte. R Pt and C Pt are the resistance and the capacitance at the Pt/electrolyte interface, respectively.

R FTO and C FTO are the resistance and the capacitance at the FTO/electrolyte interface, respectively. selleck chemical R FZ and C FZ represent the resistance and the capacitance at the FTO/ZnO interface, respectively. The three fitted parameters of R w, R k, and C μ can be used to calculate additional parameters, such as the mean electron lifetime (τ eff), effective electron diffusion coefficient (D eff), and effective electron diffusion length (L eff), which are useful for evaluating cell performance. Figure 6 Equivalent circuit and Nyquist plots. (a) Equivalent circuit for the simulation of impedance spectra. (b) Nyquist plots of cells based on 26-μm films. The experimental impedance data were determined under 1 sun AM 1.5 G simulated light. The Nyquist plots in Figure 6b show the experimental impedance data obtained at various dye adsorption times. The impedance spectra

of DSSCs generally exhibit three semicircles. The semicircle in the high-frequency range corresponds to charge transfer behavior at the Pt/electrolyte (R Pt and C Pt), the FTO/electrolyte (R FTO and C FTO), learn more and the FTO/ZnO (R FZ and C FZ) interfaces. The semicircle in the mid-frequency range (the central arc) is assigned to the electron transfer at the ZnO/dye/electrolyte interfaces, which is related to R w, R k, and C μ. The semicircle in the low-frequency range represents the Warburg diffusion process of I−/I3 − in the electrolyte (Z N) [42–45]. Table 2 presents a summary of results from fitting the experimental impedance data to the equivalent circuit. The highest R k/R w value occurs at a dye adsorption time of 2 h, which is the optimal dye adsorption time for 26-μm-thick photoanodes.