98 ± 0.25 0.56 ± 0.01 0.67 ± 0.01 2.25 ± 0.15

30.7 ± 0.3 7:3 6.64 ± 0.30 0.55 ± 0.01 0.65 ± 0.02 2.36 ± 0.17 33.1 ± 0.2 5:5 7.45 ± 0.13 0.56 ± 0.01 0.68 ± 0.03 2.81 ± 0.14 29.8 ± 0.2 3:7 7.47 ± 0.24 0.58 ± 0.01 0.67 ± 0.01 2.91 ± 0.13 31.6 ± 0.2 0:10 7.28 ± 0.18 0.56 ± 0.01 0.64 ± 0.02 2.60 ± 0.09 34.5 ± 0.3 If charge collection probabilities are similar among the cells, quantum efficiency depends on the light trapping inside the solar cell [34–37]. The NP/NS = 3:7 cell exhibits the highest IPCE values in the whole visible region (Figure 4b), and this IPCE trend is consistent with the extinction data (Figure 3b). Therefore, learn more the enhanced light-harvesting capability (i.e., J sc) by the mixed scattering layer is attributed to efficient light scattering and increased surface area. Impedance analyses were GSK126 cost performed to understand the electrical properties of the synthesized solar cells [38–41]. The Nyquist plots display two semicircles in Figure 5a; the larger semicircles in low frequency range (approximately 100 to 103 Hz) are related to the charge

transport/accumulation at dye-attached ZnO/electrolyte interfaces, and the smaller semicircles in high frequency (approximately 103 to 105 Hz) are ascribed to the charge transfer at the interfaces of electrolyte/Pt counter electrode [42]. The impedance parameters were extracted using the equivalent circuit model (inset of Figure 5a), and the www.selleckchem.com/products/cb-839.html fitting lines are shown as solid lines in the Nyquist and Bode plots. From the charge transfer resistances (R ct) in Table 1, we can see that the proper mixing ratio (e.g., 5:5 or 3:7) exhibits lower values implying more

efficient charge transfer Tolmetin processes across the ZnO/electrolyte interfaces, while the pure nanoporous sphere layer (0:10) shows the highest R ct. The low resistance favors the transport of the electrons injected within ZnO, thus eventually leading to an effective collection of electrons [11]. The better connectivity achieved by the nanoparticles likely facilitates charge transfer by providing electron transport pathways, thereby resulting in the enhancement of FF with less recombination. Figure 5 Plots with various mixing ratios of ZnO nanoparticle to nanoporous sphere. (a) Nyquist plot and (b) Bode plot. Solid lines are the fitting results using the equivalent circuit model in the inset. Conclusions To improve the utilization of scattering layer in ZnO-based DSSCs, nanoparticles and nanoporous spheres are mixed with various ratios. The nanoporous spheres play an important role in the scattering effect with the large surface area but possess disadvantages of large voids and point contacts between spheres. Nanoparticles clearly advance facile carrier transport with the additional surface area, thereby improving the solar cell efficiency by the enhanced short-circuit current (J sc) and fill factor (FF).