4. Conclusion

Undoped and doped (Ag) ZnO NPs photoanodes were successfully synthesized and mediated by the combustion method. XRD results indicated that a single phase of hexagonal wurtzite structure was formed. The XRD confirmed that no Ag peaks could be observed for 1%. The HR-TEM micrograph showed that semispherical particles (20.45 and 22.30 nm) for ZnO NPs were well crystallized with an intermediate or poor agglomeration. The average ZnO NPs size was confirmed by XRD and HR-TEM inspections. The calculated bandgap of the ZnO NPs was found to be changed with the addition of the Ag<sup>+</sup> ions. The PLE spectrum of the undoped ZnO NPs was examined and decomposed into two divisions: NUV and visible (violetblue, blue-green, and orange-red). The PLE spectrum changed with the dopant Ag. The DZ:Ag 1.0 mol% dye-sensitized cells presented the best DSSCs performance among others. The results showed an enhancement of efficiency of both the Jsc, Jm, Vm, Pm, and FF% efficiency and the Voc for the (Ag 1.0 mol%) dye-sensitized cells compared to others, which is attributed to the light-harvesting capability of dye molecules by plasmon-enhanced excitation. In addition, the recombination rate of the device based on DZ:1.0 mol% Ag NPs photoanode was slower than that of UZ NP photoanode. The lower recombination rate and shorter electron lifetime within the ZnO NP photoanode were the reason why the FF of the corresponding DSSCs increased.
