Increase the Quantum Dots Sensitized ${\rm{TiO_{2}}}$ Solar Cell Efficiency Adding n%Yb3+−1%Er3+ Doped ${\rm{NaYF_{4}}}$: Submicrometer-Sized Rods

Multilayer structure (TiO2/CdS/NaYF4:Yb3+-Er3+/ZnS) as the photoelectrode was successfully studied, and the increase of the efficiency cell depended on NaYF4:Yb3+-Er3+ layer, which worked as a scattering layer that is correlated with the morphology. The irregular rod morphology varied with the concentration of Yb3+ (1, 5, 15% mol) with an average size of 3.9 μm length and 1.13 μm width. In this article, impedance spectroscopy is used to determine the influence of the NaYF4:Yb3+-Er3+ layer showing that both photogeneration and recombination processes are affected by the Yb3+ ion concentration and its correlation to the morphology of the crystals. The optimal solar cell with 5%Yb3+−1%Er3+ codoped NaYF4 film exhibited an 80% increase in the photocurrent (15.42 mA/cm2) and 100% increase in the photoconversion efficiency (4.42%) compared with the reference solar cell (TiO2/CdS/ZnS) (2.14%).