Increase the Quantum Dots Sensitized TiO2 Solar Cell Efficiency Adding n%Yb3+−1%Er3+ Doped NaYF4: Submicrometer-Sized Rods

Multilayer structure (TiO2/CdS/NaYF4:Yb
³⁺
-Er
³⁺
/ZnS) as the photoelectrode was successfully studied, and the increase of the efficiency cell depended on NaYF4:Yb
³⁺
-Er
³⁺
layer, which worked as a scattering layer that is correlated with the morphology. The irregular rod morphology varied with the concentration of Yb
³⁺
(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:Yb
³⁺
-Er
³⁺
layer showing that both photogeneration and recombination processes are affected by the Yb
³⁺
ion concentration and its correlation to the morphology of the crystals. The optimal solar cell with 5%Yb
³⁺
-1%Er
³⁺
codoped NaYF4 film exhibited an 80% increase in the photocurrent (15.42 mA/cm
²
) and 100% increase in the photoconversion efficiency (4.42%) compared with the reference solar cell (TiO2/CdS/ZnS) (2.14%).