Effects of Polyethyleneimine on the Sonochemical Synthesis of Gadolinium Ion-Modified ZnO Nanorods.

We prepared gadolinium (Gd) ion-modified ZnO nanorods by a sonochemical decomposition of zinc acetate dehydrate and gadolinium acetate hydrate precursor solutions with and without polyethyleneimine (PEI). We investigated the effects of PEI on the sonochemical synthesis of ZnO nanorods with and without Gd ion modifications. In the case of nascent ZnO nanorods, PEI in the precursor solutions can prohibit radial growth but allow axial growth, resulting in changes in the degree of preferred crystal orientations, and in the PL properties of the resulting nanorods. In the case of Gd ion-modified ZnO nanorods, we observed that the ZnO nanorods, fabricated sonochemically in the precursor solutions with PEI, exhibited a peak broadening of the ZnO(002) crystal plane and decreasing crystal orientation with respect to the c plane. We note that PEI can negatively affect the crystal orientation and crystallinity of Gd ion-modified ZnO nanorods, even though it cannot affect the lattice constant.

Effects of lanthanum ion modifications on the photoelectrochemical properties of ZnO nanorods-based dye-sensitized solar cells.

We investigated the photoelectrochemical effects on La ion-modified ZnO nanorods for dye-sensitized solar cells (DSSCs), preparing four kinds of samples grown in solutions with 0, 1, 2, and 3 at% of La precursors. It was found that La ion modifications lead to an increase in the lattice constant of ZnO nanorods, resulting in widening of their energy bandgap. I-V results tell that the photoelectrochemical properties increase in the order of 2, 1, 0, and 3 at% La ion-modified ZnO nanorod-based DSSCs. To further analyze and explain the experimental results, we measured absorbance, IPCE, and EIS and concluded that the DSSCs fabricated by using 3 at% La ion-modified ZnO nanorods exhibit better device performances such as Voc, Jsc, and efficiency, suggesting that the amount of La ions is a key parameter of La modified-DSSCs. The results can be explained by Burstein-Mott effects, vertical growth, and La oxide coating effects of the ZnO nanorods.