Nano/Micro-Structured ZnO Rods Synthesized by Thermal Chemical Vapor Deposition with Perpendicular Configuration.

Under a one-step process, catalyst-free growth of one-dimensional (1D) ZnO hierarchical nanostructures was performed on ZnO-seeded Si substrate by thermal chemical vapor deposition with a perpendicular setup. The morphological and crystallographic properties of the nano/micro-structured ZnO rods were investigated with varying growth temperature and growth time. X-ray diffraction patterns of 1D ZnO double-structured rods showed the hexagonal wurtzite structure. The morphology and crystal structure of the ZnO double-structured rods were sensitive to the growth temperature and growth time. From Raman scattering and photoluminescence spectra, the orientation and size effects of the ZnO double-structured rods were discussed in relation to growth temperatures and growth times.

Effects of Ce Ion-Modification on an Open Circuit Photovoltage Properties of ZnO Nanowires-Based Dye-Sensitized Solar Cell.

We investigated the photoelectrochemical effects on Ce ion-modified ZnO nanowires for dye-sensitized solar cells (DSSCs), preparing four kinds of samples grown in solutions with 0, 1, 2, and 3 atomic percent (at%) of Ce precursors. It was found that Ce ion modifications lead to an increase in the lattice constant of ZnO nanowires, resulting in widening of their PL visible band and UV blueshift. I-V results tell that the photoelectrochemical properties increase in the order of 1, 2, 0, and 3 at% Ce ion-modified ZnO nanowire-based DSSCs. To further analyze and explain the experimental results, we measured absorbance, incident to photon-to-current efficiency (IPCE), and concluded that the DSSCs fabricated by using 3 at% Ce ion-modified ZnO nanowires exhibit the best device performances due to large VOC enhancements, suggesting that Ce ion modification leads to the VOC, changes of DSSCs, which can be explained by Burstein-Moss effect.

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.

Catalytic effects of ZnO nanorods grown by sonochemical decomposition of zinc acetate dihydrate.

In this study, we prepared ZnO nanorods by a sonochemical method using a zinc acetate dihydrate as a new precursor. Well-aligned high-quality ZnO nanorods were synthesized on FTO glass by the sonochemical decomposition of zinc acetate dihydrate using a ZnO thin-film as the catalytic layer. The ZnO thin-films were deposited on the FTO glass by a sputtering method. To investigate their catalytic effects on the ZnO nanorods, catalytic ZnO thin-films of 20 nm, 40 nm, and 60 nm thickness were prepared by adjusting the sputtering time. The ZnO nanorods grown on catalytic layers with different thicknesses were characterized by SEM, XRD, and PL. The ZnO nanorods grown on the catalytic layer of 40 nm thickness show the best crystal and spatial orientation and as a result display the best optical properties. It was found that a catalytic ZnO thin-film of 40 nm in thickness yields well-aligned high-quality ZnO nanorods, due to its small surface roughness and structural strain.