Jingyang Wang

Novel in situ crosslinked polymer electrolyte for solid-state dye-sensitized solar cells

A novel poly(citric acid-ethylene glycol)/LiI/I2 (PCE/LiI/I2) solid polymer electrolyte (SPE) based on the biodegradable PCE matrix has been prepared in situ, by penetrating of the PCE prepolymer sol into mesoporous TiO2 photoanode, followed by curing. The PCE prepolymer can easily penetrate into the mesoporous photoanode, which could induce good interfacial contact between the SPE and photoanode. Assembled with the SPE, highly efficient and stable solid-state dye-sensitized solar cells (DSSCs) have been gained due to the good interfacial contact of SPE/TiO2 photoanode as well as the favorable ionic conductivity of the SPE. The results show that the contents of CA determine the aggregation structure such as the inter-segmental distance and free volume of the PCE matrix, which consequently affects the ionic diffusion coefficient and conductivity of the PCE/LiI/I2 electrolyte, and accordingly the photoelectric performance of the DSSCs. With CA content of 32.4xa0wt%, the SPE reaches the optimal ionic conductivity of 5.43xa0×xa010−5xa0Sxa0cm−1 and the solid-state DSSCs obtain the best overall photoelectric conversion efficiency of 1.22xa0% at 60xa0mWxa0cm−2.

Hydrothermal growth of branched hierarchical TiO2 nanorod arrays for application in dye-sensitized solar cells

In this study, rutile branched hierarchical TiO2 nanorod arrays were prepared on transparent conductive glass (FTO) through a facile two-step hydrothermal method. The microstructure and growth mechanism of branched TiO2 nanorod arrays were investigated respectively by means of X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The dye-sensitized solar cells based on the branched TiO2 nanorod arrays which were only about 1.5xa0μm in length show a overall power conversion efficiency of 2.01%, which is nearly three times as high as that of pure nanorod arrays. The enhanced efficiency can be ascribed to the increased specific surface area from the nanobranches, which can improve the amount of dye adsorption, as well as the better light scattering effect. Furthermore, the electrochemical impedance spectra results show that the branched TiO2 nanorod arrays can also decrease the resistance of the electron transfer at the TiO2/dye/electrolyte interface, and leading to a rapid electron transport.

Upconversion luminescence properties and mechanism of Er3+ doped Ba0.65Sr0.35TiO3 ferroelectric oxide nanocrystals

Ba0.65Sr0.35TiO3 (BST) nanocrystals doped with different concentrations of Er3+ ion were fabricated using sol-gel method. The structure and morphology of these BST nanocrystals were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The X-ray diffraction patterns of all the nanocrystals prepared in the study correspond to polycrystalline perovskite BST structure. The blue and green upconversion luminescence properties of Er3+ doped BST nanocrystals were investigated under excitation by a 785-nm laser. The upconversion emission bands centered at 407, 523, and 547 nm can be attributed to 2H9/2, 4I15/2, 2H11/2, 4I15/2, and 4S3/2, 4I15/2 transitions of Er3+ ion, respectively. The upconversion mechanism was studied in detail, based on the laser power dependence of the upconverted emissions. In addition, we examined the dependence of the intensity of green upconverted luminescence on the doping concentration of Er3+ ions, and discussed the mechanism underlying the process.

Color Change Upconversion Mechanism of Y6O5F8: Er3+/Yb3+ Microtubes by Using Time-Resolve Spectra

The mechanism of the upconversion processes in Y6O5F8: 2%Er3+/X%Yb3+ (X = 3, 10, 20) microtubes has been explored. The luminescent properties of the as prepared sample is investigated by utilizing up- /downconversion, decay and time resolve spectra. The results indicate that the red and green emission are clearly competitive depending on the Yb3+ concentration. High Yb3+ concentration induces the enhancement of the energy-back-transfer (EBT), process, which leads to the quenching of green emission and enhances the red emission. So it is possible to utilize the temporal evolutions of emission bands to deeply understand the color change UC mechanisms.

Enhanced Photoelectrochemical Properties of Ti3+ Self-Doped Branched TiO2 Nanorod Arrays with Visible Light Absorption

A novel Ti3+ self-doped branched rutile TiO2 nanorod arrays (NRAs) was successfully grown on an F-doped tin oxide (FTO) transparent conductive glass by a combined hydrothermal and magnetron sputtering method. Surface morphology, structure, optical properties, and photoelectrochemical behavior of the branched TiO2 NRAs are determined. Using TiO2 nanoparticles (NPs) deposited on the top of the nanorods as seeds, TiO2 nanobranches can easily grow on the top of the nanorods. Moreover, the Ti3+ defects in the TiO2 NPs and associated oxygen vacancies, and the nanobranches expend the optical absorption edge of the TiO2 NRAs from 400 nm to 510 nm. Branched TiO2 NRAs exhibit excellent photoelectrochemical properties compared to the pure TiO2 NRAs, as revealed by photoelectrochemical measurements. This enhanced photoelectrochemical properties is induced by the increased surface area and expanded optical absorption range. Due to their favorable characteristics, these novel branched TiO2 NRAs will provide a new path to the fabrication of hierarchical nanostructured materials.

Hierarchical ZnO Superstructures: Nanoflake-Decorated Nanonail Arrays.

By using metallic Zn powders as zinc source, we synthesized unusual hierarchical ZnO superstructures, nanoflake-decorated nanonail arrays, on a large scale via a simple low-temperature thermal evaporation method. The hierarchical superstructures were characterized by using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy as well as selected area electron diffraction. Studies found that both the ZnO nanonails and the decorated ZnO nanoflakes are single-crystals, with the preferred growth orientations along the (001) direction. The possible formation mechanism for the interesting hierarchical superstructures has been discussed. It was found that the deposition of indium films on a Si substrate and the heterogeneous nucleation of ZnO nanoflakes on the main ZnO nanonails play key roles in the fabrication of ZnO superstructures. Moreover, these special hierarchical superstructures showed much strong and complicated photoluminescent emissions in the visible region.