Hanmin Tian

Effective electron collection in highly (110)-oriented ZnO porous nanosheet framework photoanode

A highly (110)-oriented ZnO porous nanosheet framework is designed as the photoanode in photoelectrochemical systems, by virtue of its anisotropic electronic properties. It can be facilely prepared in large scale via a hydrothermal method. X-ray diffraction (XRD) analyses show that the orientation index of the (110) diffraction plane is 3.54, indicating the films possess (110) preferred orientation. Field-emission scanning electron microscope (FE-SEM) images exhibit that most of the nanosheets stand nearly perpendicularly on the substrate. The {002} lattice planes work just like conducting wires and induce the electrons to transport to the substrate. Chronoamperometry measurement demonstrates an effective electron collection. When the nanostructured photoanode is introduced to dye-sensitized solar cells, a conversion efficiency of 3.7% is obtained. The photoanode also has potential application in the other photoelectrochemical systems, such as photocatalytical splitting of water.

Multilayer structure with gradual increasing porosity for dye-sensitized solar cells

Multilayer structure was prepared in a dye-sensitized solar cell work electrode by enlarging the porosity in each layer being coated on the fluorine-doped tin oxide transparent conducting glass from bottom to top. The multilayer structure exhibits an improved light scattering character, which resulted in better light harvesting of the cell. An obvious improvement in short circuit current is obtained. I-V characteristic measurement indicates an improved efficiency by 13% as compared to homogeneous pore-size samples. Diffuse reflectance spectra, scanning electron microscope images, and porosity measurements demonstrate that larger porosity is the cause of enhanced light scattering.

Correlation of crystal structures, electronic structures and photocatalytic properties in W-based oxides

We reported a novel W-based oxide NaBi(WO4)2 with WO4 tetrahedral crystal structure as a photocatalyst for decomposition of 2-propanol. The physical characteristics of the sample were examined by XRD, BET measurement and SEM, respectively. The band gap of NaBi(WO4)2 was determined to be 3.6 eV according to the diffuse reflectance spectra of the sample. The photocatalytic activity of NaBi(WO4)2 was confirmed by decomposing 2-propanol into acetone and CO2. It showed a higher acetone generation rate (211 ppm h−1) in contrast to that of WO3 (120 ppm h−1), which consisted of WO6 octahedra. Their electronic structures were further investigated by the plane-wave based density function theory. The results suggested that the crystal field (WO6 and WO4) significantly influenced the electronic structures and hence affected the photocatalytic activity.

Influence of measurement parameter on dye-sensitized solar cell efficiency

The testing time interval and voltage interval in accurately measuring the efficiency of Dye-sensitized solar cells is discussed abased on experiments and quantitative analysis. By measuring a typical dye-sensitized solar cell which was characterized with the crystalline ingredient, holes, and interface, the influences of testing time interval and voltage interval to the measured I–V curve were lay out, that the measured efficiency results fluctuated from 6.02% to 15%. Its found in experiment that both different testing time interval and voltage interval leaded to fluctuations of measured efficiency and even got much higher measured efficiency value than that in steady work state, while no such phenomena were observed in that of silicon cells. By farther analysis, the scan speed, which is the combine of the time interval and voltage interval, was attributed as the factor of influence to the measured result. According to the experimental results, the range of measurement parameters for accurate efficiency of DSSC was given.