Changgang Huang

Dye-sensitized solar cells based on nanoparticle-decorated ZnO/TiO2 core/shell nanorod arrays

Nanoparticles (NPs) decorated ZnO/TiO2 core/shell nanorod arrays were fabricated on transparent conductive glass substrates by sequential plasma deposition and post-annealing processes for dye-sensitized solar cells (DSSCs) applications. The NPs decorated ZnO/TiO2 nanorods were composed of single-crystalline ZnO nanorods, homogeneously coated thin TiO2 shells and entirely covered anatase TiO2 NPs. The photocurrent density of the composite electrode was largely enhanced due to the enlarged surface area, the dark current was suppressed and the open-circuit voltage was increased because of the energy barrier formed at the interface between the ZnO core and the TiO2 shell. The increased photocurrent and open-circuit voltage led to an improvement of twice the energy conversion efficiency.

A plasma sputtering decoration route to producing thickness-tunable ZnO/TiO2 core/shell nanorod arrays

We report a radio frequency magnetron sputtering method for producing TiO(2) shell coatings directly on the surface of ZnO nanorod arrays. ZnO nanorod arrays were firstly fabricated on transparent conducting oxide substrates by a hydrothermal route, and subsequently decorated with TiO(2) by a plasma sputtering deposition process. The core/shell nanorods have single-crystal ZnO cores and anatase TiO(2) shells. The shells are homogeneously coated onto the whole ZnO nanorods without thickness change. This approach enables us to tailor the thickness of the TiO(2) shell for desired photovoltaic applications on a one-nanometer scale. The function of the TiO(2) shell as a blocking layer for increasing charge separation and suppression of the surface recombination was tested in dye-sensitized solar cells. The enhanced photocurrent and open-circuit voltage gave rise to increased photovoltaic efficiency and decreased dark current, indicating successful functioning of the TiO(2) shell.

The effects of shell characteristics on the current-voltage behaviors of dye-sensitized solar cells based on ZnO/TiO2 core/shell arrays

The ZnO/TiO2 core/shell structure was formed through deposition of a TiO2 coating layer on the hydrothermally fabricated ZnO nanorod arrays through radio frequency magnetron sputtering. The effects of the TiO2 shell’s characteristics on the current-voltage behaviors of the core/shell-based dye-sensitized solar cells (CS-DSSC) were investigated. As the rates of injection, transfer, and recombination of electrons of such CS-DSSC were affected significantly by the crystallization, morphology, and continuity of the TiO2 shells, the photovoltaic efficiency was accordingly varied remarkably. In addition, the efficiency was further improved by enhancing the surface area in the core/shell electrode.

Physical properties and growth kinetics of co-sputtered indium-zinc oxide films

Indium-doped zinc oxide (IZO) films were fabricated by radio-frequency (RF) magnetron sputtering through co-deposition of zinc oxide (ZnO) and indium (In) at ambient temperature. Transparency of the IZO films is higher than 80% in the visible range while the optical band gap decreases with increasing In dopant concentration. The optimal measured resistivity, Hall mobility and carrier concentration of the film are 1.39 × 10−3 Ω cm, 10.11 cm2 V−1 s−1 and 5.35 × 1020 cm−3, respectively. The In dopant favors smoothing the film surface. The In dopant concentration in the film decreases vertically from the surface to the interface due to the surface segregation during the kinetic deposition process. The misfit strains of the films are gradually relaxed through dislocation.

Low content indium-doped zinc oxide films with tunable work function fabricated through magnetron sputtering

Low content indium-doped zinc oxide (LC-IZO) films have been prepared through radio-frequency (RF) magnetron sputtering. The work functions of the LC-IZO films were successfully tuned up by modulating the deposited conditions, such as indium content, substrate temperature, bias voltage and film thickness. The work functions of the films may be modulated in a large range between 4.59 eV and 5.56 eV. The change of the work function may be the results induced by the change in the surface state. The results may be helpful for widening the application of LC-IZO films.

Growth kinetics of three-dimensional ZnO islands on various substrates

Growth kinetics of three-dimensional (3D) ZnO islands on silicon, sapphire, quartz glass and lime glass substrates, fabricated by radio-frequency magnetron sputtering, were investigated through physical–statistical analysis and the scaling behaviour method. These results show that the 3D islands nucleate with only one atom, and the scattered island size distribution indicates that the strain effect is significant for disturbing the atomic diffusion kinetic process. Gradual strain relaxation through dislocation is confirmed by the decreasing trend in the aspect ratio dependence on the lateral sizes for 3D islands. Additionally, surface roughening also works during strain relaxation.