David Child

Low temperature growth of hybrid ZnO/TiO2 nano-sculptured foxtail-structures for dye-sensitized solar cells

ZnO/TiO2 nano-sculptured foxtail-structures were fabricated using two sequential low-temperature processes combining hydrothermal growth of ZnO nanorods (NRs) and plasma ion assisted evaporation of crystalline TiO2 nanostructures. The ZnO NRs were homogeneously covered with a thin layer of anatase TiO2 nanostructure to form nano-sculptured foxtail-like patterns. Power conversion efficiency of dye-sensitized solar cells made from these hybrid ZnO/TiO2 structures was improved from 0.3% to 1.8% after using the ZnO/TiO2 hybrid structure. Measurement using electrochemical impedance spectroscopy and photocurrent decay proved that the hybrid structures have good electron transport capability, because the ZnO NRs can provide a direct pathway for charge transport; the TiO2 layer can improve charge injection and prevent the formation of Zn2+/dye complex (thus reducing the recombination); the hybrid structures can further increase surface area (thus higher dye loading).

In-situ microfluidic controlled, low temperature hydrothermal growth of nanoflakes for dye-sensitized solar cells.

In this paper, an in-situ microfluidic control unit (MCU) was designed and applied in a hydrothermal synthesis process, which provides an easy way to localize liquid-phase reaction and realize selective synthesis and direct growth of nanostructures as well as their morphology, all in a low-temperature and atmospheric environment. The morphology was controlled through controlling the amount of additivities using the MCU. This achieved a facile fabrication of Al doped ZnO (AZO) nanoflakes vertically grown on flexible polymer substrates with enhanced light scattering and dye loading capabilities. Flexible DSSCs with a significant enhancement (410% compare to ZnO NRs based devices) in power conversion efficiency were obtained using AZO nanoflake photoanodes of 6 μm thick, due to the enhancement in electron mobility and reduction in recombination. This hydrothermal synthesis using the in-situ MCU provides an efficient and scalable technique to synthesize controllable nanostructures with characteristics of easy set-up, low energy consumption and low cost.

Modeling and validation of uniform large-area optical coating deposition on a rotating drum using microwave plasma reactive sputtering

Magnetron sputter deposition onto a rotating drum is a method applied to high-throughput large-area optical coating deposition, where film physical thickness uniformity is an important parameter. Techniques have been developed, such as masking/substrate movement, in order to improve sputtered film uniformity. In this study, a model is described and validated for predicting film uniformity. Experimental data show excellent agreement with modeled simulations, with and without a modified sputtering mask. Practical application is demonstrated in maximizing uniformity over an individual substrate size of 100  cm2 for a high-optical-density visible/near-infrared dual-band laser protection filter.

Modelling and Validation of a Large Area Thin Film Uniform Deposition on a Rotating Drum Using Microwave Reactive Sputtering

A model has been developed and validated for predicting film uniformity based on sputtering yield, angular distribution, mask shielding and film growth process in a multipass microwave/magnetron sputtering system using Niobium deposition on glass.

Novel Hollow Cathode Plasma Source with selfsustaining high density plasma

Description of a plasma source including a LaB6 hollow cathode hybrid configuration operating at low gas flows and low deposition pressures provides self-sustaining plasma generation over large areas.