Optimizing The Formation Of TiO₂ Nanotube And A Dual-tubular CdS/TiO₂ Structure By Ultra-fast Successive Electrochemical Deposition Towards Photovoltaic Application

Fabrication of functional materials on nanostructure substrate has been important topic due to its importance in new materials and devices research, such as solar cell. It remains a challenging issue to design and realize a complex nanostructure by a growth system with high growth rate and simple processes with controllable factors. Thus, here we study the optimization of the formation of Ti O2 nanotube, present the new sensitized solar cell- coaxial Cd S/Ti O2 dual-tubular sensitized solar cell. We made a big break though the method of fabrication, and assembled them into sensitized solar cell. The main work is presented as the following:1. Optimize the formation of Ti O2 nanotubeThe roughness in the pore could be totally eliminated instead of being enhanced by high speed stirring or periodically modulated voltage with the current oscillation still being enhanced, which indicates an important involvement of the ion transport process. It has also been found that tuning the stirring rate or the periodical modulation of the voltage could significantly accelerate the growth rate. The mechanism has been described with consideration of the local reactions and the ion transport with a key involvement of the convection process.2. Present the new structure and optimize the fabrication methodA uniform coaxial Cd S/Ti O2 dual-tubular structure can be developed on the inner surface of Ti O2 nanotubes with very short time(~90 s) under room temperature(RT). Well-matched content ratio of Cd and S can be resulted from application of alternative voltage. Moreover, significant change in crystalline structure can be detected with increasing voltage magnitudes. Characterization of quantum efficiency of the as-formed structure has shown quite broad absorption spectrum. As a result, sensitized solar cell based on Cd S thin film on Ti O2 nanotubes arrays has achieved efficiency of 1.43%, 208% higher than QDSSC under similar conditions, with short circuit current 135% larger. This system would hopefully be useful for compound material growth on various nanostructured substrates with simple and low toxic chemical circumstance but highly controlled process.This work is supported by the National Major Basic Research Project of 2012CB934302, and Natural Science Foundation of China under contracts 61234005, 11204176, and 11174202.