Tunable TiO2 Nanotube Arrays for Flexible Bio-Sensitized Solar Cells

NOTICES Disclaimers The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. Citation of manufacturer's or trade names does not constitute an official endorsement or approval of the use thereof. Destroy this report when it is no longer needed. Do not return it to the originator. Approved for public release; distribution is unlimited. Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. Highly ordered, free-standing titanium dioxide nanotube (TiNT) arrays have been of intense interest to the alternative energies field in recent years due to their barrier-free electron conduction pathway vs. TiO 2 nanoparticles in dye-sensitized solar cell (DSSC) designs. TiNT arrays prepared by electrochemical anodization of Ti foils and combined with a transparent, Indium Tin Dioxide coated PET film are attractive candidates for efficient, flexible DSSC's. Flexible solar cells offer great benefits because of the potential for low-cost, roll-to-roll production and the increase in applications due to superior robustness. This approach utilizes a two-step anodization procedure coupled with implementation of a rapid inert gas dehydration and ultrasonic agitation detachment method. By controlling the reaction conditions during anodization (voltage, duration, concentration), TiNT arrays with specific morphology, lengths, and diameters can be tailored to satisfy a particular application such as incorporating specialized protein dyes—in particular, bacteriorhodopsin. The free-standing arrays comprised of hexagonally closed-packed and regularly ordered TiNT membranes have been synthesized and detached from the original Ti substrate. Once the TiO 2 sol-gel is created, the free-standing arrays will be attached to the flexible PET film for improved photovoltaic properties and overall performance.