Control of nanogeometry for advanced energy applications

Incorporation of one-dimensional, large-surface-area, conductive nanofibers such as carbon nanotubes or 8 nm diameter TiO2 nanotubes into the dye-sensitized solar cell (DSSC) photo-anodes made of spherical TiO2 nanoparticles is shown to significantly improve the photocurrent density and the energy conversion efficiency. The observed DSSC solar cell efficiency enhancement in the presence of elongated nanoscale elements is attributed primarily to the reduction in microcracking tendency of the anode layer and associated robust electron transport, although some contributions of the electrical conducting nature of the filler material may also be possible. A use of metallic conduction paths such as embedded Ti-coated stainless steel mesh screen in the TiO2 anode layer is also described for enhanced photoanode constructions with a future possibility of FTO (fluorinated tin oxide)-glass-free DSSC. It is also shown that the control of contact resistance during DSSC assembly and electrical connection is an important aspect for more accurate evaluations of DSSC performance.