Nanowire Solar Cells

Matt Law, Lori E. Greene, Justin C. Johnson, Richard Saykally and Peidong Yang, Nanowire dye-sensitized solar cells, Nature Materials 4, 455 - 459 (2005)

Short-circuit current density versus roughness factor for cells based on ZnO wires, small TiO2 particles, and large and small ZnO particles. The TiO2 films show a higher maximum current than either of the ZnO films and a larger initial slope than the small ZnO particles, consistent with better transport through TiO2 particle networks. The large ZnO particle cells attain a smaller maximum current than the small particles because the film thickness (and therefore the electron escape length) becomes larger than the electron diffusion length at a much lower roughness factor. The wire data fall on the TiO2 line and significantly exceed the current output from both types of ZnO particle cells above a roughness factor of 100. A slight sag of the wire data off the TiO2 line at high roughness factor may be a sign of excessive scattering within the opaque wire films. Cell thickness is directly proportional to roughness factor and is labelled for each cell type at a roughness factor of 200. Error bars are provided on only two points to maximize figure clarity, and they are an estimate of the maximum range of the values. The error bars for cells with roughness factors below 250 are smaller than the size of the data points. Data points were made by measuring the roughness factor of dye-sensitized films through ultraviolet–visible spectroscopy of the desorbed dye in basic H2O and then re-sensitizing the films for fabrication into cells.