A binder-free process for making all-plastic substrate flexible dye-sensitized solar cells having a gel electrolyte

Binder-free electrophoretic deposition (EPD) and mechanical compression were employed to fabricate TiO2 photoanodes for use in all-plastic substrate flexible dye-sensitized solar cells having a gel electrolyte. The photoanodes were composed of commercial 20 nm TiO2 powders with and without the addition of 160 nm TiO2 powders. The EPD was performed under different DC powers and deposition times to obtain photoanodes having different thicknesses. Depending on the thickness, various electron diffusion times, ranging from 8.08 to 12.40 ms, and electron lifetimes, ranging from 16.79 to 32.05 ms, were obtained for the photoanodes consisting of only commercial 20 nm TiO2. The electron diffusion time was reduced and the electron lifetime remained the same as a result of the addition of another commercial 160 nm TiO2 powder. The added 160 nm TiO2 powders enhanced the light absorptance by serving as light scattering centers. All-plastic flexible dye-sensitized solar cells were made and evaluated. Compared to the 20 nm TiO2 only cells, the cells containing mixed powders exhibit enhanced efficiencies and the enhancement can be as much as 22%.