Highly Efficient Dye Sensitized Solar Cells based on Free-Standing Titania Nanotube

Dye sensitized solar cells (DSSC) attract great attention due to their respectable efficiency with very low fabrication cost, good performance under diffuse light conditions and ability to be fabricated on flexible substrates. Its main efficiency limiting factor is the random hopping of electrons within the titania nanoparticle network, which causes carrier trapping and recombination. The charge transport and collection can be enhanced by employing ordered nanostructures such as nanowire or nanotube arrays. However, nanowire/nanotube based DSSCs with efficiencies higher than those of conventional DSSCs have yet to be demonstrated. In this work, we report the fabrication of DSSCs using highly crystalline free-standing titania nanotube arrays. The high crystallinity leads to high electron mobility and diffusion length, allowing thick nanotube films to be used for improving the long wavelength light absorption. This greatly enhances the photocurrent and power conversion efficiency as compared to that of nanotube DSSCs in earlier studies.