Coating effect of electrospun nanofibers of Nb-doped TiO2 mixed in photoelectrode of dye sensitized solar cells

Electrospun nanofibers (NFs) of Nb doped TiO2 (TNO) were added as a conductive agent to TiO2 mesoporous layer in dye sensitized solar cells. In order to improve the mobility of carriers in NFs by reducing the barrier at grain boundaries among constituent nanoparticles in NFs, the surface of TNO-NFs was coated with a thin TNO layer by pulsed laser deposition with changing the deposition time td. It was found that the inter-grain space was filled first at td ≤ 5 min, and the diffusion velocity vD of carriers was increased by more than 10 times. Since Jsc showed an increase of ∼15% while vD and the electron lifetime τe decreased at td > 10 min, the carrier injection from dye/TiO2 nanoparticles to TNO-NFs was considered to be promoted.