Electrospinning processed nanofibrous TiO₂ membranes for photovoltaic applications

We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO₂ membranes as electrode materials. A thin TiO ₂ film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF₄ aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO₂ film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO₂ membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO₂ membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N^′-bis(2,2 ^′-bipyridyl-4,4^′-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO₂ film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO₂ membranes. The efficiency of the fibrous TiO₂ photoelectrode with the average membrane thickness of 3.9 νm has a maximum value of 4.14%.