Electrical and optical properties of electrospun TiO sub(2)-graphene composite nanofibers and its application as DSSC photo-anodes

The present study reports the electrospinning of TiO sub(2)-graphene composite nanofibers to develop conductive nano-fiber mats using polyvinylpyrrolidone as a carrier solution. This carrier solution was sublimated at 450 degree C to attain a complete conducting continuous nanofibrous network. It was observed during the annealing that as the graphene content was increased to 1 wt% the continuous fiber morphology was lost. Annealing did not have any impact on the fiber diameter ( similar to 150 nm) or morphology as the graphene content was maintained between 0.0-0.7 wt%. The surface porosity of these samples was found be in the range of 45-48%. The presence of graphene in TiO sub(2) nanofibers was confirmed using Raman spectroscopy. Photoluminescence spectroscopy showed excitonic intensity to be lower in graphene-TiO sub(2) samples indicating that the recombination of photo-induced electrons and holes in TiO sub(2) can be effectively inhibited in the composite nanofibers. Fluorescence spectroscopy was used to confirm this phenomenon where blue and quenched emissions were observed for the electrospun TiO sub(2) nanofibers and composite fibers, respectively. Conductivity measurements showed the mean specific conductance values obtained for TiO sub(2)-graphene composites to be about two times higher values than that of the electrospun TiO sub(2) fibers. Assembling these TiO sub(2)-graphene fiber composites as photoanodes in dye sensitized solar cells, an efficiency of 7.6% was attained.