Abstract
Flower shaped nanostructures of an architypical transparent conducting oxide, SnO2, have been synthesized by an electrospinning technique for the first time by precisely controlling the precursor concentration in a polymeric solution. The flowers were made up of nanofibrils of diameter similar to 70-100 nm, which in turn consisted of linear arrays of single crystalline nanoparticles of size 20-30 nm. Mott-Schottkey analysis shows that flowers have an order of magnitude higher electron density compared with the fibers despite their chemical similarity. Dye-sensitized solar cells fabricated using the flowers showed a record open circuit voltage of similar to 700 mV and have one of the highest photoconversion efficiencies so far achieved with SnO2 and the iodide/triiodide electrolyte. The photoaction spectra and impedance spectroscopic measurements show that the flowers are characterized by a higher electron lifetime, owing to their enhanced crystallinity, compared to the conventional fibrous structure.