Dye-Sensitized Solar Cells Employing a Multifunctionalized Hierarchical SnO2 Nanoflower Structure Passivated by TiO2 Nanogranulum

摘要

We investigated a facile multifunctionalized hierarchical SnO2 nanoflower photoelectrode passivated by a layer of TiO2 nanogranulum. The hierarchical SnO2 nanoflower with thin nanorod and nanosheet has a unique morphology that can afford excellent electron transport properties—orientation overall, which results in a significant diminution in the charge diffusion route and a rapid collection in FTO substrate. The passivated photoanode not only improved the distribution of dyes in the photoelectrode and reduced the surface defects of SnO2 photoelectrode to accommodate more dyes, but also suppressed the charge recombination and prolonged electron lifetime by introducing a barrier layer. The microstructure of the sample was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface areas (S_(BET)) and pore size distribution were detected on BET measurement. The amounts of dye were calculated from UV—vis. The interfacial charge transfer process and the charge recombination were characterized by EIS and IMPS/IMVS measurements. The DSSCs assembled with multifunctionalized photoanode exhibits favorable energy conversion efficiency. The photocurrent increased from 5.44 to 12.74 mA cm~2, the photovoltage from 440 to 760 mV, and the fill factor from 43.58% to 57.58%. As a result, the cell's conversion efficiency increased by a factor of 5.3 from 1.05% to 5.60%. The increase in efficiency originates from higher open-circuit potential and higher short-circuit current as well as from superior light scattering effect, long electron lifetime, and slower electron recombination.