The effect of the metal and selenium precursors on the properties of NbSe2and Nb2Se9nanostructures and their application in dye-sensitized solar cells

Abstract

Herein, we report on the effect of the precursors on the structural, morphological, and optical properties of niobium selenide using the heat-up colloidal method. The metal precursor was varied from the conventional NbCl5 to NbF5 whilst Se, SeO2, and selenourea were used as the selenium precursors. The NbCl5 and NbF5 resulted in the formation of NbSe2 and Nb2Se9 respectively. While maintaining the two different metal precursors and varying the selenium precursor from Se, SeO2 to selenourea, the properties of NbSe2 and Nb2Se9 changed slightly, however the effect of changing the selenium precursor was less pronounced than changing the metal precursors. From the XRD and XPS, the NbSe2 nanostructures were more susceptible to oxidation than Nb2Se9 as Nb2O5 was observed in the XRD and the percentage of M-O in the XPS was much higher in NbSe2. NbSe2 formed nanoflowers whilst Nb2Se9 formed rods with 3.29 eV and 2.43 eV band-gaps, respectively. Also, the band-gaps were red-shifted as the selenium precursors were varied. The NbSe2 nanoflowers and Nb2Se9 nanorods were used as counter electrodes in dye-sensitized solar cells. Two methods were used to fabricate the counter electrodes i.e. spin coating and drop casting. The electrochemical properties of the spin coated counter electrodes were better than the drop casted ones; hence, they were employed in dye-sensitized solar cells. The spin coated NbSe2 nanoflowers had the highest efficiency of 6.84%, attributed to the nanoflower morphology. This journal is