Facile synthesis of hollow urchin-like Nb2O5 nanostructures and their performance in dye-sensitized solar cells

Abstract

In present study, hollow urchin-like nanostructures of Nb2O5 with elongated nanofilaments as photoanode material for dye-sensitized solar cells (DSSCs) are successfully synthesized at different reaction times (viz. 12, 24, and 40 h, respectively, named as samples NB-1, NB-2, and NB-3) using facile hydrothermal route. We have studied the significant influence of hydrothermal reaction time on the structural, optical, morphological, and electrical properties. The photovoltaic performance of different samples is understood from response of current-potential (J-V) curve and incident photon-to-current efficiency (IPCE) while charge recombination behavior and resistance of the cells are studied by electrochemical impedance spectroscopy (EIS). The X-ray diffraction (XRD) study shows the orthorhombic crystalline form for the synthesized samples. Electron microscopy studies confirm the formation of porous spherical morphology with hairy filaments protruding outward. Size of urchin-like particle is found to be in the range of about 1 μm diameter, and the filaments emerging out from the surface of hollow spheres are seen to be 30–70 nm long and 5–20 nm in diameter. The DSSCs fabricated from the resultant nanostructures show the better photovoltaic performance with Nb2O5 sample synthesized at 24-h reaction time. The Jsc and efficiency for NB-2 are 8.24 mAcm−2 and 3.58% respectively, which are better than corresponding samples synthesized at the reaction time of 12 h and 40 h, respectively. These photovoltaic results obtained from the DSSCs fabricated using Nb2O5 nanostructures are comparatively exciting with TiO2 spheres. By further optimizing reaction conditions, it is expected that niobium pentoxide can emerge as better semiconductor oxide for photovoltaic and optical devices.