Nb₂O₅ porous nanotubes: potential approach as photoanode material for dye-sensitized solar cells

In this study, we have hydrothermally synthesized Nb₂O₅ nanorods of various dimensions at different reaction times. These synthesized samples were physio-chemically characterized by UV-visible, XRD, FESEM, HRTEM and XPS techniques. The absorbance spectrum has shown blue-shift than the bulk counterpart, whereas XRD and XPS confirm the formation of Nb₂O₅. FESEM and HRTEM reveal the formation of rod-like structures. The annealing temperature affects the surface porosity of the samples as the porous rod like Nb₂O₅ formed at higher annealing temperature. Further, the Nb₂O₅ was used as photoanode material in dye-sensitized solar cells and characterized by different photovoltaic characterization parameters (photocurrent density–voltage (J–V) curve, IPCE, FF and cell efficiency). The enhanced photovoltaic parameters were obtained for NB-2 with photocurrent value of 8.40 mA cm⁻² and efficiency (η) of 3.43%. This enhanced performance is the result of high surface roughness and porosity, which assisted in improving the efficiency, dye loading and better electronic conduction pathway. Electrochemical impedance spectroscopy (EIS) was studied to understand the charge transfer and recombination at Nb₂O₅|dye|electrolyte interfaces.