Niobium pentoxide nanotube powder for efficient dye-sensitized solar cells

Abstract

In this work, we demonstrate for the first time the fabrication of niobium pentoxide (Nb₂O₅) nanotube powder using a simple electrochemical anodization method. During the anodization process, the anodic oxide can be continuously and spontaneously released into the electrolyte, and after collection a white powder was obtained. The powder mainly displayed nanotube morphology with the tube length in the range of about 50–100 nm and a diameter of about 20–30 nm. The as-prepared powder was amorphous, and after annealing the powder can be crystallized to the orthorhombic phase. Based on the preparation of the powder, a thick and high quality Nb₂O₅ film on the transparent conductive substrate was produced, and was further employed as the photoanode in dye-sensitized solar cells (DSSCs). A comparably high efficiency of 3.15% was obtained, with a large open-circuit voltage of 0.738 V, which is among the highest values ever reported for porous Nb₂O₅ film based DSSCs. Furthermore, the difference in electron behavior of the device as compared to a TiO₂ counterpart was studied, which exhibited a significantly reduced recombination rate, beneficial to high efficiency DSSCs.