Elevated Temperature Anodized Nb₂O₅: A Photoanode Material with Exceptionally Large Photoconversion Efficiencies

Abstract

Here, we demonstrate that niobium pentoxide (Nb(2)O(5)) is an ideal candidate for increasing the efficiencies of dye-sensitized solar cells (DSSCs). The key lies in developing a Nb(2)O(5) crisscross nanoporous network, using our unique elevated temperature anodization process. For the same thicknesses of ∼4 μm, the DSSC based on the Nb(2)O(5) layer has a significantly higher efficiency (∼4.1%) when compared to that which incorporates a titanium dioxide nanotubular layer (∼2.7%). This is the highest efficiency among all of the reported photoanodes for such a thickness when utilizing back-side illumination. We ascribe this to a combination of reduced electron scattering, greater surface area, wider band gap, and higher conduction band edge, as well as longer effective electron lifetimes.

Formation of highly oriented nanopores via crystallization of amorphous Nb2O5 and Ta2O5

“…The highly oriented porous nanostructures are expected to enable the range of application of Nb 2 O 5 and Ta 2 O 5 to expand considerably: in the case of Nb 2 O 5 to use as dye-sensitized solar cell materials, 10 and in the case of Ta 2 O 5 to use as dielectric materials 9 and photocatalysis. 20 To obtain more highly ordered nanoporous structures, it may be worthwhile trying to control the crystal growth using external effects, e.g., under electric and magnetic fields, or on substrates with epitaxial relations.…”

“…For example, the dielectric property of Ta 2 O 5 (Ref. 9) and the power conversion efficiency of Nb 2 O 5 as a dye-sensitized solar cell material 10 can be improved by providing large surface areas in order to increase high specific charge and electron diffusion length. Therefore, for the better understanding of the formation mechanisms of self-oriented nanopores, comprehensive studies for Nb 2 O 5 as well as Ta 2 O 5 are required.…”

Synthesis and Characterization of Nano-Particles of Niobium Pentoxide with Orthorhombic Symmetry

“…Interestingly, it is believed that many of the existent phases should be metastable or, at least, stabilized by impurities [5]. A suitable combination of chemical, electronic and optical properties make this oxide useful in various applications [7][8][9][10]. However, this result is further needed in order to investigate the photoluminescence (PL) because the optical measurements provide important information about the electronic structure of niobium pentoxide [11][12][13].…”

Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films

“…[13][14][15] However, the niobium-oxygen system is particularly complex, as narrow deviations from the exact stoichiometry in Nb2O5 strongly affect the physical properties of the material. For instance, a small oxygen deficiency leads to the transition from insulating to n-type semiconducting behavior 9 . Niobium oxide films have been prepared by different methods including magnetron sputtering 15 , electrodeposition and anodization 16 , thermal oxidation 17 , sol-gel methods [18][19][20][21][22] , chemical vapor deposition (CVD) 23 or atomic layer epitaxy 24 .…”