title: Improvement of solar energy conversion with Nb-incorporated TiO2 hierarchical microspheres.
abstract: Niobium-modified TiO2 hierarchical spherical micrometer-size particles, which consist of many nanowires, are synthesized by solvothermal synthesis and studied as photoelectrodes for water photo-oxidation and dye-sensitized solar cell (DSSC) applications. Incorporation of Nb leads to a rutile-to-anatase TiO2 phase transition in the TiO2 hierarchical spheres (HSs), with the anatase percentage increasing from 0% for the pristine TiO2 HSs to 47.6% for the 1.82 at.% Nb-incorporated TiO2 sample. Incorporation of Nb leads to significant improvements in water photo-oxidation with the photocurrents reaching 70.5 μA cm(-2) at 1.23 V versus the reversible hydrogen electrode, compared with 28.3 μA cm(-2) for the pristine TiO2 sample. The photoconversion efficiency of Nb:TiO2 HS-based DSSCs reaches 6.09±0.15% at 0.25 at.% Nb, significantly higher than that for the pristine TiO2 HS cells (3.99±0.02%). In addition, the incident-photon-to-current efficiency spectra for DSSCs show that employing TiO2 and Nb:TiO2 HSs provides better light harvesting, especially of long-wavelength photons, than anatase TiO2 nanoparticle-based DSSCs.
authors.affiliation: Department of Chemical Engineering, Center for Electrochemistry, Texas Materials Institute, University of Texas at Austin, 1 University Station C0400, Austin, TX 78712-0231, USA.
authors.forename: Son
authors.initials: S
authors.lastname: Hoang
authors.forename: Thong Q
authors.initials: TQ
authors.lastname: Ngo
authors.forename: Sean P
authors.initials: SP
authors.lastname: Berglund
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Fullon
authors.forename: John G
authors.initials: JG
authors.lastname: Ekerdt
authors.forename: C Buddie
authors.initials: CB
authors.lastname: Mullins
mesh_terms: D011211:Electric Power Supplies; D004566:Electrodes; D008863:Microspheres; D009556:Niobium / Q000737:chemistry*; D010316:Particle Size; D012993:Solar Energy; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D009556:Niobium; C009495:titanium dioxide; D014025:Titanium
keywords: dye-sensitized solar cells; energy conversion; niobium; photooxidation; titania