title: Efficient solar water splitting by enhanced charge separation in a bismuth vanadate-silicon tandem photoelectrode.
abstract: Metal oxides are generally very stable in aqueous solutions and cheap, but their photochemical activity is usually limited by poor charge carrier separation. Here we show that this problem can be solved by introducing a gradient dopant concentration in the metal oxide film, thereby creating a distributed n(+)-n homojunction. This concept is demonstrated with a low-cost, spray-deposited and non-porous tungsten-doped bismuth vanadate photoanode in which carrier-separation efficiencies of up to 80% are achieved. By combining this state-of-the-art photoanode with an earth-abundant cobalt phosphate water-oxidation catalyst and a double- or single-junction amorphous Si solar cell in a tandem configuration, stable short-circuit water-splitting photocurrents of ~4 and 3 mA cm(-2), respectively, are achieved under 1 sun illumination. The 4 mA cm(-2) photocurrent corresponds to a solar-to-hydrogen efficiency of 4.9%, which is the highest efficiency yet reported for a stand-alone water-splitting device based on a metal oxide photoanode.
authors.affiliation: Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, PO Box 5045, Delft 2600GA, The Netherlands.
authors.forename: Fatwa F
authors.initials: FF
authors.lastname: Abdi
authors.forename: Lihao
authors.initials: L
authors.lastname: Han
authors.forename: Arno H M
authors.initials: AH
authors.lastname: Smets
authors.forename: Miro
authors.initials: M
authors.lastname: Zeman
authors.forename: Bernard
authors.initials: B
authors.lastname: Dam
authors.forename: Roel
authors.initials: R
authors.lastname: van de Krol
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D006801:Humans; D006859:Hydrogen / Q000737:chemistry*; D008027:Light; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D016062:Porosity; D012825:Silicon / Q000737:chemistry*; D012993:Solar Energy / Q000706:statistics & numerical data*; D013499:Surface Properties; D014638:Vanadates / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; C091754:bismuth vanadium tetraoxide; D014638:Vanadates; D006859:Hydrogen; D001729:Bismuth; D012825:Silicon