title: Design principles for maximizing photovoltage in metal-oxide-protected water-splitting photoanodes.
abstract: Metal oxide protection layers for photoanodes may enable the development of large-scale solar fuel and solar chemical synthesis, but the poor photovoltages often reported so far will severely limit their performance. Here we report a novel observation of photovoltage loss associated with a charge extraction barrier imposed by the protection layer, and, by eliminating it, achieve photovoltages as high as 630 mV, the maximum reported so far for water-splitting silicon photoanodes. The loss mechanism is systematically probed in metal-insulator-semiconductor Schottky junction cells compared to buried junction p(+)n cells, revealing the need to maintain a characteristic hole density at the semiconductor/insulator interface. A leaky-capacitor model related to the dielectric properties of the protective oxide explains this loss, achieving excellent agreement with the data. From these findings, we formulate design principles for simultaneous optimization of built-in field, interface quality, and hole extraction to maximize the photovoltage of oxide-protected water-splitting anodes.
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Scheuermann
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Lawrence
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Kemp
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.|Tokyo Electron Limited, Technology Development Center, 650, Hosaka-cho Mitsuzawa, Nirasaki, Yamanashi 407-0192, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ito
authors.affiliation: Tyndall National Institute, University College Cork, Cork, Ireland.
authors.forename: Adrian
authors.initials: A
authors.lastname: Walsh
authors.affiliation: Department of Chemistry, Stanford University, Stanford, California 94305, USA.
authors.forename: Christopher E D
authors.initials: CE
authors.lastname: Chidsey
authors.affiliation: Tyndall National Institute, University College Cork, Cork, Ireland.
authors.forename: Paul K
authors.initials: PK
authors.lastname: Hurley
authors.affiliation: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Paul C
authors.initials: PC
authors.lastname: McIntyre