title: GaP/GaNP Heterojunctions for Efficient Solar-Driven Water Oxidation.
abstract: The growth and characterization of an n-GaP/i-GaNP/p+-GaP thin film heterojunction synthesized using a gas-source molecular beam epitaxy (MBE) method, and its application for efficient solar-driven water oxidation is reported. The TiO2/Ni passivated n-GaP/i-GaNP/p+-GaP thin film heterojunction provides much higher photoanodic performance in 1 m KOH solution than the TiO2/Ni-coated n-GaP substrate, leading to much lower onset potential and much higher photocurrent. There is a significant photoanodic potential shift of 764 mV at a photocurrent of 0.34 mA cm-2, leading to an onset potential of ≈0.4 V versus reversible hydrogen electrode (RHE) at 0.34 mA cm-2for the heterojunction. The photocurrent at the water oxidation potential (1.23 V vs RHE) is 1.46 and 7.26 mA cm-2for the coated n-GaP and n-GaP/i-GaNP/p+-GaP photoanodes, respectively. The passivated heterojunction offers a maximum applied bias photon-to-current efficiency (ABPE) of 1.9% while the ABPE of the coated n-GaP sample is almost zero. Furthermore, the coated n-GaP/i-GaNP/p+-GaP heterojunction photoanode provides a broad absorption spectrum up to ≈620 nm with incident photon-to-current efficiencies (IPCEs) of over 40% from ≈400 to ≈560 nm. The high low-bias performance and broad absorption of the wide-bandgap GaP/GaNP heterojunctions render them as a promising photoanode material for tandem photoelectrochemical (PEC) cells to carry out overall solar water splitting.
authors.affiliation: Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA, 92093, USA.
authors.forename: Alireza
authors.initials: A
authors.lastname: Kargar
authors.affiliation: Materials Science and Engineering Program, University of California-San Diego, La Jolla, CA, 92093, USA.
authors.forename: Supanee
authors.initials: S
authors.lastname: Sukrittanon
authors.affiliation: School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001, P. R. China.|Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Chang
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA, 92093, USA.
authors.forename: Yun Goo
authors.initials: YG
authors.lastname: Ro
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.|Department of Chemical Engineering and Materials Science, University of California-Irvine, Irvine, CA, 92697, USA.|Department of Physics and Astronomy, University of California-Irvine, Irvine, CA, 92697, USA.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Pan
authors.affiliation: Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA, 92093, USA.|Materials Science and Engineering Program, University of California-San Diego, La Jolla, CA, 92093, USA.
authors.forename: Shadi A
authors.initials: SA
authors.lastname: Dayeh
authors.affiliation: Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA, 92093, USA.|Materials Science and Engineering Program, University of California-San Diego, La Jolla, CA, 92093, USA.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Tu
authors.affiliation: Materials Science and Engineering Program, University of California-San Diego, La Jolla, CA, 92093, USA.|Department of Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, CA, 92093, USA.
authors.forename: Sungho
authors.initials: S
authors.lastname: Jin
keywords: GaNP; GaP; alkaline electrolytes; solar-driven water oxidation; thin film heterojunctions