GaP/GaNP Heterojunctions for Efficient Solar‐Driven Water Oxidation

Journal Article · Fri Mar 31 00:00:00 EDT 2017 · Small

DOI:https://doi.org/10.1002/smll.201603574· OSTI ID:1400828

Kargar, Alireza ^[1]; Sukrittanon, Supanee ^[2]; Zhou, Chang ^[3]; Ro, Yun Goo ^[1]; Pan, Xiaoqing ^[4]; Dayeh, Shadi A. ^[5]; Tu, Charles W. ^[5]; Jin, Sungho ^[6]

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1. Department of Electrical and Computer Engineering University of California‐San Diego La Jolla CA 92093 USA
2. Materials Science and Engineering Program University of California‐San Diego La Jolla CA 92093 USA
3. 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
4. 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
5. 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
6. 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

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 TiO ₂ /Ni passivated n‐GaP/i‐GaNP/p ⁺ ‐GaP thin film heterojunction provides much higher photoanodic performance in 1 m KOH solution than the TiO ₂ /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 ⁻² for the heterojunction. The photocurrent at the water oxidation potential (1.23 V vs RHE) is 1.46 and 7.26 mA cm ⁻² for 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.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DE‐SC0000957
• OSTI ID: 1400828
• Journal Information: Small, Journal Name: Small Vol. 13 Journal Issue: 21; ISSN 1613-6810
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: Germany
• Language: English