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Title: Electrochemical Reduction Properties of Extended Space Charge InGaP and GaP Epitaxial Layers

Two lattice-matched epitaxial III-V phosphide films of thicknesses between 400 and 500 nm are grown by metal-organic chemical vapor deposition: InGaP on GaAs and GaP on Si. These structures are designed as photocathodes for solar-driven chemical reduction processes such as the hydrogen evolution reaction (HER) and CO 2 reduction into higher-order hydrocarbons. By using p + substrates and undoped epitaxial layers, an extended space-charge active region is achieved in the electrode with a design analogous to a p-i-n solar cell. When in contact with the methyl viologen MV + / + + redox couple, the InGaP/GaAs and GaP/Si cathodes generate a photovoltage of 388 mV and 274 mV, respectively, under 1 sun illumination. Incident photon-to-current efficiency (IPCE) measurements confirm that the undoped active layers are exclusively performing light absorption and minority carrier diffusion-based charge transfer of high-energy photons. This shows that performance can be significantly boosted with lower-doped substrates. The InGaP/GaAs and GaP/Si electrodes are shown to drive the HER at saturation photocurrent densities of 9.05 mA/cm 2 and 2.34 mA/cm 2, respectively, under 1 sun illumination without a co-catalyst and under a large reduction bias. As a result, thicker films did not show a corresponding increased performance, and canmore » be explained through understanding of crystalline defects and the electrostatics of the junctions.« less
Authors:
 [1] ;  [1] ;  [1]
  1. Stanford Univ., Stanford, CA (United States)
Publication Date:
Grant/Contract Number:
SC0001060
Type:
Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 163; Journal Issue: 8; Related Information: CNEEC partners with Stanford University (lead); Carnegie Institution at Stanford; Technical University of Denmark; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Research Org:
Energy Frontier Research Centers (EFRC) (United States). Center on Nanostructuring for Efficient Energy Conversion (CNEEC)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE
OSTI Identifier:
1370006

Parameshwaran, Vijay, Xu, Xiaoqing, and Clemens, Bruce. Electrochemical Reduction Properties of Extended Space Charge InGaP and GaP Epitaxial Layers. United States: N. p., Web. doi:10.1149/2.1341608jes.
Parameshwaran, Vijay, Xu, Xiaoqing, & Clemens, Bruce. Electrochemical Reduction Properties of Extended Space Charge InGaP and GaP Epitaxial Layers. United States. doi:10.1149/2.1341608jes.
Parameshwaran, Vijay, Xu, Xiaoqing, and Clemens, Bruce. 2016. "Electrochemical Reduction Properties of Extended Space Charge InGaP and GaP Epitaxial Layers". United States. doi:10.1149/2.1341608jes. https://www.osti.gov/servlets/purl/1370006.
@article{osti_1370006,
title = {Electrochemical Reduction Properties of Extended Space Charge InGaP and GaP Epitaxial Layers},
author = {Parameshwaran, Vijay and Xu, Xiaoqing and Clemens, Bruce},
abstractNote = {Two lattice-matched epitaxial III-V phosphide films of thicknesses between 400 and 500 nm are grown by metal-organic chemical vapor deposition: InGaP on GaAs and GaP on Si. These structures are designed as photocathodes for solar-driven chemical reduction processes such as the hydrogen evolution reaction (HER) and CO2 reduction into higher-order hydrocarbons. By using p+ substrates and undoped epitaxial layers, an extended space-charge active region is achieved in the electrode with a design analogous to a p-i-n solar cell. When in contact with the methyl viologen MV+ / + + redox couple, the InGaP/GaAs and GaP/Si cathodes generate a photovoltage of 388 mV and 274 mV, respectively, under 1 sun illumination. Incident photon-to-current efficiency (IPCE) measurements confirm that the undoped active layers are exclusively performing light absorption and minority carrier diffusion-based charge transfer of high-energy photons. This shows that performance can be significantly boosted with lower-doped substrates. The InGaP/GaAs and GaP/Si electrodes are shown to drive the HER at saturation photocurrent densities of 9.05 mA/cm2 and 2.34 mA/cm2, respectively, under 1 sun illumination without a co-catalyst and under a large reduction bias. As a result, thicker films did not show a corresponding increased performance, and can be explained through understanding of crystalline defects and the electrostatics of the junctions.},
doi = {10.1149/2.1341608jes},
journal = {Journal of the Electrochemical Society},
number = 8,
volume = 163,
place = {United States},
year = {2016},
month = {6}
}