Wafer-Scale Fabrication of Self-Catalyzed 1.7 eV GaAsP Core–Shell Nanowire Photocathode on Silicon Substrates

Jiang Wu,Mingchu Tang,Jun Kubota,Kazunari Domen,Thomas Ward,Alwyn Seeds,Sabina Hatch,Huiyun Liu,Richard Beanland,Yanbo Li,Yunyan Zhang,Ana Sanchez,Martin Aagesen

doi:10.1021/nl500170m

Abstract

We present the wafer-scale fabrication of self-catalyzed p-n homojunction 1.7 eV GaAsP core-shell nanowire photocathodes grown on silicon substrates by molecular beam epitaxy with the incorporation of Pt nanoparticles as hydrogen evolution cocatalysts. Under AM 1.5G illumination, the GaAsP nanowire photocathode yielded a photocurrent density of 4.5 mA/cm(2) at 0 V versus a reversible hydrogen electrode and a solar-to-hydrogen conversion efficiency of 0.5%, which are much higher than the values previously reported for wafer-scale III-V nanowire photocathodes. In addition, GaAsP has been found to be more resistant to photocorrosion than InGaP. These results open up a new approach to develop efficient tandem photoelectrochemical devices via fabricating GaAsP nanowires on a silicon platform.

Highlights

(STH) efficiency limit of only ∼2%.9,10 The bandgap of ideal semiconductor materials for single-bandgap photoelectrode should be large enough (>1.6 eV) to split water and, at the same time, small enough (
The dilemma of low STH efficiency for single-bandgap systems can be addressed by the use of two absorbing semiconductor materials, in which the wider bandgap material is placed on top for photoelectrodes and absorbing the short wavelength, while a smaller bandgap material is placed behind the wider bandgap one to absorb the long-wavelength solar spectrum
GaAsP nanowires have recently been demonstrated as a promising materials system for highefficiency photovoltaic cells.[15−17] Thanks to the one-dimensional geometry and small footprint of the nanowires, the stress induced by the lattice and thermal mismatch can be accommodated by elastic relaxation.[18,19]

Summary

Introduction

(STH) efficiency limit of only ∼2%.9,10 The bandgap of ideal semiconductor materials for single-bandgap photoelectrode should be large enough (>1.6 eV) to split water and, at the same time, small enough (

Results

Conclusion