title: GaN nano-pyramid arrays as an efficient photoelectrode for solar water splitting.
abstract: A prototype photoelectrode has been fabricated using a GaN nano-pyramid array structure grown on a cost-effective Si (111) substrate, demonstrating a significant improvement in performance of solar-powered water splitting compared with any planar GaN photoelectrode. Such a nano-pyramid structure leads to enhanced optical absorption as a result of a multi-scattering process which can effectively produce a reduction in reflectance. A simulation based on a finite-difference time-domain approach indicates that the nano-pyramid architecture enables incident light to be concentrated within the nano-pyramids as a result of micro-cavity effects, further enhancing optical absorption. Furthermore, the shape of the nano-pyramid further facilitates the photo-generated carrier transportation by enhancing a hole-transfer efficiency. All these features as a result of the nano-pyramid configuration lead to a large photocurrent of 1 mA cm-2under an illumination density of 200 mW cm-2, with a peak incident photon-to-current conversion efficiency of 46.5% at ∼365 nm, around the band edge emission wavelength of GaN. The results presented are expected to pave the way for the fabrication of GaN based photoelectrodes with a high energy conversion efficiency of solar powered water splitting.
authors.affiliation: Department of Electrical and Electronic Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK.
authors.forename: Y
authors.initials: Y
authors.lastname: Hou
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.forename: Z Ahmed
authors.initials: ZA
authors.lastname: Syed
authors.forename: S
authors.initials: S
authors.lastname: Shen
authors.forename: J
authors.initials: J
authors.lastname: Bai
authors.forename: T
authors.initials: T
authors.lastname: Wang