Investigation on AgGaSe₂ for water splitting from first-principles calculations

¹ College of Physical Science and Technology, Guangxi University - 530004 Nanning, China
² Department of Physics and Electronic Sciences, Hunan University of Arts and Science - 415000 Changde, China
³ Department of Materials Science and Engineering, Royal Institute of Technology - SE-100 44 Stockholm, Sweden
⁴ Department of Physics, University of Oslo - PO Box 1048 Blindern, NO-0316 Oslo, Norway

^(a) guojin@gxu.edu.cn

Received: 7 November 2013
Accepted: 24 January 2014

Abstract

The electronic structure of AgGaSe₂ has been investigated as a photocatalyst candidate by first-principles calculation. Our results demonstrate that the band edge positions of bulk AgGaSe₂ straddle the water redox potentials. From the band offset calculation, we find that Al-doping of AgGaSe₂ shifts the conduction band minimum upwards, whereas Cu-doping of AgGaSe₂ shifts the valence band maximum upwards. By (Ag, Cu)(Ga, Al)Se₂ alloying one can thereby tailor both the band edge positions and the band gap energy, and this effect provides an approach to optimize the band properties for overall water splitting. Moreover, AgGaSe₂ forms a suitable junction with CuGaSe₂ with a type-II band offset, which facilitates electron-hole separation. The AgGaSe₂ and CuGaSe₂ junction can be designed as a tandem photoelectrochemical device to improve the photocatalytic properties of the system.