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Proceedings Paper

Delafossite-alloy photoelectrodes for PEC hydrogen production: a density functional theory study
Author(s): Muhammad N. Huda; Yanfa Yan; Aron Walsh; Su-Huai Wei; John A. Turner; Mowafak M. Al-Jassim
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Paper Abstract

Efficient photo-electrochemical (PEC) splitting of water to hydrogen usually requires photoelectrodes to have certain electronic properties. Unfortunately, at present available semiconductors do not meet all these criteria. So, a thorough understanding of band-engineering for mixed alloys is necessary to successfully design these photoelectrodes. Among the semiconductors, transition metal oxides are of particular interest due to their low cost and relatively high stability in aqueous media. Here, we will present a theoretical study of delafossite-alloys for PEC photo-electrodes. Previous studies have indicated that the group IIIA delafossite family (CuMO2, M = Al, Ga, In) do not exhibit direct band gaps. Their fundamental band gaps are significantly smaller than their reported optical band gaps. On the other hand group IIIB delafossite family (CuMO2, M = Sc, Y, La) in general show direct band gaps and, except for CuLaO2, band gaps are above 3.00 eV. However, both of these two families exhibit p-type conductivity. We will show that by appropriate alloying of these two delafossite-families we can tune their band gaps and other opto-electronic properties. These types of alloying are desirable, as these introduce no localized impurity states in the band gap due to isovalent alloying. Also, the electronic effective masses can be lowered by selective doping of main group elements. Finally, it will be discussed that, lowering the symmetry constraints of these alloys would enhance their optical absorption properties. We'll also discuss that alloying with other 3d metal elements may decrease the band gap, but would increase the effective masses of the photo-electrons.

Paper Details

Date Published: 24 August 2010
PDF: 10 pages
Proc. SPIE 7770, Solar Hydrogen and Nanotechnology V, 77700F (24 August 2010); doi: 10.1117/12.859947
Show Author Affiliations
Muhammad N. Huda, The Univ. of Texas at Arlington (United States)
Yanfa Yan, National Renewable Energy Lab. (United States)
Aron Walsh, Univ. College London (United Kingdom)
Su-Huai Wei, National Renewable Energy Lab. (United States)
John A. Turner, National Renewable Energy Lab. (United States)
Mowafak M. Al-Jassim, National Renewable Energy Lab. (United States)

Published in SPIE Proceedings Vol. 7770:
Solar Hydrogen and Nanotechnology V
Hicham Idriss; Heli Wang, Editor(s)

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