New Visible Semiconductors for Photoelectrochemical Water Splitting

Abstract

New semiconductors with appropriate band gap and band edge energetics are needed for making serious advances in solar fuels research. This presentation will highlight our efforts in the search for new semiconductor materials specifically toward photoelectrochemical water splitting: (a) New alloys of GaN with antimony and (b) a generic informatics strategy for band gap prediction.Applicability of the Ga(Sbx)N1−x alloys for practical realization of photoelectrochemical water splitting is investigated using first-principles density functional theory incorporating the local density approximation and generalized gradient approximation plus the Hubbard U parameter formalism. Prior results with calculations revealed that a relatively small concentration of Sb impurities is sufficient to achieve a significant narrowing of the band gap, enabling absorption of visible light.1 Theoretical results predict that Ga(Sb x )N1−x alloys with 2 eV band gaps straddle the potential window at moderate to low pH values, thus indicating that dilute Ga(Sb x )N1−x alloys could be potential candidates for splitting water under visible light irradiation. Theoretical computations with Sb composition beyond 7% change the band gap from direct to indirect.2 Experimental synthesis is carried out using metal organic chemical vapor deposition using trimethyl gallium (TMGa) and Trimethyl Antimony (TMSb) and ammonia. Crystalline GaSbxN1-xfilms were obtained at x values ranging from 0-8%.In addition, highlights of our recent work3on informatics-aided predictions of band gaps for several new chalco-pyrite materials will be provided. Acknowledgements: Financial support from US Department of Energy (DE-FG02-07ER46375) and NSF (DMS1125909).