Journal
NANO LETTERS
Volume 14, Issue 8, Pages 4517-4522Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl501541s
Keywords
Solar hydrogen; aluminum plasmonics; hematite; core-shell; core-multishell; nanowires; plasmonic light harvesting
Categories
Funding
- National Science Foundation ECCS [1118934]
- Directorate For Engineering
- Div Of Electrical, Commun & Cyber Sys [1118934] Funding Source: National Science Foundation
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The poor internal quantum efficiency (IQE) arising from high recombination and insufficient absorption is one of the critical challenges toward achieving high efficiency water splitting in hematite (alpha-Fe2O3) photoelectrodes. By combining the nanowire (NW) geometry with the localized surface plasmon resonance (LSPR) in semiconductor-metal-metal oxide core-multishell (CMS) NWs, we theoretically demonstrate an effective route to strongly improve absorption within ultrathin (sub-50 nm) hematite layers. We show that Si-Al-Fe2O3 CMS NINs exhibit photocurrent densities comparable to Si-Ag-Fe2O3 CMS and outperform Fe2O3, Si-Fe2O3 CS and Si-Au-Fe2O3 CMS NWs. Specifically; Si-Al-Fe2O3 CMS NWs reach photocurrent densities of similar to 11.81 mA/cm(2) within a 40 nm thick hematite shell which corresponding to a solar to hydrogen (STH) efficiency of 14.5%. This corresponds to about 9396 of the theoretical maximum for bulk hematite. Therefore, we establish Al as an excellent alternative plasmonic material compared to precious metals in CMS structures. Further, the absorbed photon flux is close to the NW surface in the CMS NWs, which ensures the charges generated can reach the reaction site with minimal recombining. Although the NW geometry is anisotropic, the CMS NWs exhibit polarization independent absorption over a large range of incidence angles. Finally, we show that Si-Al-Fe2O3 CMS NWS demonstrate photocurrent densities greater than similar to 8.2 mA/cm(2) (STH efficiency of 10%) for incidence angles as large as 45 degrees. These theoretical results strongly establish the effectiveness of the Al-based CMS NWs for achieving scalable and cost-effective photoelectrodes with improved IQE, enabling a novel route toward high efficiency water splitting.
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