Large Area, Nanoimprinted Al Substrates for Plasmon-Enhanced Photoelectrochemistry
LaboratorySandia National Laboratories (SNL)
Capability ExpertAlec Talin
Process and Manufacturing Scale-Up
Node Readiness Category1: Photoelectrochemical (PEC)
Our capability consists of design, fabrication, and characterization of large area Al based nanopatterned electrodes for plasmon enhanced photoelectrochemistry (PEC). Variety of low cost, stable and catalytically active water splitting materials such as Fe2O3 and BiVO4 have poor charge transport characteristics leading to low PEC efficiency.1,2 Surface plasmon polaritons (SPP) excited in nanopatterned Al concentrate optical fields in the UV and visible ranges, thus enhancing light absorption within few tens of nanometers of semiconducting material deposited over the Al substrate. We use nanoimprint lithography (NIL) to pattern a range of 1D- and 2D gratings in polymers which are then metallized with Al using electron beam evaporation.3,4 This process is produces high fidelity nanopatterns over large area and is fully compatible with roll-to-roll manufacturing. Vertical nanoslits patterned in Al scatter incident light into SPP mode propagating along slit length and contained within the Al/dielectric interface. In this geometry, electrons (or holes) propagate perpendicular to the slit orientation seeing only a thin layer of active material (tens of nanometers), while light propagates as SPPs along the slit length, effectively seeing a much thicker layer. Recently we used this principle to demonstrate rapid switching electrochromic devices with nearly 100 percent light absorption using only 15 nm of active material uniformly electrodeposted over the nanoslit array surface.5 Using the same approach we will electrodeposit PEC active materials onto Al plasmonic substrates to achieve highly efficient PEC process.
SNL is an internationally recognized leader in nanofabrication, plasmonics, electrochemical energy conversion
The capability is available to staff, students and visitors of SNL-CA in Livermore, CA.
Al plasmonic structures fabricated using nanoimprint lithography combine scalability, manufacturability and low cost materials to enable efficient photoelectrochemical hydrogen productions.
(a) Al plasmonic nanoslits with active PEC anode or cathode material. Geometry ensures effective light absorption in very thin layer to minimize charge carrier recombination. (b) scanning electron micrograph of nanoslit array coated with electrochromic polymer (c) plasmonic nanoslits with 15 nm of active material absorbing/transmitting light across the visible spectrum with >80 % contrast.5
- Bohn, C. D. et al. Effect of Tin Doping on alpha-Fe2O3 Photoanodes for Water Splitting. J. Phys. Chem. C 116, 15290-15296, doi:10.1021/jp305221v (2012).
- Li, J. T. & Wu, N. Q. Semiconductor-based photocatalysts and photoelectrochemical cells for solar fuel generation: a review. Catal. Sci. Technol. 5, 1360-1384, doi:10.1039/c4cy00974f (2015).
- Skinner, J. L., Talin, A. A. & Horsley, D. A. A MEMS light modulator based on diffractive nanohole gratings. Opt. Express 16, 3701-3711, doi:10.1364/oe.16.003701 (2008).
- Skinner, J. L., L., H. L., Talin, A. A., J., P. & Horsley, D. A. Large-Area Subwavelength Aperture Arrays Fabricated Using Nanoimprint Lithography. IEEE Transactions on Nanotechnology 7, 527-531 (2008).
- Xu, T. et al. High-contrast and fast electrochromic switching enabled by plasmonics. Nat. Commun. 7, doi:10.1038/ncomms10479 (2016).