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Over the last decade, plasmonic nanoparticle arrays have been extensively studied for their light trapping potential in thin film solar cells. However, the commercial use of such arrays has been limited by complex and expensive fabrication techniques such as e-beam lithography. Nanosphere lithography (NSL) is a promising low-cost alternative for forming regular arrays of nanoscale features. Here, we use finite-difference time-domain (FDTD) simulations to determine the optical enhancement due to nanosphere arrays embedded at the rear of a complete thin film device. Array parameters including the nanosphere pitch and diameter are explored, with the FDTD model itself first validated by comparing simulations of Ag nanodisc arrays with optical measurements of pre-existing e-beam fabricated test structures. These results are used to guide the development of a nanosphere back-reflector for 20 μm thin crystalline silicon cells. The deposition of polystyrene nanosphere monolayers is optimized to provide uniform arrays, which are subsequently incorporated into preliminary, proof of concept device structures. Absorption and photoluminescence measurements clearly demonstrate the potential of nanosphere arrays for improving the optical response of a solar cell using economical and scalable methods.

The scattering properties of a plasmonic array can be reinforced by placing the array near a planar reflector. Finite- Difference-Time-Domain (FDTD) simulations have been used to demonstrate the key design challenge of modulating the electric field that drives the plasmonic scattering, by varying the distance of a single Ag nanodisc from a Ag reflector. We show that the thickness of the dielectric separation layer plays a critical role in determining the spectral characteristics and the intensity of the power scattered by a Ag nanodisc near a reflector. A possible application of the designed structure as a plasmonic light-trap for thin Si solar cells is also experimentally demonstrated. Electron-beam lithography has been used to fabricate a pseudo-random array of 150nm plasmonic Ag nanodiscs on SiO 2 on a Ag reflector substrate. The plasmonic reflector shows a high diffuse reflectance of ~54% in the near-infrared, near-bandgap 600-900nm wavelength region for thin Si solar cells, with a low broadband absorption loss of ~18%. Wavelength-angle resolved scattering measurements indicate an angular scattering range between 20° to 80° with maximum intensity of the scattered power in the 20° to 60° angular range.

We have experimentally and theoretically demonstrated plasmonic couplers based on metal nanoparticles film (metal islands) deposited upon the optical dielectric waveguide. These nanoparticles forward scatter radiation into the optical waveguide that would otherwise be reflected and transmitted. Design, fabrication and optimisation of the plasmonic silver islands and tantalum pentoxide waveguide are reported. Broadband characteristics of light transmission showing plasmons excitation have been measured and in good agreement with simulated results from 400 nm to 800 nm. Coupling spectrum up to 15% is measured for the plasmonic coupler and in good agreement with the simulated results.

Using electron beam lithographic techniques we have manufactured left and right-handed forms of an artificial medium consisting of high densities of microscopic planar chiral metallic objects distributed regularly in a plane. In this artificial medium we have for the first time observed optical manifestations of planar chirality in the form of handedness-sensitive rotation of the polarization state and elliptization of visible light diffracted from the structure. Applications of such media in functional materials are discussed.