Optical characterisation of a spectrally tunable plasmonic reflector for application in thin-film silicon solar cells

We have investigated the interaction between a random two-dimensional array of Ag islands neara Ag reflector, with the aim of producing a plasmonic back reflector structure with high diffuse reflectivity in the near-infrared, 6001100 nm wave length, region. We have demonstrated the ability to tune the power scattered and absorbed by varying the distance between the plasmonic layer and there flector. Finite-difference-time-domain (FDTD) simulations demonstrate the tenability of the scattered and abs or bed power with separation distance for asing le Ag nanosphere near a planar Ag reflector. The tenability of the optical properties can be attributed to the modulation in the electric field driving the plasmonic resonance with separation distance. The simulation results indicate an intermediate distance where the scattered power peaks with minimal absorption losses. Random arrays of metal-islands were fabricated on varying thicknesses of a ZnO separation layer on a Ag reflector. Comparedtoa conventional textured Ag reflector, whichhas ∼2% diffuse reflectance in the near-infrared spectral region, the fabricated plasmonic reflector with ∼200 nm sized Ag metal islands at 100 nm separation distance from the Ag reflector shows a relatively higher, ∼24%, integrated diffuse reflectance in the near bandgap, 6001100 nm wave length, region for thin film silicon solar cells.