Targeting better absorption at longer wavelengths using surface plasmons

A very promising approach of reducing the cost of Si solar cells is thin film technology. Good light trapping is crucial for thin Si cells, but standard wet etching techniques cannot be used when the device is only a few microns thick. Metal nanoparticles have the potential to improve light trapping in thin Si devices using the coupling of the surface plasmon resonance of the nanoparticles with the waveguide modes of the Si layer. In this work metallic nanostructures are fabricated on silicon-on-insulator devices and then optically characterised. A theoretical approach is undertaken to calculate the wavelength dependence of the power enhancement by considering the metal particles to be electric dipoles. We show that using surface plasmons more power is transferred into the guided modes with increasing wavelength.