Nanoplasmonics for light trapping in solar cells

Reducing the thickness of solar cells can significantly reduce material usage and hence the cost of solar cell fabrication. However, thin cells suffer from significant optical losses, especially at weakly absorbed wavelengths, which can seriously degrade performance. Light trapping is essential to maintain high efficiencies, while reducing the thickness of solar cells. Traditional light-trapping techniques, employing geometrical optics, are not feasible for thin cells as, in general, they cannot support these structures Novel light-trapping techniques are needed for the next generation of thin solar cells We demonstrate that nanoplasmonics can provide a solution Metal nanoparticles can support optically driven localised surface plasmons. These oscillations can lead to highly concentrated near fields around the particle and can scatter incident light from an area several times larger than the geometrical area of the particle. In the vicinity of a high-refractive-index substrate the angular emission spectrum of the excited resonance is modified such that over 90% of the scattered light is coupled into the optically dense material. We show that it is possible to design strongly scattering plasmonic structures that can enhance the photocurrent generated in a solar cell The particles can be separated from the surface of the solar cell by a dielectric layer, isolating the cell from metal contamination and allowing the optical properties of the nanoparticles to be tuned by modifying the local dielectric environment In the following chapter we discuss design considerations for nanoparticles for light-trapping applications and present experimental results for an enhanced photocurrent from thin silicon solar cells. Due to the tunability of the optical properties of the nanoparticles, plasmonic light trapping is very versatile and could be tailored to suit the needs of any future solar cell technology.