The aims of this project are to investigate the optical properties of metal nanoparticles, to the study the interaction of metal nanoparticles with solar cells, and to optimize this interaction to increase the efficiency of silicon solar cells.
Reducing the thickness of silicon solar cells increases carrier collection and decreases material costs. However, thin layers cannot absorb as much light as thicker layers, and so light-trapping schemes are required to improve absorption. Conventional light-trapping techniques are based on surface texturing, and result. Additionally, these techniques often do not perform well in the near-infrared (NIR), where silicon is most weakly absorbing.
Metal nanoparticles can strongly scatter UV, visible and NIR despite being substantially sub-wavelength in size. The wavelength at which maximum scattering occurs can be tuned by modifying the nanoparticle size, shape and composition. We have studied the optical properties of metal nanoparticles using simulations and experimental methods. To fabricate metal nanoparticles we use top-down techniques such as electron-beam lithography, or bottom-up techniques such as thin-film annealing.
Currently we are investigating the interaction of metal nanoparticles with amorphous silicon solar cells. The optical properties of metal nanoparticles are altered by the presence of the silicon layer, and so we wish to study and optimize this effect. To aid this study we are also investigating the interaction of metal nanoparticles with planar dielectric layers, which may have additional applications such as coupling of light to planar waveguides and improved planar concentrators.