Resonant nanophotonic structures for photovoltaics

Efficient photovoltaic energy conversion requires accurate control over the flow and absorption of light in semiconductor materials to optimize the conversion from optical power to electrical power. For thin semiconductor films in particular, light trapping inside the active layer is essential to achieve sufficient absorption. Such light management requires control over the light-matter interaction at the nanoscale. Nanostructures with a size comparable to the wavelength of light show strong interaction with light as a result of optical resonances. These resonances can be designed to give rise to strong localized absorption or directional scattering, which provides control over the flow of light. In this thesis, we explore how resonant nanophotonic structures can be used to control optical processes in photovoltaic energy conversion. We study the fundamental aspects of resonant light scattering by metallic and dielectric nanostructures, and apply these insights to design novel photovoltaic architectures with improved light management. First, we study how resonant networks of silver nanowires are transparent for light and conductive for electrical charge, and how fundamental understanding of the plasmon scattering mechanisms can be used to optimize the transmission through these networks. Next, we demonstrate how metal nanostructures can directly induce photo-voltages as a result of their resonant behavior, and how this effect can be used to realize all-metal optoelectric power conversion. Then, we investigate the resonant properties of dielectric nanoparticles, and how interference between the resonant modes gives rise to directional scattering. Finally, we describe two photovoltaic applications inspired by the work in this thesis