Design and fabrication of nanostructures for enhaced light absorption in silicon

Abstract

Nanostructures are being widely studied in the scientific community for many different applications because they present novel properties different from those observed in matter at the macroscale. For example, electromagnetic waves interact in an unusual way with periodic nanostructures with sizes in the order of magnitude of the wavelength. Structures with periods in the nanoscale can indeed manage light in the ultraviolet, visible and near infrared regions of the electromagnetic spectrum. In this work, we use periodic nanostructures to control the optical properties of Si, since it is one of the most common elements in the world and also one of the most used materials in the industry. We focus on the light reflection at Si surface, which is an important limitation in optoelectronic devices nowadays. This thesis is organized in two different parts. First, we present the optimization and fabrication of periodic nanostructures to maximize light absorption in photovoltaic cells. We have fabricated periodic structures on both polished and unpolished Si substrates, which have been successfully integrated in solar cells following standard industrial processes. In the second part, we explain the fabrication and optical characterization of ultrahigh aspect ratio nanocones for more broadband applications.