Nanoscale Architecture for Site-controlled Epitaxy and Antireflective Coatings

Abstract

The deployment of novel nanofabrication and -characterization techniques has paved the way for tunable functionalities of materials by engineering the size of the structures at the nanoscale. The key concepts in this thesis are the exploitation of quantum mechanical properties in nanostructures and sub-wavelength optical materials. This thesis covers nanoimprint lithography based fabrication techniques for the realization of quantum dot based semiconductor devices and the formation of sub-wavelength antireflection coatings for high efficiency solar cells. Both types of patterning processes were developed aiming for the integration with molecular beam epitaxy, which was used for the material fabrication. The structural and optical properties of the quantum dots fabricated by this new method indicated excellent suitability of the fabrication process for large scale quantum dot based devices.

The increasing demand of renewable energy sources has led to rapid development in the field of photovoltaics. In addition to the significant improvements in the preparation of active materials, the performance of a solar cell is directly increased by carefully designing the antireflection coating on the surface of the cell. The reflectivity of the solar cell surface has to be minimized in order to transfer the maximum amount of solar energy into the cell to be converted into electricity. In this thesis, a novel nanostructured antireflection coating was developed. The antireflective properties of the coating were outstanding within a broad spectral range and a clear increase in the solar cell performance was achieved.