Spectroscopic ellipsometry analysis on materials for energy efficient applications

The improvement of technologies towards a more sustainable use of resources has received an increasing interest worldwide in recent decades. Particular technology examples include the generation of electricity using more efficient solar cells, the improvement in energy density capacity of batteries for the efficient storage of electricity, and the development of spintronic devices, for more energy efficient type of electronics. In the present work, we use spectroscopic ellipsometry as principal experimental technique to characterize (i) anti-reflection coatings on textured surfaces for solar cells, (ii) tungsten oxide upon hydrogen intercalation and (iii) the intrinsic and the magnetic field induced optical birefringence in Zn1-xMn xSe for potential spintronic applications. For topic (i), we analyze the effect of texture on the ellipsometry data and we present a method to determine the index of refraction and thickness of antireflecting films on textured substrates for solar cells. Particularly for alkaline etched monocrystalline silicon solar cells, we find specific measurement geometries that allow ellipsometry measurements in a wide range of angles of incidence and photon energies, despite of the strong surface roughness. In (ii), we investigate the proton intercalation of tungsten oxide, a material which has potential application in high energy density batteries. In particular, we investigate the polaron and phonon parameters dependence upon hydrogen ion intercalation, which provide insight into the related effects at the structural and microscopic level. Finally in topic (iii), we investigate the magnetooptic and birefringence properties of Zn 1-xMnxSe thin films in dependence of the Mn content. We provide a description of the found band gap anisotropy, the magnetization, and effective spin of the Mn-ions in dependence of x and its influence on the optical properties at room temperature