Efficient anti-reflection coatings (ARC) improve the light collection and thereby increase the current output of solar cells. By simple electrochemical etching of the Si wafer, porous silicon (PS) layers with excellent broadband anti-reflection properties can be fabricated. In this work, ageing of graded PS has been studied using Spectroscopic Ellipsometry, Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. During oxidation of PS elements such as pure Si (Si 0 ), Si2O (Si + ), SiO (Si 2+ ), Si2O3 (Si 3+ ), and SiO2 (Si 4+ ) are present. In addition both hydrogen and carbon is introduced to the PS in the form of Si3SiH and CO. The oxide grows almost linearly with time when exposed to oxygen, from an average thickness of 0 -3.8 nm for the surface PS. The oxidation is then correlated to the optical stability of multi-layered PS ARCs. It is found that even after extensive oxidation, the changes in the optical properties of the PS structures are small. PACS numbers:

The defect chemistry of foreign transition metals in perovskite oxides was investigated by first-principles calculations in combination with experiments with focus on Ni and Zn in Y-doped BaZrO3.

The atomic structure and composition of non-interfacial ITO and ITO-Si interfaces were studied with Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The films were deposited by DC magnetron sputtering on mono-crystalline p-type (100) Si wafers. Both as deposited and heat treated films consisted of crystalline ITO. The ITO/Si interface showed a more complicated composition. A thin layer of SiOx was found at the ITO/Si interface together with In and Sn nanoclusters, as well as highly oxygen deficient regions, as observed by XPS. High energy electron exposure of this area crystallized the In nanoclusters and at the same time increased the SiOx interface layer thickness.