This lecture covers the fundamentals and processes for photovoltaic devices, focusing on very high efficiency concepts. It discusses various types of high efficiency cells, such as C-Si based, III-V single junction, and multi-junction cells. It also explores the basics of efficiency limits in crystalline silicon and the ultimate possible evolution of C-Si solar cell technologies. The lecture delves into concepts like passivating contacts, epitaxial growth, and rear contact recombination, aiming to achieve very high efficiency in solar cells.