The rapid development of novel solar cell concepts requires an accurate and reliable modeling to obtain a better physical understanding of the solar cells, as well as to reduce the number of time consuming and expensive experimental investigations. In order to get a rough overview about industrially relevant silicon solar cell concepts in production and their efficiency potential an overview over different solar cell architectures is presented at the beginning of the work.For a higher accuracy of the numerical simulations of silicon solar cells, the effect of free carrier absorption is discussed in detail. Also, an advanced method for precise modeling of highly aluminum-doped p+ silicon is presented. By using this method, a detailed analysis on the optimization of n+np+ silicon solar cells with aluminum-alloyed rear p+ emitter for industrial applications is shown. As a high-efficiency approach, lateral conductance effects of locally contacted rear surface passivated p-Si solar cells are investigated. Furthermore, a future orientated solar cell concept, bifacial monocrystalline Si solar cells have been optimized for upconversion applications via numerical simulations.