The knowledge of the loss mechanisms in industrial back-contact back-junction (BC BJ) silicon solar cells and their dependence on geometrical and substrate parameters provides the opportunity to further increase the cell efficiency of this cell type. In the presented paper the influences of the different loss mechanisms on the cell parameters of BC BJ solar cells were analyzed. The basis of the simulations was an advanced 1-d model that regards the detrimental influences of intrinsic losses, optical losses, series resistance losses and recombination losses on the cell efficiency. In this context the main influence of electrical shading losses will be discussed in particular, due to the restrictions of the minimum base width as a result of industrial structuring processes. The predictions of the theoretical calculations will be compared with the measured cell parameters of BC BJ solar cells for various cell designs. In order to further improve the cell design the influences of geometrical parameters (pitch, base width) and substrate parameters (base resistivity) on the cell efficiency will be analyzed. The modeling data show that the optimum cell geometry defines a balance between series resistance and electrical shading losses. (C) 2009 Elsevier B.V. All rights reserved.