Modeling of transport and recombination of charge carriers in solar cells is useful for understanding and improving the device performance. We implement the fully coupled transport equations for electrons and holes into the finite-element partial differential equation solver COMSOL. The dopant-diffused surface regions such as junctions, floating junctions, or back surface field layers are treated as conductive boundaries of the volume in which the semiconductor equations are solved. This so-called conductive boundary (CoBo) model characterizes diffused layers by their sheet resistances and diode saturation current densities. Both are directly experimentally accessible. The CoBo model exhibits excellent numerical stability and enables two-dimensional simulations on a laptop. We find agreement when testing the two-dimensional COMSOL implementation of the CoBo model for one-dimensional devices against simulations using the code PC1D. We apply the CoBo model to elucidate how the sheet resistance of diffused vias impacts the power conversion efficiency of emitter wrap through solar cells. Copyright © 2010 John Wiley & Sons, Ltd.