The high current generated in cells under concentrated sunlight causes a voltage drop on the front contact grid. This drop, proportional to the current intensity and combined with the non-linear I/V characteristic of the diode, limits the cell efficiency in the mid- and high-concentration region. A simulation method capable of evaluating this kind of loss for general contact patterns and different concentration levels is therefore proposed. The simulated I-V curve can be employed for concentration-dependent pattern and coverage optimization. (C) 2003 Elsevier B.V. All rights reserved.