The J-V equation of a solar cell is implicit and requires iterative calculation to determine the fill factor and the maximum power point. Here an explicit model for J-V characteristic is proposed which is applicable to a large variety of solar cell. This model allows an easy estimation of fill factor from four simple measurements of the bias points corresponding to V-oc, J(sc), and any two voltage values lying between 0 and V-oc, where V-oc is the open circuit voltage and J(sc) is the short circuit current density. (C) 2011 Elsevier Ltd. All rights reserved.