Analytical model for the diode saturation current of point-contacted solar cells

Point-contacted solar cells exhibit three-dimensional transport effects due to a spatially inhomogeneous surface recombination. Complex multi-dimensional finite element simulations are commonly applied to model such devices. This paper presents an empirical analytic equation for the diode saturation current of a point-contacted base of a solar cell that accounts for three-dimensional transport. The input parameters of the model that characterize the back surface are: recombination velocity at the contacts; recombination velocity between the contacts; fraction of surface area covered by the contacts; and the contact spacing. We test this model experimentally by conducting spatially resolved minority-carrier lifetime measurements on silicon wafers with point contacts of various sizes and spacings. The diode saturation currents derived from the lifetime measurements agree with the values predicted by the analytic model. Copyright © 2005 John Wiley & Sons, Ltd.