The paper describes a new method to characterize solar cell dynamic impedances in the dark with forward biasing using square wave inputs. The solar cell dynamic impedance is calculated from the output responses by MATLAB using the FFT technique to analyze harmonic contents. The impedances are shown as impedance loci plotted in the complex plane. Comparison is made with results obtained from available reports using sinusoidal inputs. The advantages of this method, compared with the sinusoidal input method, are less expensive equipment setup, simpler measurement, and reduction in measuring steps, yielding comparable results. (C) 2003 Elsevier B.V. All rights reserved.