A model for solar cells

A solar cell electrical model which gives a voltage and temperature function with parameters constant for a given cell is proposed. It is valid from dc to a few megahertz for EMC analysis. The admittance components Gp and Cp are derived from a theoretical study of the junction. The conductance Gp consists of four terms in parallel where exponential laws come from recombination phenomena near the junction and outside the depletion domain. Two terms for the capacitance Cp represent the barrier and the diffusion capacitance. The Gp (v) and Cp (v) functions are determined by measurements of the impedance variation with frequency by means of a network analyzer at fixed dc polarization voltage values. The cell model constants are computed by a least square regression on Cp (v) and Gp (v) functions. Experimental results prove that ambiant temperature measurements are sufficient to determine the cell parameters used to calculate Cp and Gp at any temperature or voltage.