Using electroluminescence of subcells for obtaining fundamental resistive-less dark IV characteristic of multi-junction solar cells

A new experimental method for obtaining resistive-less dark current-voltage (IV) characteristic of multi-junction solar cells has been developed. The method realizes by measuring dark voltage, dark current, and additional measurements of the electroluminescence (EL) intensity of subcells. It has been shown that in the resistive-less mode (low currents), the dark voltage depends logarithmically on the product of EL intensities of subcells. Experimental definition of this dependence has made it possible to determine the relationship between the intensities and the voltage. The method has been applied to a GaInP/GaAs solar cell, in which three effects have an influence on IV characteristic: the mismatch of photocurrents generated by subcells, the nonlinear series resistance, and counter-electromotive force. It has been experimentally found that the result of the method does not depend on these effects and allows obtaining a fundamental dark resistive-less IV characteristic of multi-junction solar cells.