Evaluation of the solar cell internal resistance in I-V measurements under flash illumination

Abstract

At fabrication of the concentrator SCs one of the central problems is radical reduction of the internal ohmic losses. To distinguish the presence of the internal resistance components in an I-V curve, uncertainty due to the shape of the p-n junction(s) I-V curve should be eliminated. In this connection, it is more adequate to analyze the shape of the "resistance curve", which can be constructed by subtraction of the voltage coordinates of the illuminated or dark I-V curve of a SC from those of the p-n junction at the same current magnitudes. In turn, the p-n junction I-V curve of a real SC can be constructed as a dependence of photocurrent Iph on open circuit voltage V oc in varying the illumination level from low up to the level producing Iph of a required magnitude. In the simplest case of a SC model with series resistance, the "resistance curve" is a straight line. In a general case, not only one, but several components of the "distributed" resistance may be present, so that the shape of the "resistance curve" may indicate this. In the present work, both hard- and software have been created for constructing the "resistance curves" in I-V measurements of the cells with using a flash solar tester. © 2012 American Institute of Physics.