The most basic of the current-voltage measurments (IV) in the previous section is often supplemented by other IV measurements since the principle of superposition shows that the IV curve under illumination is the IV curve in the dark shifted by the light generated current (See https://www.pveducation.org/pvcdrom/solar-cell-operation/iv-curve). However, there are no idealities in solar cells so that by comparing the measurements under conditions enables the determination of sollar cell parameters. For example, the dark IV curve will give a good measure of the cell shunt resistance. Comparing the Suns-Voc with the light IV gives a good estimate of the cell series resistance.