A solar cell, also called a photovoltaic cell, converts solar energy into electrical energy. The V-I characteristics of a solar cell describe the relationship between the current flowing through the cell and the voltage applied across it. The product of the open-circuit voltage (V_OC ) and the short-circuit current (I_SC ) is known as the ideal power:
Ideal Power = V_OC × I_SC
The maximum useful power corresponds to the area of the largest rectangle that can be formed under the V-I curve. If Vm and Im are the voltage and current at this maximum power point, then : Maximum Useful Power = V_m × I_m The ratio of the maximum useful power to the ideal power is called the fill factor:
Fill Factor = (V_m × I_m ) / (V_oc × I_sc )