# IV Curve

The IV curve of a solar cell is the superposition of the IV curve of the solar cell diode in the dark with the light-generated current.[1] The light has the effect of shifting the IV curve down into the fourth quadrant where power can be extracted from the diode. Illuminating a cell adds to the normal "dark" currents in the diode so that the diode law becomes:

where IL = light generated current.

The effect of light on the current-voltage characteristics of a p-junction.

The equation for the IV curve in the first quadrant is:

$I={I}_{L}-{I}_{0}\left[\mathrm{exp}\left(\frac{qV}{nkT}\right)-1\right]$

The -1 term in the above equation can usually be neglected. The exponential term is usually >> 1 except for voltages below 100 mV. Further, at low voltages the light generated current IL dominates the I0 (...) term so the -1 term is not needed under illumination.

$I={I}_{L}-{I}_{0}\left[\mathrm{exp}\left(\frac{qV}{nkT}\right)\right]$

Light Biased IV Curve Calculator

Several important parameters which are used to characterise solar cells are discussed in the following pages. The short-circuit current (ISC), the open-circuit voltage (VOC), the fill factor (FF) and the efficiency are all parameters determined from the IV curve.