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 I_L = 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=IL−I0[exp(qVnkT)−1] $I = I_{L} - I_{0} [\exp (\frac{q V}{n k T}) - 1]$

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 I_L dominates the I₀ (...) term so the -1 term is not needed under illumination.

I=IL−I0[exp(qVnkT)] $I = I_{L} - I_{0} [\exp (\frac{q V}{n k T})]$

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

1. Lindholm FA, Fossum JG, Burgess EL. Application of the superposition principle to solar-cell analysis. IEEE Transactions on Electron Devices. 1979 ;26:165–171.

IV Curve

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