Solar cell - current delivered by the illuminated diode


Operation of a solar cell can be understood from the equivalent circuit at right. Light, of sufficient energy (greater than the bandgap of the material), creates mobile electron–hole pairs in a semiconductor. Charge separation occurs because of a pre-existing electric field associated with the p-n junction in thermal equilibrium (a contact potential creates the field). This charge separation between positive holes and negative electrons across a p-n junction (a diode) yields a forward voltage, the photo voltage, between the illuminated diode terminals. As has been noted earlier in the terminology section, the photo voltage is sometimes referred to as the photo emf, rather than distinguishing between the effect and the cause. The charge separation causes a photo voltage that drives current through any attached load.

The current delivered by the illuminated diode, to the external circuit is calculated by the shown formula

Related formulas


Icurrent delivered by the illuminated diode (A)
ILgreatest current obtained under short-circuit conditions (A)
I0reverse saturation current (A)
qelementary charge
Vthe voltage (V)
mideality factor (dimensionless)
kBoltzmann constant
Tabsolute temperature (K)