An ideal solar cell may be modelled by a current source in parallel with a diode; in practice no solar cell is ideal, so a shunt resistance and a series resistance component are added to the model. The resulting equivalent circuit of a solar cell is shown on the left. Also shown, on the right, is the schematic representation of a solar cell for use in circuit diagrams.

By the Shockley diode equation, the current diverted through the diode is:

where

I

_{0} = reverse saturation current

n = diode ideality factor

q = elementary charge

k = Boltzmann's constant

T = absolute temperature

Temperature affects the characteristic equation in two ways: directly, via T in the exponential term, and indirectly via its effect on I0. The net effect is to reduce V

_{OC} linearly with increasing temperature. The magnitude of this reduction is inversely proportional to V

_{OC}; that is, cells with higher values of V

_{OC} suffer smaller reductions in voltage with increasing temperature.

Author : Hamid - From: IRAN