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:
= 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 VOC
linearly with increasing temperature. The magnitude of this reduction is inversely proportional to VOC
; that is, cells with higher values of VOC
suffer smaller reductions in voltage with increasing temperature.