20.3.3
where B i is another constant that is essentially independent of temperature. The exponent 3
was replaced by γ to account for possible other material-dependent temperature
dependencies. Hence, we find for the saturation current density
with B := B J B i . Substituting Eq. (20.12) into Eq. (20.9) yields
As the temperature dependence of J sc and B is very small, we can neglect it when
determining the derivative. Hence, we find
with V g = E g / q.
The slight increase in the generated current is due to a moderate increase in the photo
generated current resulting from an increased number of thermally-generated carriers. The
overall reduction of power at high temperatures shows that cold and sunny climates are
the best environments for placing PV systems.
Example
The temperature-dependent change of V oc for a c-Si solar cell with V oc (STC) = 700mV can be estimated with Eq.
(20.14): using E g (Si) = 1.12 eV, T(STC) = 298.15K and γ = 3, we find
Effect of irradiance on solar cell performance
Intuitively, the power output of a solar cell decreases considerably with decreasing
irradiance incident on the PV module. However, the quantitative evaluation of how
changing irradiance affects the PV module parameters is less straightforward than for the
effect of temperature. This is because solar manufacturers often do not explicitly provide
parameters that would allow to derive the PV module parameters at every irradiance level.
By definition the PV module efficiency is given as
where B i is another constant that is essentially independent of temperature. The exponent 3
was replaced by γ to account for possible other material-dependent temperature
dependencies. Hence, we find for the saturation current density
with B := B J B i . Substituting Eq. (20.12) into Eq. (20.9) yields
As the temperature dependence of J sc and B is very small, we can neglect it when
determining the derivative. Hence, we find
with V g = E g / q.
The slight increase in the generated current is due to a moderate increase in the photo
generated current resulting from an increased number of thermally-generated carriers. The
overall reduction of power at high temperatures shows that cold and sunny climates are
the best environments for placing PV systems.
Example
The temperature-dependent change of V oc for a c-Si solar cell with V oc (STC) = 700mV can be estimated with Eq.
(20.14): using E g (Si) = 1.12 eV, T(STC) = 298.15K and γ = 3, we find
Effect of irradiance on solar cell performance
Intuitively, the power output of a solar cell decreases considerably with decreasing
irradiance incident on the PV module. However, the quantitative evaluation of how
changing irradiance affects the PV module parameters is less straightforward than for the
effect of temperature. This is because solar manufacturers often do not explicitly provide
parameters that would allow to derive the PV module parameters at every irradiance level.
By definition the PV module efficiency is given as