Free-to-free carrier recombination

A free-carrier-to-free-carrier recombination (bi-molecular) pathway is also included. Free-to-free recombination is described using equation [equ:freetofree]

\[R_{free}=k_{r}(n_{f}p_{f}-n_{0}p_{0}) \label{equ:freetofree}\]

in some situations where one is trying to fit rate equations to the model it can be useful to have equation [equ:freetofree] written in another form,

\[R_{free}=k_{r}(n_{f}p_{f}-n_{0}p_{0})^{\frac{\lambda+1}{2}} \label{equ:freetofree_lambda}\]

this can be turned on using the option called Enable \(\lambda\) power in free to free recombination. in the configure window of the Electrical parameter editor.

Free to free recombination is equivalent to Langevin recombination. However, most organic solar cells have a great deal of trap states and an ideality factor greater than 1.0 suggesting that free-to-free recombination is not the dominant mechanism. See section 9.12 for a general discussion on the need for trap states and why generally Langevin recombination should not be used in organic solar device models.

Auger recombination

Auger recombination is as

\[R^{AU}=(C^{AU}_{n}n+C^{AU}_{p}p)(np-n_{0}p_{0})\]

where \(C^{AU}_{n}\) and \(C^{AU}_{p}\) are the Auger coefficient of electrons and holes in \(m^6 s^{-1}\). This can be set in the electrical paramter editor.