C.1
1.
2.
C
Some aspects of surface recombination
In this appendix we look at several aspects of surface recombination for a p-type substrate
with dopant concentration N B . In Section C.1 we look at the case when the surface
recombination velocity is S → ∞. The opposite case, S = 0, is studied in Section C.2.
Finally, in Section C.3 we look at how the open circuit voltage of solar cells is dependent
on the absorber thickness, if S = 0.
Infinite surface recombination velocity S
In order to calculate the current density, first the minority-carrier distribution should be
worked out. For this we start with the continuity equation,
Taking into account that in the quasi-neutral region the electric field is zero, that there is
no generation, and that we are considering the steady state condition, this equation reduces
to
The general solution for this reduced continuity equation is:
To solve this problem, we need to apply the right boundary conditions:
with n B0 the thermal equilibrium electron concentration in the p-type Si.
δn(x = W) = 0 expressing the fact that for x = W the recombination velocity S is
infinite.
We then find the following set of equations