Surface Recombination of Excitons in Solar Cells

We studied the influence of parameters that govern the surface recombination of excitons in a silicon solar cell subjected to a monochromatic illumination.
In this study we considered two values of the exciton binding coefficient, b=3×10^-7cm³ s^-1 and b=10^-15cm³ s^-1, corresponding to strong coupling and weak coupling. We also defined a recombination velocity of excitons Sex reflecting loss of these pseudo particles to metal-semiconductor contacts. The study of excitonic recombination boils down to study the influence of recombination velocity S_ex on the carrier density. This study found that the recombination of excitons has no impact on electrons density when the coupling is low because exciton and electron diffuse independently with their own diffusion length. However, in the strong coupling we have a negative effect of this parameter on the densities of electrons and excitons. We note also that in these conditions the increase of the electron recombination velocity results in lower of excitons density. These results confirm the coupling theory between electron and exciton developed by R. Corkish and Y. Zhang.