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Saliou Ndiaye ¹, Mamadou Niane ¹, Modou Faye ¹, B. A. Bassirou ¹

Affiliations
1 Laboratoire des Semi-Conducteurs et d’Energie Solaire de la Faculté des Sciences et Techniques de l’Universite Cheikh Anta Diop de DAKAR, BP 5005, Dakar-fann, SN

Abstract

We studied the influence of parameters that govern the excitonic conversion phenomena in semiconductors. In this study we defined a surface conversion velocity of excitons to free electron-hole pairs b_s and a parameter of exciton dissociation in the space charge layer b (x) related to the electric field E(x). The influence of b_s on the electrons and excitons densities and on the short-circuit current shows that this parameteris a generation term for electrons and a recombination term for excitons. In the organic semiconductor where the excitons have a very short lifetime and a binding energy superior to thermal energy, an exciton conversion model is essential to increase the performance of these solarcells. Our study showed that the short circuit current has a high value when the exciton conversion speed is of the order of 10⁴ cm.s^-1.

Keywords

Exciton, Excitonic Conversion, Binding Coefficient.

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Saliou Ndiaye ¹, Modou Faye ¹, Mamadou Niane ¹, B. A. Bassirou ¹

Affiliations
1 Laboratoire Des Semi-Conducteurs Et D’Energie Solaire De La, Universite Cheikh Anta Diop De DAKAR, BP-5005, Dakar, Fann, SN

Abstract

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.

Keywords

Exciton, Coupling Coefficient, Exciton Recombination, Excitonic Conversion.

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