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In the context of organic solar cells, electron-hole dissociation is sometimes mentioned with regard to excitons (refs 1, 2) and sometime with regard to geminate pairs (refs 3, 4).

Also, exciton binding energy is 10meV (Wannier) - 1eV (Frenkel), while geminate pair binding energy is generally up to 0.5eV.

So what's the difference between an exciton and a geminate pair?

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A geminate pair can be considered as a charge-transfer exciton, i.e., when an electron from the electron-hole (exciton) pair in some homogeneous material experiences a transfer through the interface between electron donor and electron acceptor materials. The electron in the electron-accepting material and the hole in the electron-donor material remain bound by electrostatic interaction, so they exist as a geminate pair. The binding energy of this pair is less as compared to the exciton in the homogeneous medium by the difference in electron affinities of the contacting materials.

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