The available experimental and theoretical data suggest that if the exciton formed in photovoltaic devices leads to a Coulombically bound electron-hole pair at the interface, the electron and hole are unlikely to separate into free charge.  Considering an idealized model Hamiltonian, we explore in this work the possibility that an exciton localized away from the donor-acceptor interface can efficiently produce a relatively well separated electron-hole pair. Non adiabatic electron transfer theory, modified to take into account of the multi acceptor structure, has been employed to compute charge transfer reaction rate constants between a donor and a cluster of acceptors. Several different geometries have been considered for the cluster of acceptors.  Effective electronic coupling between donor and acceptor has been estimated from a phenomenological formula based on superexchange theory. The modelling shows that there is a optimum range of distances over which the charge separation can take place which may lead to the formation of quasi-free charge. The connection between these models and recent computational chemistry modelling of the photovoltaic donor-acceptor interface is discussed.

Charge separation rates between a donor and a cluster of acceptors: Impact on the physics of organic photovoltaics interfaces

243rd National Meeting (2012)

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