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VOLUME 62 (1995) | ISSUE 5 |
PAGE 407
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Photovoltaic effect in asymmetrical donor-acceptor organic superlattices
Agranovich V.M., La Rocca G.C., Bassani F.
We predict a novel photovoltaic mechanism in donor-accept or superlattices. We consider an asymmetrical organic superlattice such as...D-A-N-D-A-N-D-A' JV...P where D,A and JV indicate layers of materials which are, respectively, donor, acceptor and neither donor nor acceptor, all neutral in the ground state. In such a structure, the lowest lying electronic excitations are charge-transfer excitons (CTEs) at the D-A interfaces with electrons displaced from the donor to the acceptor side. We show that the excitation of CTEs under illumination is accompanied by the appearance of a macroscopic voltage drop along the growth direction. The resulting average electric Held can separate and drive the photogencrated free carriers (partly coming from the ionization of the CTEs themselves) producing a photovoltaic current.
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