Donor-acceptor heterojunctions

The use of interpenetrating donor-acceptor heterojunctions, such as PPVs/C60 composites, polymer/CdS composites, and interpenetrating polymer networks, substantially improves photoconductivity, and thus the quantum efficiency, of polymer-based photo-voltaics. In these devices, an exciton is photogenerated in the active material, diffuses toward the donor-acceptor interface, and dissociates via charge transfer across the interface. The internal electric field set up by the difference between the electrode energy levels, along with the donor-acceptor morphology, controls the quantum efficiency of the PV cell (Fig. 51). 

Yu, G., Gao, J., Hummelen, J.C., Wudl, F., and Heeger, A.J. (1995) Polymer photovoltaic cells enhanced efficiencies via a network of internal donor-acceptor heterojunctions. Science 270, 1789-1791. 

Fig. 3 Contemporary organic solar cell devices are based on donor/acceptor heterojunction device architectures, (a) Energy level diagram, (b) Planar heterojunction conligmation. (c) Bulk heterojunction configuration...

G. Yu, AJ. Heeger, Charge separation and photovoltaic conversion in polymer composites with internal donor/acceptor heterojunctions, J. Appl. Phys. 78 (1995) 4510 1515. 

Organic Donor-Acceptor Heterojunction Solar Cells... 

Organic Donor-Acceptor Heterojunction Solar Cells (a) (b) (c)... 

Recently, geminate polaron pairs have been proposed for polymer-polymer [35,56,57] and polymer-fullerene [58,59] blends as photoinduced intermediates. Here the hole and electron remain coulombically bound across the interface of the donor-acceptor heterojunction. Only via an electric field and/or a temperature-assisted secondary process, these geminate polaron pairs are dissociated, leading to free charge carriers. This can have a considerable effect on the achievable charge separation efficiencies, since the geminate... 

Pacios R, Bradley DDC (2002) Charge separation in polyfluorene composites with internal donor/acceptor heterojunctions. Synth Met 127 261... 

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