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Understanding the open circuit voltage in organic solar cells on the basis of a donor-acceptor abrupt (p-n++) heterojunction

•Voc in organic solar cells is quantified by considering band bending at the heterojunction.•The non intentional doping in organic heterojunctions determines band bending.•Fullerene based organic solar cells form an abrupt p-n heterojunction.•The dominant recombination determining Voc occurs at the...

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Bibliographic Details
Published in:Solar energy 2019-05, Vol.184, p.610-619
Main Authors: Nolasco, J.C., Castro-Carranza, A., León, Y.A., Briones-Jurado, C., Gutowski, J., Parisi, J., von Hauff, E.
Format: Article
Language:English
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Summary:•Voc in organic solar cells is quantified by considering band bending at the heterojunction.•The non intentional doping in organic heterojunctions determines band bending.•Fullerene based organic solar cells form an abrupt p-n heterojunction.•The dominant recombination determining Voc occurs at the heterojunction. By using electrical characterization and classical solid state semiconductor device theory, we demonstrate that the open circuit voltage (Voc) in organic solar cells based on non-intentional doped semiconductors is fundamentally limited by the built-in potential (Vbi) originated at a donor-acceptor abrupt (p-n++) heterojunction in case of selective contacts. Our analysis is validated using P3HT:PCBM devices fabricated in our research group. We also demonstrate that such a result can be generalized using data already reported in literature for fullerene-based solar cells. Finally, we show that the dependence of Voc on the device contacts can be understood in terms of the potential barriers formed by the Fermi level alignment of semiconductors at the heterojunction and at the Schottky junctions.
ISSN:0038-092X
1471-1257
DOI:10.1016/j.solener.2019.04.031