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Role of the effective mass and interfacial dipoles on exciton dissociation in organic donor-acceptor solar cells

Title data

Schwarz, Christian ; Tscheuschner, Steffen ; Frisch, Johannes ; Winkler, Stefanie ; Koch, Norbert ; Bässler, Heinz ; Köhler, Anna:
Role of the effective mass and interfacial dipoles on exciton dissociation in organic donor-acceptor solar cells.
In: Physical Review B. Vol. 87 (2013) Issue 15 .
ISSN 0163-1829
DOI: https://doi.org/10.1103/PhysRevB.87.155205

Official URL: Volltext

Abstract in another language

Efficient exciton dissociation at a donor-acceptor interface is the crucial, yet not fully understood, step for obtaining high efficiency organic solar cells. Recent theoretical work suggested an influence of polymer conjugation length and of interfacial dipoles on the exciton dissociation yield. This necessitates experimental verification. To this end, we measured the dissociation yield of several polymer/C60 planar heterojunction solar cells up to high electric fields. The results indeed prove that the yield of exciton dissociation depends strongly on the conjugation length of the polymers. Complementary photoemission experiments were carried out to assess the importance of dipoles at the donor-acceptor interfaces. Comparison of exciton dissociation models with experimental data shows that the widely used Onsager-Braun approach is unsuitable to explain photodissociation in polymer/C60 cells. Better agreement can be obtained using “effective mass” models that incorporate conjugation length effects by considering a reduced effective mass of the hole on the polymer and that include dielectric screening effects by interfacial dipoles. However, successful modeling of the photocurrent field dependence over a broad field range, in particular for less efficient solar cell compounds, requires that the dissociation at localized acceptor sites is also taken into account.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie - Univ.-Prof. Dr. Anna Köhler
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 11 Feb 2015 11:05
Last Modified: 11 Feb 2015 11:05
URI: https://eref.uni-bayreuth.de/id/eprint/6690