Journal Article

PreJuSER-16879

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

Schafer, S. ; Petersen, A. ; Wagner, T. A. ; Kniprath, R. ; Lingenfelser, D. ; Zen, A. ; Kirchartz, T.FZJ* ; Zimmermann, B. ; Wurfel, U. ; Feng, X. J. ; Mayer, T.

2011
APS College Park, Md.

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Please use a persistent id in citations: http://hdl.handle.net/2128/10913  doi:10.1103/PhysRevB.83.165311

Abstract: In this paper we investigate the performance and stability of small-molecule organic solar cells with respect to the indium tin oxide (ITO)/organic interface. Different zinc-phthalocyanine (ZnPc)/fullerene (C-60) cell architectures with and without ITO O-2-plasma treatment are compared and tested with respect to their degradation behavior under illumination in inert atmosphere. Photoelectron spectroscopy (UPS and XPS) shows that the O-2-plasma treatment increases the ITO work function from 4.3 eV up to 5.6 eV. We find that both the increased ITO work function as well as the introduction of an electron blocking layer between ITO and the mixed donor/acceptor layer increases the open-circuit voltage V-oc by more than 200 mV. For both cases our continuum approach device simulation quantitatively relates the increase of V-oc to a reduced contact recombination and thus a reduced dark current. For cells built on ozone treated ITO we find a fast cell degradation caused by the UV part of the AM 1.5 spectrum. We identify the degradation, which manifests itself in a decrease of V-oc of up to 25%, as a partial reversion of the plasma induced ITO work function increase. Additionally, we demonstrate that the degradation can be reduced by structural changes in the cell architecture, leading to improved cell stability. We present a comprehensive study of the recombination at the ITO/organic interface and its influence on the open-circuit voltage and the cell stability.

Keyword(s): J

Note: The authors thank Stephen En Rong Tay, Nguyen Thi Minh Hieu, and Mathias Geissler for their help with cell measurements and Alexandros Dimopoulos for the helpful discussions. We also thank the BMBF for the financial support in the framework of the OPEG project (13N9715). T. K. acknowledges support by an Imperial College Junior Research Fellowship.

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Contributing Institute(s):

1. Photovoltaik (IEK-5)

Research Program(s):

1. Erneuerbare Energien (P11)

Appears in the scientific report 2011

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