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Tailoring organic heterojunction interfaces in bilayer polymer photovoltaic devices

Nature Materials volume 10, pages 450–455 (2011)Cite this article

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Abstract

In an ideal model, a p–n junction is formed by two stacked slabs of semiconductors. Although the construction of actual devices is generally more complex, we show that such a simple method can in fact be applied to the formation of organic heterojunctions. Two films of the organic semiconductors poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) can be connected by a simple film-transfer method without disturbing their flat surfaces. Each film can further be modified with a surface-segregated monolayer to tune the strength and direction of the surface dipole moment. Using this method, we fabricated bilayer organic photovoltaic devices with interfacial dipole moments that were selected to align the energy levels at the heterojunction. The open-circuit voltages of the P3HT/PCBM devices could be tuned over a wide range between 0.3 and 0.95 V, indicating that, even if the same combination of bulk materials is used, the interfacial properties drastically alter the performance of organic photovoltaic devices.

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Figure 1: Schematic representation and energy diagrams of the P3HT/PCBM bilayer devices.
Figure 2: Chemical structures of the materials used and schematic representations of the insertion of the SSM.
Figure 3: J–V characteristics under 100 mW cm−2, AM1.5 irradiation of three types of bilayer device fabricated by the CFT method.
Figure 4: UPS spectra for the four types of film using He(I) irradiation.

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Acknowledgements

Y.F.G. thanks the Chinese Scholarship Council for financial support.

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Authors and Affiliations

  1. Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

    Akira Tada, Yanfang Geng, Kazuhito Hashimoto & Keisuke Tajima

  2. Department of Materials, School of Materials, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China

    Yanfang Geng

  3. HASHIMOTO Light Energy Conversion Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), Japan

    Qingshuo Wei, Kazuhito Hashimoto & Keisuke Tajima

Authors
  1. Akira Tada
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  2. Yanfang Geng
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  3. Qingshuo Wei
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  4. Kazuhito Hashimoto
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  5. Keisuke Tajima
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Contributions

A.T. and Y.F.G. contributed equally to this work. A.T. fabricated and evaluated the OPV devices and carried out the external quantum efficiency, XPS, UPS and X-ray reflectivity measurements. Y.F.G. synthesized and characterized the P3DDFT and carried out the XPS depth profile measurements. Q.S.W. synthesized and characterized the FC8. K.H. and K.T. directed the research. A.T., K.H. and K.T. wrote the paper.

Corresponding authors

Correspondence to Kazuhito Hashimoto or Keisuke Tajima.

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The authors declare no competing financial interests.

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Tada, A., Geng, Y., Wei, Q. et al. Tailoring organic heterojunction interfaces in bilayer polymer photovoltaic devices. Nature Mater 10, 450–455 (2011). https://doi.org/10.1038/nmat3026

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