High Fill Factor Polymer Solar Cells Incorporating a Low Temperature Solution Processed WO3 Hole Extraction Layer

Authors

  • Tobias Stubhan,

    Corresponding author
    1. Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany
    • Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany.
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  • Ning Li,

    1. Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany
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  • Norman A. Luechinger,

    1. Nanograde Llc., Wolfgang-Pauli-Strasse, P/O Box 239, 8093 Zurich, Switzerland
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  • Samuel C. Halim,

    1. Nanograde Llc., Wolfgang-Pauli-Strasse, P/O Box 239, 8093 Zurich, Switzerland
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  • Gebhard J. Matt,

    1. Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany
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  • Christoph J. Brabec

    Corresponding author
    1. Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany
    2. Bavarian Center for Applied Energy Research (ZAE Bayern), Haberstraße 2a, 91058 Erlangen, Germany
    • Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, Martensstraße 7, 91058 Erlangen, Germany.
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Abstract

We demonstrate solution-processed tungsten trioxide (WO3) incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) with active layers comprising either poly(3-hexylthiophene) (P3HT) or poly[(4,4'-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,50-diyl] (Si-PCPDTBT) mixed with a fullerene derivative. The WO3 layers are deposited from an alcohol-based, surfactant-free nanoparticle solution. A short, low-temperature (80 °C) annealing is sufficient to result in fully functional films without the need for an oxygen-plasma treatment. This allows the application of the WO3 buffer layer in normal as well as inverted architecture solar cells. Normal architecture devices based on WO3 HELs show comparable performance to the PEDOT:PSS reference devices with slightly better fill factors and open circuit voltages. Very high shunt resistances (over 1 MΩ cm2) and excellent diode rectification underline the charge selectivity of the solution-processed WO3 layers.

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