Controllable Molecular Doping and Charge Transport in Solution-Processed Polymer Semiconducting Layers

Authors

  • Yuan Zhang,

    1. Molecular Electronics, Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen (The Netherlands)
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  • Bert de Boer,

    1. Molecular Electronics, Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen (The Netherlands)
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    • Deceased.

  • Paul W. M. Blom

    Corresponding author
    1. Molecular Electronics, Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen (The Netherlands)
    2. Holst Centre High Tech Campus 31, 5605 KN Eindhoven (The Netherlands)
    • Molecular Electronics, Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen (The Netherlands).
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Abstract

Here, controlled p-type doping of poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) deposited from solution using tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) as a dopant is presented. By using a co-solvent, aggregation in solution can be prevented and doped films can be deposited. Upon doping the current–voltage characteristics of MEH-PPV-based hole-only devices are increased by several orders of magnitude and a clear Ohmic behavior is observed at low bias. Taking the density dependence of the hole mobility into account the free hole concentration due to doping can be derived. It is found that a molar doping ratio of 1 F4-TCNQ dopant per 600 repeat units of MEH-PPV leads to a free carrier density of 4 × 1022 m−3. Neglecting the density-dependent mobility would lead to an overestimation of the free hole density by an order of magnitude. The free hole densities are further confirmed by impedance measurements on Schottky diodes based on F4-TCNQ doped MEH-PPV and a silver electrode.

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