Self-assembled organic molecules for electronic devices

  • Authors

    F.del Pozo,1 S. Fabiano,2 R. Pfattner,1 S. Georgakopoulos,1 S. Galindo,1 X. Liu,3 S. Braun,3 M. Fahlman,3 J. Veciana,1 C. Rovira,1 X. Crispin,2 M. Berggren,2 F. Leonardi,1 S. Casalini,1 Q. Zhang,1 D. Gutierrez,1 E. Marchante,1 N. Crivillers,1 M. Buhl,1 M. Mas-Torrent1

  • Publication

    Single Crystal-Like Performance in Solution-Coated Thin-Film Organic Field-Effect Transistors
    Advanced Functional Materials, 26 (14), 2379-2386, 2016

    Electrolyte-Gated Organic Field-Effect Transistor Based on a Solution Sheared Organic Semiconductor Blend
    Advanced Materials, 28 (46), 10311-10316, 2016

    An Electrically Driven and Readable Molecular Monolayer Switch Based on a Solid Electrolyte
    Angewandte Chemie-International Edition, 55 (1), 368-372, 2016
  • Figure

    A) Scheme of the bar-assisted meniscus shearing technique (BAMS) and optical microscopy image of a crystalline semiconducting film. B) Self-assembled monolayer (SAM) of a ferrocene molecule and electrochemically switchable fabricated employing a solid electrolyte. The reading of the switch was monitored by its capacitance response.

The self-assembly of electroactive molecules on surface is a promise route to fabricate electronic devices. Here, in the framework of the ERC StG 2012-306826 e-GAMES project, we reported on two types of devices: A) Organic field-effect transistors (OFETs) based on self-assembled semiconducting thin films, and B) Molecular switches based on electroactive molecular self-assembled monolayers (SAMs).

  1. Ideal electrical characteristics in organic materials are typically only found in single crystals. Tiresome growth and manipulation of these hamper practical production of flexible OFETs circuits. We demonstrated that the use of the bar-assisted meniscus shearing (BAMS) technique with blends of organic semiconductors and the insulating polymer polystyrene (PS) gives rise to highly crystalline semiconducting films with high reproducibility. During the crystallisation process, a vertical phase separation takes place leading to the passivation of the dielectric surface by PS and simultaneously the formation of a continuous self-encapsulated polycrystalline organic semiconductor thin film. The resulting OFETs exhibited ideal electrical characteristics such as electric field- and temperature-independent charge carrier mobility and no bias stress effects.

    Further, these films have been successfully applied in electrolyte-gated organic field-effect transistors (EGOFETs), which are recently gaining much attention because they can operate in water and, thus, can be directly turned into biochemical applications. We showed for the first time that EGOFETs can be fabricated by printing techniques compatible with upscaling (i.e., BAMS) and, remarkably, that the use of semiconducting blends provides devices with state-of-the-art performance and enhanced stability in aqueous environment due to the protecting PS top layer.

  2. Self-assembled monolayers (SAMs) of bistable molecules that can be externally interconverted between two or more states with different properties show great potential as active elements in information storage in future emerging devices. SAMs of electroactive molecules have been exploited in the last few years as electrochemical switches. Typically, the state of these switches could be read out through their optical and/or magnetic responses. These output reading processes are difficult to integrate into devices and in addition there is a need to use liquid environments to switch the redox-active molecular systems. Here, we overcome both these challenges employing SAMs of ferrocene and using an ion-gel as electrolyte medium achieving an unprecedented solid state device based on a single molecular layer. Further, electrochemical impedance has been successfully exploited as the output of the system. These results represent a step forward in the field raising the perspectives of employing hybrid surfaces as molecular switches for their future integration in electronic applications.
1 Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), CIBER-BBN, Spain
2 Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, Sweden
3 Department of Physics, Chemistry and Biology, Linköping University, Sweden.

Institut de Ciència de Materials de Barcelona
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