Organic Semiconductors

Organic semiconductors can potentially be used in low-cost, disposable devices for chemical or biochemical sensing. However, operating the device in an aqueous environment raises difficulties when it comes to operational voltages or stability. One approach to reduce the gate voltage is increasing the capacitance of the gate dielectric. Several different materials, including high-k dielectrics, ultra-thin cross-linked polymers, and electrolytes have been tested for this purpose. In particular, electrolyte gates offer extraordinarily large capacitances, up to several µF/cm2 at low frequencies. The high capacitance, which is the result of the electrical double layer formation at the electrolyte – semiconductor interface, makes low-voltage operation possible without high production costs. We investigate the behavior of organic thin-film transistors with an aqueous electrolyte gate. Electrochemical impedance spectroscopy and cyclic voltammetry measurements indicate a nearly perfectly polarizable interface with negligible parasitic Faradaic currents. For gate voltages below 1 V, a conductive channel is induced at the organic semiconductor/electrolyte interface via an electrical field effect. The transistor is stable for several hours and sensitive to changes in the ionic strength (as shown in the figure on the left) or the pH of the solution. These devices have, thus, the potential of being used in disposable chemo- or bio- sensing applications.



People on the project:

Felix Buth, Deepu Kumar


Selected publications:

  • Electrolyte-gated organic field-effect transistors for sensing applications
    F.Buth, D.Kumar, M.Stutzmann, J.A. Garrido
    Applied Physics Letter 98, 153302 (2011)
    Online Reference


  • Photoresponse and morphology of pentacene thin films modified by oxidized and reduced diamond surfaces
    W. Gajewski, M. Huth, F. Buth, B. Nickel, M. Stutzmann, and J. A. Garrido
    Physical Review B 80, 235311 (2009)
    Online Reference


Nanosystems Initiative Munich (NIM)

TUM Technische Universität München TUM Technische Universität München Physik Department Elektrotechnik und Informationstechnik TUM Technische Universität München

Upcoming Events

Benno Blaschke
Graphene SGFETs for biosensing applications

poster, Graphene Week 2013, Chemnitz, Germany


Jose A. Garrido
Graphene sensors for bioelectronic applications

plenary talk, Graphene Week 2013, Chemnitz, Germany


Roberta Caterino 
Novel functionalization of diamond surfaces for protein-based hybrid systems

talk, International Conference on Diamond and Carbons Materials, Riva del Garda, Italy


Roberta Caterino
Bio-photovoltaics based on hybrid systems of reaction centers and diamond

talk, International Conference on Diamond and Carbons Materials, Riva del Garda, Italy