Fig 1: A NOR gate by all-printed electrochemical transistors. The research is supported by the "OPEN" project within COE, Center of Organic Electronics, LiU and includes joint projects with the physics department (IFM) and the department of Science and Technology (ITN) at Linköping University.
Organic electronics is an emerging branch of electronics, which provides an option to use organic materials in electronic devices and circuits for some particular applications. Because of their remarkable mechanical flexibility, low-cost and tunable functionality, organic electronics attracts growing attention currently and tremendous effort has been devoted to organic semiconductors, dielectrics and light emitters. However, organic components behave differently from traditional silicon devices and in many cases their internal mechanisms are not fully understood. Our work is mainly focused on the following aspects: modelling of organic transistors, design methodology for circuit design and organic nanoelectronics.
Our early contributions in the field concerned the electrochemical transistor (ECT) which are printable using ink-jet or screen printing. These components use electrochemical doping of a semiconducting polymer to modulate the current through the transistors. There is no comparable silicon device but we have shown that the behaviour is similar to that of vacuum tubes, albeit with inverse polarity and lower working voltages. Our work has been focused on developing SPICE models, a design methodology and electrical design rules for ECT circuits. Logic inverters, ring oscillators, and NOR/NAND gates have been demonstrated using our design methodology, paving a feasible and low-cost way for mass production of electrochemical circuits (Fig. 1).
Fig 2: A compact model for electrolyte-gated field effect transistors. Recently, a new generation of organic field effect transistors, named EGOFETs (electrolyte-gated field effect transistors), has been proposed by using polymer electrolyte as gates. We have presented a compact model to simulate the dc performance of the EGOFETs, taking the electric double layer capacitance, contact effect and gate leakage current into account. Comparisons between experimental data and model simulations exhibit good agreements (Fig. 2). The model is also applicable for conventional organic field effect transistors with insulating gate dielectrics. Further developments, including transient models and H-SPICE device library, are still under investigation.
Finally, we are involved in the design of organic components in the nano-scale format. Nano-scale electronic devices are studied by self-assembly of biomolecules Fig 3: A typical helical structured nanofiber. (amyloid fibrils/DNA) bringing new issues to the understanding of the components as well as to circuit design, interconnection and layout techniques. For organic nanoelectronics, we intend to electrically functionalize helical nanostrucutres and explore their potential applications in high frequency resonance and stretchable nanoelectronic devices. An example of a helical structure by buckling a nanofiber is shown in Fig. 3.
- D. Tu, L. Herlogsson, L. Kergoat, X. Crispin, M. Berggren, and R. Forchheimer, “A static model for electrolyte-gated organic field effect transistors,” IEEE Trans. Electron Devices, vol. 58, no. 10, pp. 3574-3582, Oct. 2011.
- D. Tu and R. Forchheimer, “Self-oscillation in electrochemical transistors: An RLC modeling approach,” Solid-State Electron., vol. 69, no. , pp. 7-10, Mar. 2012.
- D. Tu, L. Herlogsson, X. Crispin, M. Berggren, and R. Forchheimer, “Parameter extraction for electrolyte-gated organic field effect transistor modeling,” 20th European Conference on Circuit Theory and Design (ECCTD), Linkoping, Sweden, 2011.
- D. Tu, D. Nilsson, and R. Forchheimer, “Electrochemical transistors gated with polyelectrolyte-decorated amyloid fibrils,” 8th International Conference of Thin-Film Transistors (ITC), Lisbon, Portugal, 2012.
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Last updated: 2014-10-14