Per-Olof Svensson

Active Matrix Displays Based on All‐Organic Electrochemical Smart Pixels Printed on Paper

An organic electronic paper display technology (see Figure and also inside front cover) is presented. The electrochromic display cell together with the addressing electrochemical transistor form si ...

On the Current Saturation Observed in Electrochemical Polymer Transistors

Electrochemical transistors based on conjugated polymers are proposed as a path to printed electronics on paper. The electrochemical doping/dedoping of conjugated polymers clearly plays a role in the current vs potential (I-V) characteristics of these devices, however, the mechanism of current saturation (often referred to as pinch-off) is not clearly understood, and the relationship between electrochemical devices and field-effect transistors is unclear. This paper offers a semiempirical model of the steady-state behavior of electrochemical transistors and compares this model with experimental observations of potential and electrochromic measurements within a device to illustrate the science behind the functionality observed. ©2006 The Electrochemical Society

A sensor circuit using reference-based conductance switching in organic electrochemical transistors

Using organic electrochemical transistors as sensors, the sample-receptor reaction often induces moderate changes only in the drain current dynamics as the gate voltage level is switched. Here, we report an electrochemical sensor circuit including electrochemical transistors based on poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate that puts out a static sensor response signal. The circuit includes a sample and a reference transistor that are both driven in the resistive mode at 0.1 V. Measurements were performed on aqueous salt electrolytes ranging from 100 to 500 mM concentrations. The signal-ON sensor circuit provides a tenfold increase in the sensitivity as compared to single transistor sensors.

PEDOT:PSS-Based Electrochemical Transistors for Ion-to-Electron Transduction and Sensor Signal Amplification

The chapter reports the use of organic electrochemical transistors in sensor applications. These transistors are excellent ion-to-electron transducers and can serve as very sensitive transducers in amperometric sensor applications. To further improve their sensitivity, we outline various amplification circuits all realized in organic electrochemical transistors.

Visualizing the electric field in electrolytes using electrochromism from a conjugated polymer

Electrochromic polymer films, employed as display elements, smart windows, and the base material for electrochemical electronic devices, can be addressed solely through ionic transport via an elect ...

Organic Electrochemical Smart Pixels

Major efforts have been spent during recent years in worldwide attempts to achieve an electronic paper technology; the common name for novel flexible displays utilizing substrates such as paper, plastics or thin metal sheets. Various kinds of technology are available that potentially will be used for an electronic paper, which differs from each other mainly with respect to the choice of active materials, substrates and manufacturing techniques. There are many applications for electronic paper technology, ranging from high-resolution displays used in electronic books to updateable large-area billboards. The latter suggests a novel electronic display function that could extend the utilization of cellulose-based paper, which is one of the most common materials ever produced by mankind, by using the paper as a thin and flexible carrier. The requirement for fast update speed in such large area applications would probably be a bit more relaxed compared to traditional display technologies, while low-power consumption and bi-stability are among the factors that should be further emphasized, together with the utilization of well-established printing techniques to enable low-cost manufacturing of the displays. The choice of active materials is therefore crucial in order to reach these objectives in reality and this paves the way for printable conjugated polymers with electrochromic properties. Chemical synthesis of these materials during the last decades has resulted in a vast variety of electrochromic polymers with custom-tailored functionality covering a broad range of optical absorption and electrical conductivities. This thesis review the studies done on the electrochemical switching of poly(3,4-ethylenedioxythiophene) (PEDOT). For this material both the electrical conductivity and the optical absorption is controlled by the oxidation state. Active matrix addressed displays that are printed on flexible substrates have been obtained by arranging electrochemical smart pixels, based on the combination of electrochemical transistors and electrochromic display cells, into cross-point matrices. The resulting polymer-based active-matrix displays are operated at low voltages and the same active material can be used in electrochemical transistors and conducting lines and in electrochromic display cells employing the electronic and the opto-electonic properties of the material, respectively. In addition to this, a switchable optical polarizer is briefly discussed. This is a device utilizing electrochromism of stretch-aligned polyaniline (PANI). The combination of two identical devices in a vertical architecture, orthogonally oriented with respect to each other, results in a filter in which the orientation of the polarized optical absorption is governed by the voltage polarity applied to the device.

All-organic electrochemical device with bi-stable and dynamic functionality

We will present organic electrochemical transistors that show both bi-stable and dynamic current modulation. In electrochemical devices, both ions and electrons are used as charge carriers. The device is all-organic and has been realized using common printing techniques, such as screen-printing. As the substrate, both cellulose-based paper and polyester foil have been used. PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrene sulphonic acid)) is used as the conducting and electrochemical active material. PEDOT:PSS is switched between different redox states, corresponding to semi-conducting and conducting states. Operating voltages is below 2V and on/off ratios up to 105 have been reached (typical value is 5000). The operation of these devices does not depend on any critical dimensions; typical dimensions used are around 200 microns. With a certain geometrical design the dynamic transistor can be employed for frequency doubling. For the bi-stable transistor the modulation of the current is done by direct electronic contact, compared to the dynamic transistor that is modulated by induction of electrochemistry. The electrolyte in these devices can either be solidified or a liquid. The bi-stable device in combination with a layer of Nafion as electrolyte demonstrates humidity sensor functionality. Since substrates based on paper and common printing techniques can be used for fabrication, this give rise to an environmental friendly and non-expensive device setup.