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 simple smart pixels that are included in matrix displays, which are achieved on coated cellulose‐based paper using printing techniques. The ion‐electronic technology presented offers an opportunity to extend existing use of ordinary paper.

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-V͒ characteristics of these devices, however, the mechanism of current saturation ͑often referred to as pinch-off͒ 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.

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.

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An all-printed organic smart pixel is achieved through the combination of an electrochemical transistor and an electrochromic display cell. Smart pixels of this kind are arranged into a cross-point matrix resulting in an active-addressed display. This type of display has been realized on coated fine paper, operates at voltages less than 2 Volts and exhibits good bistability properties. Here we report on the operation characteristics of electrochemical smart pixels in which the ion concentration of the electrolyte has been varied.