Novel architectures for flexible electrochemical devices and systems

Kawahara, J.
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Electrically conducting polymers were discovered in the late 1970s. This finding generated a whole new research area named organic electronics, an area which has attracted great interest and tremendous achievements, in terms of devices and applications, have been reached by different research groups all over the world. Replacing inorganic materials by their organic counterparts in various kinds of electronic devices provides novel device functionalities as well as new opportunities in device manufacturing. One of the major advantages of utilizing organic materials in electronic devices is the high degree of freedom regarding fabrication methods. Since organic materials can be processed from solution various printing, coating and lamination techniques can be used to manufacture entire electronic systems on flexible carriers and substrates in a truly reel-to-reel fashion.

The main theme of this thesis relates to exploring novel device architectures to enable easy manufacturing of flexible electrochromic displays based on organic materials. After the introduction, the second part of the thesis treats some of the fundamentals of conducting polymers, and the third part explains the building blocks of matrix-addressed electrochromic displays: those systems combine electrochemical transistors and electrochromic display pixels. A brief introduction to printed electronics is also given in the fourth section. Then, active matrix addressed displays utilizing electronic vias manufactured through the substrate, which enable to use the substrate more efficiently in the resulting three-dimensional architecture, are presented in the fifth section. This novel system arrangement results in a matrix-addressed display with a relatively high fill-factor since its subcomponents are located on opposite sides of the substrate. The sixth section of the thesis is related to the achievement of passive matrix addressed displays. The architecture and the manufacturing process of these electrochromic displays are both very simple: an electrolyte is sandwiched in between the counter and the pixel electrode layers. The electrode materials chosen results in a non-linear current versus voltage characteristics, which enables matrix addressability also without the transistors. At last, in the seventh section, nanofibrillated cellulose (NFC) is used as the scaffold for either an electroactive polymer or the electrolyte. Various components, such as electrochromic pixels and electrochemical transistors, can be built from the resulting solid films thanks to the stable, soft and tacky properties of the hybridized NFC layer. Hence, a new concept for integration and reconfiguration of electronic systems consisting of electrochemical devices is achieved.

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Linköping Studies in Science and Technology