Printed transistors, structure

This chapter summarizes some of our recent work in printing techniques and plastic electronics. It also presents new data from printed transistors that use several different organic semiconductors in a variety of device geometries. In all cases, we observed good performance. pCP for the source/drain electrodes is attractive because it provides a simple and potentially low-cost route to high resolution (i.e. small channel lengths, L) structures that can be used to build transistors which... 

Step coverage — From the process flow schematics shown previously, it is apparent that printed transistors inherently have substantial topology within their cross-sectional structure. As a consequence, step coverage becomes an important parameter in process optimization. Given the large steps (typically several tens of nm or more) and the use of relatively thin subsequent layers, it is important that the layers cover each other adequately liquids must be able to coat the vertical sidewaUs of steps during a multilayer print process. This places constraints on fluid viscosity, evaporation rate, wetting, etc. 

Regardless of the patterning technique employed, many electronic devices place requirements on the placement (registration) and size of the areas patterned. For example, a multiple layer field-effect transistor structure that could be patterned via printing is shown in Figure 4.5. 

Figure 12.14. Structure and fabrication process flow of a printed bottom-gated thin-film transistor (TFT).

Brandt, N., Fischer, T., Fugmann, U., Hahn, U., Hubler, A. and Zielke, D., Offset Printed Functional Polymer Structures for Transistors, Technologies for Polymer Electronics - TPE 04 (TITK). Internationales Symposium, Rudolstadt, 2004. 

Organic transistor matrix and organic fine printing technique. The chemical structure... 

The fabrication of organic transistors requires both patterned structures and thin continuous layers. Films can be produced by combining printing... 

Zielke, D. et al., Polymer-based organic field-effect transistor using offset printed source/drain structures, A/)/)/. Phys. Lett. 87 (12), 123508, 2005. 

Fig. 3.7. The structure of several functionalized pentacenes. (a) TIPS-pentacene, one of a family bulky group functionalized pentacenes developed by Anthony et al. [25]. (b) A soluble conversion material which can be printed and then converted into an insoluble transistor through heat exposure [26]. (c) A thiophene containing pentacene analog which incorporates a thiophene ring for greater stability [27]...

Figure 7.14 (a) Schematic diagram of the fabrication process and optical microscopy image of an inkjet-printed single-droplet transistor based on the P3HT/PS blend. P3HT/PS blend films printed from a CB/CHN mixed solvent had unique structures, with P3HT nanowires dispersed in a PS matrix. 

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