Printed plastic transistors

Figure 4. I-V characteristic of a printed plastic transistor with regioregular poly(3-hexylthiophene) semiconducting layer on polyimide dielectrics coated ITO plastic substrate with printed Ag drain and source electrodes.

Figure 20. Structure of an all-printed plastic transistors by Bao et al. G gate S source D drain [89], Reprinted with permission. Copyright 1997. American Chemical Society.

Figure 21. The current voltage characteristics of a printed plastic transistor operated in the accumulation mode at different gate voltages.

The field-effect mobilities of printed plastic transistors are slightly higher (about two times) when measured in air compared to under vacuum (10 or 10 Torr) [89]. Spin-coated films tend to have lower mobility than cast or printed films possibly because the latter films have better ordering resulting from slower solvent evaporation and consequent slower crystal growth. 

Bao, Z. Feng, Y. Dodabalapur, A. Raju, V. Lovinger, A. 1997. High-performance plastic transistors fabricated by printing techniques. Chem. Mater. 

Project (by Sarnoff Corp with DuPont de Nemours and Co Central Research and Development) to print organic transistors on plastic for electronic displays and circuits. The goal is to develop materials, thin flexible plastic substrates, and methods for continuous high-resolution printing. 

M. Lefenfeld, G. Blanchet, and J. A. Rogers. High-Performance Contacts in Plastic Transistors and Logic Gates That Use Printed Electrodes of DNNSA-PANl Doped with Single-Walled Carbon Nanotubes. Advanced Materials, 15(14) 1188-1191, 2003. 

Methods for printing of transistor arrays on plastic substrates have been described in detail (33). The substrate can be made of an insulating polymer, such as PET, poly(ethersulfone), poly(carbon-ate), or a PI film. Small drops of a conductor or a semiconductor can be deposited in precise locations on the substrate to create fine lines having a width smaller than 50 /rm, with precisely controlled spaces between the lines. 

G.M. Duthaler, P.T. Kazlas, and P. Drzaic, Method for printing of transistor arrays on plastic substrates, US Patent 6 506 438, assigned to E Ink Corporation (Cambridge, MA), January 14, 2003. 

DuPont s nanotechnology activities include the development of a polyaniline containing single-walled carbon nanotubes to be used in a laser ablation dry printing process to produce plastic transistors. 

Menard, E. Nuzzo, R. G. Rogers, J. A. 2005. Bendable single crystal silicon thin film transistors formed by printing on plastic substrates. Appl. Phys. Lett. 86 093507. 

Micro-contact printing can be used in plastic electronics to form high-resolution source/drain electrodes with short channel lengths [14]. Depositing an organic semiconductor on top of these electrodes yields a transistor with a layout like that... 

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... 

Therefore, it is possible to summarize the motivation for printed electronics quite simply. Printed electronics is attractive as a means of fabricating electronic systems where reduced cost per unit area is an advantage. Based on the poor linewidth of printed electronics, this will almost certainly only be true for systems with low functional density, i.e., systems with no need for dense arrays of tiny transistors, etc. Printed electronics also potentially enables the use of low cost, flexible substrates such as plastics and metallic foils, and additionally, by using different inks in an inkjet printer, it also allows for the easy deposition of a range of materials onto a substrate in a spatially specific way. 

Kawase et al. [17] fabricated All-polymer thin film transistors by inkjet printing technique. They used these transistors as active-matrix backplane for information displays. This field has been dominated by amorphous Si TFTs and large liquid crystal displays with an amorphous Si TFT active matrix backplane have been manufactured at a reasonable cost. An organic TFT is expected to reduce the cost even more, and to be applied to flexible displays based on a plastic substrate. The TFT characteristics required for active-matrix displays are (1) sufficient drain cmrent, (2) low off current, (3) low gate leakage current through an insulator, (4) small gate overlap capacitance and (5) uniform characteristics. 

Another important applieation field for printable electronics are backplanes for active-matrix displays. These baekplanes, which contain up to several millions of transistors, ideally will be fully printed. When flexible plastic substrates are used, the displays can be bendable and rollable while retaining their original performance. The stacked layers of materials are extremely thin, in the order of hundreds of nanometers, and therefore light-weight ideal properties for an E-book reader. 

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