Carbon boosts plastic circuits

Plastic thin film transistors promise to enable flexible displays, radio frequency ID tags, electronic paper, and electronic textiles.

Transistors switch on and off to provide the binary logic of computing using source, drain and gate electrodes and a channel. The source electrode introduces electrical current into the channel, and the drain electrode receives it at the other end. The gate, or control, electrode uses an electrical current to allow or block the flow of electricity through the channel.

Researchers working to construct organic transistors usually have to choose between traditional metal electrodes, and polymer electrodes, which are more flexible and easier to process but do not conduct electricity as well.

Researchers from the California Institute of Technology have devised an inexpensive way to add better-conducting organic source and drain electrodes to organic thin-film transistors.

The source and drain electrodes are made from polymer films filled with conducting carbon particles. The researchers' found that they could connect carbon-filled polymer contacts directly to organic semiconductors at room temperature using the stencil printing technology used to put logos on T-shirts.

The researchers' method could be used in practical plastic transistors in the next few years, according to the researchers. The work appeared in the November 10, 2003 issue of Applied Physics Letters.