Lucent eyes plastic transistors

Lucent Technologies is developing a plastic transistor to be used in display screens and smart cards that is much less expensive to produce and more durable than today's silicon transistors.

Prototypes of Bell Labs' plastic transistors are three times the size of silicon transistors, which makes them suited for use in smart cards but not in devices requiring a high level of transistor integration, where microprocessors are employed. Transistors are the building blocks for almost all integrated circuits and are used in everything from talking toys to computer processors.

Commercial devices with these transistors are not expected to reach the market for another five years.

Bell Labs, the research and development subsidiary of Lucent, today presented its research on the use of plastic transistors at the American Chemical Society's national meeting.

The plastic transistors are being developed as a way to make inexpensive and durable flat-panel displays for notebook computers. These displays could be thinner and lighter than current liquid crystal display (LCD) screens because the plastic transistors would be implanted directly onto a single plastic display, adjacent to the light source. LCDs today use two sheets of glass with a liquid crystal solution between them.

The one-layer plastic display would weigh less than a typical LCD screen and would also be much less expensive to manufacture. Plastic transistors could be manufactured in a typical laboratory or plant, whereas silicon transistors must be manufactured in temperature-controlled vacuum conditions.

The equipment to manufacture silicon transistors can easily cost upwards of $500 million per plant, according to David Mentley, an analyst with Stanford Resources. Plastic transistor production equipment would theoretically cost a fraction of this.

Bell-Labs is also developing a process that would spray the liquid plastic onto a stainless steel mesh, instead of printing it, further reducing manufacturing costs.

Devices made using plastic transistors would be more flexible and durable, said Reddy Raju, one of the researchers developing the technology. "One of the common complaints about smart cards is that they're not very durable," Raju said. "These materials are inherently flexible, and therefore durable."

Questions remain about the need for flexibility in display screens, however. "They've been talking about this for 15 years or so," Mentley pointed out. "It sounds really nifty, but it's hard to think of things that actually need flexible displays."