June 5, 2009 Researchers at Stanford University have discovered a more reliable way of printing semiconducting organic compounds which also delivers improved performance - a breakthrough which could finally pave the way for the mass production of plastic electronics.
The concept of using cheaper carbon-based materials in place of silicon to produce transistors is not new. In late 2005, Chemnitz University in Germany developed an intriguing method for printing integrated circuits on paper, cardboard and plastic. The process was later abandoned, however, because the gap in performance between the carbon-based and silicon components was too noticeable.
Improving performance
Research led by Stanford associate professor Zhenan Bao has produced a set of techniques for manufacturing organic films that can be placed directly underneath electron-carrying organic semiconductors. Such films are consistently smooth at a molecular level, which helps conduct electrical particles and improve the components' performance by up to two orders of magnitude. The smooth layers were produced via spin-coating, a common process already used in the production of CD and DVD layers.
When Bao's group tested the film with pentacene, one of the most commonly used organic semiconductors, its ability to carry an electrical charge improved 100-fold, with other semiconductors showing comparable performance gains. Nevertheless, several further improvements still need to be made, including better electrical contact between the crystals forming the smooth surface and the components' electrodes.
While organic electronics are cheaper than their silicon-based counterpart, further breakthroughs are needed before performance is on a par. Until then, organic electronics are likely to be used only in embedded systems, where performance requirements aren't as high as those needed in personal computer microprocessors.
Dario Borghino
Stanford University via MIT Technology Review.