Silicon is the basic material for most microprocessors and memory chips. But for a long time the electronics industry has been pursuing novel organic materials to create semiconductor products—materials that perhaps could not be packed as densely as state-of-the-art silicon chips, but that would require less power and cost less.

According to scientists at the National Institute of Standards and Technology (NIST), an organic semiconductor may be a viable candidate for creating large-area electronics, such as solar cells and displays that can be sprayed onto a surface as easily as paint.

Writing in Applied Physics Letters, The NIST team explains that a commonly used organic transistor material, poly(3-hexylthiophene), or P3HT, works well as a spray-on transistor material because transistors aren't very deep. When sprayed onto a flat surface, inhomogeneities give the P3HT film a rough and uneven top surface that causes problems in other applications. But because the transistor effects occur along its lower surface—where it contacts the substrate—it functions quite well.

This airbrush technique deposits a well-studied material called P3HT to create spray-on transistors, which perform comparably to lab-standard equivalents made by spin coating.
(Photo Credit: NIST)

While the electronics will not be ready for market anytime soon, the research team says the material they studied could overcome one of the main cost hurdles blocking the large-scale manufacture of organic thin-film transistors, the development of which also could lead to a host of devices inexpensive enough to be disposable.

Proponents predict that organic semiconductors, once perfected, might permit the construction of low-cost solar cells and video displays that could be sprayed onto a surface just as paint is.

"At this stage, there is no established best material or manufacturing process for creating low-cost, large-area electronics," says Calvin Chan, an electrical engineer at NIST. "What our team has done is to translate a classic material deposition method, spray painting, to a way of manufacturing cheap electronic devices."

Chan says the simplicity of spray-on electronics gives it a potential cost advantage over other manufacturing processes for organic electronics. Other candidate processes, he says, require costly equipment to function or are simply not suitable for use in high-volume manufacturing.

Citation:Chan et al., 'High performance airbrushed organic thin film transistors', Appl. Phys. Lett. 96, 133304; doi:10.1063/1.3360230