research team at the National Institute of Standards and Technology
(NIST) has found* that 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.
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
Silicon is the iconic material of the
electronics industry, the basic material for most microprocessors and
memory chips. Silicon has proved highly successful as a substance
because billions of computer elements can be crammed into a tiny area,
and the manufacturing process behind these high-performance chips is
But the electronics industry for a long time
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, cost
less and do things silicon devices cannot: bend and fold, for example.
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.”
The team’s work showed that a commonly used
organic transistor material, poly(3-hexylthiophene), or P3HT, works well
as a spray-on transistor material because, like beauty, 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.
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.
* C.K. Chan, L.J. Richter, B.Dinardo, C.Jaye,
B.R. Conrad, H.W. Ro, D. S. Germack, D.A. Fischer, D.M. DeLongchamp, D.
J. Gundlach. High performance airbrushed organic thin film transistors. Applied
Physics Letters, 96, 133304. March 30, 2010 doi:10.1063/1.3360230.
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