A team of researchers from Stanford University and the University of Nebraska-Lincoln (UNL) announced last week the development of a new high-carrier-mobility, high-performance and high-transparency transistor that can be used as a building block for flat-panel displays and sensor arrays.
For years engineers all over the world have been trying to manufacture transistors with inexpensive organic and plastic materials capable of performing as well as their silicon-based counterparts for these applications and others.
The process used by the research team, led by Zhenan Bao and Jinsong Huang, from Stanford and UNL, respectively, used a new process called off-center spin method to produce thin films on glass. Traditionally, to produce thin films, the solution is dropped onto a surface (normally a wafer) sitting on a spinner platter. The spinning action distributes the solution evenly on top of the wafer, creating a thin coating.
The researchers at Stanford and UNL made two changes to this process. First, they rotated the spinner faster than usual and, second, they coated only a small postage stamp-sized portion of the spinning surface. These changes had the effect of creating a denser concentration of organic material in a smaller, more regular structure, which in turn improved the carrier’s mobility.
The researchers reported a transistor hole mobility of 43 cm2 Vs−1, which is the highest value reported to date for all organic molecules. The transistors produced by this method show high transparency of more than 90 percent over the visible spectrum, making them suitable for transparent, high-performance organic electronics.
The method is still an experimental one. The researchers cannot yet precisely control the alignment of organic materials or achieve uniformity in the carrier mobility. However, even at this experimental stage they could be able to produce transistors with a range of speed much faster than existing organic semiconductors.
The work was funded by the U.S. Defense Advanced Research Projects Agency, the Air Force Office of Scientific Research and the National Science Foundation. It was published in the Jan. 8 issue of Nature Communications.
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