Speedier flexible electronics possible with new fabrication process

Mar 16, 2009
A view through the microscope shows microwires aligned in the same direction laying across electrodes below. Courtesy of Zhenan Bao

(PhysOrg.com) -- A clever but simple new way of making transistors out of high-performance organic microwires presents a potential path for products such as smart merchandise tags, light and cheap solar panels, and flexible "digital paper." Engineers at Stanford and Samsung report the new method in a paper to be published online this week in the Proceedings of the National Academy of Sciences.

Academic and industrial researchers have been toiling all decade to create flexible electronics based on inexpensive organic materials. These materials can be cheaper than silicon and (albeit slower in performance), and amenable to cheaper manufacturing processes such as roll-to-roll printing of . They are also more compatible with flexible substrates, such as plastics.

"This paper brings together progress on key aspects of building flexible ," said Zhenan Bao, a Stanford associate professor of chemical engineering and a senior author of the paper. "In our process we can create organic semiconducting microwires with the most desirable , flow a dispersed solution of them into a stencil, or mask, and then stamp them onto a pattern of electrodes. Because these wires can be precisely aligned with high density, the result is high-performance ."

Although the research alone is not enough to enable economical mass production of low-cost, high-performance flexible electronics, it could make their eventual manufacturing more feasible, said Jong Min Kim, a Samsung Fellow and senior vice president and a co-author of the paper.

"This technology can be applied to printable electronics such as low-cost and large-area display device components, ID tags, sensors, and many different types of energy devices," Kim said.

In electronics, transistors act as switches. The team reported measurements showing that in their "on" state—when they transmit current—the group's dense transistors operated about two-and-a-half times more quickly than the organic transistors most other research groups have announced to date. The transistors also transmit more current. In a flexible electronic display, faster operation results in blur-free motion, and higher current yields a brighter picture.

The performance improvements come from three factors, Bao said: the inherently fast conductivity of the single crystalline microwires, the new alignment method they developed and the ability to pack a high density of wires onto the electrodes. Because almost all of the wires span the electrodes, a large number of them make the connection, ensuring that more current gets across.

The Stanford-Samsung team's transistors are also among the best of a rare breed of organic "n-type" transistors, which transmit negative charges. They are just as necessary as more common "p-type" transistors for making integrated circuits, but have been harder to build.

In addition, the microwires, made from a chemical called BPE-PTCDI, are formulated to be "air stable," meaning that their electrical properties aren't spoiled by exposure to oxygen, as are many n-type organic transistors.

Prototype process

Because the process depends only on a stencil to align and concentrate the wires, the team was able to create patterns in which wires could be aligned in different directions in different places, a necessary capability for producing complex circuit designs. Also, Bao said, the team fabricated transistors over an area of several square centimeters, which suggests that patterning a large area could be feasible.

Demonstrating patterning over larger areas is a key goal for future work, Bao said. The team also hopes to study whether the technique could allow for more cost-effective fabrication of devices such as solar cell panels that use inorganic and organic micro- or nanowires.

Provided by Stanford University (news : web)

Explore further: Revealing faded frescos

Related Stories

New research could lead to 'invisible' electronics

Dec 22, 2006

Imagine a car windshield that displays a map to your destination, military goggles with targets and instructions displayed right before a soldier's eyes or a billboard that doubles as a window.

Sensor of plastic can be produced in a printing press

Feb 08, 2005

Electrochemical transistors made of plastic open myriad possibilities. Since both electrons and ions are active, they can function as a bridge between traditional electronics and biological systems. A new dissertation from ...

Recommended for you

Revealing faded frescos

20 hours ago

Many details of the wall and ceiling frescos in the cloister of Brandenburg Cathedral have faded: Plaster on which horses once "galloped" appears more or less bare. A hyperspectral camera sees images that remain hidden to ...

Device could detect driver drowsiness, make roads safer

22 hours ago

Drowsy driving injures and kills thousands of people in the United States each year. A device being developed by Vigo Technologies Inc., in collaboration with Wichita State University professor Jibo He and ...

New capability takes sensor fabrication to a new level

Jun 30, 2015

Operators must continually monitor conditions in power plants to assure they are operating safely and efficiently. Researchers on the Sensors and Controls Team at DOE's National Energy Technology Laboratory ...

Smart phones spot tired drivers

Jun 30, 2015

An electronic accelerometer of the kind found in most smart phones that let the device determine its orientation and respond to movement, could also be used to save lives on our roads, according to research ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.