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Organic Semiconductors Now Made More Conductive Than Ever

Stanford investigators toy with new molecular arrangement patterns

Dec 22, 2011 08:50 GMT  ·  By
These semiconductor crystals have more than doubled the record for electrical conductivity of an organic semiconductor
   These semiconductor crystals have more than doubled the record for electrical conductivity of an organic semiconductor

Thanks to the work of a team of Stanford engineers, a new type of improved organic semiconductors could soon be used to develop better TV and computer screens, more advanced and efficient solar panels, as well as cell phones and other electronics that can be bent and twisted in all directions.

What the team did during the new research was to dramatically improve the electrical conductivity of organic semiconductors, so much so that an entire new class of applications now lay open ahead.

When organic semiconductors were first developed, they were heralded as the way forward in terms of advanced electronics, but it soon became apparent to experts that these materials do not conduct electricity very well. Improving their conductivity was therefore the key to progressing.

A technique referred to as “straining the lattice,” details of which appear in the latest issue of the top scientific journal Nature, was used at the university to pack the molecules within organic semiconductors closer together, making it easier for electrons to move through.

Stanford chemical engineer Zhenan Bao and her team were thus able to improve the electrical conductivity levels in this class of materials by more than 200 percent over the previous record-holder. At the same time, the strained lattices are 11 times more efficient than unstrained ones of exactly the same material.

“Strained lattices are no secret. We've known about their favorable electrical properties for decades and they are in use in today's silicon computer chips, but no one has been successful in creating a stable strained lattice organic semiconductor with a very short distance between molecules,” Bao explains.

“Our analysis made it possible not only to see the impact of the strain on the lattice geometry, but also to determine the exact way in which the molecules pack in the lattice,” explains Stefan Mannsfeld.

“As a result, we obtained a better understanding of why such structures improve the molecule-to-molecule electrical coupling that improves the electrical efficiency,” he adds. The expert is a coauthor of the Nature paper.

Mannsfeld holds an appointment as a staff scientist at the Stanford Synchrotron Radiation Lightsource, where he is also an expert in X-ray scattering.