Thermoelectric efficiency doubled

A research team from the University of Michigan has found a way to nearly double the efficiency of a particular class of thermoelectric materials made with organic semiconductors.

Organic semiconductors are carbon-rich compounds that are relatively cheap, abundant, lightweight and tough.

Eventually this technology could allow us to create a flexible sheet

But they haven’t traditionally been considered candidate thermoelectric materials because they have been inefficient in carrying out the essential heat-to-electricity conversion process.

U-M researchers improved upon the state-of-the-art in organic semiconductors by nearly 70 percent, achieving a figure-of-merit of 0.42 in a compound known as PEDOT:PSS.

“That’s about half as efficient as current inorganic semiconductors,” said project leader Kevin Pipe, an associate professor of mechanical engineering as well as electrical engineering and computer science.

One of the ways scientists and engineers increase a material’s capacity for conducting electricity is to add impurities to it in a process known as doping.

When these added ingredients, called dopants, bond to the host material, they give it an electrical carrier. Each of these additional carriers enhances the material’s electrical conductivity.

“Eventually this technology could allow us to create a flexible sheet — think of Saran Wrap — that can be rolled out or wrapped around a hot object to generate electricity or provide cooling,” Pipe said.