|A benzenedithiol molecule trapped between two gold surfaces. Click to enlarge. Credit: Ben Utley.|
Researchers at the University of California, Berkeley, have successfully generated electricity from heat by trapping organic molecules between metal nanoparticles to create an organic thermoelectric material. The new UC Berkeley study marks the first time the Seebeck effect has been measured in an organic molecule.
The discovery, described in a study published today in Science Express, could lead to the development of more cost-effective thermoelectric converters that could be applied to waste heat recovery—including in vehicles. (Earlier post.)
Utilizing wasted heat has been a major focus of research into thermoelectric converters, which rely upon the Seebeck effect, a phenomenon in which the application of heat to combinations of certain metals induces an electric current.
In 2005, the DOE selected BSST, a subsidiary of Amerigon, to lead the development of an efficient and practical thermoelectric system that will improve fuel economy by converting waste heat in automobile engine exhaust into electrical power. (Earlier post.)
Although the efficiency of thermoelectric materials has improved dramatically, it is still rather low and the materials are costly.
The goal is to make things out of materials that are more abundant and more easily processed. Organics are cheap and can be processed easily.—Rachel Segalman, UC Berkeley professor of chemical engineering
The researchers coated two gold electrodes with molecules of benzenedithiol, dibezenedithiol or tribenzenedithiol, then heated one side to create a temperature differential. For each degree Celsius of difference, the researchers measured 8.7 microvolts of electricity for benzenedithiol, 12.9 microvolts for dibezenedithiol, and 14.2 microvolts for tribenzenedithiol. The maximum temperature differential tested was 30 degrees Celsius (54 degrees Fahrenheit).
The effect may seem quite small now, but this is a significant proof of concept, and the first step in organic molecular thermoelectricity. We are going down the road of cheap thermoelectric materials.—Pramod Reddy, co-lead author
The next step for the researchers includes testing different organic molecules and metals, as well as fine tuning the assembly of the structure.
This research was supported by the US Department of Energy, the National Science Foundation and the Berkeley-ITRI Research Center. The Industrial Technology Research Institute, or ITRI, is a large research organization in Taiwan that is collaborating with UC Berkeley on nano-energy innovation.
“Thermoelectricity in Molecular Junctions”; Pramod Reddy, Sung-Yeon Jang, Rachel Segalman, Arun Majumdar; Science DOI: 10.1126/science.1137149