Researchers at the Laboratory of Organic Electronics at Linkoping University in Sweden have developed a thermoelectric, organic transistor in which even a one-degree rise in temperature is enough to cause a detectable current modulation, making it the world’s first heat-controlled transistor, according to an article on the university website.
Researchers developed the world's first heat-controlled transistor. (Linkoping University)
This research builds on work that was done to create a supercapacitor last year that converted solar heat into electricity that the capacitor stored until it was needed. The key to the development was a new liquid electrolyte consisting of ions and conductive polymer molecules that was 100 times more efficient at converting a temperature gradient to electric voltage.
As the article explained, “The positively charged ions are small and move rapidly, while the negatively charged polymer molecules are large and heavy. When one side is heated, the small ions move rapidly towards the cold side and a voltage difference arises.”
That technology has now been demonstrated to work in the transistor and opened the door for a number of possible applications including building circuits that are controlled by infrared light for thermal cameras.
“The high sensitivity to heat, 100 times greater than traditional thermoelectric materials, means that a single connector from the heat-sensitive electrolyte, which acts as sensor, to the transistor circuit is sufficient,” the article noted.
This could lead to thermal cameras being incorporated in smart phones because of the low cost and non-hazardous materials being used.
The research was recently published in Nature Communications. The abstract stated:
“Temperature is one of the most important environmental stimuli to record and amplify. While traditional thermoelectric materials are attractive for temperature/heat flow sensing applications, their sensitivity is limited by their low Seebeck coefficient (∼100 μV K−1).
“Here we take advantage of the large ionic thermoelectric Seebeck coefficient found in polymer electrolytes (∼10,000 μV K−1) to introduce the concept of ionic thermoelectric gating a low-voltage organic transistor. The temperature sensing amplification of such ionic thermoelectric-gated devices is thousands of times superior to that of a single thermoelectric leg in traditional thermopiles.
“This suggests that ionic thermoelectric sensors offer a way to go beyond the limitations of traditional thermopiles and pyroelectric detectors. These findings pave the way for new infrared-gated electronic circuits with potential applications in photonics, thermography and electronic-skins.”