A new material could be used as thermoelectric semiconductors in wearable devices by using a technique that focuses on the manipulation of spaces between atoms in crystals.
Researchers from Queensland University of Technology used “vacancy engineering” to enhance the ability of AgCu semiconductors, which are alloys made up of silver, copper, tellurium, selenium and sulphur, to convert body heat into electricity.
Vacancy engineering is the study and manipulation of empty spaces, or “vacancies,” in a crystal where atoms are missing, to influence the material’s properties, such as improving its mechanical properties or optimising its electrical conductivity, or thermal properties.
The new research details the process of creating synthesised flexible thermoelectric semiconductors through a simple and cost-effective melting method.
Precise control of the material’s atomic vacancies not only improved its capability of converting heat into electricity but also gave the material excellent mechanical properties, meaning that it could be shaped in different ways to adapt to more complex practical applications.
Improving heat-to-electric conversion in semiconductors
To demonstrate the practical application potential of the material, the researchers designed several different micro-flexible devices based on the material that could be easily attached to a person’s arm.
Mr Li said the study addressed the challenge of improving the heat-to-electricity conversion ability of AgCu semiconductors while still remaining flexible and stretchable, which were properties desired for wearable devices.
“Thermoelectric materials have drawn widespread attention over the past few decades in light of their unique ability to convert heat into electricity without generating pollution, noise, and requiring moving parts,” explained Nanhai Li, first author of the study.
“As a continuous heat source, the human body produces a certain temperature difference with the surroundings, and when we exercise, that generates more heat and a larger temperature difference between the human body and the environment.”
Facilitating the growing demand for thermoelectric materials
With the swift advance of flexible electronics, the demand for flexible thermoelectric devices is growing significantly, and QUT researchers were at the forefront of research in this area.
In a separate recent study, researchers from the ARC Research Hub in Zero-emission Power Generation for Carbon Neutrality developed an ultra-thin, flexible film that could power next-generation wearable devices using body heat, eliminating the need for batteries.
Professor Zhi-Gang Chen, from the ARC Research Hub in Zero-emission Power Generation for Carbon Neutrality and co-author of the study, said: “The key to advancing flexible thermoelectric semiconductors is to examine wide-ranging possibilities.
“Mainstream flexible thermoelectric devices are currently fabricated using inorganic thin-film thermoelectric materials, organic thermoelectric materials deposited on flexible substrates, and hybrid composites of both.
“Both organic and inorganic materials have their limitations – organic materials typically suffer from low performance, and while inorganic materials offer better conductivity of heat and electricity, typically they are brittle and not flexible.
Chen concluded: “The type of semiconductor used in this research is a rare inorganic material with striking potential for flexible thermoelectric performance.
“However, the underlying physics and chemistry mechanisms for enhancing its performance while maintaining exceptional plasticity remained largely unexplored until now.”
