The path to converting wasted heat into electricity has significantly widened. Domestic researchers have succeeded in raising efficiency by utilizing the structural characteristics of existing materials instead of developing complex new materials.
Professor Jin Hyun-kyu of the Department of Mechanical Engineering at Pohang University of Science and Technology (POSTECH) and Dr. Kim Min-young, along with professors Lee Dong-hwa and Choi Si-young from the Department of Material Science and Engineering, and Joseph P. Heremans from Ohio State University, noted on the 25th that they have dramatically enhanced the performance of a technology that generates electricity from wasted heat by adjusting tiny defects known as 'vacancies' of oxygen.
Every day, a tremendous amount of heat simply disappears around us. Hot steam billowing from factory chimneys, heat emitted from engines while driving cars, and even the heat generated while using smartphones or computers all dissipate into the air. If this heat could be converted back into electricity, we could simultaneously solve energy waste and environmental problems.
In this context, the technology that scientists are focusing on is 'thermoelectric technology,' which converts heat into electricity using temperature differences. In particular, 'lateral thermoelectric technology' generates electric current perpendicular to the direction of heat flow, and this method is gaining attention as a future eco-friendly energy technology due to its simple structure and high efficiency. However, there has been a limitation in that the types of materials usable in actual industries are restricted, primarily relying on the properties of the materials themselves.
To address this issue, the research teamfocused on the vacancies of oxygen. Vacancies refer to the very small spaces that occur when an oxygen atom that should originally be there is missing. At first glance, this may seem like a defect in the material, but the researchers discovered that by precisely controlling the number of these vacancies, they could significantly enhance performance.
By actually adjusting the amount of oxygen vacancies differently to create three types of samples for experimentation, they achieved a remarkable result where the thermoelectric performance improved by as much as 91% in the sample with the most vacancies.
The researchers explained the reasons for this phenomenon in two ways. First, as the number of oxygen vacancies increases, electric charges can move more actively in the direction of the temperature difference within the material. This enhances the 'entropy-driven transport,' which is important for generating electricity, thus increasing overall efficiency. Additionally, vacancies slightly twist the crystal structure of the material, causing some of the straight-flowing electric charges to change direction sideways. This principle is similar to a car wheel experiencing lateral torque that changes its forward direction, significantly enhancing the efficiency of lateral thermoelectric technology, which is perpendicular to the temperature difference.
The greatest significance of this research is that performance has been dramatically improved without developing complex and expensive new materials, but rather by simply adjusting the defects within existing materials.
Professor Jin Hyun-kyu, who led the research, said, "This strategy can be widely applied to various thermoelectric materials and will greatly contribute to the development of more efficient and practical energy recovery technologies."
This research has been published as a cover paper in the international academic journal 'Advanced Science.'
References
Advanced Science(2025), DOI: https://doi.org/10.1002/advs.202502892