The next generation of electronics will feature smaller and more powerful components that require new solutions for cooling. A new thermoelectric cooler developed by Penn State scientists greatly improves cooling power and efficiency over current commercial thermoelectric units and could help control heat in future high-power electronics, researchers said.
“Our new material can provide thermoelectric devices with very high cooling power density,” said Bed Poudel, a research professor in Penn State’s Department of Materials Science and Engineering. “We were able to demonstrate that this new device is not only competitive in terms of techno-economic measures, but can also outperform current leading thermoelectric cooling modules. New generations of electronics will benefit from this development.”
Thermoelectric coolers transfer heat from one side of the device to the other when power is applied, creating a module with cold and hot sides. Placing the cold side on heat-producing electronic components, such as laser diodes or microprocessors, can help pump out excess heat and regulate temperature. But as those components become more powerful, thermoelectric coolers have to pump more heat, the scientists said.
Compared to the leading commercial device made of bismuth telluride, the new thermoelectric device showed a 210% increase in cooling power density, while potentially maintaining a similar coefficient of performance (COP), or ratio of useful cooling to required energy, the scientists reported. Inn Nature communication.
“It solves two of the three biggest challenges in making thermoelectric cooling devices,” said Shashank Priya, vice president for research at the University of Minnesota and a co-author on the paper. “First, it can provide a high cooling power density with a high COP. This means that a small amount of power can pump a lot of heat. Second, for high-power lasers or applications that require localized heat removal. From a small area, it can provide the best solution. .”
The new device is made from a compound of Haf-Heusler alloys, which have special properties that offer promise for energy applications such as thermoelectric devices. These materials offer good strength, thermal stability and efficiency.
The researchers used a special annealing process — which involves how materials are heated and cooled — that allowed them to modify and manipulate the material’s microstructure to remove defects. It had not been used before to make half-Heusler thermoelectric materials, the scientists said.
The annealing process greatly increased the material’s grain size, leading to fewer grain boundaries—areas in a material where crystallite structures meet, reducing electrical or thermal conductivity.
“In general, the Hafs-Heusler material has a very small grain size — a nano-sized grain,” said Wenjie Li, assistant research professor in Penn State’s Department of Materials Science and Engineering. “With this annealing process we can control grain growth from the nanoscale to the microscale—a difference of three orders of magnitude.”
Reducing grain boundaries and other defects significantly increased the material’s carrier mobility, or how well electrons can travel through it, giving it a higher power factor, the scientists said. The power factor determines the maximum cooling power density and is particularly important in electronics-cooling applications.
“For example, in laser diode cooling, a significant amount of heat is generated in a very small area and must be maintained at a specific temperature for optimal device performance,” Li said, “and that’s where our technology becomes possible. It has a good future for local high thermal management.”
In addition to the high power factor, the scientists said the materials produced the highest average figure of merit, or efficiency, of any quasi-Heusler material in the temperature range of 300° to 873° Kelvin (80 to 1,111° Fahrenheit). The results show a promising strategy for optimizing Half-Heusler materials for room-temperature thermoelectric applications.
“As a country we invest so much in the CHIPS and SCIENCE Act, one issue is how we can handle higher power densities as microelectronics get smaller and run at higher power,” Poudel said. “This technology may be able to address some of these challenges.”
Hangtian Zhu et al, Emerging Half-Heusler Alloys as High Power Density Thermoelectric Cooling Materials, Nature communication (2023). DOI: 10.1038/s41467-023-38446-0