More than half the energy produced by factories, power plants, and vehicles worldwide escapes as waste heat, according to International Energy Agency estimates. Thermoelectric devices, which generate electricity directly from temperature differences, have long promised to recapture some of that lost energy. But the best-performing materials have depended on toxic lead and scarce tellurium, limiting their real-world use. Now, a wave of research from South Korean laboratories is producing alternatives built from cheaper, safer elements, and the results, published across several peer-reviewed studies, suggest the field may be approaching a turning point.
Cracking the contact problem in magnesium-antimonide modules
The most persistent engineering headache for magnesium-antimonide (Mg3Sb2) thermoelectrics has been contact resistance: the energy lost at the internal junctions where thermoelectric legs meet metal electrodes. A study published in Nature Communications details how a Korean research team manipulated the interface chemistry of Mg3Sb2 modules to achieve very low contact resistivity, meaning more of the generated power actually reaches an external circuit instead of dissipating at the joints.
“Contact resistance has been the main obstacle preventing Mg3Sb2 from competing with lead-telluride devices at the system level,” said Byungki Ryu, a senior researcher at the Korea Electrotechnology Research Institute (KERI) and a co-author of the study. “Our interface engineering approach brings device efficiency much closer to what the material’s intrinsic properties predict.”
That matters because Mg3Sb2 is built from magnesium and antimony, elements that are roughly 50 to 100 times cheaper per kilogram than tellurium and carry none of lead’s toxicity concerns. The material has shown strong thermoelectric performance in lab settings for years, but high contact resistance kept device-level output well below theoretical potential. By solving that bottleneck, the team moved Mg3Sb2 closer to practical use in high-temperature waste-heat recovery, the kind found in steel mills, cement kilns, and automotive exhaust systems.
Tuning the crystal structure for higher efficiency
A separate study, also in Nature Communications, attacked the problem from the material side. Researchers improved the “figure of merit” (known as zT) for Mg3Sb2-based compounds by carefully controlling which atoms are added as dopants and how long the material is heated during fabrication. The zT value is the single most watched number in thermoelectric research: it captures, in one dimensionless figure, how efficiently a material converts a temperature difference into voltage. A higher zT at both room temperature and elevated ranges means a module can squeeze more useful electricity from the same heat source.
The gains came from reducing structural disorder inside the crystal lattice through precise sintering-time adjustments. In practical terms, the researchers found that small changes in processing conditions produced measurable jumps in performance, a finding that could simplify manufacturing if it holds up at larger batch sizes.
An hourglass shape that boosts power output
Thermoelectric devices are typically assembled from rectangular blocks of active material. A Korea-linked team challenged that convention with copper selenide (Cu2Se), shaping the thermoelectric legs into an hourglass profile. Their study, published in Nature Energy, showed that the tapered geometry concentrates heat flux through a narrower cross-section at the midpoint, increasing the effective temperature gradient across the material without changing its chemistry.
The result was a meaningful boost in both power output and conversion efficiency. What makes this approach especially appealing is that geometric gains stack on top of any improvements in the material itself. An engineer could, in principle, combine a better Cu2Se composition with the hourglass shape and capture benefits from both.
Flexible films for body heat and wearables
A fourth study broadens the material palette into an entirely different application space. Researchers developed flexible silver selenide (Ag2Se) thin films that, according to their paper in Nature Communications, achieved a reported zT of approximately 1.06 at 303 K, which is near room temperature. If confirmed by independent replication, that figure would be exceptionally high for a flexible thin film; most previously reported room-temperature zT values for Ag2Se films have fallen in the range of 0.5 to 0.8, and values above 1.0 in any thin-film thermoelectric remain rare. The films also delivered meaningful power density at a temperature difference of just 20 K and retained their performance through repeated bending cycles.
Room-temperature, flexible thermoelectrics open a category of applications that rigid, high-temperature modules cannot reach: wearable health sensors, medical patches, and small Internet-of-Things devices that could run on the few degrees of warmth between human skin and ambient air. If the films can be manufactured affordably, they could eliminate the need for batteries in certain low-power electronics.
A shared goal: moving past lead and tellurium
Across these four studies, the common thread is a deliberate shift away from legacy lead-telluride (PbTe) systems. Magnesium, antimony, copper, silver, and selenium are not without environmental footprints of their own. Antimony and selenium production, for instance, is heavily concentrated in China, which introduces supply-chain considerations. But none of these elements carry the acute toxicity of lead, and most are significantly more abundant in the Earth’s crust than tellurium.
That alignment of performance goals with environmental and resource considerations reflects a broader trend in clean-energy materials research, where governments and funding agencies increasingly require that next-generation technologies account for the full lifecycle of their components.
What still needs to happen
Promising lab results are not the same as commercial products, and several critical gaps remain.
None of the published studies include data on large-scale manufacturing costs, production yields, or direct economic comparisons with established PbTe modules. A thermoelectric material can post excellent zT numbers on a benchtop and still fail commercially if it cannot be fabricated cheaply at volume. The Mg3Sb2 interface work, for example, reports device-level contact resistivity but does not disclose whether the processing steps scale to industrial throughput.
Commercialization timelines are also absent. As of May 2026, no press releases or official statements from the affiliated Korean research institutions have surfaced with target dates for pilot production or manufacturer partnerships.
Long-term reliability is another open question. The studies report stability under controlled test conditions, such as repeated bending for the Ag2Se films and thermal cycling for bulk modules, but decade-scale durability data of the kind industrial buyers require has not yet been published. High-temperature waste-heat recovery systems must withstand thousands of heating and cooling cycles, mechanical vibration, and chemically aggressive exhaust streams.
Finally, it remains unclear whether insights from these separate research tracks will converge. The Mg3Sb2 work targets high-temperature waste heat, the Cu2Se hourglass geometry addresses mid-range power generation, and the Ag2Se thin films aim at near-room-temperature harvesting. Whether any single group or consortium plans to combine techniques across platforms, for example, applying the interface optimization from the Mg3Sb2 work to the geometric design principles from the Cu2Se study, has not been confirmed in any of the reviewed publications.
Why it matters now
The global thermoelectric generator market remains small compared to solar or wind, but the sheer volume of waste heat available for capture is enormous. If even a fraction of the energy lost from industrial processes, vehicle engines, and data centers could be converted to electricity, the emissions and fuel savings would be substantial. The barrier has always been cost and efficiency, and the Korean research addresses both by targeting cheaper, nontoxic materials and smarter device designs.
For now, these advances live in the pages of peer-reviewed journals, the strongest available evidence that the reported numbers are methodologically sound but not yet proof that the technology will work on a factory floor. The next milestones to watch for are pilot-scale manufacturing trials, named industry partnerships, and independent replication of the key performance figures. Until those arrive, the Korean thermoelectric portfolio represents one of the most credible bets in the field, but still a bet.
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*This article was researched with the help of AI, with human editors creating the final content.
