Thermoelectric (TE) materials, which can directly convert heat into electricity and vice versa, are attracting significant attention as key energy technologies for applications such as electronic cooling and waste heat recovery.
A research team led by Dr. Young Hun Kang at the Korea Research Institute of Chemical Technology (KRICT) has developed an eco-friendly, high-performance thermoelectric material based on silver selenide (Ag₂Se), fabricated under significantly milder temperature and pressure conditions than conventional methods.
Thermoelectric materials operate based on two main principles: the Peltier effect, where electrical current induces heating or cooling, and the Seebeck effect, where electricity is generated from a temperature gradient.
The Peltier effect is widely used in cooling devices such as computer components and portable refrigerators, while the Seebeck effect is utilized in thermoelectric generators for applications including space exploration equipment and power generation from industrial or automotive waste heat.
Currently, the most widely used commercial thermoelectric materials are based on bismuth telluride (Bi₂Te₃). However, these materials rely on rare elements such as tellurium, which suffer from price volatility and environmental concerns. Moreover, their fabrication typically involves complex alloying and doping processes to achieve high performance.
To address these limitations, the research team employed silver selenide (Ag₂Se), a material composed of relatively abundant elements (Ag and Se), offering a simpler and more environmentally benign alternative.
The team synthesized Ag₂Se nanoparticles via a solution-based process and introduced excess selenium to design a Se-rich composition (Ag₂Se₁.₂). Through a simple heat-treatment process, they successfully fabricated a dense bulk thermoelectric material.
The key mechanism lies in leveraging the relatively low melting point of selenium. During annealing, selenium transitions into a liquid phase and infiltrates the interparticle voids between Ag₂Se grains, promoting liquid-phase-assisted grain growth and densification. This process enhances grain connectivity while reducing porosity, resulting in improved electrical conductivity and suppressed lattice thermal conductivity.
As reported in the study, the optimized Ag₂Se₁.₂ material achieved a maximum figure of merit (zT) of 0.927 at 393 K (approximately 120°C), approaching the performance of commercial Bi₂Te₃-based materials.
In addition, the material exhibited more than twofold improvements in compressive strength and Young's modulus, enabling robust mechanical performance and applicability to complex or curved device geometries.
Notably, the developed process enables the formation of dense bulk structures through simple annealing at approximately 350°C under ambient pressure, eliminating the need for conventional high-temperature (~1000°C) or high-pressure (hundreds of MPa) sintering processes. This represents a significant advancement in process simplification and cost reduction.
This technology is expected to be applicable to small-scale power generation systems that convert heat into electricity in industrial processes, data centers, and solar thermal systems. In the long term, it also holds promise as a power source for wearable IoT devices and healthcare sensors.
The research team stated, "The key achievement is the realization of high-performance thermoelectric materials without complex doping or high-temperature and high-pressure processes."
The study was published in January 2026 in Advanced Composites and Hybrid Materials.
