The Shanghai Institute of Ceramics has achieved breakthrough progress in the research of high-performance thermoelectric devices

Thermoelectric technology can generate electricity by harnessing tiny temperature differences between the human body and its surroundings or between different environmental zones. It boasts advantages such as small size, silence, and high reliability, making it highly promising for applications in flexible electronics and self-powered IoT devices. However, flexible electronics and IoT devices typically operate in indoor environments with no wind, and their highly integrated internal structures and confined spaces limit the use of external heat-dissipating components like metal fins. As a result, the temperature differences that can be established across thermoelectric devices are usually small, leading to low output performance—such as low voltage density and power density. Taking Bi2Te3-based thermoelectric devices as an example, when worn on the human body, their voltage density typically falls below 20 mV/cm², and their power density is below 10 μW/cm², failing to meet the requirements of practical applications. Therefore, selecting suitable thermoelectric materials to enhance the output performance of thermoelectric devices has become a critical issue that urgently needs to be addressed for the current application of thermoelectric technology in the fields of flexible electronics and IoT.

Recently, Researcher Qiu Pengfei, Researcher Shi Xun, and Researcher Chen Lidong from the Shanghai Institute of Ceramics, Chinese Academy of Sciences, went beyond traditional performance evaluation metrics for thermoelectric materials and proposed two new indicators to screen thermoelectric materials that are better suited for flexible electronics and Internet of Things applications. Experimentally, they fabricated novel Ag-based thermoelectric devices based on these materials, which exhibited significantly superior output performance compared to conventional Bi2Te3-based thermoelectric devices. The related findings were published under the title “Screening thermoelectric materials for high-output performance in wearable electronics” in Energy Environ. Sci. 2025, 18, 5416-5423. Xinjie Yuan, a Ph.D. student at the Shanghai Institute of Ceramics, is the first author of the paper.

When the temperature difference across the two ends of a thermoelectric device is fixed, the higher the thermoelectric figure of merit (zT) of the thermoelectric material, the better the output performance of the thermoelectric device typically is. However, for thermoelectric devices intended for flexible electronics and IoT applications, the temperature difference across the two ends is not fixed; therefore, it is no longer possible to simply screen and match thermoelectric materials based on their zT values alone. Based on a one-dimensional heat transfer model, the research team derived theoretical formulas for the output voltage density and power density of thermoelectric devices operating in indoor, windless environments with low convective heat transfer coefficients (less than 10 Wm⁻² K⁻¹). They found that these quantities are proportional to |S|/κ and S²σ/κ², respectively (where S is the Seebeck coefficient, κ is the thermal conductivity, and σ is the electrical conductivity). By analyzing representative thermoelectric materials, the team further discovered that certain Ag-based thermoelectric materials—such as Ag1.995Au0.005Te0.7S0.3 and Ag0.9Sb1.1Te2.1—exhibit higher values of |S|/κ and S²σ/κ² than conventional Bi₂Te₃-based thermoelectric materials. Consequently, these materials may be more suitable for developing thermoelectric devices tailored for self-powered applications in flexible electronics and the Internet of Things.

To verify the effectiveness of the proposed performance evaluation metrics, the research team selected n-type Ag1.995Au0.005Te0.7S0.3 and p-type Ag0.9Sb1.1Te2.1 materials, which exhibit high |S|/κ and S2σ/κ2 values. They developed matching W/Sn/Cu multi-level metallization layers and a low-temperature soldering method to fabricate novel Ag-based thermoelectric devices. As a comparison, they also prepared Bi2Te3-based thermoelectric devices with the same structure and dimensions using conventional Bi2Te3-based materials that have high zT values but lower |S|/κ. The test results showed that, in a windless environment, the voltage density and power density of the Ag-based devices were significantly higher than those of the Bi2Te3-based devices. For example, when the ambient temperature and the hot-side temperature of the device were 295 K and 303 K, respectively, the voltage density and power density of the Ag-based thermoelectric device were 14.3 mV/cm² and 6.4 μW/cm², while those of the Bi2Te3-based device were 7.9 mV/cm² and 5.5 μW/cm². When the Ag-based thermoelectric device was worn on the arm at an ambient temperature of 280 K, its voltage density and power density reached 33 mV/cm² and 42 μW/cm², respectively—also markedly higher than the output performance of the Bi2Te3-based device under the same conditions. The electrical energy generated by the Ag-based thermoelectric device can power an electronic watch.

This research not only provides a brand-new approach for the design and development of high-performance thermoelectric devices aimed at flexible electronics and IoT applications, but also holds significant value for future research on novel, high-performance thermoelectric materials operating at room temperature.

This research was supported by the National Key Research and Development Program and the National Natural Science Foundation of China.

Paper link: https://doi.org/10.1039/D5EE00216H

Figure 1. |S|/κ and S²σ/κ² for representative thermoelectric materials.