Thermoelectric conversion, the generation of electricity from waste heat, is gaining attention as a sustainable way to power electronics. Transparent thermoelectrics could even generate power from the glass windows in cars and buildings in the future. However, traditional transparent thermoelectric materials, which use nanostructure interfaces, struggle to achieve both a low thermal conductivity and a high optical transmittance.
Ishibe et al. developed a novel thermoelectric material using zinc oxide and tin oxide to allow for simultaneous control of thermal conductivity and optical transmittance in transparent thermoelectric films.
The team created their films using pulsed laser deposition of zinc oxide and tin oxide multilayers in a vacuum chamber. They studied the resulting products with transmission electron microscopy, atomic force microscopy, and X-ray diffraction.
The imaging showed the large atomic mass difference yet similar refractive index between the two materials gave the thermoelectric film a low thermal conductivity while remaining highly transparent. In fact, it had the lowest thermal conductivity and highest optical transmittance ever measured for a transparent thermoelectric film. By using industry-compatible materials, the authors hope that the new design will be easy to implement commercially.
“Typically, heavy elements including rare or toxic materials are used for the reduction of thermal conductivity,” said author Yoshiaki Nakamura. “Zinc oxide and tin oxide offer an alternative, ubiquitous, eco-friendly, and low cost option.”
The authors are continuing to study the film’s nanostructure to increase the power output and are looking at next steps to implement their design in thermoelectric power generation devices.
Source: “Interface design of transparent thermoelectric epitaxial ZnO/SnO2 multilayer film for simultaneous realization of low thermal conductivity and high optical transmittance,” by Takafumi Ishibe, Yuki Komatsubara, Toranosuke Katayama, Yuichiro Yamashita, Nobuyasu Naruse, Yutaka Mera, Azusa N. Hattori, Hidekazu Tanaka, and Yoshiaki Nakamura, Applied Physics Letters (2023). The article can be accessed at https://doi.org/10.1063/5.0124814.