By Josh Perry, Editor
[email protected]

Researchers at Osaka University (Japan) developed a new method for enhancing thermoelectric power factor while decreasing thermal conductivity using films embedded with zinc oxide nanowires, according to a report from the university.

Transparent thermoelectric material using ZnO nanowires. (Osaka University)

“In the developed films, the thermoelectric power factor was increased by selective transmission of energetic electrons through nanowire interfaces with intentionally-controlled energy barriers, and thermal conductivity was decreased by scattering phonons at the nanowire interfaces,” the report explained.

The research team believes that this breakthrough will lead to high-performance transparent thermoelectric (TEC) devices that can be used in energy recovery from other transparent objects, such as window glass.

Researchers were able to overcome issues in previous studies by controlling the dopant concentration at the nanowire interface, which scattered low-energy electrons and increased the thermoelectric power factor. It also increased the phonon scattering at the interface, which lowered the material’s thermal conductivity by as much as 20 percent.

“In the future, it will be possible to greatly decrease the thermal conductivity of Embedded-ZnO nanowire structure by increasing nanowire areal density,” the report added. “The thermoelectric devices composed of films with this structure are expected to be realized and see widespread use due to their use of low-cost and environmentally-friendly ZnO.”

The research was recently published in Applied Materials and Interfaces. The abstract stated:

“The simultaneous realization of low thermal conductivity and high thermoelectric power factor in materials has long been the goal for the social use of high-performance thermoelectric modules. Nanostructuring approaches have drawn considerable attention because of the success in reducing thermal conductivity. On the contrary, enhancement of the thermoelectric power factor, namely, the simultaneous increase of the Seebeck coefficient and electrical conductivity, has been difficult.

“We propose a method for the power factor enhancement by introducing coherent homoepitaxial interfaces with controlled dopant concentration, which enables the quasiballistic transmission of high-energy carriers. The wavenumber of the high-energy carriers is nearly conserved through the interfaces, resulting in simultaneous realization of a high Seebeck coefficient and relatively high electrical mobility.

“Here, we experimentally demonstrate the dopant-controlled epitaxial interface effect for the thermoelectric power factor enhancement using our “embedded-ZnO nanowire structure” having high-quality nanowire interfaces. This presents the methodology for substantial power factor enhancement by interface carrier scattering.”