13.04.2023 by Aileen Sammler

Solid-State Electrochemical Thermal Transistors – A New Transistor Class with Great Potential

Solid-State Electrochemical Thermal Transistors (SETTs) are a new class of transistors that can regulate the heat flow by exploiting the electrochemical properties of certain materials. They according to the principle of thermo-electrochemical coupling, which allows for the efficient and reversible conversion of electrical energy into thermal energy.

SETTs are becoming more and more important because they have the potential to revolutionize the field of thermal management, which is crucial for many applications such as electronics, energy conversion, and refrigeration. They offer a promising alternative to conventional thermal management that could enable more compact, energy-efficient, and cost-effective thermal management systems.

First Development of a Solid-State Electrochemical Thermal Transistor

Scientists from Hokkaido University have now developed a groundbreaking solid-state electrochemical thermal transistor, which can be used to control the heat flow through electrical signals.

Traditional liquid-state thermal transistors have critical limitations as any leakage will cause the device to stop working. A team, headed by Professor Hiromichi Ohta at the Research Institute for Electronic Science at Hokkaido University, constructed their thermal transistor based on of yttrium oxide-stabilized zirconium oxide, which also acted as the switching material, and used strontium cobalt oxide as active material. Platinum electrodes were employed to supply the power required to control the transistor. The results showed that the Conduttività TermicaThermal conductivity (λ with the unit W/(m•K)) describes the transport of energy – in the form of heat – through a body of mass as the result of a temperature gradient (see fig. 1). According to the second law of thermodynamics, heat always flows in the direction of the lower temperature.thermal conductivity of the active material was comparable to some liquid-state thermal transistors, and the device was stable over ten use cycles, making it more durable than most liquid-state thermal transistors.


The solid-state thermal transistor consists of a multilayered structure. The upper and the bottom electrode consists of platinum whereas strontium cobalt oxide (SrCoOx) is used as active layer. The crystal structure of strontium cobalt oxide can be modified due to electrochemical OxidationOxidation can describe different processes in the context of thermal analysis.oxidation and reduction at 280°C in air. The thermal conductivity of the fully oxidized strontium cobalt oxide layer, the so called “on” state is ~4 times higher compared to the thermal conductivity of a fully reduced strontium cobalt layer, the so called “off” state. (Source: Yang et.al, Adv. Funct. Mater, 2023, 2214939)
Measurements by Means of NETZSCH PicoTR

To measure the thermal conductivity of thermal transistors, the research team used the NETZSCH Time Domain Thermoreflectance method PicoTR. We are very proud to have contributed to this development.

This breakthrough technology offers new possibilities for thermal management in electronics, paving the way for more efficient and reliable devices.

To learn more, download the following research article - a publication in Advanced Functional Materials Journal (Advancedsciencenews.com):