Development of an Electric Double-Layer Capacitor-Type Heat Flow Switching Device with Ag<sub>2</sub>S<sub>0.8</sub>Se<sub>0.2</sub> as the Functional Electrode

An electric double-layer capacitor-based heat flow switching device working with a bias voltage was developed as a key technology of thermal management. This device allows us to rapidly control the magnitude of heat flow passing through the device using variations in electronic thermal conductivity of component material induced by the bias voltage. We employed a thin film of Ag2S0.8Se0.2 as the most important component material, because it possesses an exceptionally low lattice thermal conductivity and a semiconducting electronic structure. The thermal conductivity of the fabricated device was measured by means of a periodic heating method under various applied bias voltages. The thermal conductivity of Ag2S0.8Se0.2 was found to increase linearly with increasing bias voltage VB up to a factor of 1.9 at VB = 2.4 V. The transient current response during the charging and discharging processes revealed that the response time for switching was fast enough to be less than 0.2 sec. By measuring the stored charge and comparing it with the electronic thermal conductivity, we confirmed that the observed variation in thermal conductivity of the component material is attributed to the accumulated charge in the material.