Solid‐State Electrochemical Thermal Transistors

Abstract

Thermal transistors that electrically control heat flow have attracted growing attention as thermal management devices and phonon logic circuits. Although several thermal transistors are demonstrated, the use of liquid electrolytes may limit the application from the viewpoint of reliability or liquid leakage. Herein, a solid‐state thermal transistor that can electrochemically control the heat flow with an on‐to‐off ratio of the thermal conductivity (κ) of ≈4 without using any liquid is demonstrated. The thermal transistor is a multilayer film composed of an upper electrode, strontium cobaltite (SrCoOx), solid electrolyte, and bottom electrode. An electrochemical redox treatment at 280 °C in air repeatedly modulates the crystal structure and κ of the SrCoOx layer. The fully oxidized perovskite‐structured SrCoO3 layer shows a high κ ≈3 .8 W m−1 K−1, whereas the fully reduced defect perovskite‐structured SrCoO2 layer shows a low κ ≈ 0.95 W m−1 K−1. The present solid‐state electrochemical thermal transistor may become next‐generation devices toward future thermal management technology.

Solid-State Electrochemical Thermal Transistors with Strontium Cobaltite–Strontium Ferrite Solid Solutions as the Active Layers

“…Solid-state electrochemical thermal transistors with SrCo 1−x Fe x O y solid solution films (60 nm thick, 5 mm × 5 mm) as active layers were fabricated according to the previous report. 5 (See the Experimental Section.) The electrochemical redox treatment was performed at 280 °C in air by applying a constant current of ±50 μA.…”

“…Solid-state electrochemical thermal transistors with SrCo 1– x Fe x O y solid solution films (60 nm thick, 5 mm × 5 mm) as active layers were fabricated according to the previous report . (See the Experimental Section.)…”

“…The specific heat capacities of the SrCo 1– x Fe x O y solid solutions were calculated by the Kopp–Neumann law . Details of the TDTR method are described elsewhere. ,− …”

“…demonstrated the first thermal transistor in 2014, this emerging field has gradually attracted increased attention. Thermal transistors − have the potential to convert waste heat into useful energy, making them useful for both thermal management devices and phononic logic circuits. , Although several researchers have demonstrated thermal transistors using liquid electrolytes, − these devices are unsuitable for practical thermal transistors due to the electrolyte leakage problem or their low on/off ratio.…”

“…Recently, we realized solid-state electrochemical thermal transistors that exhibit an on/off thermal conductivity (κ) ratio of ∼4 at room temperature . Compared to previously reported thermal transistors, our solid-state electrochemical thermal transistors offer clear advantages, including the absence of liquids and the ability to withstand high temperatures due to their inorganic structure.…”