Optimization of Interface Materials between Bi2Te3-Based Films and Cu Electrodes Enables a High Performance Thin-Film Thermoelectric Cooler.

Abstract

Thermoelectric interface materials (TEiMs) are key to optimizing the electrical contact and stability of the interface between thermoelectric material and metal electrode in high-performance thin-film thermoelectric coolers (TECs). Herein, we explored TEiMs applicable to representative Bi-Te films and found that Cr and Ag are effective TEiMs for p-type Bi0.5Sb1.5Te3 and n-type Bi2Te3, respectively. By introducing 200 nm Cr and 200 nm Ag as TEiMs for p-type Bi0.5Sb1.5Te3/Cu and n-type Bi2Te3/Cu interfaces, Cu diffusion is suppressed, and excellent electrical contact is achieved (1.81 × 10-12 Ω m2 for p-type and 3.32 × 10-12 Ω m2 for n-type) and remains stable after heat treatment (2.37 × 10-12 Ω m2 for p-type and 1.63 × 10-12 Ω m2 for n-type). Furthermore, the cooling flux of TECs with optimized TEiMs increases from 122.74 to 296.56 W/cm2, while the performance degradation caused by contact resistance decreases from 50.81 to 4.15%. In addition, our results show that diffusion occurs between not only Cu but also Ag and the thermoelectric material, as TEiMs diffuse slightly. The diffusion of Cu and Ag at the interface can optimize the electrical contact of Bi2Te3/Cu but strongly degrade the electrical contacts of Bi0.5Sb1.5Te3/Cu. Our work provides an optimal selection of TEiMs for high-performance Bi-Te thin film coolers and provides guidance for further miniaturization of devices.