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

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 Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te₃, respectively. By introducing 200 nm Cr and 200 nm Ag as TEiMs for p-type Bi_0.5Sb_1.5Te₃/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 Bi_0.5Sb_1.5Te₃/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.