A Slot‐Interlocking Modular Flexible Thermoelectric Device Based on High‐Performance Bi ₂ Te ₃ Thin Films for Wearable Energy Harvesting

ABSTRACT

Thin‐film flexible thermoelectric devices (F‐TEDs) offer excellent conformability and adaptability but remain limited by material performance and device design. Here, a high‐performance F‐TED with an overall size of 30 × 38 mm ² is developed using a vertically aligned array of p‐type and n‐type Bi ₂ Te ₃ ‐based thin films, delivering a maximum output power of 31.9 μW. This outstanding performance arises from synergistic optimization of both materials and device design. High power factors of 31.0 and 20.3 μW cm ⁻¹  K ⁻² are achieved for the p‐type and n‐type films, respectively. Meanwhile, the rationally designed array architecture maximizes the utilization of temperature difference (Δ T ) between thermoelectric legs. With an optimized leg spacing of 5 mm and a leg length of 11 mm, the F‐TED yields an output power density of 2.1 mW cm ⁻² at Δ T  = 25 K and a normalized power density of ∼3.5 μW cm ⁻²  K ⁻² . Furthermore, the F‐TED exhibits excellent mechanical robustness and environmental stability, and the slot‐based modular design enables flexible integration of thermoelectric legs and modules to meet diverse power demands. These features make the proposed F‐TED promising as a sustainable power supply for self‐powered wearable electronics and low‐power sensing systems.