Superelastic NiTi Thin Layer Triggering High-Performance and High-Durability Thermoelectric Devices

The durability of thermoelectric devices (TEDs) has been a critical concern since they need to sustain frequent current or temperature shocks during operation. Herein, a shape memory alloy NiTi thin film is developed as a potential barrier layer to significantly enhance the durability of Bi₂Te₃-based TEDs. Atomic-resolution microscopy analysis confirms that the sputtered NiTi thin-film barrier layers coexist with B2 austenite and B19' martensitic phases, which form NiTi/Bi₂Te₃ joints exhibiting excellent superelasticity and strain recovery ability. Among these, the NiTi barrier layer at the equimolar ratio possesses the highest η_e and η_d (52.1% and 59.3%, respectively), exhibiting unique superelasticity. The NiTi/Bi₂Te₃ jointed TEDs achieve a maximum cooling power density of 3.55 W·cm^-2, much higher than other reported TEDs. Importantly, after 10,000 aging cycles of pulsed current, the decay of maximum cooling temperature difference for the NiTi/Bi₂Te₃ jointed device is only half of that for the traditional Ni/Bi₂Te₃ jointed one, exhibiting remarkably enhanced durability. This work reveals that the superelastic NiTi barrier layer as an outstanding stress buffer provides insight for realizing high-performance and high-durability TEDs.