Kirigami-Inspired Organic and Inorganic Film-Based Flexible Thermoelectric Devices with Built-In Heat Sink

Thermoelectric (TE) technology presents a unique opportunity to convert waste heat directly into electricity, offering a promising solution to address energy harvesting and sustainability challenges. However, conventional TE devices with π-type structures always need a heat sink to thermally link to the air during operation which remains a significant limitation for their practical applications.<br/>Herein, we report a new configuration of a TE device that has a built-in heat sink for the first time. Furthermore, the device modified with shape-memory polymer films can be self-folded into a hexagonal structure via heating above its glass transition temperature. We demonstrate the feasibility of our design through experimental characterization and modelling. The device with built-in fins exhibits superior thermoelectric performance with both organic (carbon nanotube veils) and inorganic (bismuth telluride, Bi₂Te₃) TE materials. The maximum power output of the Bi₂Te₃-based device can reach 180 µW, which is 4.4 times higher than that of the carbon-based device (41 µW) when the temperature difference is 43 K and airflow is 1.5 m s^-1. Bi₂Te₃-based devices show better TE performance but less stability compared to carbon-based devices. Moreover, carbon-based devices can be self-folded via external temperature stimulus and keep resistance no change (95 Ω) while Bi₂Te₃-based devices cannot.<br/>This work provides a path to optimize the thermoelectric performance of TE devices by designing rational structures. This approach has the potential to reduce the cost, mass, and volume of TE devices, making them more attractive for a wide range of applications, such as waste heat recovery, energy harvesting, and thermal management.