Finite Element Analysis and Design of a Flexible Thermoelectric Generator with a Rhombus Gap Structure.

Flexible thermoelectric generators (f-TEGs) offer an opportunity to realize wearable, self-powered electronic devices. A typical f-TEG consists of flexible electrodes and rigid thermoelectric (TE) legs in a flexible package. In the realm of f-TEGs utilizing flexible electrodes and TE cuboids, our unwavering objective lies in the attainment of enhanced flexibility and elevated energy conversion efficiency. In this paper, we employ a quasi-three-dimensional thermal model to design an f-TEG with a rhombus gap structure (E/A-RhTEG) with its optimized performance validated by simulation and experiment. Additionally, the lateral and vertical thermal resistances are introduced to further explain the optimizing principle in the f-TEG's output performance. Compared with the conventional TEG with a rectangular air gap structure (E/A-ReTEG), E/A-RhTEG demonstrates improved energy conversion efficiency to some extent. Simulation results indicate that the output power and energy conversion efficiency of a 25-np-pair E/A-RhTEG at a 30 K temperature gradient reach 8.45 mW and 2.55%, which represent a performance improvement of 3.09 and 6.28%, respectively, compared to E/A-ReTEG. To further elucidate the optimization principle in the performance of f-TEGs, additional considerations are given to the lateral and vertical resistances. In this study, E/A-RhTEG comprising 25 np pairs is fabricated utilizing TE cuboids. Experimental findings indicate that E/A-RhTEG exhibits a voltage output of 127.07 mV when subjected to a temperature difference of 30 K, which demonstrates a performance enhancement of 4.06% compared to E/A-ReTEG. Furthermore, this study also demonstrates its implementation when wrapped around a curved surface and successfully achieves a self-powered device system after device performance optimization.