Poly(benzodifurandione) Coated Silk Yarn for Thermoelectric Textiles

Abstract Thermoelectric textile devices represent an intriguing avenue for powering wearable electronics. The lack of air‐stable n ‐type polymers has, until now, prevented the development of n ‐type multifilament yarns, which are needed for textile manufacturing. Here, the thermomechanical properties of the recently reported n ‐type polymer poly(benzodifurandione) (PBFDO) are explored and its suitability as a yarn coating material is assessed. The outstanding robustness of the polymer facilitates the coating of silk yarn that, as a result, displays an effective bulk conductivity of 13 S cm −1 , with a projected half‐life of 3.2 ± 0.7 years at ambient conditions. Moreover, the n ‐type PBFDO coated silk yarn with a Young's modulus of E = 0.6 GPa and a strain at break of ε break = 14% can be machine washed, with only a threefold decrease in conductivity after seven washing cycles. PBFDO and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated silk yarns are used to fabricate two out‐of‐plane thermoelectric textile devices: a thermoelectric button and a larger thermopile with 16 legs. Excellent air stability is paired with an open‐circuit voltage of 17 mV and a maximum output power of 0.67 µW for a temperature difference of 70 K. Evidently, PBFDO coated multifilament silk yarn is a promising component for the realization of air stable thermoelectric textile devices.