A Wearable All‐Fabric Thermoelectric Generator

DOI: 10.1002/admt.201800615 demonstrate the ability to produce power when exposed to a temperature gradient. The low thermal conductivity of the material prevents rapid heat equilibration, which creates an inequity of energy across the material. This disparity in energy induces the migration of charges within the material toward the colder side.[9–12] Researchers have theorized that up to 5 mW of power can be harvested from a normal human body after an 8 h workday in an indoor environment by clipping silicon thermopiles to the outer surfaces of garments.[13] However, the form factor and garment integration of these thermopiles needs to be optimized before practical thermoelectric generators (TEGs) can be expected.[14,15] Additionally, the availability and toxicity/biocompatibility of materials must be considered when constructing a wearable device. While the most efficient thermoelectric generators are composed of Bi2Te3, tellurium is a toxic, rare earth chalcogenide of limited availability.[21] Silicon-based devices do not face this hurdle but demonstrate significantly lower thermoelectric harvesting efficiencies and poor flexibility.[22] Alternatively, conjugated polymers are biocompatible, flexible and lightweight materials comprised of earth-abundant elements, that are perfectly positioned for integration with bodyworn electronics.[23] However, the observed thermoelectric performance of typical, solution-processed polymers have not matched those of inorganic counterparts to date[24,25] and, therefore, polymers have only been used as composites with higher efficiency materials, such as carbon nanotubes,[26–29] that often demonstrate attenuated or unreliable performances when incorporated into natural fibers or fabrics.[30] In this work, we show that vapor-printed conjugated polymer films on fabrics display remarkably high thermoelectric power factors and can be incorporated into a custom-knit garment that yields high, stable thermovoltage outputs when worn on the body.