A Free-Standing High-Output Power Density Thermoelectric Device Based on Structure-Ordered PEDOT:PSS

A free-standing high-output power density polymeric thermoelectric (TE) device is realized based on a highly conductive (≈2500 S cm⁻¹) structure-ordered poly(3,4-ethylenedioxythiophene):polystyrene sulfonate film (denoted as FS-PEDOT:PSS) with a Seebeck coefficient of 20.6 µV K⁻¹, an in-plane thermal conductivity of 0.64 W m⁻¹ K⁻¹, and a peak power factor of 107 µW K⁻² m⁻¹ at room temperature. Under a small temperature gradient of 29 K, the TE device demonstrates a maximum output power density of 99 ± 18.7 µW cm⁻², which is the highest value achieved in pristine PEDOT:PSS based TE devices. In addition, a fivefold output power is demonstrated by series connecting five devices into a flexible thermoelectric module. The simplicity of assembling the films into flexible thermoelectric modules, the low out-of-plane thermal conductivity of 0.27 W m⁻¹ K⁻¹, and free-standing feature indicates the potential to integrate the FS-PEDOT:PSS TE modules with textiles to power wearable electronics by harvesting human body's heat. In addition to the high power factor, the high thermal stability of the FS-PEDOT:PSS films up to 250 °C is confirmed by in situ temperature-dependent X-ray diffraction and grazing incident wide angle X-ray scattering, which makes the FS-PEDOT:PSS films promising candidates for thermoelectric applications.