Dual Post‐Treatments Boost Thermoelectric Performance of PEDOT:PSS Films and Their Devices

Abstract

Owing to intrinsically high electrical conductivity and low thermoelectric conductivity, poly(3,4‐ethylenedioxithiophene):poly(styrenesulfonate) (PEDOT:PSS) shows promising thermoelectric properties. However, its relatively low power factor limits the practical applications of PEDOT:PSS. Here, unique dual post‐treatments by sodium sulfite (Na2SO3) and formamide (CH3NO) to boost the thermoelectric performance of flexible PEDOT:PSS films with an optimized power factor of 74.09 µW m–1 K–2 are used. Comprehensive characterizations confirm that CH3NO reduces the excessive insulating PSS and thereby increases the electrical conductivity, while Na2SO3 lowers the reduction of the doping level of PEDOT, leading to an increased Seebeck coefficient. Furthermore, the rationally post‐treated PEDOT:PSS films are assembled into a flexible thermoelectric device that exhibits an open‐circuit voltage of 2.8 mV using the heat from the human arm and an output power density of 2.56 µW cm–2 by a temperature difference of 25 K, indicating great potential for practical applications on sustainably charging low‐grade wearable electronics.

Optimization of Wet-Spun PEDOT:PSS Fibers for Thermoelectric Applications Through Innovative Triple Post-treatments

“…Following dual treatment with H 2 SO 4 and NaBH 4 , the Raman peak shifts from 1420 cm to 1424 cm −1 . This is correlated with the deformation of the main chain during the chemical reduction process of polarons and neutral states and the transition between benzoid and quinoid types [37,41]. After the treatment with EMIM:DCA/CH 3 OH solution, the Raman peak at 1424 cm −1 undergoes a redshift of around 6 cm −1 .…”

“…For the XRD results, a characteristic peak was observed around 6.6° in the pristine fibers, corresponding to the alternate arrangement of layers on the (100) planes of PEDOT and PSS [25,[33][34][35]. Through H 2 SO 4 treatment, H 2 SO 4 -NaBH 4 treatment, and H 2 SO 4 -NaBH 4 -EMIM:DCA/ CH 3 OH treatment, the peak at around 6.6° became sharper, indicating an increase in fiber crystallinity due to the efficient elimination of PSS [36,37]. This is consistent with the SEM results.…”

Weavable thermoelectrics: advances, controversies, and future developments

“…Last but not least, many organic materials can be obtained through sustainable production methods, reducing reliance on hazardous chemicals and scarce resources. The electrical properties of organic materials, such as σ and S, can often be adjusted through molecular design and chemical modification to optimize thermoelectric performance [195,196].…”

Advances in flexible inorganic thermoelectrics

“…29 The most commonly used conducting polymers are poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT: PSS). [101][102][103][104] Sometimes, there may be an energy-filtering effect at the interfaces between the organic and inorganic materials due to the difference in their electronic structures, which can help maintain a high S while keeping a high σ since such an interface can potentially filter lowenergy carriers. 29 Therefore, some works are focusing on the interface design between organic and inorganic materials.…”

“…Generally, the conducting polymers used for hybridization should be highly conductive, which can be achieved by rational pre‐ or post‐treatments 29 . The most commonly used conducting polymers are poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) 101–104 . Sometimes, there may be an energy‐filtering effect at the interfaces between the organic and inorganic materials due to the difference in their electronic structures, which can help maintain a high S while keeping a high σ since such an interface can potentially filter low‐energy carriers 29 .…”