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Abstract: High‐performance n‐type thermoelectric polymers are vital in the development of polymer thermoelectric generators (PTEGs). However, the progress is very slow due to their low stability and low thermoelectric properties. Here, aniline oligomer‐block‐polyethylene glycol‐block‐aniline oligomer (ANI)n‐b‐PEO‐b‐(ANI)n) (n = 4, 8, 16) are prepared and studied. The results indicate that the (ANI)n‐b‐PEO‐b‐(ANI)n show unique temperature sensitivity and switch from p‐type to n‐type when the temperature is above 300 K. Differential scanning calorimetry curves show that the Tg of the (ANI)n‐b‐PEO‐b‐(ANI)n is lower than 300 K, indicating that PEO segments of the (ANI)n‐b‐PEO‐b‐(ANI)n easily move above 300 K and have high flexibility. Temperature‐dependent Raman spectra confirm that there are strong interactions between PEO segments and aniline oligomers during the raising temperature, and PEO chains might provide plenty of negative charge at high temperature, which can convert the (ANI)n‐b‐PEO‐b‐(ANI)n into n‐type thermoelectric materials. To adjust the number of aniline unit, (ANI)8‐b‐PEO‐b‐(ANI)8 shows excellent n‐type characteristics with Seebeck coefficient as large as −1171 µV K−1 at 381 K. The strong interaction between PEO and aniline oligomers plays a dominant role in the n‐type thermoelectric performance of the triblock copolymers, which have potential application in the field of PTEGs and temperature sensors. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) generators consisting of flexible and lightweight p- and n-type single-walled carbon nanotube (SWCNT)-based composites have potential applications in powering wearable electronics using the temperature difference between the human body and the environment. Tuning the TE properties of SWCNTs, particularly p- versus n-type control, is currently of significant interest. Herein, the TE properties of SWCNT-based flexible films consisting of SWCNTs doped with polyethyleneimine (PEI) were evaluated. The carrier type of the SWCNT/PEI composites was modulated by regulating the proportion of SWCNTs and PEI using simple mixing techniques. The as-prepared SWCNT/PEI composite films were switched from p- to n-type by the addition of a high amount of PEI (>13.0 wt.%). Moreover, interconnected SWCNTs networks were formed due to the excellent SWNT dispersion and film formation. These parameters were improved by the addition of PEI and Nafion, which facilitated effective carrier transport. A TE generator with three thermocouples of p- and n-type SWCNT/PEI flexible composite films delivered an open circuit voltage of 17 mV and a maximum output power of 224 nW at the temperature gradient of 50 K. These promising results showed that the flexible SWCNT/PEI composites have potential applications in wearable and autonomous devices. [ABSTRACT FROM AUTHOR]

Flexible thermoelectric materials are important as self-powered systems in wearable and flexible thermoelectric devices; to this end, using single-walled carbon nanotubes (SWCNTs) is advantageous for enhancing the overall thermoelectric performance. In this study, to further enhance the thermoelectric properties of SWCNTs and overcome the weak interfacial interaction between hydrophilic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and hydrophobic pristine SWCNTs, a graphene quantum dots (GQDs) intermediate layer is used to couple PEDOT:PSS and SWCNTs. Multilayer films comprising PEDOT:PSS, GQDs, and SWCNTs are constructed and prepared by successively drip-coating the GQDs and PEDOT:PSS on the SWCNTs film surface. Analysis of the interfacial morphology reveals that the hydrophilic GQDs improve interfacial adhesion between PEDOT:PSS and the SWCNTs. Compared to a PEDOT:PSS/SWCNT bilayer film, the electrical conductivity of the PEDOT:PSS/GQDs/SWCNT multilayer films is enhanced, while the Seebeck coefficient is slightly lower. Meanwhile, the thermal conductivity is significantly decreased due to the increased interfacial phonon scattering. The minimum in-plane thermal conductivity for the PEDOT:PSS/GQDs/SWCNT films is 7.4 W‧m−1‧K−1, resulting in an enhanced figure of merit of 1.96 × 10−3 at 298 K. Thus, the GQDs intermediate layer is beneficial for coupling PEDOT:PSS and SWCNTs layers. The strategy employed herein offers novel insights into the preparation of high-performance SWCNTs-based thermoelectric materials. [Display omitted] • Layer structural PEDOT:PSS/GQDs/SWCNTs thermoelectric films are prepared. • GQDs improves the interfacial adhesion between PEDOT:PSS and SWCNTs. • The minimum thermal conductivity for PEDOT:PSS/GQDs/SWCNT is 7.4 W•m−1•K−1. • PEDOT:PSS/GQDs/SWCNT hybrid film exhibits an optimized ZT of 1.96 × 10−3 at 298 K. [ABSTRACT FROM AUTHOR]

In the present study, Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS), with the incorporation of graphene quantum dot (GQD)-coated single-walled carbon nanotubes (SWCNTs), has been used in the preparation of PEDOT:PSS/SWCNTs/GQDs thermoelectric films (PSG). The effect of SWCNTs/GQDs (as a nanofiller) on the microstructure and thermoelectric properties of the composite films has been especially investigated. It was observed that the addition of GQDs will induce a phase separation between PEDOT and PSS. Furthermore, the enhanced interfacial bonding induced a microstructure ordering and an accelerated transport of carriers. The in-plane electrical conductivity and Seebeck coefficient of the obtained film reached 1036 S•cm−1 and 13.8 μV•K−1, respectively, for 1 wt% of SWCNTs/GQDs. These results gave a high power factor (PF) of up to 19.9 µW•m−1•K−2, which is about six times as high as for pristine PEDOT:PSS and also higher than that of PEDOT:PSS/SWCNTs. The obtained maximum ZT reaches 3.22 × 10−3 with high PF value and low in-plane thermal conductivity. The present research provided a new strategy for developing high performance organic thermoelectric materials. [Display omitted] • Good dispersion of SWCNTs in PEDOT:PSS after GQDs being incorporated. • Strong interfacial interaction between SWCNTs and PEDOT chains induced by GQDs. • Assembly of PEDOT chain on the surface of SWCNTs enhancing carriers transporting. • Energy-filtering effect provided by SWCNTs and GQDs improving the Seebeck coefficient [ABSTRACT FROM AUTHOR]

• Ordered multilayer-structure films and fiber-structure films have been prepared via supramolecular self-assembly of PEDOT:PSS and conductive triblock copolymers. • PEDOT:PSS dominated multilayer structure exhibits p-type characteristics, while conductive triblock copolymer dominated fiber structure shows n-type characteristics. • Supramolecular self-assembly provides a new strategy to develop high performance PEDOT:PSS based thermoelectric films. To improve the thermoelectric properties of poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), ordered multilayer-structure films and fiber-structure films were prepared via self-assembly of PEDOT:PSS and aniline tetramer-b-polyethylene glycol-b-aniline tetramer triblock copolymer (APA). Compared to PEDOT:PSS, the multilayer PEDOT:PSS/APA showed stable electrical conductivity and a higher Seebeck coefficient. A maximum power factor of 14.6 μW/(m·K2) was obtained when the mass ratio of PEDOT:PSS to APA was 100:20 at an electrical conductivity of 288 S/cm and a Seebeck coefficient of 21.5μV·K−1, 113% higher than that of PEDOT:PSS. Although the fiber-structure films had relatively low electrical conductivity and Seebeck coefficient, they showed n-type characteristics. The multilayer-structure films and fiber-structure films both have low thermal conductivity, correspondingly, their ZT values are beyond 0.01. The structure tuning of PEDOT:PSS/APA via supramolecular self-assembly between the polymer segments may provide a strategy to develop high performance organic thermoelectric materials. [ABSTRACT FROM AUTHOR]