Polyaniline (PANI)/graphene (GP) thermoelectric (TE) composite films were prepared by a combination of in situ polymerization and a solution process. It was found that there existed a large number of graphene–polyaniline nano-interfaces in the composite films with graphene nanoplates aligned in the PANI matrix in the direction parallel to the substrate. SEM, TEM, Raman, XPS and UV-Vis analyses indicated that polyaniline coated on the surface of graphene by the strong π–π conjugation interactions during in situ polymerization, and then the PANI molecular chains were expanded by the chemical interactions between polyaniline and solution. Both the in situ polymerization process and solution process contributed to the uniform dispersion of graphene in the PANI matrix, which not only increased the number of graphene–polyaniline nano-interfaces in the composite, but also strengthened the π–π conjugation interactions between graphene and polyaniline, resulting in more ordered regions forming in the composite films. Consequently, the Seebeck coefficient of the composite films was remarkably improved and higher than the values calculated based on the series-connected two-component mixture model. The optimal electrical conductivity and Seebeck coefficient of the composite with 48 wt% graphene reached 814 S cm⁻¹ and 26 μV K⁻¹, respectively, resulting in a maximum power factor of 55 μW m⁻¹ K⁻², which is the highest value among the reported polymer/graphene composite TE materials.

Carbon nanotube (CNT)/Polyaniline (PANI) thermoelectric composite nanofibers were prepared by a combination of in situ polymerization and electro-spinning processes. The obtained composite nanofibers were macroscopically aligned, while the CNTs were embedded in the nanofibers and oriented along the fiber axis. Polarized Raman spectra and X-ray diffraction (XRD) studies verified that the PANI backbone chains were orientated along the CNT axis and therefore along the fiber axis due to the strong chemical interactions between PANI and CNTs. The highly ordered arrangement of the PANI backbone chains not only reduces the π–π conjugated defects in the polymer backbone, but also increases the effective degree of electron delocalization and therefore enhances the carrier mobility in PANI, which results in the anisotropic thermoelectric properties especially with more than a doubled improvement of power factor in the orientation direction. This study not only provides an effective route to orient the conducting polymer chains at the molecular level but also demonstrates a possibility to design a conducting polymer with high thermoelectric performance through constructing a highly extended and orderly aligned backbone chain structure by chemical routes.

Polyaniline (PANI)/graphene thermoelectric (TE) nanocomposite films with three types of graphene have been prepared by a solution-assistant dispersing method. The graphene nanoplates were aligned in the PANI matrix in the direction parallel to the substrate. The structural defects and oxygen content in the graphene had great influence on the TE performance of the PANI/graphene composites. The composite films prepared with graphene with lower structural defects and oxygen impurities showed higher TE properties. The maximum electrical conductivity and power factor of the composite film reached 856 S cm⁻¹ and 19 μW m⁻¹K⁻² respectively, which were the highest values among the reported polymer/graphene TE composites. These outstanding TE properties can be ascribed to the strong π–π conjugation interactions between PANI and low-defect graphene as well as to the solution process, which expands the PANI molecular conformation and therefore results in the enhancement of carrier mobility and electrical conductivity. This work provides a simple and effective approach to preparing polymer/graphene composite materials with high TE performance.

We have developed a novel strategy to in situ synthesize water-soluble ternary PANI/SWNT/Te nanocomposites with uniform structures and high thermoelectric (TE) properties. An abnormally high Seebeck coefficient was obtained for the ternary PANI/SWNT/Te nanocomposite films due to the energy filtering effect at the interfaces of PANI/SWNTs and PANI/Te, while the electrical conductivity still remained relatively high. As a result, the TE power factor of the ternary composite films was up to 101 μW m⁻¹ K⁻², which was much higher than that of the individual components (PANI, SWNTs and Te nanorods). Moreover, a TE module made up of the ternary PANI/SWNT/Te nanocomposite films was fabricated, which was able to generate a high power density of 62.4 μW cm⁻². Our results reveal a successful approach through designing the nanostructures and energy barriers of ternary nanocomposites to improve the TE properties of PANI.

The inhibitor-dependent poly(3,4-ethylenedioxythiophene) (PEDOT) fabrication suffers major problems in the areas of controllability and film thickness. In this work, we found that anions play a key role in both the polymerization and the structure of PEDOT. As a precursor, anions greatly influence the reaction rate and oxidant solubility. In its role as a counter-ion, the anions also affect chain conductance and crystal growth. With these behaviors in mind, a self-inhibited polymerization approach using novel oxidants with appropriate anions was successfully developed to facilitate the fabrication of high quality in situ polymerized PEDOT films and solve the thickness limitation problem. Inhibitor-free heavy oxidative solutions with weakly basic anions enable the spin-coating of thick and homogeneous oxidant layers and also effectively inhibit both the crystallization of the oxidant and H⁺ formation throughout the polymerization process. PEDOT: dodecylbenzenesulfonate (PEDOT:DBSA) exhibits the highest performance among all candidates due to its appropriate anion basicity and low steric effect. An extremely high doping level of 42.9% is achieved, and an electrical conductivity of ~1100 S cm⁻¹ is successfully maintained for film thicknesses between 310 nm and 1.79 μm. In addition, the thermoelectric power factor (RT) for pristine films was improved to 77.2 μW mK⁻² from 69.6 μW mK⁻² by the dedoping treatment. This study provides a new approach for fabricating high performance PEDOT thick films using anion-based design.