Low Interfacial Energy Barrier and Improved Thermoelectric Performance in Te-Incorporated Polypyrrole

Abstract

Controlled carrier dynamics and energy band engineering in polymer systems can provide a wider scope for studying the thermoelectric (TE) performance of such systems. With such an objective, polypyrrole (PPy) powders were prepared, incorporating a small amount of tellurium (Te) during the polymerization of pyrrole. The polymerization process was conducted through an oxidative chemical polymerization technique using ammonium peroxydisulfate (APS) as an oxidizing agent. The crystal structure, morphological, optical, and electrical transport properties were studied to explore the possibility of the better performance of PPy as a thermoelectric material when incorporated with Te. Since achieving a high thermo emf at a considerably low temperature difference is of great significance, and the thermoelectric performances of the prepared samples were studied in a 100 °C temperature difference range in this work. A TE power factor of as much as 23.89 μW/mK2 has been recorded for Te-incorporated PPy, which is about 859 times larger than that of pure PPy. This has been achieved by influencing the carrier dynamics in the system mainly in two ways: first, by inducing a carrier-filtering effect acquired by lowering the interfacial energy barrier between the polymer and Te and, second, by improving the carrier transport over the polymer chains with enhanced carrier hopping. As a result, a noticeably improved electrical conductivity of 0.472 S/cm and an exceptionally high Seebeck coefficient of 0.74 mV/°C have been recorded.

Full-Electrochemical Construction of High-Performance Polypyrrole/Tellurium Thermoelectrical Nanocomposites

“…Specifically, the two bands located at 933 and 966 cm –1 arise from the ring-deformation vibrations caused by the neutral state and the bipolaron state, respectively. , The band at around 1088 cm –1 is defined as the C–H in-plane deformation, while the band at 1238 cm –1 is attributed to the antisymmetrical C–H in-plane bending and ring-stretching vibrations, respectively . Besides, two characteristic bands corresponding to the C–C stretching and CC backbone stretching vibration modes for the pristine PPy appear at approximately 1373 cm –1 (denoted D band) and 1577 cm –1 (denoted G band), respectively, which are notably blue-shifted to larger wavenumber in the PPy/Te composites, indicating the occurrence of the effective charge transfer from the PPy conjugated chains to the Te due to the strong π–π interactions and van der Waals forces between them. , …”

“…The PF of the composites best embodies the synergistic effects produced by a combination of a high σ from the PPy and a large S from the Te. Specifically, the PF curve of the composites goes through a process of rising first and then descending under the co-effect of increasing σ and decreasing S upon prolonging the deposition time of the PPy on the surfaces of the Te nanocrystals, and finally reaching a peak value of 234.3 ± 4.1 μW m –1 K –2 at 14 min of the PPy deposition, which is about 45 times higher than that of the pristine PPy film, 7 times higher than that of the pure Te, and nearly 10 times as much as that of the PPy/Te composites prepared by the chemical oxidation method . To the best of our knowledge, it almost equaled the value for the PPy-based composites (240.3 ± 5.0 μW m –1 K –2 ) .…”

“…For example, Fan et al significantly enhanced the TE performance of PPy by mixing electrochemically deposited PPy with highly conductive single-walled carbon nanotubes (SWCNTs), achieving a PF of up to 240.3 ± 5.0 μW m –1 K –2 at room temperature, which is the highest value for PPy-based composites reported so far. Very recently, Debnath et al prepared tellurium (Te)-incorporated PPy powders utilizing the oxidative polymerization of pyrrole (Py) in the presence of a small amount of Te powder, and the PF was as much as 23.89 μW m –1 K –2 at 373 K, which is about 859 times higher than that of pure PPy in spite of a fairly moderate value. To our knowledge, it is a sole report on the TE performance of the PPy/Te composites to date.…”

Advances in conducting polymer-based thermoelectric materials and devices

“…Therefore, high-performance, low-toxic, and high-stability F-TEGs are the most promising candidates to meet the demand of the future electronic market [33][34][35] . Similar to conventional TE devices, the structure of F-TEGs can be described as the combination of several pairs of p-and n-type TE materials, as shown in Figure 1C [1,[36][37][38] .…”

Band Alignment Enabling Effective Charge Transfer for the Highly Enhanced Raman Scattering and Fluorescence of Metal-Nanoparticle-Decorated Conjugated Polymer Nanowires

“…Those two peaks were usually reported in bulk PPy film , where an adhesion strength between the PPy and the substrate is expected to be stronger . On the contrary, these peaks are not distinct nor easily observed in nanostructures. ,− The SERS EF can be calculated using the peak intensity obtained in the metal-NPs-decorated PPy NW (PPy MetalNPs NW) and the PPy NW (see Experimental Section for details). The SERS EF is calculated as 1,000 ± 50 from the peak of CC stretching and as 2,000 ± 100 from the peak of ring stretching.…”