Carrier transport and thermoelectric property enhancement of polypyrrole-Nio/single-walled carbon nanotube composite system-experimental and DFT study

High-efficiency and chalcogenide (sulphides, selenides, tellurides, and polonides) free green thermoelectric power generation is a reliable and sustainable way to solve environmental and energy issues. We report an investigation on a ternary composite of Polypyrrole (PPy), Nickel (NiO) and Single-walled carbon nanotube (SWCNT) nanostructure prepared by an inexpensive two-step simple chemical route. Incorporating 50 weight% of SWCNT provides heterogeneous sites for NiO grain nucleation. It indicates a homogeneous SWCNT distribution in the PPy matrix, sensitive to the crystallinity and interaction between constituents to tune thermoelectric performance. The growth of PPy along the SWCNT's surface, due to strong pi-pi interaction with NiO encapsulation, leads to a well-ordered packed structure of the PPy chain, promoting the carrier mobility in the composite. Thermoelectric parameters and charge carrier transport are correlated with carrier concentration and mobility. Density functional theory is analysed to investigate the details of electronic structure and charge transportability, which shows an adequate amount of density of states near the Fermi level. This offers a 279 times enhanced dimensionless figure of merit (ZT) of 0.12 for PPy-NiO/SWCNT-50% as compared to that of the PPy-NiO composite at temperature 400 K, where for PPy, it is 8.94 x 10-6.