PANI coupled hierarchical Bi₂S₃nanoflowers based hybrid nanocomposite for enhanced thermoelectric performance

Bismuth sulfide (Bi₂S₃) is a promising material for thermoelectric applications owing to its non-toxicity and high abundance of bismuth (Bi) and sulfur (S) elements on earth. However, its low electrical conductivity drastically reduces the value of the figure of merit (ZT). In this work, we have synthesized three-dimensional (3D) hierarchical Bi₂S₃nanoflowers (NFs) by the hydrothermal route and further incorporated them with conducting polymer polyaniline (PANI) by simple chemisorption method. We have investigated the thermoelectric properties of the as-prepared Bi₂S₃NFs and PANI/Bi₂S₃nanocomposite samples and it is demonstrated that the incorporation of the PANI matrix with the 3D hierarchical Bi₂S₃NFs provides a conducting substrate for the easy transport of the electrons and reduces the barrier height at the interface, resulting in ∼62% increment in the electrical conductivity as compared to Bi₂S₃NFs. Moreover, a decrement in the thermal conductivity of the PANI/Bi₂S₃nanocomposite is observed as compared to pristine Bi₂S₃NFs due to the increased phonon scattering at the interfaces facilitated by the hierarchical morphology of the NFs. Furthermore, an increment in the electrical conductivity and simultaneous decrement in the thermal conductivity results in an overall ∼20% increment in the figure of merit (ZT) for PANI/Bi₂S₃nanocomposite as compared to pristine Bi₂S₃NFs. The work highlights an effective strategy of coupling 3D hierarchical metal chalcogenide with conducting polymer for optimizing their thermoelectric properties.