A Comprehensive Investigation into Thermoelectric Properties of PEDOT:PSS/Bi0.5Sb1.5Te3 Composites

Abstract

The demand for sustainable power sources for wearable electronic devices has spurred exploration into novel energy harvesting technologies. Among these, flexible thermoelectric (TE) materials and generators (TEGs) hold promises for transforming body heat into electrical power. For this purpose, organic and polymeric semiconducting materials, such as Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), have been in the forefront of research recently due to their flexibility, nontoxicity, easy processability, high electrical conductivity, and low thermal conductivity. However, hybridization with inorganic materials, optimization of doping levels, and structural modifications to enhance their TE conversion efficiency is still an ongoing area of investigation, and a comprehensive study encompassing all these approaches is lacking. In this research, Bi0.5Sb1.5Te3 particles with a wide range of size and concentration were mixed with PEDOT:PSS and the microstructure and TE properties of resulting composite films were systematically studied. Then, the optimal composite, exhibiting a maximum power factor at room temperature, underwent various single and sequential post-treatments using secondary dopants and chemical dedoping agents. While a post-treatment with 0.5 M H2SO4 increased the power factor 240 times compared to the pristine thin film composite, a sequential pos-treatment with 0.5 M H2SO4 and 0.1 M NaOH resulted in a 864-fold increase of the power factor at room temperature. Furthermore, temperature-dependent electrical conductivity and Seebeck coefficient analyses revealed that charge carrier transport mechanism changed from three-dimensional variable range hopping in pristine samples to metallic conduction in post-treated samples. This comprehensive study explores the relationship between particle engineering, post-treatment strategies, and the resulting microstructural, morphological, and TE properties of PEDOT:PSS/ Bi0.5Sb1.5Te3 composite thin films. The findings offer critical insights into optimizing flexible TE materials and TEGs for efficient energy harvesting in wearable electronics.