Electrochemical Preparation and Regulation of Flexible Polypyrrole Film toward Enhanced Thermoelectric Performance

Flexible thermoelectric (TE) materials have received significant attention for their key role in developing renewable energy. Polypyrrole (PPy) film, as a promising TE material, shows poor flexibility and electrical conductivity by common oxidation polymerization due to π-conjugated rigid molecules. However, the dynamic conductive network formed between soft and rigid conductive polymers can dissipate mechanical energy while maintaining the integrity of the π-conjugation structure, enabling flexible and conductive thin films. To obtain a flexible free-stranding PPy film, pentaerythritol ethoxylate (PEE)-borate was introduced into the PPy matrix to form a dynamic composite network (PPy/PEE) and enhance the elongation at the break (∼5.4%) due to the strong intermolecular interaction between PPy and PEE with the dopant anions (BF3–). The as-prepared PPy films obtained at the PEE concentration of 0.07 M have achieved an enhanced electrical conductivity as high as 132.30 S cm–1 and a power factor of 0.33 μW m–1 K–2. After the electrochemical treatment at 0.8 V, the electrical conductivity and power factor are further improved to 177.83 S cm–1 and 0.54 μW m–1 K–2, respectively. The Seebeck coefficient dramatically increased up to 17.27 μV K–1 in the dedoped state. The PPy/PEE composite film still exhibits good flexibility after electrochemical dedoping, which makes it a promising way to optimize TE for flexible PPy films.