This study presents a novel method to enhance the thermoelectric performance and flexibility of PEDOT:PSS fiber bundles. The researchers used a rapid and cost-effective wet-spinning method to prepare dimethyl sulfoxide (DMSO)-doped PEDOT:PSS fiber bundles, followed by post-treatment with concentrated sulfuric acid (98% H₂SO₄) to improve their thermoelectric properties. The fiber bundles, composed of multiple individual PEDOT:PSS fibers, exhibited reduced resistance, high tensile strength, and stability. The H₂SO₄ post-treatment partially removed excess PSS, increasing the electrical conductivity to 4464 S cm⁻¹ and the power factor to 80.8 μW m⁻¹ K⁻². The fiber bundles also demonstrated high flexibility and promising output power of 2.25 nW at a temperature difference of 25 K. The study provides insights into the fabrication of all-organic, flexible, and highly conductive textiles with superior thermoelectric properties, making them suitable for wearable and implantable electronic devices.This study presents a novel method to enhance the thermoelectric performance and flexibility of PEDOT:PSS fiber bundles. The researchers used a rapid and cost-effective wet-spinning method to prepare dimethyl sulfoxide (DMSO)-doped PEDOT:PSS fiber bundles, followed by post-treatment with concentrated sulfuric acid (98% H₂SO₄) to improve their thermoelectric properties. The fiber bundles, composed of multiple individual PEDOT:PSS fibers, exhibited reduced resistance, high tensile strength, and stability. The H₂SO₄ post-treatment partially removed excess PSS, increasing the electrical conductivity to 4464 S cm⁻¹ and the power factor to 80.8 μW m⁻¹ K⁻². The fiber bundles also demonstrated high flexibility and promising output power of 2.25 nW at a temperature difference of 25 K. The study provides insights into the fabrication of all-organic, flexible, and highly conductive textiles with superior thermoelectric properties, making them suitable for wearable and implantable electronic devices.