Poly(3,4-ethylenedioxythiophene) nanofibers (PEDOT-NFs) with 10–50 nm diameters and high electrical conductivity (up to 83 S cm−1) have been fabricated chemically within micelles composed of sodium dodecyl sulfate (SDS) as nanoreactors. Dimethyl sulfoxide (DMSO, 5 wt%) was added to a methanol-based colloidal dispersion containing PEDOT-NFs to improve dispersibility. The dye-sensitized solar cells (DSSCs) using PEDOT-NFs as a counter electrode (CE) with low surface resistance and a highly porous surface exhibited enhanced power conversion efficiency (9.2%) compared to bulk PEDOT (6.8%). To date, PEDOT-NFs have shown the highest performance among CEs using PEDOT. It also surpassed the efficiency of platinum (Pt) CEs (8.6%). Electrochemical characterization, such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), showed that PEDOT-NFs efficiently reduced triiodide due to the enhanced electrical and morphological properties, which contributed to the high current density (17.5 mA cm−2) and fill factor (72.6%).
