Highly conductive PEDOT films with enhanced catalytic activity for dye-sensitized solar cells

•Highly conductive PEDOT film was formed via iron oxide vapor-phase polymerization.•The resulting PEDOT film was used as CE in DSSC for the first time.•The PEDOT CE showed outstanding catalytic activity for iodine/triiodide reduction.•The PEDOT CE showed 6 times lower charge transfer resistance than of with Pt electrode.•The PEDOT-based DDSC achieved an efficiency of 8.4% slightly higher than Pt. Low-cost poly (3,4 ethylenedioxythiophene) (PEDOT) films with a high electronic conductivity of 1021 S/cm were successfully deposited via iron oxide-based vapor-phase polymerization and used as a counter electrode (CE) in dye-sensitized solar cells for the first time. Reaching a high efficiency of 8.4%, the CE showed outstanding catalytic activity in iodine/triiodide (I-/I3-) reduction, with a six times lower charge transfer resistance than a standard Pt CE. Combining low cost, easy fabrication, and high electro-catalytic activity, our PEDOT films are a promising replacement for expensive platinum CEs. This efficiency is one of the highest reported among the PEDOT-based DSSC.