A composite of poly(3,4-ethylendioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and multi-walled carbon nanotubes (MWNTs) was electrochemically polymerized on a fluorine-doped tin oxide (FM) substrate and used as a photocathode for a dye-sensitized solar cell. The MWNTs were previously O-2 plasma treated and simultaneously entrapped while the PEDOT:PSS film was electropolymerized. The resulting plasma-functionalized MWNT-entrapped PEDOT:PSS composite showed enhanced electrocatalytic activity for the reduction of I-3 to I, this was confirmed by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and incident photon-to-current conversion efficiency (IPCE) measurements. An improved energy conversion efficiency by about 13.9% was observed in optimized conditions as compared to a platinized FTO-based photocathode. (C) 2014 Elsevier Ltd. All rights reserved.