Three-dimensional (3D) poly(3,4-ethylenedioxythiophene) (PEDOT) films were demonstrated as an efficient Pt-free catalyst in dye-sensitized solar cells (DSSCs). The 3D PEDOT films were fabricated by the deposition of a polystyrene (PS) bead (diameter = 1 mu m) monolayer on fluorine-doped tin oxide (FTO) glass, followed by electrochemical polymerization (EP) of ethylenedioxythiophene (EDOT) monomer. For comparison, a flat PEDOT film and Pt counter electrodes were additionally prepared by solution casting polymerization (SCP) and the thermal reduction of a spin-coated H2PtCl6 solution, respectively. When these films were implemented as counter electrodes in quasi-solid-state DSSCs with a nanogel electrolyte, the cell efficiency of the 3D PEDOT film prepared by EP for 30sec reached 5.05%, which is higher than those of the flat PEDOT (4.11%) and Pt counter electrode (4.59%). The improved efficiency of the 3D PEDOT-based cell is attributed to its higher electrocatalytic performance and improved light reflectance, as determined by cyclic voltammogram (CV), incident photon-to-current efficiency (IPCE), and electrochemical impedance spectroscopy (EIS) analyses. (C) 2014 Elsevier Ltd. All rights reserved.