In this study, we report a composite film composed of the cobalt sulfide (CoS1.097) nanoclusters/multiwall carbon nanotube nanocomposites ([email protected]) embedded polyaniline (PANI) film (denoted as PANI/[email protected]) by an in situ electropolymerization onto a fluorinated tin oxide (FTO) glass substrate as a counter electrode (CE) for Pt-free dye-sensitized solar cells (DSCs) for the first time. The extensive cyclic voltammograms (CVs) and electrochemical impedance measurements show the PANI/[email protected] CE with an enhanced electrocatalytic activity for I-3(-) reduction compared to PANI and [email protected] CEs. Moreover, the peak current densities of the PANI/[email protected] CE show no sign of degradation after consecutive 200 CV tests, suggesting its great chemical and electrochemical stability. Furthermore, the DSC based on the in situ electropolymerized PANI/[email protected] CE achieves an improved photovoltaic conversion efficiency of 7.02%, which is higher than those of the DSCs with PANI CE (6.06%) and with [email protected] CE (5.54%), and is even comparable to that of the DSC using the Pt CE (7.16%). Therefore, the PANI/[email protected] CE can be regarded as a promising alternative CE for Pt-free DSCs. (C) 2014 Elsevier B.V. All rights reserved.