This work presents the synthesis and immobilizing of bimetallic PtMo nanoparticles (NPs) on a Fluorine doped tin oxide (FTO) substrate using a dry plasma reduction under atmospheric pressure at a low temperature and without using toxic reagents. These alloys are placed as counter electrodes (CEs) for efficient dye sensitized solar cells (DSCs). For this purpose, an experimental approach is designed for the co-reduction of Pt and Mo precursors with different volume ratios. The TEM, HRSEM, XRD and XPS measurements are also obtained in order to analyze the morphology and chemical composition of the PtMo alloys, respectively. Furthermore, the electrochemical catalytic activities are examined through CV, EIS and Tafel measurements. The effect of the CEs on the efficiency of the devices is further confirmed using photovoltaic measurements. It is confirmed that the bimetallic PtMo NPs, with a small particle size, are successfully immobilized and well distributed on the FTO surface without agglomeration. The electrochemical catalytic activity of the electrodes follows the sequence of Pt0.52Mo0.48 > Pt0.83Mo0.17 > Pt1Mo0 > Pt0.43Mo0.57 > Pt0.19Mo0.81 > Pt0.08Mo0.92 > Pt0Mo1. The improvement in the catalytic activity of the developed materials results from the electronic effect that originates from the upward shift of the platinum d-band to the Fermi energy level upon alloying. Thus, the highest efficiency of 8.51% is archived for the cell using the Pt0.52Mo0.48 CE. Note that the efficiency of the device using a Pt CE is only 7.86%. The results also indicate the improved stability of the developed CEs in iodide electrolyte. (C) 2017 Elsevier Ltd. All rights reserved.