Full Length ArticleCost-effective CoPd alloy/reduced graphene oxide counter electrodes as a new avenue for high-efficiency liquid junction photovoltaic devices

•Bimetallic CoPd nanoparticles/reduced graphene oxide are prepared by dry plasma reduction.•The electrocatalytic activity as well as electric conductivity is significantly enhanced.•The highest efficiency is recorded from DSC employed Co0.9Pd0.1/reduced graphene oxide counter electrode.•The strategy is for Pt-free counter electrode in PV-device using bimetallic CoPd nanoparticles/reduced graphene oxide.

This work presents the synthesis of CoxPd1-x alloys (0 ≤ x ≤ 1) on a reduced graphene oxide (RGO) surface using the dry plasma reduction method. The formation of CoPd alloys on the RGO surface is confirmed through high-resolution scanning electron microscopy (HRSEM) and X-ray photoelectron spectroscopy (XPS) measurements, and transmittance electron microscopy (TEM). Then, the developed materials are applied as Pt-free counter electrodes (CEs) in dye-sensitized solar cells (DSCs). In order to obtain efficient CEs, the chemical composition of the CoxPd1-x/RGO is controlled through optimizing the volume ratio of the Co and Pd precursors during the synthesizing process. Due to the optimization of the charge-transfer resistance (Rct) and the diffusion impedance (Zw) values of the Co0.9Pd0.1/RGO CE, the device using the Co0.9Pd0.1/RGO CE exhibits the highest efficiency among the fabricated cells. Note that the cells using Co/RGO and Pd/RGO exhibit efficiencies of 5.17% and 5.41%, respectively. The proposed strategy is simple and efficient; thus, it is promising for fabricating highly efficient and low-cost CE materials for DSCs.