Influence of cobalt redox couple concentration on the characteristics of liquid and quasi-solid electrolytes and on the photovoltaic parameters of dye-sensitised solar cells

Dye-sensitised solar cell (DSSC) is a next-generation solar energy conversion device. The electrolyte, which is one of the key components of a DSSC, greatly affects its short-circuit current density (J_sc) and open-circuit voltage (V_oc) and hence, its overall performance. In this work, bis(trifluoromethane)sulfonimide (TFSI) cobalt complex was used for the first time as redox couple in DSSC, and an effort was carried out to study the effects of the varying concentration of cobalt complex redox ions on the characteristics of the prepared liquid electrolytes (LEs) and quasi-solid electrolytes (QEs), and on the photovoltaic parameters of DSSCs. Specifically, the electrolyte characteristics include the viscosity and electrical conductivity, while the photovoltaic parameters of DSSCs include J_sc, V_oc, fill factor (FF) and power conversion efficiency (PCE). The viscosity of electrolytes was found to increase with increasing molar concentrations and then further increased with the addition of polyethylene oxide (PEO); the highest viscosity of 2.49 cP was obtained at 44 rpm for QE-50. The highest conductivity measured by electrochemical impedance spectroscopy was 83 mS cm^− 1 for LE-50. Finally, zinc oxide-based DSSCs with platinum counter electrodes were fabricated for current-voltage measurements. Among the synthesised electrolytes, QE-35-based DSSC showed a better combination of J_sc and V_oc, resulting in a PCE of 0.48%.

Graphical Abstract