Fabrication and characterization of a new dye sensitized solar cell with a new Schiff base cobalt complex as a redox mediator

Abstract

One-electron fast redox mediators like cobalt complexes are a new important class of mediator system in dye sensitized solar cells (DSCs) that have some special features such as fast regeneration reactions, low absorption in the visible light range without the occurrence of destructive reactions with the materials of the DSCs. In this research, for the first time, a new Schiff base cobalt complex has been synthesized and used as an efficient redox mediator system in dye sensitized solar cells which are fabricated using D35 organic dye as a sensitizer and mesoporous nanostructured titania as a photoanode. J–V measurements of the prepared DSC were carried out under AM1.5G irradiation and photoelectrochemical parameters like the open-circuit voltage (V_oc), short-circuit current density (J_sc), fill factor (FF), voltage decay and the overall efficiency were measured and compared to the conventional symmetric cobalt polypyridine complexes. The J–V curve results show enhancement of the open-circuit voltage in the DSC with the new Schiff base cobalt complex mediator compared with classic polypyridine cobalt complexes. Comparison between the dark currents of the investigated cells provides qualitative information about the electron recombination process. Lower dark currents were observed in DSCs with a titania blocking layer. Voltage decay measurements, the calculated electron lifetime and the effective recombination order (β) show lower average β values for the DSC with the Schiff base cobalt complex as a redox mediator.