Preparation of reduced graphene oxide/macrocyclic manganese complex composite materials as counter electrodes in dye-sensitized solar cells

This study developed an innovative composite material using graphene oxide (GO) and macrocyclic Mn complex, which can be used as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). Varying weight ratios of GO and macrocyclic Mn complex were used, and the GO/Mn composite materials were comprehensively analyzed with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and cyclic voltammetry. The results indicate that the reaction between the GO and the macrocyclic Mn complex can be used to evenly graft the latter onto the surface of graphene. Furthermore, the redox capacity of the macrocyclic Mn complex, along with the high surface area and highly conductive graphene, can enhance the conductivity and electrochemical catalytic capacity of the CE. This study used several GO/Mn CEs for the DSSC, and the current density-voltage, incident photo-to-current conversion efficiency, and electrochemical impedance spectroscopy results all suggest that the CE made of GO and macrocyclic Mn complex with a weight ratio of 1:10 (GO/Mn (1:10)) has the greatest redox capacity and the highest device efficiency of 7.47%, which is even higher than a DSSC using platinum CE. Evidently, the GO/Mn composite material is successful as a CE for the DSSC, and because of its low cost and excellent performance, it is an ideal substitute for the expensive Platinum CE.