Cobalt and carbon complex as counter electrodes in dye-sensitized solar cells

Abstract

We developed cobalt and carbon complex materials as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) to replace conventional platinum (Pt) CEs. Co12 and Co15, both of which are basic cobalt derivatives, showed good redox potential with a suitable open-circuit voltage (VOC); however, their poor electrical conductivity engendered a low short-circuit current (JSC) and fill factor (FF). Mixing them with carbon black (CB) improved the electrical conductivity of the CE; in particular, JSC and FF were considerably improved. Further improvement was achieved by combining cobalt derivatives and CB through thermal sintering to produce a novel CoCB material as a CE. CoCB had good electrical conductivity and electrocatalytic capability, and this further enhanced both JSC and VOC. The optimized device exhibited a power conversion efficiency (PCE) of 7.44%, which was higher than the value of 7.16% for a device with a conventional Pt CE. The conductivity of CoCB could be further increased by mixing it with PEDOT:PSS, a conducting polymer. The device’s JSC increased to 18.65 mA/cm2, which was considerably higher than the value of 14.24 mA/cm2 for the device with Pt CEs. The results demonstrate the potential of the cobalt and carbon complex as a CE for DSSCs.