This paper describes the photovoltaic performance of dye-sensitized solar cells (DSSCs) containing graphene-incorporated counter electrodes (CEs). The location and thickness of graphene in CEs are optimized to improve the photovoltaic performance of DSSCs, compared with typical Pt CEs. The DSSC, with a Pt/few-layer graphene (FLG) CE, achieved 8% in short-circuit current density and 13% in power conversion efficiency (PCE). Electrochemical impedance spectroscopy shows that the DSSC, with a Pt/FLG CE, exhibits a series resistance lower than that with a Pt CE. The lower series resistance is attributed to the contact resistance at the interface of platinum and fluorine doped tin oxide. The contact resistance is reduced by the formation of the thin platinum-carbon composite layer. It is demonstrated that the consumption of Pt could be reduced with a Pt/FLG CE. However, graphene/Pt CEs resulted in a slow charge-transfer process and consequently a worse photovoltaic performance of DSSCs. ? 2013 AIP Publishing LLC.
