Measurement and simulation of current-voltage relation in dye-sensitized solar cells with reduced graphene oxide at the counter electrodes

Abstract

The performance of counter electrodes (CEs) dramatically affects the overall performance of dye-sensitized solar cells (DSSCs). To make the DSSCs perform with the fullest capacity of their photoelectrodes (PEs), the CEs must efficiently regenerate electrolyte and conduct electron. Thus, characterizing CEs and finding its essential features, which affect the photovoltaic performance of DSSCs, are of great importance for developing new efficient and low-cost CEs of DSSCs. Here, we report on the development of two different rGO electrodes for CEs of DSSCs by screen printing a viscous rGO paste on FTO substrates and comparison of the rGO electrodes with a thermally deposited Pt electrode. Moreover, we explain the photovoltaic performance of the DSSCs with an analytical model that resembles a diode model of DSSCs with a series resistance (Rs) comprising all the series resistive elements including a potential dependent charge transfer resistance (Rct) at the CE. The model parameters were extracted from a j-V and EIS data of the DSSCs. The model calculation suggests that Rct should be as low as possible and the higher the catalytic activity, the higher the fill-factor; however, the higher catalytic activity comes with an adverse effect to the current density of the cells. Thus, developing materials for CEs with a smaller Rct without affecting the performance of the PEs is the key to develop high-efficiency Pt-free DSSCs.