Pt-free spray coated reduced graphene oxide counter electrodes for dye sensitized solar cells

• Counter electrode: FTO glass spray coated with reduced graphene oxide.
• Lowering of charge transfer resistance at the counter electrode/electrolyte interface.
• Effective reduction of I−3 to I− due to heat treatment with N2 for increasing JSC.
• Energy conversion efficiency of 3.96% without using Pt as a counter electrode.
• Easy fabrication method for scaling up active area of counter electrode.

Graphene oxide (GO) was synthesized using a modified Hummers method and was reduced by using focused sunlight to obtain solar reduced graphene oxide (SRGO). GO and SRGO are then used as Pt-free counter electrode materials in dye sensitized solar cells (DSSCs). GO and SRGO counter electrodes were prepared by a simple spray coating method to produce homogeneous electrode layers. The DSSCs with GO and SRGO counter electrodes exhibited an overall power conversion efficiencies of ∼3.4 and ∼4%, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy reveal that the DSSC with SRGO counter electrode exhibits higher electro-catalytic activity and lower charge transfer resistance at the electrode/electrolyte interface (in comparison to the DSSC with GO) resulting in higher conversion efficiency. Moreover, the microstructural features of SRGO are found to be suitable for its improved interaction with the liquid electrolyte and the enhanced electro-catalytic activity at its surface.

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