Electrocatalytic Activation of a DSSC Graphite Composite Counter Electrode Using In Situ Polymerization of Aniline in a Water/Ethanol Dispersion of Reduced Graphene Oxide

Abstract

Major drawbacks of a Pt-free counter electrode in dye-sensitized solar cells (DSSCs) are low electrical conductivity and low electrocatalytic activity. One of the promising materials for use in the counter electrode in DSSCs is graphite. It is well-known that graphite provides notable electrical conductivity, but has low electrocatalytic activity. Therefore, the surface of the graphite electrode has to be covered by an electrocatalytically active material. The presence of an electrocatalytically active layer will facilitate charge transfer at the electrode–electrolyte interface. In this report, we demonstrate the combination of reduced graphene oxide (rGO) and polyaniline (PANI) to enhance the electrocatalytic activity of a graphite counter electrode. rGO is synthesized from graphite using the sonication–oxidation method followed by reduction using ascorbic acid. This technique produced two types of rGO: floated and precipitated rGOs. PANI was grown on the surfaces of dispersed rGO in a water/ethanol system using an in situ polymerization technique. This technique resulted in both low-conductivity PANI–floated rGO (PANI–FrGO) and high-conductivity PANI–precipitated rGO (PANI–PrGO). In the composite electrode, rGO acts as a bridge between the graphite surface, and polyaniline acts as the electrocatalytically active material. The highest photovoltaic performance was obtained for a cell using the graphite/PANI–PrGO composite counter electrode. This cell gives an optimal open-circuit voltage (Voc), fill factor (FF), overall conversion efficiency (η), and short-circuit current density (Jsc) of 0.66 V, 0.508, 1.83% and 4.899 mA/cm2, respectively. Measurement of photovoltaic performance was carried out under 100 mW cm−2 of air mass (AM) 1.5 illumination. The contribution of PANI–rGO on the graphite composite counter electrode was demonstrated to enhance photovoltaic performance that opens an alternative route for the low-cost fabrication of Pt-free DSSC counter electrodes.