Abstract:
A counter electrode (CE) fabricated with thermally reduced graphene oxide synthesized from Sri
Lankan graphite is proposed for promising Platinum-free dye sensitized solar cells (DSSC). As it is
well known, Sri Lankan natural graphite has become more attractive and demanding in the world due
to its high purity and high crystallinity. In a DSSC, a thin film of Platinum (Pt) is generally used as
the catalytic material on the CE due to its high conductivity and superior electro-catalytic activity.
However, there is a considerable attention to replace Pt based CEs due to their high cost and limited
supply. Recently, extensive research has been performed on using carbon materials for the CEs due to
their low cost, high conductivity and good catalytic activity. In this study, reduced graphene oxide
(RGO) was synthesized and deposited on FTO conducting glass substrate by spray method. To
investigate the effect of sintering temperature of the CE on the performance of DSSCs, a series of
RGO based CEs were prepared with different sintering temperatures from 100 oC to 300 oC by
increasing the temperature by 50 oC intervals. Results confirmed that the DSSCs prepared with
sintered CEs exhibit a better photovoltaic performance compared to the DSSCs made with un-
sintered CEs essentially due to the enhanced adhesion to the FTO glass substrate in the sintered
composite material. DSSCs with CEs sintered at 250 oC have exhibited the highest efficiency of 4.52
% compared to the DSSC with un-sintered CEs (efficiency=1.35 %). This low cost RGO CE exhibits
good stability and acceptable efficiency compared to Pt CE (7.82 %) in DSSCs operating under
similar conditions. Synthsized RGO sheets were characterized using scanning electron microscopy,
Raman spectroscopy and X-ray diffraction. The electro-catalytic activity of RGO CE was determined
by cyclic voltammetry. Results suggested that this CE can be one of the alternatives to the Pt CEs in
DSSCs with further modifications.
Keywords: Dye sensitized solar cells; Counter electrode; Reduced graphene oxide; Sintering
temperature
