A Significant
Improvement in the Electrocatalytic
Stability of N‑Doped Graphene Nanosheets Used as a Counter
Electrode for [Co(bpy)<sub>3</sub>]<sup>3+/2+</sup> Based Porphyrin-Sensitized
Solar Cells
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Abstract
A significant improvement
in efficiency is achieved for porphyrin
(YD2-o-C8) based dye-sensitized solar cells, coupled with [Co(bpy)<sub>3</sub>]<sup>3+/2+</sup> mediator electrolyte. However, the poison
of the counter electrode (CE) by the [Co(bpy)<sub>3</sub>]<sup>3+/2+</sup> mediator remains a significant barrier to producing a reliable high-performance
device. In this paper, nitrogen-doped graphene nanosheets (NG) are
produced using a low-cost solution-based process and are used as the
CE for [Co(bpy)<sub>3</sub>]<sup>3+/2+</sup> based porphyrin-sensitized
solar cells. These produce significantly better electrocatalytic activity
than the commonly used Pt CE. The superior performance is a result
of the increased number of catalytic sites and the wettable surface
that is caused by the substitution of pyridinic and pyrrolic N into
the carbon-conjugated lattice. To the authors’ best knowledge,
the significantly improved cycling stability (>1000 times) of NG
CE
for [Co(bpy)<sub>3</sub>]<sup>3+/2+</sup> redox complexes is demonstrated
for the first time