ReducedGraphene Oxide-NiO Photocathodes for p‑Type Dye-SensitizedSolar Cells
2019
Reduced
graphene oxide (rGO) has been prepared from commercial graphene oxide
by a thermal reduction method, and NiO/rGO photocathodes were obtained
by a mixed NiCl2/rGO sol–gel process by using different
amounts of rGO material. A detailed characterization of NiO/rGO films
was carried out by SEM, Raman, and surface analysis. BET analysis
revealed that the optimum surface area of the films was between 0.0
and 0.3 mg of rGO, while the surface area was lower with increasing
graphene content. Despite the lower surface area, in the presence
of the higher amount of rGO material, a higher dye uptake was detected,
possibly because of a π-staking interaction between the phenyl
group of the dye and the graphene sheets. The p-type dye-sensitized
solar cells prepared from these films showed a gradual increase in JSC up to 2.6 mA/cm2 with the higher
amount of rGO and a VOC of 125 mV; in
this case, the efficiency was almost 2 times higher with respect to
the solar cell with NiO alone. An EIS study showed that the charge
recombination resistance was lower in the presence of the rGO, but
the hole lifetime was similar. This behavior suggests that the higher JSC obtained with the higher amount of rGO can
be ascribed to the higher dye uptake, which leads to a higher concentration
of holes in the photocathodes.
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