Electrospinning in Situ Synthesis of Graphene-Doped Porous Copper Indium Disulfide/Carbon Composite Nanofibers for Highly Efficient Counter Electrode in Dye-Sensitized Solar Cells

• P-GN@CuInS2(*)/C nanofibers were fabricated via electrospinning, in situ synthesis.
• CuInS2 nanocrystals were uniformly anchored in wrapped RGO to form nanofiber structure.
• P-GN@CuInS2/C nanofibers exhibited porous and 3D superfine fiber morphology.
• Graphene nanosheets led well-dispersed growth of CuInS2 nanocrystals in nanofibers.
• DSSC assembled using p-GN@CuInS2/C CE delivered a conversion efficiency of 7.23%.

Porous graphene-doped copper indium disulfide/carbon (p-GN@CuInS2/C) composite nanofibers were fabricated via electrospinning, in situ synthesis, and carbonization. A polyacrylonitrile (PAN) solution containing graphene oxide nanosheets, copper dichloride (CuCl2), indium trichloride (InCl3), and thiourea (Tu.) in a mixed solvent of N,N-dimethylformamide/trichloromethane (DMF/CF) was used as the precursor solution for electrospinning. The resulting porous GN@CuInS2/C nanofibers were 107 ± 24 nm in diameter, and graphene nanosheets anchored with chalcopyrite CuInS2 nanocrystals 7–12 nm in diameter were overlapped and embedded in the carbon matrix, aligning along the fiber axial direction. The Brunauer–Emmett–Teller (BET) surface area of the p-GN@CuInS2/C composite nanofibers was 795 m2/g, with a total pore volume of 0.71 cm3/g. These values were significantly larger than those of the sample without graphene and CuInS2/C nanofibers. A dye-sensitized solar cell (DSSC) assembled using the p-GN@CuInS2/C nanofibers as the counter electrode (CE) delivered a photoelectric conversion efficiency of 7.23%, which was higher than the efficiencies of DSSCs assembled using the samples without graphene (6.48%) and with the CuInS2/C nanofibers (5.45%). It was also much higher than that of the DSSC with a Pt CE (6.34%). The excellent photoelectric performance of the p-GN@CuInS2/C CE was attributed to its special hierarchical porous structure, which facilitated permeation of the liquid electrolytes and provided additional active catalytic sites for the oxidation reaction of the electrolytic (I−/I3−). The doping of reduced graphene oxide (RGO) resulted in the well-dispersed growth of CuInS2 nanocrystals in the carbon nanofibers, which further increased the number of active catalytic sites and promoted electron and ion transfer.

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