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

Highlights: • P-GN@CuInS_2(*)/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%. - Abstract: 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.