Effects of Graphene in Dye-Sensitized Solar Cells Based on Nitrogen-Doped\nTiO₂ Composite

Abstract

Graphene\n(GR) exhibits impressive photoelectric properties, including a large\nspecific surface area, high charge-carrier mobility, high conductance,\nand fast electron transfer. In this study, the effect of GR on the\nperformance of dye-sensitized solar cells (DSSCs) was investigated\nby mixing GR into N-doped TiO₂ photoelectrodes. GR/N-doped\nTiO₂ (GNT) nanoparticles were prepared using the sol–gel\nmethod. After preparation, the presence of GR in the photoelectrodes\nwas confirmed using transmission electron microscopy (TEM), X-ray\ndiffraction (XRD), and Raman spectroscopy analyses. After the addition\nof GR, the photoelectrodes displayed enhanced dye adsorption properties\nwith lower internal resistances and faster transport times. Accordingly,\nDSSCs with these photoelectrodes generated high current density with\na low electron-recombination rate. The maximum power conversion efficiency\nof DSSCs with GR/N-doped photoelectrodes was 9.32% with optimized\nDSSC parameters; this represents an enhancement of approximately 22%\nover that of DSSCs with N-doped photoelectrodes. The addition of excess\nGR weakened the crystallization of particles on the surface of photoelectrodes,\nwhich resulted in low dye adsorption and decreased efficiency of the\nDSSCs. In summary, the addition of GR promoted increased dye loading\nand enhanced DSSC efficiency. The optimal amount of GR for high-efficiency\nDSSCs was successfully determined in this study.