Plasmonic effect of Ag@TiO2 core–shell nanocubes on dye-sensitized solar cell performance based on reduced graphene oxide–TiO2 nanotube composite

• Systematic investigation is carried out based on reduced graphene oxide (RGO)–TiO2 nanotube (TNT) composites as photoanodes.
• Surface Plasmon Resonance of Ag@TiO2 core–shell nanocubes are incorporated in RGO–TNTs to improve the light absorption in near IR regions.
• RGO improved the electron transportation by suppressing charge recombination, and also increases the dye loading.
• 21% of PCE is enhanced (to 5.19%) by integration of Ag nanocubes in RGO–TNTs.

The role of reduced graphene oxide (RGO) and plasmonic Ag@TiO2 core–shell nanocubes has been investigated on dye-sensitized solar cell (DSSC) performance based on 1-D TiO2 nanotubes (TNTs) as photoanodes. A series of cells are fabricated with different amounts of RGO (0.2 to 1.0 wt.%) in TNTs. The incorporation of RGO in TNTs is confirmed by photoluminescence, Raman, and X-ray photoelectron spectroscopy studies. The best performance is achieved with 0.8 wt.% RGO–TNT composite, which exhibited a power conversion efficiency (PCE) of 4.26%, while with bare TNTs, it showed a PCE of 2.85%. The ~ 49% enhancement in PCE with RGO is attributed to the improved dye loading, reduced charge carrier recombination, and high electron transfer efficiency. The enhancement in open circuit voltage (maximum of 50 mV) is also observed with RGO, which is due to the increased electron density in the conduction band of TiO2 leading to the change in position of quasi Fermi level to higher levels, resulting in shifts towards negative potential side. To further enhance the PCE of DSSCs based on RGO–TNT composites, surface plasmon resonances (SPRs) of silver (Ag) @TiO2 core–shell nanocubes are also exploited by integrating differing concentrations from 0.1 to 0.3 wt.%. The PCE of plasmonic DSSC is further enhanced to 5.19% with 0.2 wt.% Ag nanocubes. The strong near-fields around the nanocubes (SPR peak spread from 600 to 1000 nm) stimulated the N719 dye for generating more photoelectrons with enhanced light absorption process in broad wavelength region.