Effect of graphene and Au@SiO2 core–shell nano-composite on photoelectrochemical performance of dye-sensitized solar cells based on N-doped titania nanotubes†
We have investigated the role of graphene and Au@SiO2 core–shell nano-composite (NC), on the performance of dye-sensitized solar cells (DSSC) based on nitrogen doped TiO2 nanotubes (N-TNTs) as photoanodes. The N-TNTs were synthesized by an environmentally-friendly solvothermal method. The photoelectrochemical performance of DSSCs with N-TNTs improved compared to undoped TNTs; due to extended absorption in the visible part of the solar spectrum. An improved open circuit voltage was also observed with N-TNTs due to a change in the TiO2 Fermi energy level with increased electron density. After that, we investigated DSSC performance using graphene in N-TNTs with varying concentration from 0.2 to 1.0 wt%. With an optimal concentration of graphene (0.6 wt%), we have achieved 6.33% energy conversion efficiency, which is ∼47.5% enhancement in performance compared to pure N-TNTs. The enhanced device performance with graphene is mainly due to better dye loading, improved electron transport and charge collection process. To further boost the conversion efficiency of the DSSC based on graphene/N-TNTs NC, we introduced Au@SiO2 core–shell nanoparticles (NPs) of different concentration into the device structure. Finally, we are able to fabricate a DSSC having an energy conversion efficiency of 7.01% with 1.8% (w/w) of Au@SiO2 NPs, due to an improved excitation of dye molecules by generated strong near-fields around the Au NPs along with incident light far-fields.