Controllable synthesis of concave cubic gold core–shell nanoparticles for plasmon-enhanced photon harvesting

[Display omitted] •Controllable synthesis of concave cubic Au@TiO2 core–shell nanoparticles was demonstrated.•Improved photon harvesting and charge separation were observed in Au@TiO2-containing photoelectrodes.•New insights were provided in maximizing the plasmon-assisted enhancement. Well-defined core–shell nanoparticles (NPs) containing concave cubic Au cores and TiO2 shells (CA@T) were synthesized in colloidal suspension. These CA@T NPs exhibit Localized Surface Plasmon Resonance (LSPR) absorption in the NIR region, which provides a unique property for utilizing the low energy range of the solar spectrum. In order to evaluate the plasmonic enhancement effect, a variety of CA@T NPs were incorporated into working electrodes of dye-sensitized solar cells (DSSCs). By adjusting the shell thickness of CA@T NPs, the plasmonic property can be tuned to achieve maximum photovoltaic improvement. Furthermore, the DSSC cells fabricated with the CA@T NPs exhibit a remarkably plasmonic assisted conversion efficiency enhancement (23.3%), compared to that (14.8%) of the reference cells assembled with spherical Au@TiO2 core–shell (SA@T) NPs under similar conditions. Various characterizations reveal that this performance improvement is attributed to the much stronger electromagnetic field generated at the hot spots of CA@T NPs, resulting in significantly higher light harvesting and more efficient charge separation. This study also provides new insights into maximizing the plasmonic enhancement, offering great potential in other applications including light–matter interaction, photocatalytic energy conversion and new-generation solar cells.