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.