Superior Visible Photoelectric Response with Au/Cu₂NiSnS₄ Core-Shell Nanocrystals

The incorporation of plasmonic metal nanostructures into semiconducting chalcogenides in the form of core-shell structures provides a promising approach to enhancing the performance of photodetectors. In this study, we combined Au nanoparticles with newly developed copper-based chalcogenides Cu₂NiSnS₄ (Au/CNTS) to achieve an ultrahigh optoelectronic response in the visible regime. The high-quality Au/CNTS core-shell nanocrystals (NCs) were synthesized by developing a unique colloidal hot-injection method, which allowed for excellent control over sizes, shapes, and elemental compositions. The as-synthesized Au/CNTS hybrid core-shell NCs exhibited enhanced optical absorption, carrier extraction efficiency, and improved photosensing performance owing to the plasmonic-induced resonance energy transfer effect of the Au core. This effect led to a significant increase in the carrier density of the Au/CNTS NCs, resulting in a measured responsivity of 1.2 × 10³ AW^-1, a specific detectivity of 6.2 × 10¹¹ Jones, and an external quantum efficiency of 3.8 × 10⁵ % at an incident power density of 318.5 μW cm^-2. These results enlighten a new era in the development of plasmonic core-shell nanostructure-based visible photodetectors.