  The incorporation of plasmonic metal nanostructures into semiconducting
chalcogenides, in the form of core-shell structures, represents a promising
approach to boosting 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 structure was synthesized
by developing a unique colloidal hot-injection method, which allowed excellent
control over sizes, shapes, and elemental compositions. The fabricated Au/CNTS
hybrid core-shell structure exhibited enhanced optical absorption, carrier
extraction efficiency, and improved photo-sensing performance, owing to the
plasmonic-induced resonance energy transfer effect of the Au core. This effect
led to a significant increase in carrier density between the Au core and CNTS
shell. These values outperformed a CNTS-based gate-free visible photodetector.
