Near-Infrared Emission of Ag+ Doped CuInSe2 Quantum Dots

Copper-indium-selenide (CISe) quantum dots (QDs) are a class of appealing materials due to their near-infrared (NIR) photoluminescence (PL) and as a non-toxic alternative to lead and cadmium-based QDs. To improve the low photoluminescence quantum yield (PLQY) of CISe core QDs, the zinc sulfide (ZnS) shell was grown to passivate surface defect states on the CISe core. CISe/ZnS core-shell QDs were synthesized with tetrahedral structure and chalcopyrite phase, resulting in an emission wavelength of 992 nm and a PLQY of 90%. Additionally, Ag 2+ was doped into the CISe core to redshift the emission wavelength. The combination of electrons in the conduction band and holes in the trap state formed by Ag 2+ led to light emission and a red-shifted emission wavelength. By tuning the stoichiometry and shelling time, Ag-doped CISe/ZnS core-shell QDs were successfully synthesized with a PLQY of 18% at an emission wavelength of 1200 nm. This wavelength falls in the NIR-II range, characterized by minimum absorption, biological autofluorescence, reduced scattering, and deep tissue penetration. The tunable emission and high luminescent CISe QDs have great potential in biological labeling, sensing and optoelectronics applications. Figure 1