Green Ag–In–Ga–S quantum dots as highly absorption-capable, efficient, and color-pure emitters

Environment-friendly quaternary I–III–VI AgInGaS2 (AIGS) quantum dots (QDs) offer merits such as sharp emissivity via band-edge recombination as well as composition-tunable photoluminescence (PL) particularly in the visible region. To date, AIGS cores have demonstrated significantly broad-emissive characteristics emerging from the defect-involved recombinations, which then converted to band-edge emission after the growth of an amorphous gallium sulfide (GaSx) shell. Even after the GaSx shell growth, however, they still preserved a notable magnitude of defect emission with an unsatisfactory PL quantum yield (QY). Herein, we develop synthesis of a series of band-edge recombination-dominant, green-emissive AIGS cores, wherein PL properties are judiciously tailored via growth temperature control along with in-situ surface treatment. Notably, these AIGS QDs are found to possess much greater molar absorption coefficients than green-emissive InP counterparts. Our analytical findings suggest that the shell grown on AIGS core is crystalline quasi-AgGaS2 (AGS) rather than amorphous GaSx. Benefiting from the effective surface passivation by heteroepitaxial AGS shell growth, the resulting AIGS/AGS core/shell QDs display unprecedentedly bright, sharp emissivity (i.e., PL QY up to 95 %, PL width of 33 nm) together with fully suppressed defect emission. These distinct features position AIGS QDs as highly promising alternatives to cadmium-based and even indium phosphide-based ones for next-generation display technologies.