Synthesis of widely emission-tunable Ag-Ga-S and its quaternary derivative quantum dots

Chalcopyrite I -III-VI chalcogenides have attracted great attention as environmentally benign, non-Cd compositions for synthesis of colloidal quantum dot (QD) emitters. Various Cu-based I-III-VI compositions have been intensively investigated for synthesis of highly fluorescent QDs, while the compositional diversity of Ag-based QD emitters remains still limited. Here, we explore synthesis of Ag-based I-III-VI QDs of ternary Ag-Ga-S (AGS) and its derivative quaternary Zn-Ag-Ga-S (ZAGS) and Ag-In-Ga-S (AIGS) QDs through alloying AGS with Zn2+ and In3+ ions, respectively. Being in line with the variation of band gap of a series of these QDs, they exhibit a systematic, wide photoluminescence (PL) tunability from blue (450 nm, the shortest PL wavelength reported to date from I-III-VI QD emitters) from the highest-band gap ZAGS to amber color (570 nm) from the lowest-band gap AIGS with high PL quantum yields of 58-69% after elaborate ZnS shelling. Among QDs above, two AIGS/ZnS QDs with different In contents, which are capable of efficiently absorbing blue photons, are further applied as down-converters in combination with a blue light-emitting diode (LED) to produce bicolored white solid-state lighting devices and down-conversion emission properties of the resulting white QD-LEDs are described in detail.