Synthesis of emission tunable AgInS2/ZnS quantum dots and application for light emitting diodes

Indium-rich environmentally-friendly quantum dots (QDs) have received widespread attention due to the absence of cadmium. In this paper, AgInS2 (AIS) QDs are synthesized by hot injection method. By adjusting the ratio of indium/silver (In/Ag = 1, 2, 3, 4, 5), the AIS QDs exhibit a blue shift from 868 nm to 603 nm with the indium composition increases. Therein, the AIS QDs with the ratio of In/Ag = 4 show a highest photoluminescent (PL) quantum yields (QYs) up to 57%. AIS QDs are coated with ZnS shell to passivate the surface defects, and the PL QYs of obtained core/shell AIS/ZnS QDs is increased to 72%. By using these AIS/ZnS QDs as light emitters, light emitting diodes are assembled with a stacked multi-layer structure ITO/PEDOT:PSS/Poly-TPD/QDs/ZnO:Mg/Al. The resulted electroluminescent (EL) device exhibits a maximum external quantum efficiency (EQE) of 1.25% and an open circuit voltage of 4.6 V corresponding to a maximum brightness of 1120 cd m−2. Although the performances of the as fabricated AIS/ZnS-based device lag much behind than those of the Cd-based ones, they are expected to be enhanced with much more studies on the synthesis of the QDs and the optimization of device structure.