Amino group and F- ions tailored aggregation-based phase transition for manipulating optical properties of AgInS2 quantum dots

Due to aggregation-based kinetics characterized by the formation of either amorphous aggregates or large crystals, tailoring optical properties via flexible control of size, morphology, and phase structure of AgInS2 (AIS) nanocrystals proves to be a challenge in the field of I-III-VI semiconductors. We synthesized ultra-small AIS quantum dots (QDs) with exciton absorption in this work. Growth kinetics investigations suggest that oriented assembly or aggregation plays critical roles in the anisotropic growth and transition of aggregates of AIS QDs. Microstructural investigations reveal that oriented aggregation leads to orthorhombic hierarchical structure with internal defects, such as stacking faults and dislocations, showing defect-dominated red emissions. F- can effectively inhibit the aggregation and result in larger sizes with more uniform size distributions of tetragonal AIS QDs than growth in the absence of F-. As a result, yellow-emitted AIS QDs exhibiting native emission characteristics can be achieved. The strategy of F--promoted aggregation is expected to forge crystal morphologies or metaphase junctions of various I-III-VI group nanocrystals for exploiting photoelectric properties and improving photoelectric application performance.