Insight into the Synthetic Mechanism of Cadmium-Free Blue-Emissive Quantum Dots for Eco Light-Converting System

Abstract

Cd-free nanocrystals, such as CuCrS 2 /ZnS (CCS/ZnS) quantum dots (QDs), have been highlighted as potential blue-emitting probes. However, the relatively irregular and less uniform morphological structure of QDs synthesized by conventional methods indicated low optical performance with a photoluminescence quantum yield (PLQY) of ∼0.05. Herein, we modified the synthetic method for CCS/ZnS QDs based on the hard and soft acids and bases (HSAB) theory. By using the HSAB-based precursors and appropriate ligand moieties, we synthesized QDs with a uniform morphology and enhanced PLQY of ∼0.16. The core−shell formation of the CCS/ZnS QDs was confirmed using X-ray spectroscopic methods. Consequently, a QD-incorporated polymer matrix as a color filter for a white-light-emitting diode (LED) by hybridizing Cd-free blue-emitting CCS/ZnS QDs and yellow-emitting CuInS 2 / ZnS/ZnS QDs in poly(methyl methacrylate) was fabricated. Their optical properties were systematically controlled by modifying the ratio of the two QDs, resulting in (CIE x , CIE y = 0.254−0.34, 0.245−0.299) of color coordinates and 21914.48 to 5071.39 K of correlated color temperature. This study demonstrates the potential of the environmentally friendly QD-based display technology.