Emission and Decay Lifetime Tunability in Less-Toxic Quaternary ZnCuInS Quantum Dots

Due to the increasing need for the use of safer nanomaterials in the electronic and optoelectronic sectors, there is a growing emphasis on the development of less-toxic quantum dots (QD) as replacements for traditional cadmium or lead-based QD technologies. Although the ternary Cu-In-S (CIS) QDs have gained prominence due to their advantageous optical properties and unique tunability, their intrinsically defective structures present some drawbacks for device applications. A one-pot, high-throughput process was developed to synthesize quaternary Zn-Cu-In-S (ZCIS) QDs, which show higher structural crystallinity and lattice stability. Stoichiometric variation was explored to determine its impact on QD optical and structural properties. It was found that the trial-cationic structure of the quaternary ZCIS QDs allowed further variation and flexibility of QD properties. Induction of Cu deficiency via In- or Zn-excess precursor ratios improved photoluminescence (PL) intensity and structural stability. ZnS overcoating was investigated, but it was found that the Zn-containing ZCIS cores, which are more stable than core CIS QDs, benefitted only minimally from Zn-passivation. The highly emissive quaternary QDs produced through this scalable synthesis procedure are widely tunable and functionalizable, capable of emission from 564-650 nm, and with a high lifetime up to 159 ns, making them more suitable for a variety of device applications.