Near-Unity Photoluminescence Quantum Yield of Green-Emitting Graded-Alloy Core/Shell Giant Quantum Dots by z-Type Ligand Passivation for Display Applications

Abstract

As-synthesized, green-emitting graded-alloy core/shell “giant” quantum dots have outstanding properties that can be utilized for different optoelectronic applications. But often, defects arise upon nonuniform growth of the shell. These surface defects affect the photoluminescence quantum yield (PLQY), lifetime, and stability of the green-emitting graded-alloy core/shell “giant” quantum dots. So, to overcome these surface traps, the graded-alloy core/shell g-QDs were passivated with z-type ligands (ZnCl2, CdCl2, and MgCl2). The change in the PLQY, lifetime, and photoluminescence emission confirmed that the z-type ligands are passivating the trap states of g-QDs by bonding with an unsaturated chalcogenide atom on the surface, and this was confirmed by X-ray photoelectron spectroscopy. All three cases (treated with ZnCl2, CdCl2, and MgCl2) showed outstanding enhancement in the photoluminescence quantum yield. Fascinatingly, the ZnCl2-treated g-QDs showed maximum enhancement in the PLQY from 62% to unity. Furthermore, the photostability test was performed under continuous UV-light irradiation for 24 h, which clearly showed superior photostability. Moreover, the temperature-dependent stability of untreated and treated g-QDs was studied from 10 to 90 °C. Furthermore, the green-emitting down-converted LED was fabricated by utilizing ZnCl2-treated g-QDs, which show great potential for display application.

Atomistic Insights on Facet-Dependent Functional Properties in CdSe Nanocrystals

“…Such modification ultimately improves the low-energy absorption characteristics of these NCs. Our findings align with several experimental studies that report significant improvements in optical properties in CdSe NCs with salt passivation. ,,− …”

Advancements in semiconductor quantum dots: expanding frontiers in optoelectronics, analytical sensing, biomedicine, and catalysis

“…Since then, a great deal of strategic work has been done to increase the PLQY as in these early stages of synthetic technique development, CQDs suffered from a range of surface defects, which acted as traps for excitons and reduced the PLQY. These methods include core–shelling, 87–92 alloying, 93 alloy-shelling, 94,95 addition of foreign solvent or substrate, 96 ligand exchange or passivation 97–100 and ligand cleavage 101 etc. as described in Table 1 along with external quantum efficiency (EQE).…”

“…Finally, a green-emitting down-converted LED was successfully fabricated using ZnCl 2 -treated g-CQDs, showcasing their potential for display applications. 98 InP/ZnSe/ZnS core/shell/shell CQDs with a near-unity photoluminescence quantum yield were formed through the addition of ZnF 2 during synthesis. The ZnF 2 reacted with a carboxylic acid at high temperature to in situ generate HF, eliminating surface oxide impurities and facilitating epitaxial shell growth.…”

Cationic Molecular Metal Chalcogenide Ligand‐Passivated Colloidal Quantum Dots and Their Application to Suppressed Dark‐Current Near‐Infrared Photodetectors

“…Hence, their binding strength is weaker than that of ionic bonds, such as carboxylic acid and thiol. [ 36 ] However, cationic inorganic ligands have rarely been reported, [ 37 ] likely because these ligands (i) are less adaptable to QD synthesis compared with anionic inorganic ligands because colloidal QD synthesis adopts cation precursor‐rich conditions and, thus, requires only anion‐based surfactants and (ii) cannot efficiently stabilize the electron‐rich regions of the QD surface because of their bulky head group (e.g., ammonium group).…”