Crystallographic and Photophysical Analysis on Facet‐Controlled Defect‐Free Blue‐Emitting Quantum Dots

Abstract

The burgeoning demand for commercializing self‐luminescing quantum dots (QD) light‐emitting diodes (LEDs) has stimulated extensive research into environmentally friendly and efficient QD materials. Hydrofluoric acid (HF) additive improves photoluminescence (PL) properties of blue‐emitting ZnSeTe QDs, ultimately reaching a remarkable quantum yield (QY) of 97% with an ultra‐narrow peak width of 14 nm after sufficient HF addition. The improvement in optical properties of the QDs is accompanied by a morphology change of the particles, forming cubic‐shaped defect‐free ZnSeTe QDs characterized by a zinc‐blende crystal structure. This treatment improves QD emitting properties by facilitating facet‐specific growth, selectively exposing stabilized (100) facets, and reducing the lattice disorders. The facet‐specific growth process gives rise to defect‐free monodisperse cubic dots that exhibit remarkably narrow and homogeneous PL spectra. Meticulous time‐resolved spectroscopic studies allow an understanding of the correlation between ZnSeTe QDs particle shape and performance following HF addition. These investigations shed light on the intricacies of the growth mechanism and the factors influencing the PL efficiency of the resulting QDs. The findings significantly contribute to understanding the role of HF treatment in tailoring the optical properties of ZnSeTe QDs, thereby bringing us closer to the realization of highly efficient and bright QD‐LEDs for various practical applications.This article is protected by copyright. All rights reserved

ZnSeTe quantum dots modified with zinc chloride toward bright trap-state emission

“…The sizes of ZnSeTe:ZnCl 2 /ZnSe/ZnSeS/ZnS QDs modified with 2 mmol and 4 mmol ZnCl 2 were smaller than those of the as-synthesized ZnSeTe/ZnSe/ZnSeS/ZnS QDs, and the changes in their morphology occurred from the initial spherical shape to a more-likely square shape, which could be attributed to the selective facet growth induced by ZnCl 2 . 29 QDs modified with 6 mmol and 8 mmol ZnCl 2 were slightly larger than as-synthesized QDs, but their shapes became irregular, and the size distribution also broadened. Meanwhile, the dispersity of the particles began to deteriorate; by the time the concentration of ZnCl 2 reached 8 mmol, the emergence of dimer or trimer nanoparticles could be easily observed (as shown by the dashed circle in Fig.…”

“…12,28 The most representative substance is hydrogen fluoride (HF), which can etch the oxide on the surface of QDs, passivate surface dangling bonds, and induce the growth of crystal facets, forming uniformly sized single crystals, thus significantly reducing defects and achieving near-unity PLQY. 17,29 However, the binding ability and corrosiveness of chlorides are slightly weaker. The impact of using zinc chloride (ZnCl 2 ) as a ligand on the surface state and radiative recombination process of ZnSeTe QDs is not yet clear.…”

Blue-Emissive ZnSeTe Quantum Dots and Their Electroluminescent Devices

“…Later, Kim's group demonstrated synthesis of highly emissive (PL QY of 97%), ultranarrow (fwhm of 14 nm) cubic-shaped blue ZnSeTe QDs through directly using excess amounts of HF additive, which facilitates the controlled facet-specific growth in favor of the reduction of lattice disorders. 37 The subsequent shelling process applied to the ZnSeTe core plays a pivotal role in influencing its PL properties. Earlier attempts to passivate nonradiative surface sites by encapsulat- ing the ZnSeTe core simply with a high-band gap ZnS shell were somewhat unsuccessful.…”

“…This innovative approach ensured a uniform distribution of Te atoms within the blue-emissive ZnSeTe lattice during both nucleation and growth, leading to a reduction in the emission full-width-at-half-maximum (fwhm) from 36 to 22 nm. Later, Kim’s group demonstrated synthesis of highly emissive (PL QY of 97%), ultranarrow (fwhm of 14 nm) cubic-shaped blue ZnSeTe QDs through directly using excess amounts of HF additive, which facilitates the controlled facet-specific growth in favor of the reduction of lattice disorders …”