Efficient Blue-Light-Emitting Cd-Free Colloidal Quantum Well and Its Application in Electroluminescent Devices

Abstract

To obtain highly efficient, stable, and environmentally friendly blue-light-emitting materials for display applications, we prepared a specially tailored Cd-free, colloidal quantum-well (CQW) structure of ZnS/ZnTeSe/ZnS. We optimized the synthetic methods to construct a very uniform ZnS core having a diameter of ∼2.9 nm within 10% of the size distribution. In addition, it was found that the ZnS QD structures were either a cube with the (100) surface facets or a tetrahedron with the (111) facets. As the ZnTeSe mid-shell grew on the ZnS core surface, the CQW maintained the initial facet and shape of the core. The photoluminescence of the CQW could be tuned from 375 to 458 nm by controlling the thickness of the ZnTeSe mid-shell. Furthermore, the spectral width changed depending on the Te composition in the ZnTeSe. After the final ZnS shell passivation, the optimized blue-light-emitting CQW showed a high quantum yield (QY) of up to 85% and a narrow spectrum width of 23 nm at 446 nm. Moreover, we fabricated light-emitting diodes (LEDs) with the CQW and demonstrated an external quantum efficiency of 6.8% at 3.6 V with a maximum brightness of 14 146 cd/m 2 at 8 V.

High Efficiency and Narrow Emission Band Pure-Red Perovskite Colloidal Quantum Wells

“…Semiconductor colloidal quantum wells (CQWs) could strengthen the quantum confinement effect only by reducing the thickness of nanocrystals in the vertical direction rather than the size in all directions like small nanocrystals, which presents many excellent optical properties related to thickness, including ultranarrow emission, large molar extinction coefficients, and high oscillator strength. − On the basis of these properties, CQWs have been considered to be one of the promising luminescent materials for lighting and displays. , …”

“…1−3 On the basis of these properties, CQWs have been considered to be one of the promising luminescent materials for lighting and displays. 4,5 Recently, colloidal lead halide perovskite nanocrystals represented by CsPbX 3 (X = Cl, Br, and I) have shown huge potential in high-definition displays due to excellent performance, such as a wide color gamut (∼140%), an adjustable forbidden bandwidth, excellent defect tolerance, mild synthesis conditions, and high photoluminescence (PL) efficiency. 6−10 At present, the synthesis methods of CsPbX 3 nanocrystals are mainly divided into two types: hot injection and ligand-assisted reprecipitation (LARP).…”

Single and Dual Doping of Blue‐Emissive ZnSeTe Quantum Dots with Transition Metal Ions

“…The long τ avg of Cu emission, which results from the intragap state involved radiative recombination, is also in line with the values in other Cudoped QD systems. [3,19,20,23] Meanwhile, τ avg of excitonic host PL of ZnSeTe:Cu QDs was longer compared to undoped blue QDs (47-51 ns) in literature [30,31] and in this work (54 ns, inset of Figure S1 in the Supporting Information), attributable to the spectral intrusion of broad Cu emission into host one.…”

“…ZnSeTe is an emerging ternary composition for synthesis of QD emitters, whose emissive range is widely tunable in bluetoorange color via the modu lation of their anionic proportion (Te/Se) and heterostructural dimension. [30][31][32][33][34] In this work, based on blueemissive ZnSeTe QDs with a given Te/Se ratio, single and dual doping with Cu + and/or Mn 2+ are implemented, which is, to the best of our knowledge, the first case to date. The conucleation approach, which works well in single doping, is found not to be effec tive in dual doping.…”

Technology progress on quantum dot light-emitting diodes for next-generation displays

“…3 (d). 34 Normally, ZnTeSe is used as emissive core materials for blue QDs and ZnS is used as shell material covering the core materials. However, the distribution of the particle size of ZnTeSe/ZnS (core/shell) QD is broadened by the different reactivities of Te and Se to Zn precursors, causing wide FWHM in PL spectra.…”