58‐1: Invited Paper: Progress in High‐Efficiency Heavy‐Metal‐Free QD‐LED Development

Abstract

Electroluminescent QD-LEDs with heavy metal free InP and ZnTeSe quantum dots are one of the most promising future display technologies. Here we report improved efficiency of 19.6%, 17.6%, and 11.5% for red, green, and blue QD-LEDs, respectively. The blue QD-LEDs exhibit true blue emission with peak wavelength of 453 nm.

How NanoLED Will Enable Next‐Generation Displays

“…8 Cadmium is extremely limited under the Restrictions of Hazardous Substances (RoHS) regulation, making it impractical to use Cd-based QDs in display applications. Consequently, alternative non-toxic QD materials, such as indium phosphide (InP), [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] zinc selenide (ZnSe), zinc selenium telluride (ZnSeTe), 18,22, and others, are under consideration for nanoLED devices.…”

“…The highest efficiency of red nanoLED using InP QD reached more than 20 percent, 17,19,21,22 and green nan-oLED has reached 17.6 percent. 18 InP cannot be used to realize blue-emitting nanoLED, as such a particle would be too small to reliably synthesize. However, ZnSe or ZnSeTe are suitable alternatives.…”

“…17 This was achieved using a chemical treatment to reduce oxygen formation at the interface between the core and the shell of the QD structure. However, the lifetime of green 18,[25][26][27] and blue 22,31,32 still is less than 100,000 hours, which is insufficient for industrial applications. These lifetimes could be improved substantially in the future to realize nanoLED using all Cd-free QDs.…”

Complete Issue

“…8 Cadmium is extremely limited under the Restrictions of Hazardous Substances (RoHS) regulation, making it impractical to use Cd-based QDs in display applications. Consequently, alternative non-toxic QD materials, such as indium phosphide (InP), [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] zinc selenide (ZnSe), zinc selenium telluride (ZnSeTe), 18,22, and others, are under consideration for nanoLED devices.…”

Top-Emission ZnSeTe/ZnSe/ZnS-Based Blue Quantum Dot Light-Emitting Diodes with Enhanced Chroma Efficiency

“…The record external quantum efficiencies (EQEs) of Cd/Pb-based R/G/B QLEDs have almost reached the theoretical EQE limit in bottom emission (BE) architecture (red: 24.1%, green: 27.6%, blue: 21.4%). , However, as highly toxic heavy metals, environmental and health concerns are increasing for Cd/Pb-containing QDs, and there are restrictions on their use in commercial products in the future. Among the candidates for cadmium-free QD emitters, InP is proven to be more suitable as a red and green luminescent material, while ZnSe shows more potential as a blue emitter, due to their intrinsic band gap of 1.35 eV, 2.7 eV for InP and ZnSe, respectively. − However, the energy band of ZnSe QDs limits its typical emission to violet-blue (370–440 nm), making it hard to achieve the pure blue emission within 450–470 nm. , Therefore, alloying of the ZnSe core with a lower bandgap ZnTe (2.25 eV) was proposed to achieve a redshift emission. , In 2019, Kim et al reported ZnSeTe/ZnSe/ZnS blue QDs, which exhibited an emission peak position at 457 nm. The maximum brightness, EQE max, and lifetime of the blue QLEDs were 88900 cd m –2 , 20.2%, and 15850 h (LT50@100nits), respectively .…”