InP/ZnSeS/ZnS Quantum Dot-Embedded Alumina Microbeads for Color-by-Blue Displays

Abstract

Currently, heavy-shelled and gradient-shelled InP/ZnSeS/ZnS quantum dots (QDs) are commercially utilized as green (G) and red (R) color-converting layers in color-by-blue (B) QD-based displays. There is still a lack of systematic approaches to solve optical issues created when transforming QD nanoparticles into QD films. Here, triply protected approaches, such as using an Al dopant to passivate shell defects, Hf-nbutoxide (Hf(OtBu) 4 )-complex treatment to reduce ligand detachment, and the Al tri-sec-butoxide (Al(OsBu) 3 ) electrospray (E-spray) process to form an outer protecting layer and transform the material into QD-embedded Al 2 O 3 microbeads, are sequentially performed to improve the photoluminescence quantum yield (PLQY) and environmental stability of QDs. Moreover, QDembedded microbeads improve QD distribution uniformity inside Al 2 O 3 microbeads for high loading of nonagglomerated QDs and promote a scattering effect of QD green emission and blue excitation light in color-by-blue QD films. Therefore, the luminous efficacy (LE) of a mixed norland optical adhesive (NOA) film of QD@Al&Hf nanoparticles and QD@Al&Hf microbeads reaches ∼145.2 lm/W, which is 2.86 times higher than that of a QD@Al&Hf nanoparticle-only NOA film (50.8 lm/W). This combined approach can provide one example of promising combined approaches to fabrication of QD composite structures and suitable shapes for highly efficient and stable InP/ZnSeS/ZnS QD films in color-by-blue QD displays.

Passivation and Interlayer Effect of Zr(i-PrO)4 on Green CuGaS2/ZnS/Zr(i-PrO)4@Al2O3 and Red CuInS2/ZnS/Zr(i-PrO)4@Al2O3 QD Hybrid Powders

“…Finally, the passivation effect of Zr(i-PrO) 4 secondary ligand was investigated by comparing the optical properties of two down-converted white LEDs (DC-WLEDs), which include G-CGS/ZnS and R-CIS/ZnS QDs@Al 2 O 3 QD hybrid powders and G-CGS/ZnS and R-CIS/ZnS/Zr(i-PrO) 4 @Al 2 O 3 QD hybrid powders. We confirmed that secondary ligand passivation such as a coating of Zr(i-PrO) 4 not only improves the environmental stability of the eco-friendly I–III–VI QDs itself, but also mitigates further degradation of I–III–VI QDs during additional inorganic coating and device fabrication processes [ 25 , 39 ].…”

“…Furthermore, metal–organic frameworks (MOFs) were developed as a method to enhance the stability of QDs [ 24 ]. As previously reported, the hydrolysis reaction of metal alkoxide precursors is a well-known and facile encapsulation process to embed QDs into an inorganic–organic matrix powder [ 22 , 23 , 25 ]. In most hydrolysis reactions of metal alkoxides, acid and base catalysts are used to accelerate hydrolysis reactions, and a small amount of water is necessary to complete the hydrolysis reactions.…”

“…In this study, we enhanced the stability of both G-CGS/ZnS and R-CIS/ZnS QDs in two steps involving a secondary ligand and aluminum tri-sec-butoxide (Al(sec-BuO) 3 ) [ 14 , 22 , 25 ]. Due to the introduction of zirconium isopropoxide (Zr(i-PrO) 4 ) as a secondary ligand, the stability of both G-CGS/ZnS and R-CIS/ZnS QDs primarily increased.…”

Surface Chemistry Dictates the Enhancement of Luminescence and Stability of InP QDs upon c-ALD ZnO Hybrid Shell Growth

“…The FTIR analysis (Figures e,f and S14–S15) further confirms the presence of ZnO after c-ALD in both systems, with new strong absorption bands appearing in the low-wavenumber region (750–1275 cm –1 ). The bands at 1258, 1087, and 1018 cm –1 correspond to bending of Zn–OH (highlighted in the yellow region), while we tentatively assign the resonance at 800 cm –1 to the stretching of ZnO 4 . − …”

Light-Emitting Diodes with Cd-Free Quantum Dots Embedded in a Carrier Transport Matrix Grown by a Wet Process

“…Additional advantages of the present method include low damage to the underlayer due to the low-temperature process, mass production capability, and ease in modifying the QD surface and carrier transport materials, for instance, by doping. Embedding QDs in inorganic matrices has also been conducted by coating a precursor solution followed by annealing, − electrospray of the solution and subsequent UV exposure, and thermal atomic layer deposition . However, the thermal or UV process could damage the QD and other layers.…”