Abstract:In this report, to tackle the thermal fluorescent quenching issue of II-VI semiconductor quantum dots (QDs), which hinders their on-chip packaging application to light-emitting diodes (LEDs), a QD-ZnS nanosheet inorganic assembly monolith (QD-ZnS NIAM) is developed through chemisorption of QDs on the surface of two-dimensional (2D) ZnS nanosheets and subsequent assembly of the nanosheets into a compact inorganic monolith. The QD-ZnS NIAM could reduce the thermal fluorescent quenching of QDs effectively, possib… Show more
“…From the color of the encapsulated white LED device and the CIE chromaticity diagram, we can see that the light emitted by this mixture is not pure white light, but a cyanish white-like light. According to the emission spectrum of the mixture, we speculate that the reason is that the emission wavelength of red light is mostly in the invisible near-infrared region after 650 nm, and there is an empty window in the wavelength range of 600–650 nm, resulting in the emission color of encapsulated white LED being a cyan white light, rather than a pure white light like the results made by other phosphors 31 , 32 . Figure 5 ( a ) Encapsulated white LED devices and emitting colors.…”
Gallate material, a luminescent matrix with excellent performance is normally prepared by vapor deposition or solid phase sintering method at high temperature. However, it has not been solved to prepare gallate-based fluorescent materials with full-color luminescent properties at low temperature. In this paper, ZnGa2O4 undoped or doped with Cr or Mn nanoflowers composed of nanosheet-level structure were prepared by hydrothermal method at low temperature. Under ultraviolet light irradiation, ZnGa2O4, ZnGa2O4:Mn2+ and ZnGa2O4:Cr3+ display three primary colors of blue, green and red luminescence through self-excitation, Mn2+ and Cr3+ excitation respectively. The solid fluorescence yields of blue, green, and red colors are 32.3, 36.5, and 40.7%, respectively. It is highly expected to be applied to color display, biological imaging, white light devices.
“…From the color of the encapsulated white LED device and the CIE chromaticity diagram, we can see that the light emitted by this mixture is not pure white light, but a cyanish white-like light. According to the emission spectrum of the mixture, we speculate that the reason is that the emission wavelength of red light is mostly in the invisible near-infrared region after 650 nm, and there is an empty window in the wavelength range of 600–650 nm, resulting in the emission color of encapsulated white LED being a cyan white light, rather than a pure white light like the results made by other phosphors 31 , 32 . Figure 5 ( a ) Encapsulated white LED devices and emitting colors.…”
Gallate material, a luminescent matrix with excellent performance is normally prepared by vapor deposition or solid phase sintering method at high temperature. However, it has not been solved to prepare gallate-based fluorescent materials with full-color luminescent properties at low temperature. In this paper, ZnGa2O4 undoped or doped with Cr or Mn nanoflowers composed of nanosheet-level structure were prepared by hydrothermal method at low temperature. Under ultraviolet light irradiation, ZnGa2O4, ZnGa2O4:Mn2+ and ZnGa2O4:Cr3+ display three primary colors of blue, green and red luminescence through self-excitation, Mn2+ and Cr3+ excitation respectively. The solid fluorescence yields of blue, green, and red colors are 32.3, 36.5, and 40.7%, respectively. It is highly expected to be applied to color display, biological imaging, white light devices.
“…Reproduced with permission. [ 112 ] Copyright 2017, The Authors, under an open access Creative Commons CC BY 4.0 license.…”
Section: Light Management Of Qd Compositesmentioning
confidence: 99%
“…As a result, the QD converter could maintain more than 90% of its initial brightness when the operating temperature reached 85 °C. [ 112 ]…”
Section: Light Management Of Qd Compositesmentioning
confidence: 99%
“…f) Illustration of the preparation procedure for the QD-ZnS nanosheet inorganic assembly monolith. Reproduced with permission [112]. Copyright 2017, The Authors, under an open access Creative Commons CC BY 4.0 license.…”
Mini/microlight‐emitting diodes (LEDs) are one of the most promising technologies for next‐generation displays to meet the requirements of demanding applications, including augmented reality/virtual reality displays, wearable devices, and microprojectors. To realize full‐color displays, the strategy of combining miniaturized blue nitride‐based LEDs with color conversion layers is promising due to the high efficiencies of the LEDs and the advantageous manufacturing. Quantum dots (QDs), owing to their high photoluminescence quantum yield, small particle size, and solution processability, have emerged as the color conversion material with the most potential for mini/micro‐LEDs. However, the integration of QDs into display technologies poses several challenges. From the material side, the stability of QD materials is still challenging. For the case of packaging QDs in a matrix, the dispersion quality of QDs and the light extraction of the emission need to be improved. From the fabrication side, the lack of high‐precision mass manufacturing strategies in QD pixelation hinders the widespread application of QDs. Toward the issues above, this review summarizes the research on QD materials for color conversion display in recent years to systematically draw an overview of the packaging strategies, the light management approaches, and the pixelation methods of QD materials toward mini/micro‐LED‐based display technologies.
“…Moreover, monolayer ZnS based pristine and defected heterostructures, nanocomposites structure, quantum dots structure, and transition metal doped structure have also been successfully employed in visible light photocatalysis for H 2 production from water splitting, lighting and display applications, field-effect transistors, photocatalysis for CO 2 reduction, sensors, dye-sensitized solar cells, and Quantum dot LEDs applications [25][26][27][28][29][30][31][32]. However, the performance parameters such as thermal stability, thermal emission quenching, display brightness, current-voltage performance, and power conversion efficiency of such ZnS-based nano and optoelectronic devices are significantly affected by the Joule heating produced by the electric current [33][34][35][36]. To better design nano and optoelectronic devices using 2D-ZnS, investigation of the thermal transport behavior is thus very essential.…”
Of late, atomically thin two-dimensional zinc-sulfide (2D-ZnS) shows great potential for advanced nanodevices and as a substitute to graphene and transition metal di-chalcogenides owing to its exceptional optical and electronic properties. However, the functional performance of nanodevices significantly depends on the effective heat management of the system. In this paper, we explored the thermal transport properties of 2D-ZnS through molecular dynamics simulations. The impact of length, temperature, and vacancy defects on the thermal properties of 2D-ZnS are systematically investigated. We found that the thermal conductivity (TC) rises monotonically with increasing sheet length, and the bulk TC of ∼30.67 W mK−1 is explored for an infinite length ZnS. Beyond room temperature (300 K), the TC differs from the usual 1/T rule and displays an abnormal, slowly declining behavior. The point vacancy (PV) shows the largest decrease in TC compared to the bi vacancy (BV) defects. We calculated phonon modes for various lengths, temperatures, and vacancies to elucidate the TC variation. Conversely, quantum corrections are used to avoid phonon modes’ icing effects on the TC at low temperatures. The obtained phonon density of states (PDOS) shows a softening and shrinking nature with increasing temperature, which is responsible for the anomaly in the TC at high temperatures. Owing to the increase of vacancy concentration, the PDOS peaks exhibit a decrease for both types of defects. Moreover, the variation of the specific heat capacity and entropy with BV and PV signify our findings of 2D-ZnS TC at diverse concentrations along with the different forms of vacancies. The results elucidated in this study will be a guide for efficient heat management of ZnS-based optoelectronic and nano-electronic devices.
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