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Schematic illustration of the (a) side-by-side R/G/B QD pixel array and the (b) white + CFs scheme for QLED full-color displays.
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White-light-emission quantum dot light-emitting diodes (WQLEDs) have attracted great attention of late because they could have potential applications in both flat-panel displays and solid-state lighting due to their advantages of tunable emission spectra, low driving voltage, high luminous efficiency, and high brightness. Over the past decades, wit...
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Context 1
... are mainly two technological ways of realizing the full-color QLED display. In the first scheme, as shown in Figure 1(a), the red, green, and blue (R/G/B) pixels are arranged side by side, which means that the QD light emission layer (EML) should be finely patterned. As the QDs cannot be evaporated like the organic small molecules used in OLEDs, solution-processed methods CONTACT Shuming Chen chen.sm@sustech.edu.cn ...
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... addition, the solution-printing methods are far from mature, and their performances have not been successfully verified in industrial applications. Instead of patterning the EML, another way of realizing the full-color display is using the white + color filters (CFs) scheme (Figure 1(b)). In this scheme, the CFs can be patterned using the mature photolithography technology, which has a relatively high resolution. ...
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... The light-emitting diode based on II-VI semiconductor colloidal quantum dots (QLED) is a groundbreaking lighting and display technology with immense growth potential. It offers customizable emission wavelengths, exceptional color purity, and a high photoluminescence quantum yield (PL QY) close to 100%, making it a compelling alternative to organic light-emitting diodes (OLEDs) [1][2][3][4]. Since its introduction in 1994 [5], extensive research on the luminescent mechanism of QLEDs has resulted in substantial advancements J Mater Sci: Mater Electron (2024) 35:754 754 Page 2 of 11 largely unaffected during doping. ...
Colloidal quantum-dot light-emitting diodes (QLEDs) are rapidly gaining recognition as formidable contenders in the realm of next-generation lighting and display devices. Notwithstanding, the journey to commercialization of QLED devices encounters a roadblock in the form of inadequate flexibility exhibited by the electron transport layer, which is typically made of ZnO nanoparticles. The hindrance stems from the substantial specific surface area, existence of surface defect states, and the fixed ZnO bandgap. To surmount these obstacles, we delved into the potential of integrating Mg element as a dopant in ZnO, aiming to enhance the surface chemistry, electrical characteristics, and film morphology of colloidal ZnO nanoparticles. The results clearly indicated that Mg doping played a critical role in diminishing surface defects in ZnO, while simultaneously reducing the density of oxygen vacancies, thereby regulating its electron mobility. Through modulation of the Mg doping concentration, the bandgap width of ZnO can be fine-tuned, leading to the creation of a more suitable electron transport layer. The inverted QLED devices based on Zn1−xMgxO electron transport layers exhibited remarkable advancements, with a peak external quantum efficiency and current efficiency of 6.7% and 29 cd A⁻¹, respectively. These values surpassed those of reference devices by 35 and 28%, underscoring the efficacy of Zn1−xMgxO as a viable approach for enhancing the efficiency of QLED devices.
... Tb 3+ is one of the most attractive lanthanide ions for doping in the phosphor composition owing to its efficient green emission provided by the 4f-5d transitions. Besides, the Tb 3+ ion-doped glass matrix is reported to exhibit four emission regions of green, blue, yellow, and red [11], [12]. Thus, Tb 3+ ion-doped phosphors can be potential for increasing the luminous output of a phosphor-converted WLED (pc-WLED). ...
The use of CaO:Tb3+ with light green emission on for improvement of both luminescent output and chromatic fidelity of the white light emitted from a light-emitting diode (LED). The CaO:Tb3+ is combined with the yellow-emitting phosphor of YAG:Ce3+ to provide sufficient colored spectral proportion for the white light generation, enhancing the color performance. The phosphor combination is utilized for the three most applied LED structures: conformal, in-cup, and remote phosphor structures. The changes in optical properties of these three LEDs are monitored with adjustments in the proportion of CaO:Tb3+. The higher proportion of the green phosphor results in higher scattering efficiency in all structures, offering better color coordination and stronger luminous flux. The color quality scale is somehow reduced when CaO:Tb3+ concentration is more than a certain level. Therefore, depending on the phosphor configuration of the white light-emitting diode (WLED), the concentration of CaO:Tb3+ should be modified to achieve a good color rendition with improved color consistency and luminous properties.
... QDs exhibit a unique property known as the quantum confinement effect, which enables the precise control of the emission wavelength. QDs are highly suitable for various optoelectronic devices owing to their excellent color purity, high internal quantum efficiency, and solution processability [1,2]. Quantum dot light-emitting devices (QLEDs) do not require a vacuum system to form the emission layer (EML), simplifying the fabrication process. ...
Colloidal quantum dots (QDs) have emerged as promising candidates for optoelectronic devices. In particular, quantum dot light-emitting devices (QLEDs) utilizing QDs as the emission layer offer advantages in terms of simplified fabrication processes. However, the use of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) as a hole injection layer (HIL) in QLEDs presents limitations due to its acidic and hygroscopic nature. In this study, NiO/ZnS core–shell nanostructures as an alternative HIL were studied. The ZnS shell on NiO nanoparticles effectively suppresses the exciton quenching process and regulates charge transfer in QLEDs. The fabricated QLEDs with NiO/ZnS HIL demonstrate high luminance and current efficiency, highlighting the potential of NiO/ZnS as an inorganic material for highly stable all-inorganic QLEDs.
... Tandem devices are appropriate for large, high-brightness, and low-cost devices CONTACT (e.g. large TVs and surface illuminations [9,10]). An OLED TV features a technology that derives three primary color lights from a white or blue light. ...
High-performance tandem quantum-dot light-emitting diodes (QLEDs) are needed for practical next-generation displays. This study designed a high-performance interconnecting layer (ICL) that combines QLED units into tandem QLEDs and demonstrated its effectiveness. The ICLs were designed for charge generation, for interconnecting QLEDs, and for protecting the underlayers from damage during upper-layer fabrication. Using the ICLs with a first layer of thermally evaporated WO 3 and a second layer of sputtered SnO 2 or zinc tin oxide, the required roles of the ICL were fulfilled. The current efficiencies of tandem QLEDs using a double-layer ICL were about triple those of a single QLED, an improvement from 26 cd/A for a single QLED to 82 cd/A for a tandem QLED connecting two QLED units. This current efficiency was much higher than previously reported values for tandem QLEDs connecting QLED units with CdSe/ZnS green quantum dots and ZnO electron-transport layers. The method presented here will contribute to the practical application of QLEDs for large TVs and light-illumination devices. ARTICLE HISTORY
... Quantum dot (QD) light emitters have great potential for light-emitting diodes (LEDs) and lasers for end-use applications such as solid-state lighting and displays [1][2][3][4]. QDs are synthesized either epitaxially [5,6] or in free-standing, colloidal form [7][8][9][10]. Of interest here are epitaxially grown InGaN QDs. Theoretically, QD-based LEDs should have a larger spontaneous emission rate than quantum well (QW) LEDs [11]. ...
Near-infrared electroluminescence of InGaN quantum dots (QDs) formed by controlled growth on photoelectrochemical (PEC) etched QD templates is demonstrated. The QD template consists of PEC InGaN QDs with high density and controlled sizes, an AlGaN capping layer to protect the QDs, and a GaN barrier layer to planarize the surface. Scanning transmission electron microscopy (STEM) of Stranski–Krastanov (SK) growth on the QD template shows high-In-content InGaN QDs that align vertically to the PEC QDs due to localized strain. A high-Al-content Al 0.9 Ga 0.1 N capping layer prevents the collapse of the SK QDs due to intermixing or decomposition during higher temperature GaN growth as verified by STEM. Growth of low-temperature (830°C) p-type layers is used to complete the p-n junction and further ensure QD integrity. Finally, electroluminescence shows a significant wavelength shift (800 nm to 500 nm), caused by the SK QDs’ tall height, high In content, and strong polarization-induced electric fields.
... Colloidal quantum dots (QDs) are unique semiconductor nanomaterials with emission colors that can be tuned by controlling their size [1][2][3]. Furthermore, their organic ligands render them solution-processable, leading to cost-effective processing. ...
In this work, we fabricated quantum dot light-emitting diodes using solution-processed NiO as the hole injection layer to replace the commonly used poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate) (PEDOT:PSS) layer. We successfully prepared NiO films by spin coating the NiO precursor, then annealing them, and then treating them with UV-ozone under optimized conditions. The best device with the NiO film shows higher current efficiency (25.1 cd/A) than that with the PEDOT:PSS layer (22.3 cd/A). Moreover, the long-term stability of the devices with NiO which is annealed at 500 °C is improved substantially. These results suggest that the NiO layer can be a good alternative for developing stable devices.
... QD-OLED is a display made of OLED and semiconductor nanocrystals called quantum dots (QD) which produce pure monochromatic colors. In other words, the red QD and the green QD are stacked on a blue OLED that is used as an incident light source to express the desired colors of red and green by means of light conversion [11]. Several studies on QD unit devices are in progress, although few studies have reported on how to proceed from the device or the process architecture to improve the overall color gamut [12,13]. ...
In this study, the optimal structure for obtaining high green color purity was investigated by modeling quantum dot (QD)–organic light-emitting diodes (OLED). It was found that even if the green quantum dot (G-QD) density in the G-QD layer was 30%, the full width at half maximum (FWHM) in the green wavelength band could be minimized to achieve a sharp emission spectrum, but it was difficult to completely block the blue light leakage with the G-QD layer alone. This blue light leakage problem was solved by stacking a green color filter (G-CF) layer on top of the G-QD layer. When G-CF thickness 5 μm was stacked, blue light leakage was blocked completely, and the FWHM of the emission spectrum in the green wavelength band was minimized, resulting in high green color purity. It is expected that the overall color gamut of QD-OLED can be improved by optimizing the device that shows such excellent green color purity.
... They present a relatively high quantum yield (>80%) but, mostly, they present a wide tunability as a function of the dimension of the dots. [74]. The relative narrow emission (in the order of tens of nanometer) associated with the possibility to be pumped by a blue LED increases their possibility of being applied in display technology (such as Q-LED TV). ...
In everyday life, we are continually exposed to different lighting systems, from the home interior to car lights and from public lighting to displays. The basic emission principles on which they are based range from the old incandescent lamps to the well-established compact fluorescent lamps (CFL) and to the more modern Light Emitting Diode (LEDs) that are dominating the actual market and also promise greater development in the coming years. In the LED technology, the key point is the electroluminescence material, but the fundamental role of proper phosphors is sometimes underestimated even when it is essential for an ideal color rendering. In this review, we analyze the main solid-state techniques for lighting applications, paying attention to the fundamental properties of phosphors to be successfully applied. Currently, the most widely used materials are based on rare-earth elements (REEs) whereas Ce:YAG represents the benchmark for white LEDs. However, there are several drawbacks to the REEs’ supply chain and several concerns from an environmental point of view. We analyze these critical issues and review alternative materials that can overcome their use. New compounds with reduced or totally REE free, quantum dots, metal–organic framework, and organic phosphors will be examined with reference to the current state-of-the-art.
Through employing the fluid ignition technique, we created the samples CaSr2(PO4)2:Eu3+ with Eu3+ incorporated then assessed them in the form of contactless optical heat measurement as well as solid-state illumination. We identified the attributes for these samples including X-ray diffraction (XRD), photoluminescent spectroscopy, Fourier transmute infrared spectroscopy (FTIS) along with photoluminescent spectroscopy correlating with temperature. XRD, along with FTIS, validates that the one-stage samples were formed via the orthophosphate anion (PO4)3- . In the case of these samples, nUV recreation under 395 nm generated potent, orange-red discharge lines under 592 nm as well as 615 nm, which is consistent with the standard shifts between 5D0 and 7F1 as well as 5D0 and 7F2 for the Eu3+ ions. The International Commission on Illumination (CIE) coordinates (0.65, 0.35) based on the hue scale validate the red discharge. For the task of attaining optical heat measurement, we took advantage of the fluorescent intenseness proportion technique that utilizes heat-incorporated discharge states of 5D1 as well as 5D0 for Eu3+ . The samples have maximum responsiveness reaching roughly 0.0023 K-1 under 323 K or small heat levels. According to the outcomes, it is possible to utilize the samples when it comes to contactless optical heat measurement as well as solid-state illumination.
