Color Quantum Dots Research Articles

Efficient Quantum Dot Color Conversion Layer with Mixed Spherical/Rod-Shaped Scattering Particles

A quantum dot (QD) color conversion layer (CCL) with mixed-shaped scattering nanoparticles exhibits enhanced light conversion and reduced blue leakage in QD-organic light-emitting diodes (OLEDs). In this study, nontoxic bright red QDs and spherical and rod-shaped zinc oxide (ZnO) nanoparticles were mixed in an ultraviolet-curable resin without aggregation. The mixture of spherical and rod-shaped ZnO nanoparticles enhanced the blue light scattering inside the QD CCL, which results in an increase of the blue absorption by the QDs and a dramatic improvement of the color conversion. Extraction of the converted red light was also attributed to the Mie scattering of the rod-shaped scattering nanoparticles. The QD CCL with 15 wt % mixed-shaped scattering particles showed seven times increase of red intensity and four times decrease of blue intensity compared to that without scattering particles. We fabricated direct coat-type QD-OLEDs and confirmed that the color conversion and output/input efficiencies were improved and the blue leakage was decreased with increasing number of QD CCLs. This method improves the color conversion efficiency without increasing the amount of QDs and reducing the blue leakage without using a color filter.

Inkjet Printed Quantum Dots Color Conversion Layers for Full-Color Micro-LED Displays

With the ever-growing demands for larger size and high resolution displays, Micro-light-emitting diode (Micro-LED) display with quantum dots (QDs) film as color conversion layers (CCLs) has become one of the most promising candidates of future display for its advantages in low power consumption and wide color range. In this study, we report a novel full-color display based on blue Micro LED, which has patterned red and green QDs color conversion (QDCC) layers fabricated by inkjet printing (IJP). A structure of double-layer bank was designed to reduce color deviation, prevent crosstalk, and flatten the QDCC layer. By optimizing the thickness of the red/green QDCC layers and the wavelength of blue Micro LED backlights, a full-color QDCC-LED display with 228 PPI resolution and size of 1.11-inch was successfully fabricated and showed superb performance. We not only effectively reduced crosstalk, but also improved the color conversion efficiency of QDs. In addition, this QDCC-LED display prepared by embedded bonding process shows a color gamut of 107.53% NTSC.Graphical

Cover Image, Volume 30, Issue 11

The cover image is based on the Research Article Quantum-dot color conversion towards white-balanced healthy displays: Theoretical and simulation study by Sheng Xu et al., https://doi.org/10.1002/jsid.1173

Freestanding High-Resolution Quantum Dot Color Converters with Small Pixel Sizes

Designing the next generation of high-resolution displays requires high pixel density per area and small pixel sizes without compromising the optical quality. Quantum dots (QDs) have been demonstrated as a promising material system for down-conversion of blue emission as they provide pure colors on the wide color gamut. However, for high color-conversion efficiency, the required QD film thickness has not been compatible with small pixel sizes. In this work, we develop a new type of freestanding QD-based color converter for efficient optical down-conversion from inorganic blue light-emitting diodes (LEDs) in a color-by-blue configuration. CdSe/ZnS core-shell QDs in a UV-curable polymer matrix are encapsulated within cavities formed by patterning and bonding a pair of patterned quartz substrates. By controlling the required QD thickness and the pixel size independently, we demonstrate freestanding monochrome red and green converters with small pixel sizes down to 5 × 5 μm2 and a high resolution of >3600 ppi. The optical studies show that the QD film thickness required for efficient color conversion can be successfully realized even for the small pixel sizes. We further combine green and red pixels in a single converter to achieve white emission when combined with blue LED emission. The QD color converter design and processing are decoupled from the LED fabrication and can be easily scaled to wafer-size integration with arbitrary pixel sizes for QD-based RGB displays with ultrahigh resolution.

Ratiometric fluorescent immunochromatography for simultaneously detection of two nitrofuran metabolites in seafoods

Competitive immunochromatographic assay (ICA) has been widely used in food safety on-site monitoring. However, traditional competitive ICA relies on the change of single-signal intensity to discriminate the results, leading to limited sensitivity and accuracy of naked-eye visual inspection. In this study, we developed a sensitive ratiometric fluorescent immunochromatographic assay (RFICA) judging results based on the color changes of fluorescence. Two different color quantum dot nanobeads (QBs) were introduced as signal labels for rapid and accurate detection of 3-amino-2-oxazolidinone (AOZ) and semicarbazide (SEM) in seafoods. Under the optimal conditions, the visual detection limit for 2-NPAOZ and 2-NPSEM reached up to 1 and 0.5 ng/mL, which were 5- and 14-fold lower than that of traditional single-signal response fluorescent ICA strips. In addition, the RFICA strips were applied to real samples with acceptable recoveries of 81.33 ∼ 99.23 %. These results demonstrate that the developed RFICA platform possesses considerable potential in the on-site detection.

14.4: Inkjet Printing Patterned Quantum Dot Microarrays

14.4: Inkjet Printing Patterned Quantum Dot Microarrays

26‐3: Optical Modeling of Quantum Dot‐OLED (QD‐OLED) Color Conversion

Quantum Dots (QDs) as a color converting layer paired with a blue OLED emitter are investigated through a ray‐tracing model. By adjusting various properties of the QD layer, trends in performance such as the color of emitted light, green photon output, blue leakage, and loss mechanisms are investigated. This simple model and associated data analysis provide insight into important design considerations for QD color converted pixels for future display technologies such as QD‐OLED and microLEDs.

19‐2: Design Heuristics of Color Conversion Films in Micro LED Displays

Scaling challenges and design requirements needed to support high external color conversion efficiency (ECCE) for light emitters based on blue emitting Micro LEDs and QD color conversion films are quantified using a novel physical model. The model is shown to reproduce published data of ECCE dependence on quantum dot (QD) film thickness. Using this model, it is shown that scaling the QD film thickness from 10μm to 1μm in order to minimize cross talk and reduce manufacturing cost results in ECCE reductions of ~2x and ~10x for red and green QD films, respectively. Moreover, the blue leakage is found to be ~1% for QD film thickness of ~2.5μm.

Red and Green Quantum Dot Color Filter for Full-Color Micro-LED Arrays.

This work demonstrated color-conversion layers of red and green quantum dots color filter for full-color display arrays. Ligands exchange using (3-glycidyloxypropyl) trimethoxysilane with epoxy functional groups to treat QDs in the liquid phase was performed for photolithography use. The combination of ligands of QDs with photo-initiator played a protective role on QDs. Moreover, the pixel size of green QDCF can be reduced to 50 μm, and a high optical density (OD) of 1.2 is realized.

Flexible White Lighting Fabricated With Quantum Dots Color Conversion Layers Excited by Blue Organic Light-Emitting Diodes

In this study, HATCN is coated on flexible PET/indium tin oxide (ITO) substrate as a modified layer and a hole injection layer to improve the hole injection from ITO. Then a blue organic light emitting diode (OLED) can successfully be fabricated without a surface treatment procedure (O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma or UV Ozone treatment). The new blue TADF series fluorescent material is employed as emitting layer with a luminescence wavelength of 456 nm. Also, it has a narrow full width at a half maximum (FWHM) of 26 nm featuring excellent color chromaticity. Quantum dot (QD) photoresist is a perfect color conversion material featuring good color adjustability, narrow emission spectrum, high luminous efficiency, and simple spin-coating processes. In this study, the photoresist mixed with green and red quantum dots is used as a color conversion layer (CCL), and a blue OLED is utilized to excite green and red CCL. To test the material of QD photoresist, it is coated on the substrate of another piece of glass first and then the blue OLED is utilized to remotely excite green and red QD CCL. The fluorescence characteristic of QD photoresist is explored to acquire a spectrum of 528 nm and 620 nm. In the device structure of a blue OLED, the electron-and hole-only current density is compared and the hole transport layer TAPC thickness is adjusted to improve the luminance and efficiency. Finally, green and red quantum dot photoresist is mixed using a proper ratio and then directly coated on the back of the PET/ITO substrate. Furthermore, the thickness of the QD photoresist is adjusted to increase the QD excited fluorescence. The blue OLED and QD CCL was integrated to generate three primary colors, i.e., blue, green, and red. Finally, a flexible white OLED lighting panel is successfully fabricated using simple processes. Moreover, it features high-spectrum stability. The CIE coordinates will not drift with bias, thus, it can resist the voltage variation.

Tripling Light Conversion Efficiency of μLED Displays by Light Recycling Black Matrix

Quantum-dot color conversion film (QDCCF) with a partitioned black matrix (BM) realizes effective color generation with low crosstalk for micro-light-emitting diode (μLED) displays. However, this traditional BM seriously deteriorates light conversion efficiency (LCE) of QD converted μLED displays due to its absorption energy loss. In this paper, a novel internal and external reflective black matrix (IERBM) is proposed to improve the LCE and blue light utilization (BLU) by light recycling and reuse. Based on the IERBM structural optimization, the LCE can be respectively improved by 3.39× and 2.74× for red and green QDCC sub-pixels, and the BLU can be effectively increased by 1.11×. Accurate white balance and high color uniformity are achieved by this μLED display. Meanwhile, both the crosstalk of 1.72% and the color gamut of 89.8% Rec. 2020 are comparable with traditional absorptive BM. It is also found that the proposed IERBM has the potential to weaken μLED's sidewall effect. This work may open up a new technological route for improving the optical performance in advanced self-emissive displays.

Dual-color quantum dots nanobeads based suspension microarray for simultaneous detection of dual prostate specific antigens

Featured with high multiplexibility, suspension microarray technology usually involves the conjugation of second-antibody with organic dye based fluorescent proteins, which are inherently unsuitable for multicolor signaling under single wavelength excitation. In addition, application of single QDs-based fluorescent reporter in suspension microarray is dramatically hampered since its preparation often suffers from poor reproducibility and stability. Herein, a novel suspension microarray system based on dual color quantum dots (QDs) nanobead as fluorescence label was developed for simultaneous detection of prostate specific antigen (PSA) biomarkers. When both antigens are present in sera sample, free (f)-PSA antibody-conjugated green and complexed (c)-PSA antibody-conjugated red QDs nanobeads would be both specifically absorbed onto the surface of total PSA antibody-conjugated magnetic beads, leading to the formation of magnetic fluorescent hybrid that can be purified from the mixture by an external magnet prior to flow cytometry analysis. The proposed method demonstrates simultaneous detection ability for f- and c- PSA antigen assay with high detection sensitivity that is comparable to clinical approaches including ELISA and chemiluminescence assay. Furthermore, result of clinical application of the proposed method is consistency with clinical data, demonstrating its potential in suspension microarray for accurate prostate cancer diagnosis.

High-speed visible light communication based on micro-LED: A technology with wide applications in next generation communication

The evolution of next-generation cellular networks is aimed at creating faster, more reliable solutions. Both the next-generation 6G network and the metaverse require high transmission speeds. Visible light communication (VLC) is deemed an important ancillary technology to wireless communication. It has shown potential for a wide range of applications in next-generation communication. Micro light-emitting diodes (μLEDs) are ideal light sources for high-speed VLC, owing to their high modulation bandwidths. In this review, an overview of μLEDs for VLC is presented. Methods to improve the modulation bandwidth are discussed in terms of epitaxy optimization, crystal orientation, and active region structure. Moreover, electroluminescent white LEDs, photoluminescent white LEDs based on phosphor or quantum-dot color conversion, and μLED-based detectors for VLC are introduced. Finally, the latest high-speed VLC applications and the application prospects of VLC in 6G are introduced, including underwater VLC and artificial intelligence-based VLC systems.

Micro‐Light‐Emitting Diodes Based on InGaN Materials with Quantum Dots

AbstractMicro‐light‐emitting diodes (Micro‐LEDs) based on gallium nitride (GaN) materials offer versatile platforms for various applications, including displays, data communication tools, photodetectors, and sensors. In particular, the introduction of Micro‐LEDs in the optoelectronic industry enables the development of novel short‐distance wireless communication applications for the Internet of Things as well as near‐to‐eye displays for virtual reality and augmented reality. Micro‐LEDs used in conjunction with colloidal quantum dots (QDs) as color‐conversion layers provide efficient full‐color displays as well as white LEDs for high‐speed visible light communications (VLCs). Here, the latest progress on full‐color Micro‐LED displays with a printed QD color conversion layer, GaN material‐based Micro‐LEDs for VLC systems, and the photostability of novel QD materials for Micro‐LEDs is comprehensively reviewed. Outlooks on the efficiency of Micro‐LEDs with sizes ≤10 µm, QD stability issues, and flexible Micro‐LED displays are also provided.

Vertically Stacked Full Color Quantum Dots Phototransistor Arrays for High-Resolution and Enhanced Color-Selective Imaging.

Color-selective multifunctional and multiplexed photodetectors have attracted considerable interest with the increasing demand for color filter-free optoelectronics which can simultaneously process multispectral signal via minimized system complexity. The low efficiency of color-filter technology and conventional laterally pixelated photodetector array structures often limit opportunities for widespread realization of high-density photodetectors. Here, low-temperature solution-processed vertically stacked full color quantum dot (QD) phototransistor arrays are developed on plastic substrates for high-resolution color-selective photosensor applications. Particularly, the three different-sized/color (RGB) QDs are vertically stacked and pixelated via direct photopatterning using a unique chelating chalcometallate ligand functioning both as solubilizing component and, after photoexposure, a semiconducting cement creating robust, insoluble, and charge-efficient QD layers localized in the a-IGZO transistor region, resulting in efficient wavelength-dependent photo-induced charge transfer. Thus, high-resolution vertically stacked full color QD photodetector arrays are successfully implemented with the density of 5500 devices cm-2 on ultrathin flexible polymeric substrates with highly photosensitive characteristics such as photoresponsivity (1.1 × 104 AW-1 ) and photodetectivity (1.1 × 1018 Jones) as well as wide dynamic ranges (>150dB).

A quantum dot microspheres-based highly specific and sensitive three-dimensional microarray for multiplexed detection of inflammatory factors

The development trend of in vitro diagnostics is to obtain various biological information from a sample at extremely low concentration and volume, which has promoted its progress in accurate and sensitive multiplexed detection. Here, we developed a single color quantum dot (QD) based three-dimensional (3D) structure matrix microarray and conducted the detection of two inflammatory factors (C-reactive protein (CRP) and serum amyloid A (SAA)) by a self-built fluorescence detection system. This strategy increased detection sensitivity by immobilizing the antibody specifically on the 3D substrate because it captured more than about 7 times of ‘effective’ antibodies compared to the two-dimensional (2D) plane. Compared to the dual QDs-2D fluorescence-linked immunosorbent assay, the limit of detection (LOD) of 3D microarray based on QDs modified with amphiphilic polymers has been further improved to 0.11 ng ml−1 for SAA assay and to 0.16 ng ml−1 for CRP assay, respectively. By using QD microspheres (SiO2@QDs@SiO2-COOH, containing approximately 200–300 hydrophobic QDs on per SiO2 sphere) as fluorescent labels, the LOD for CRP and SAA of 3D microarray reached as high as 15 pg ml−1 and 86 pg ml−1, and the sensitivity was further improved by 28-fold and 425-fold, respectively. Because of its excellent performance, this QD microspheres-based 3D microarray has great application potential for highly sensitive and multiplexed quantitative detection of other biomarkers, small molecules, and antibiotic residues in biomedicine and food safety.

Programmable nanoparticle patterning by droplet electrophoretic deposition

Here, we demonstrated the printing of a circular pattern of 200 nm nanoparticles by droplet electrophoretic deposition (EPD). For programming the deposition of the pattern, the circular electrode array circuit was designed on a printed circuit board (PCB) based on a polyimide substrate. A 5 μl 200 nm fluorescent nanoparticle suspension (Ex. 505/Em. 515) was dropped onto the PCB for single droplet EPD. For the programmable pattern, a 20 μl nanoparticle suspension was patterned in the shape of a checkerboard and the letter ‘N’ on an array of 4 × 4 electrodes using an expanded droplet EPD. Furthermore, the extended programmable droplet EPD performed respectably on all areas of a 10 × 10 electrodes array when the letters ‘N’, ‘A’, ‘N’, and ‘O’ were patterned. To provide optical transparency with flexibility, the patterned nanoparticles on the PCB were transferred to the polydimethylsiloxane. The extended programmable droplet EPD could provide a simple, fast, two-dimensional maskless patterning fabrication process for nanoparticles such as biomaterials and color quantum dots.

Quantum-dot color conversion film patterned by screen printing and overprinting process for display backlights

The paper presents an effective preparation approach for patterning quantum-dot color conversion films (QDCCF) in white-balance display backlights, where the red and green sub-pixel arrays are respectively fabricated by precise screen printing technology and the subsequent overprinting process. By using the D65 light source as a design target, a theoretical adjustment method for output white balance is proposed, in which the quantity ratio of QDs can be obtained by combining the theoretical balance of three primary colors, the experimental balance of the QD’s intensity, and the transmittance of color filter (CF). The ratio of green/red QDs for the target white balance was verified by both the experiment and theoretical calculation. Results show that the measured chromaticity coordinates of the backlight sample are (0.3138, 0.3402), the corresponding color temperature is 6385 K, and the color gamut can reach 86.1% Rec. 2020 in CIE 1976 chromaticity diagram. The experimental results accords well with the design theory, which supports that this method could be an alternative way for the fabrication of QDCCF.

P‐4.6: Ultra‐high‐resolution Quantum Dots Color Converter with Notable Uniformity

Using blue Micro‐LED back light and red‐green quantum dot (QD) color converter (QDCC) is a full color display technology with great potential to achieve high resolution, color purity and luminous efficiency. In this work, we try a new method of ligands exchange, using 3‐Mercaptopropionic acid (MPA) ligands with two functional groups to treat QDs in the liquid phase. The modified QDs can be sufficiently dispersed in the negative‐tone molecular resists. In our current process, the pixel size can be reduced to 5 fim and the large‐area ultra‐high‐resolution QDCC with great uniformity is realized.

P‐9.2: Quantum Dots Color Filter Liquid Crystal Display

In recent years, as a hot inorganic luminescent materials, Quantum dots have been widely used in display devices because of their high photoluminescence efficiency and excellent color gamut. In order to further improve the performance of LCD display devices, we consider introducing quantum dot color film into the structure of LCD. In this report, we pixelate the QDs to replace the traditional color film, this is different from the QD was widely used method which QDs was made into thin film as part of the back light unit. Compared with the general LCD, QDCF can achieve higher efficiency, higher color gamut and wider viewing angle, in order to solve the polarization of the liquid crystal cell, we use WGP In liquid crystal cell to achieve high contrast ratio.