Conversion Layer Research Articles

Stable colour conversion layer with enhanced conversion efficiency by incorporating nanoparticles for micro-LED display application

Due to their promising optical performance, micro-light emitting diodes (micro-LEDs) based on colour conversion layer (CCL) have garnered significant attention as the next-generation display technology. However, fabricating CCL with excellent conversion efficiency (CE) with minimal blue light leakage for miniaturized sub-pixel designing is still in its infancy. Herein, we have demonstrated CCL of a thickness (<3.5 μm) based on an organic-inorganic hybrid system incorporated with Titanium dioxide (TiO2) and Zinc Oxide (ZnO) Nanoparticles (NPs) with high CE. The inclusion of the NPs enhances the absorption of blue light within the CCL. We further combined the CCL with a colour purification filter to mitigate blue light leakage, which recycles blue light and suppresses blue light loss, resulting in improved CE. Specifically, we achieved a CE of 83.80 % for the green CCL and 66.97 % for the red CCL. Subsequently, full-colour arrays with a pixel size of 4 μm × 4 μm were successfully patterned and fabricated based on reduced thickness and improved optical performance using NP-doped CCL. This paves the way for cost-effective higher-resolution micro-LED displays for various applications.

Improving the Corrosion Resistance of Anodized Al 1050 Alloy by Sealing in Cerium-Containing and Mixed Sodium Phosphate Mono Basic and Calcium Nitrate Solutions

This investigation presents results on the improvement of the corrosion-protective effect of consecutive sealing treatments of anodized Al 1050 (AlAnod). The treatments were performed in cerium-containing and mixed NaH2PO4 + Ca(NO3)2 solutions. The changes of the surface morphology, structure and chemical composition, chemical state of the elements, and basic corrosion parameters of the studied systems were investigated by SEM, EDXS, XRD, XPS, and a complex of electrochemical techniques (PDP, EOCP vs. timeplot, chronoamperometric transients, Rp and CR at EOCP, etc.). The results obtained show that the basic components of the obtained sealing conversion layers (before and after exposure to model Cl−-containing corrosion media) are characterized by Ca10(PO4)6(OH)2, AlO(OH), CePO4, and CeAlO3 (after the corrosion tests, they are converted to insoluble Me-PO3 and Me-P4O10). We conclude that the observed decrease in the corrosion rate of Al and the corresponding increase in the polarization resistance are accomplished by the two-step sealing treatment, which fills up the AlAnod pores with insoluble deposits.

Efficient white light-emitting electrochemical cells based on quantum-dot color conversion layers with high EQE >20 %

Solid-state light-emitting electrochemical cells (LECs) offer promising benefits, including simple device architecture, low operating voltage, and insensitivity to electrode work functions. These advantages make them highly suitable for low-cost display and lighting applications, with significant potential for widespread adoption. However, great challenges remain in realizing stable and efficient white LECs. In this work, the blue LECs integrated with red or yellow/red quantum-dot (QD) color conversion layers (CCLs) are shown to achieve efficient and stable white emissions. When the blue LECs are combined with red QD CCLs, they achieve an external quantum efficiency (EQE) exceeding 20 % at a low current density of 0.003 mA cm−2. Alternatively, the blue LECs integrated with yellow/red QD CCLs deliver white emissions with a low CCT <2500 K and a high CRI up to 93 while the peak EQE at a low current density of 0.005 mA cm−2 still remains high (>16 %). The data effectively showcase that efficient and stable white emission can be achieved through partial energy down-conversion from the blue LECs to the QD CCLs, and the proposed white light sources are potential candidates for lighting applications.

SIMULATING MOLECULAR OPTICAL PROPERTIES OF POLYIMIDE FOR NONVOLATILE RESISTIVE PHOTOMEMORY DEVICES

In this study, the focus was on utilizing the polyimide (PI) thin film as a resistive conversion layer for organic polyimide-based resistive random-access memory (ReRAM) applications. We utilized the 3D molecular editor WebMO to manipulate and analyze the structures of Aromatic-PI and Quinoid-PI molecules. The molecular chain length, molecular weight, and HOMO/LUMO molecular orbitals were investigated to gain insights into the fundamental properties of PI molecular structures. The analysis revealed that the Quinoid-PI molecule exhibited a shorter molecular chain compared to Aromatic-PI, attributed to the inability of the cyclic structure in Quinoid-PI to maintain a planar conjugated structure, resulting in an uneven overall structure and reduced molecular chain length (Norcorss, 1988). The research results demonstrate that the optical energy gap of Aromatic-PI remains constant regardless of the number of molecular bonds, with a value of approximately 3.2661 eV. In contrast, for Quinoid-PI, the optical energy gap undergoes a significant decrease as the number of molecular bonds ranges from 1 to 5. As the bond count increases to 20~23, the change in the optical energy gap gradually diminishes, ultimately resulting in an optical energy gap of 0.6932 eV. This observation indicates that longer molecular chains composed of Aromatic-PI act as insulators, while Quinoid-PI transforms into a low-energy gap conductor.

Effects of in-situ incorporation of h-BN nanosheets, low-melting nanoclays and corrosion-inhibiting stannate on plasma electrolytic oxidized AZ31B Mg alloy

Boron nitride nanosheets and organo-modified nanoclays are in-situ incorporated into the plasma electrolytic oxidation (PEO) layer fabricated on AZ31B Mg alloy. A stannate-based corrosion inhibitor with an inherent self-repairing effect is also tested. The modified PEO/Mg alloys are characterized for micro/nano-scale surface morphology and roughness, phase and microstructure, elemental composition and distribution, surface wettability and are studied for mechanical properties, bonding strength and electrochemical corrosion resistance. The results suggested fruitful benefits of the combined in-situ incorporation on PEO/Mg alloy’s corrosion resistance. The hard ceramic nanomaterials with high melting points, such as boron nitride, could be more effectively incorporated into the PEO layer with the co-deposition of low-melting nanoclays. Besides, an inhibitor such as stannate in the PEO deposition bath could make an effective protective conversion layer, providing an additional protective effect without significantly interfering with the PEO layer formation. The results provided could be beneficial in developing better PEO/Mg alloys for industrial applications.

P‐256: Late‐News Poster: Enhancement of OLED Color Conversion Efficiency and Viewing Angle Dependency Using Organic Color Conversion Layers

Applying the Host‐Dopant System to organic color conversion layers (OCCL) has resulted in a high color conversion efficiency CCE) compared to previous commercial methods. The OCCL exhibited an impressive CCE of 123.1%, surpassing that of quantum dot (QD) conversion layer by 61.3%. Furthermore, we observed that the viewing angle characteristics of blue top‐emission organic light emitting diodes (OLED) with OCCL was significantly improved due to their corrugated surface compared to the pristine top‐emission OLED.

P‐152: The method of QD color conversion layer and pattern‐able Encapsulation with high thickness BM fabricated by inkjet‐printed process

This study develops a novel high‐thickness BM QD color conversion layer structure and a surface‐planarization process for QD materials after inkjet printing. This process reduces the height differences caused by the multi‐step exposure‐developing process. Following the fabrication of 8μm BM structure and 2μm CF structure, precise inkjet printing of QD materials is conducted within the 100ppi pixel area. we adjusted the surface energy of the color conversion layer by using an organic solution treatment to control the thickness profile and improve the color conversion efficiency. The printed QD materials are covered by a high‐transparency, low‐density polymer. After the color conversion layer component is encapsulated, reliability verification with a reliability assessment of 240 hours at RA (60℃ degrees, 90%RH) demonstrates an encapsulation effect where QD brightness retention rate remains above 90%.

36‐4: CQD‐Based Sensors for Large Format SWIR Imaging

Quantum dots have been rapidly developed in the display field, especially as photoluminescent color conversion layers. At the same time, quantum dots have also made increasing research progress in the detection field. We reported a short‐wave infrared sensor based on colloidal quantum dot technology. The photosensitive layer of the sensor uses HgTe colloidal quantum dot material. The detection band is 0.9~1.7um, the resolution is 1280*1024, and the pixel pitch is 15um. Colloidal quantum dot short‐wave infrared sensors get rid of the limitations of the indium pillar flip‐chip bonding process of traditional indium gallium arsenide CMOS short‐wave infrared focal plane sensors. The preparation process is simple, the yield is higher, and the cost is low. Based on the colloidal quantum dot shortwave infrared sensor, we implemented a shortwave infrared camera and characterized its performance parameters, and then we successfully captured shortwave infrared images through the shortwave infrared camera.

12‐4: Inorganic Halide Perovskite Thin Films Realized by Pulsed Laser Deposition over Large Area for MicroLEDs Color Conversion Layers

This paper reports the deposition of inorganic halide perovskite thin films, using pulsed laser deposition, as a way to fabricate green and red color conversion layers for microLEDs. The photoluminescence of the thin film reveal pure colors and uniform emission on 200 mm wafers. The unencapsulated thin films are stable under ambient air.

P‐261: Late‐News Poster: Highly Efficient Color Conversion Layers Using Organic Nano‐dots

In this study, we report color conversion layers (CCLs) developed by new organic nano‐dots (ONDs). These ONDs, comprised of organic fluorescent materials and surfactant molecules, offer unique advantages such as tunable optical properties, high (100%) photoluminescence quantum yield (PLQY), and narrow (25‐35 nm) full‐width at half‐maximum (FWHM). Compared to the inorganic (InP) reference CCLs, OND CCLs exhibit almost double (80‐85%) color conversion efficiencies with good photo and thermal stability.

Dual-Interface Solar Evaporator with Highly-Efficient Thermal Regulation via Suspended Multilayer Design.

Facing the increasing global shortage of freshwater resources, this study presents a suspended multilayer evaporator (SMLE), designed to tackle the principal issues plaguing current solar-driven interfacial evaporation technologies, specifically, substantial thermal losses and limited water production. This approach, through the implementation of a multilayer structural design, enables superior thermal regulation throughout the evaporation process. This evaporator consists of a radiation damping layer, a photothermal conversion layer, and a bottom layer that leverages radiation, wherein the bottom layer exhibits a notable infrared emissivity. The distinctive feature of the design effectively reduces radiative heat loss and facilitates dual-interface evaporation by heating the water surface through mid-infrared radiation. The refined design leads to a notable evaporation rate of 2.83kg m-2 h-1. Numerical simulations and practical performance evaluations validate the effectiveness of the multilayer evaporator in actual use scenarios. This energy-recycling and dual-interface evaporation multilayered approach propels the design of high-efficiency solar-driven interfacial evaporators forward, presenting new insights into developing effective water-energy transformation systems.

Improvement of X-ray Photoelectric Conversion Performance of MAPbI3 Perovskite Crystals by Ionic Liquid Treatment

Although perovskite has great potential in optoelectronic devices, the simultaneous satisfaction of material stability and high performance is still an issue that needs to be solved. Most perovskite optoelectronic devices use quantum dot spin coating or the gas-phase growth of perovskite thin films as the photoelectric conversion layer. Due to stability limitations, these materials often experience a significant decrease in photoelectric conversion efficiency when encountering liquid reagents. The self-assembled growth of hybrid perovskite crystals determines superior lattice ordering and stability. There are three types of ionic liquids—[Emim]BF4, EMIMNTF2, and HMITFSI—that can effectively enhance the X-ray photoelectric conversion performance of hybrid perovskite crystal CH3NH3PbI3 (MAPbI3), and the enhancement in the photocurrent leads to an improvement in the sensitivity of X-ray detectors. We soak the perovskite crystals in an ionic liquid and perform two treatment methods: electrification and dilution with ETOH solution. It is interesting to find that MAPbI3 perovskite single crystal materials choose the same optimized ionic liquid species in X-ray detection and photovoltaic power generation applications, and the effect is quite the opposite. Compared with untreated MAPbI3 crystals, the average photocurrent density of Electrify-HMITFSI MAPbI3 increased by 826.85% under X-ray excitation and the sensitivity of X-ray detectors made from these treated MAPbI3 crystals significantly increased by 72.6%, but the intensity of the PL spectrum decreased to 90% of the untreated intensity.

Maximization of cytochrome C oxidase enzyme activity by optimizing color conversion from red organic light-emitting diodes

Photobiomodulation (PBM) therapy using red and near-infrared (NIR) light can effectively activate cytochrome C oxidase (CCO) enzyme to promote wound healing in living organisms. To maximize this therapeutic effect, the use of a light source with a spectrum absorbed by the CCO enzyme is necessary. A red/NIR light source optimized for CCO enzyme was obtained by partially color-converting a red organic light-emitting diode with copper indium sulfide/zinc sulfide quantum dots (QDs). To increase color conversion efficiency, the dispersion of QDs was improved by using a fibrous color conversion layer (FCCL). By optimizing the QD content in the FCCL, a red/NIR light source similar to the absorption spectrum of CCO enzyme was obtained with a spectral matching ratio of 81.7 %. When this light source was used in PBM therapy, it was experimentally verified that it showed a much faster wound closure effect compared to general red light, and it was proven that this was due to increased activity of the CCO enzyme. This study is a method of obtaining a red/NIR light source for PBM suitable for a specific enzyme performing a specific function, and is particularly useful due to its excellent form factor of being large, thin, and flexible.

Superhydrophilic and heterostructured NiCu/polyaniline nanocomposites as highly efficient electrocatalyst and photothermal conversion layer integrated thermoelectric device for overall water splitting

The large-scale production of green hydrogen from water electrolysis has recently gained extensive attention. However, the high overpotential leads to the excessive costs of electricity consumption. Herein, a novel research scheme was proposed to design photothermal electrocatalyst with photothermal effect and highly efficient hydrogen evolution reaction (HER) performance, which can be integrated with thermoelectric (TE) device to effectively lower the cell voltage in the overall water splitting. Experimental and DFT calculations results demonstrated that NiCu/PANI/NF catalyst displayed superior HER performance (28 mV@10 mA cm−2, 89 mV@50 mA cm−2), exceptional durability (110 h@10, 50 mA cm−2), as well as good infrared photoresponsivity (93.4 ℃@200 mW cm−2 @10 min). It can be mainly attributed to the synergy of polyaniline and the introduction of Cu, which can effectively modulate the d-band center of Ni active site, and attenuate H adsorption energy, then promote H2 generation. Additionally, superhydrophilicity of NiCu/PANI/NF can facilitate mass transfer and accelerate H2 evolution. Notably, in a self-designed electrolyzer-TE integrated device, the cell voltage was significantly lowered for the overall water splitting (0.29 V @50 mA cm−2). This work presented an efficient photothermal electrocatalyst and provided novel insights for investigations into water electrolysis with cost-effective hydrogen production in the future.

Integration of functional modules in a unified photoelectrochemical device for highly efficient solar-driven cathodic metal protection

The ever-increasing energy consumption stimulated the development of various solar energy conversion systems. Photocathodic protection (PCP), emerges as a promising photoelectrochemical technology to alleviate metal corrosion, but the centralization of all core reaction steps on one photoelectric-conversion-unit induces extremely low energy conversion efficiencies. Herein, a proof-of-concept modular PCP device incorporating electron transport layer (ETL), photoelectric conversion layer (PCL), hole transport layer (HTL) and hole consumption layer (HCL) is fabricated to delocalize the key reaction steps for the first time. Such a unified ETL/PCL/HTL/HCL architecture facilitates the efficient extraction of photoexcited electrons from the small-gap PCL to the protected metal through ETL, and holes to HCL for water oxidization through HTL. The directional “macroscopic” charge migration, prolonged charge lifetime and accelerated water oxidation lead to significantly improved PCP effectiveness in simulated seawater. Our findings provide a groundbreaking PCP design, allowing fine-tuning individual functional modules and inter-modular interfaces to vastly elevate performance.

Electrohydrodynamic Inkjet Printing of Three-Dimensional Perovskite Nanocrystal Arrays for Full-Color Micro-LED Displays.

Perovskite nanocrystal (PeNC) arrays are showing a promising future in the next generation of micro-light-emitting-diode (micro-LED) displays due to the narrow emission linewidth and adjustable peak wavelength. Electrohydrodynamic (EHD) inkjet printing, with merits of high resolution, uniformity, versatility, and cost-effectiveness, is among the competent candidates for constructing PeNC arrays. However, the fabrication of red light-emitting CsPbBrxI(3-x) nanocrystal arrays for micro-LED displays still faces challenges, such as low brightness and poor stability. This work proposes a design for a red PeNC colloidal ink that is specialized for the EHD inkjet printing of three-dimensional PeNC arrays with enhanced luminescence and stability as well as being adaptable to both rigid and flexible substrates. Made of a mixture of PeNCs, polymer polystyrene (PS), and a nonpolar xylene solvent, the PeNC colloidal ink enables precise control of array sizes and shapes, which facilitates on-demand micropillar construction. Additionally, the inclusion of PS significantly increases the brightness and environmental stability. By adopting this ink, the EHD printer successfully fabricated full-color 3D PeNC arrays with a spatial resolution over 2500 ppi. It shows the potential of the EHD inkjet printing strategy for high-resolution and robust PeNC color conversion layers for micro-LED displays.

Multi-layer photothermal film inspired by polar bear fur for anti-icing and photothermal de-icing in cold environments

As climatic conditions worsen and time passes, icing becomes an unavoidable issue. Drawing inspiration from the thermal regulatory properties inherent in polar bear fur, we introduce a biomimetic three-layer film. This film comprises a hydrophobic shield, a photothermal conversion layer, and an insulating layer through electrospinning. The multilayered micro/nanostructure within this film amplifies its light absorption capabilities, achieving an average absorption rate of 96.27 % across wavelengths ranging from 200 to 2500 nm. Thanks to the insulation layer's thoughtful design, the film boasts high photothermal conversion efficiency. When exposed to solar radiation for 360 s at an ambient temperature of 20 °C, its surface temperature swiftly climbs to 98.3 ± 1.1 °C. The film's anti-icing capabilities are evidenced by the fact that a droplet of water takes 2964.7 s to freeze on its surface, which is approximately 118 times that of aluminum. Additionally, it demonstrates excellent photothermal de-icing performance, swiftly eliminating thick layers of ice or frost under sunlight. Moreover, this film maintains its anti-icing and hydrophobic qualities even after multiple icing and de-icing cycles, as well as durability testing. It also possesses self-cleaning properties. Given its outstanding performance, this film has tremendous potential for long-term outdoor anti-icing applications.

Enhanced photoluminescence of a microporous quantum dot color conversion layer by inkjet printing

Owing to their high color purity, tunable bandgap, and high efficiency, quantum dots (QDs) have gained significant attention as color conversion materials for high-end display applications. Moreover, inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode (micro-LED)-based displays. As a color conversion layer, the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering. Conventional scatterers, such as titanium dioxide microparticles, have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process. In our work, as an alternative approach, we use inkjet printing for depositing a phase separating polymer ink based on polystyrene (PS) and polyethylene glycol (PEG). QD/polymer composite pixels with scattering micropores are realized. The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability. With the presence of the microporous structure, the photoluminescence intensity of the QD film is enhanced by 110% in drop-cast films and by 35.3% in inkjet-printed QD pixel arrays compared to the reference samples.

Fluorescence behaviors of perylene-dispersed super engineering plastic films

We attempted to manufacture films in which fluorescent dye is dispersed using engineering plastic as a matrix which has high heat and chemical resistance as well as excellent mechanical performance. In this study, films containing highly dispersed perylene in colorless and transparent aromatic polyamide (PA) and polyimide (PI) were manufactured. The perylene-dispersed PA film emitted strong blue light with a maximum fluorescence at 457 nm. On the other hand, the perylene-dispersed PI film showed significant fluorescence quenching with its maximum fluorescence wavelength significantly red-shifted to 546 nm. The perylene-dispersed PI film treated with ethylene diamine at 80 °C showed strong blue fluorescence, and when the film was further heated at 200 °C, the fluorescence was quenched. These films are expected to be applied as back light unit or color conversion layer for OLED and Micro LED due to their excellent physical properties.

InGaN blue resonant cavity micro-LED with RGY quantum dot layer for broad gamut, efficient displays

The technology of RGBY micro resonant cavity light emitting diodes (micro-RCLEDs) based on quantum dots (QDs) is considered one of the most promising approaches for full-color displays. In this work, we propose a novel structure combining a high color conversion efficiency (CCE) QD photoresist (QDPR) color conversion layer (CCL) with blue light micro RCLEDs, incorporating an ultra-thin yellow color filter. The additional TiO2 particles inside the QDPR CCL can scatter light and disperse QDs, thus reducing the self-aggregation phenomenon and enhancing the eventual illumination uniformity. Considering the blue light leakage, the influences of adding different color filters are investigated by illumination design software. Finally, the introduction of low-temperature atomic layer deposition (ALD) passivation protection technology at the top of the CCL can enhance the device's reliability. The introduction of RGBY four-color subpixels provides a viable path for developing low-energy consumption, high uniformity, and efficient color conversion displays.