Application In Light-emitting Diodes Research Articles

Tunable light emission of Bi and V-doped borosilicate glasses for application in white light-emitting diodes

Melt-quenched borosilicate glasses, co-doped with Bi and V ions, exhibited broad visible spectrum emissions. Bi ions primarily existed as Bi3+, acting as network modifiers, lowering the glass transition temperature linearly with increasing Bi content. V5+ ions adopted tetrahedral coordination as [VO4]3- units. Photoluminescence of Bi ions is shifted from blue to longer wavelengths with higher Bi content, associated with the stabilization of Bi2+ and the presence of Bi3+ in different local environments. Combined with V ions, the glasses emitted light covering the entire visible spectrum, offering the potential for white LED applications with correlated color temperatures ranging from 6135 to 4010 K. The highest QY was 11.9 and 8.0 % upon excitation at 325 and 340 nm.

InCl3-Assisted Surface Defects Restoring to Enhance Lead-Free Cs2ZrCl6 Nanocrystals for X-Ray Imaging and Blue LED Applications.

As one type of recent emerging lead-free perovskites, Cs2ZrCl6 nanocrystals are widely concerned, benefiting from the eminent designability, high X-ray cutoff efficiency, and favorable stability. Improving the luminescence performance of Cs2ZrCl6 nanocrystals has great importance to cater for practical applications. In view of the surface defects frequently formed by the liquid phase method, the particle morphology and surface quality of this material are expected to be regulated if certain intervention is made in the synthesis process. In the work, differing from normal cell lattice modulation based on the ion doping, the grain size and surface morphology of Cs2ZrCl6 nanocrystals are optimized via adding a certain amount of InCl3 to the synthetic solution. The surface defects are restored to inhibit the defect-induced non-radiative transition, resulting in the improvement of the luminescence properties. Moreover, a flexible Cs2ZrCl6@polydimethylsiloxane film with excellent heat, water, and bending resistance and a light-emitting diode (LED) device are fabricated, exhibiting excellent application potential for X-ray imaging and blue LED.

Efficient tunable visible and near-infrared emission in Sb3+/Sm3+-codoped Cs2NaLuCl6 for near-infrared light-emitting diode, triple-mode fluorescence anti-counterfeiting and information encryption

Rare earth ions (RE3+)-doped double perovskites have attracted tremendous attention for its fascinating optical properties. Nevertheless, RE3+ generally exhibits poor photoluminescence quantum yield (PLQY) for their parity-forbidden 4f-4f transition and the low doping concentration. Herein, we reported Sb3+/Sm3+-codoped rare earth-based double perovskite Cs2NaLuCl6 that enables efficient visible and near-infrared (NIR) emission, which stems from self-trapped exciton (STE) and Sm3+, respectively. Benefit from up to 72.89% energy transfer efficiency from STE to Sm3+ and high doping concentrations due to similar ionic activity between Sm3+ and Lu3+, thus eruptive PLQY of 74.58% in the visible light region and 23.12% in the NIR light region can be obtained. Moreover, Sb3+/Sm3+-codoped Cs2NaLuCl6 exhibits tunable emission characteristic in the visible light region under different excitation wavelengths, which can change from blue emission (254 nm excitation) to white emission (365 nm excitation). More particularly, only the NIR emission can be captured by the NIR camera when a 700 nm cutoff filter is added. The excellent stability and unique optical properties of Sb3+/Sm3+-codoped Cs2NaLuCl6 enable us to demonstrate its applications in NIR light-emitting diode, triple-mode fluorescence anti-counterfeiting and information encryption. These findings provide new inspiration for the application of rare earth-based double perovskite in optoelectronic devices.

Enhancing thermal efficiency of aluminum heat sink by reduced graphene oxide-layer coating approach

Light emitting diode (LED) technology plays a significant role in the market of lighting technologies due to its high efficiency compared to conventional lighting solutions. Cooling of high-power LEDs, on the other hand, is a critical aspect in maximizing LED performance. Furthermore, due to the powder, rain, and muds, LED armatures including a finned heat sink may not be efficient according to its design and utilization areas especially for outdoor illumination. Eliminating these factors, un-finned heat sink LED armatures are also preferred, yet the temperature dissipation of the un-finned type is not homogeneous relatively according to finned type. In this study, a graphene coated un-finned heat sink was developed to obtain relatively homogeneous temperature distribution and increase heat transfer of aluminum plate. An un-finned heat sink comprising thin graphene film was designed by a computer-aided-design (CAD) program and the thermal analysis was conducted by a finite element analysis (FEA) program. The experimental measurements offered that the maximum and minimum junction temperatures for the bare, and reduced graphene oxide (rGO)-layers coated aluminum heat sinks were obtained as 90 − 70◦C, and 59–54◦C, respectively. The outstanding in-plane thermal conductivity of rGO-layers facilitated the homogenous heat distribution throughout the aluminum heat sink. Moreover, the design and thermal analysis of developed heat sinks were validated with experimental results with the 2.4% error with respect to maximum junction temperature. It can be concluded that rGO-layers coated aluminum heat sink enabled to facilitated the heat transfer more than bare aluminum due to its higher thermal conductivity. In brief, this work opens a new gate for designing the graphene based materials-integrated cooling solution for LED applications.

Enhanced Photoluminescence Quantum Yield of Colloidal MoS2 Quantum Dots by Optimization of Oleic Acid and Oleylamine for Light-Emitting Diode Applications

Enhanced Photoluminescence Quantum Yield of Colloidal MoS₂ Quantum Dots by Optimization of Oleic Acid and Oleylamine for Light-Emitting Diode Applications

The emergence and prospects of carbon dots with solid-state photoluminescence for light-emitting diodes.

The significant features of carbon dots (CDs), such as bright and tunable photoluminescence, high thermal stability, and low toxicity, endow them with tremendous potential for application in next generation optoelectronics. Despite great progress achieved in the design of high-performance CDs so far, the practical applications in solid-state lighting and displays have been retarded by the aggregation-caused quenching (ACQ) effect ascribed to direct π-π interactions. This review provides a comprehensive overview of the recent progress made in solid-state CD emitters, including their synthesis, optical properties and applications in light-emitting diodes (LEDs). Their triplet-excited-state-involved properties, as well as their recent advances in phosphor-converted LEDs and electroluminescent LEDs, are mainly reviewed here. Finally, the prospects and challenges of solid-state CD-based LEDs are discussed with an eye on future development. We hope that this review will provide critical insights to inspire new exciting discoveries on solid-state CDs from both fundamental and practical standpoints so that the realization of their potential in optoelectronic areas can be facilitated.

Solution-grown millimeter-scale Mn-doped CsPbBr3/Cs4PbBr6 crystals with enhanced photoluminescence and stability for light-emitting applications.

Metal halide perovskites are particularly emerging for optoelectronic applications in light-emitting diodes, photodetectors, and solar cells due to their flourishing photophysical properties. However, the poor stability of three-dimensional (3D) lead halide perovskite nanocrystals (NCs) significantly hampers their optoelectronics and photovoltaics applications. Embedding 3D perovskites into zero-dimensional (0D) perovskite crystals and doping ions of appropriate elements into host lattices provide effective approaches to improve the stability and optical-electronic performance. In this study, millimeter-scale Mn-doped and undoped CsPbBr3/Cs4PbBr6 perovskite crystals were successfully fabricated by a one-step slow cooling method. We systematically investigated the effects of Mn2+ ion doping on the PL performance and stability of CsPbBr3/Cs4PbBr6 crystals. Compared with undoped crystals, the existence of Mn2+ ions not only blue-shifted the PL peak but also improved the luminescence performance and stability of the prepared millimeter-sized crystals. Moreover, doping Mn2+ ions can increase the proportion of radiative recombination at low temperature, which may be because Mn2+ ions can effectively accelerate the decay of a dark exciton by the magnetic mixing of bright and dark excitons. In addition, green LED devices with high efficiency packaged as-grown crystals are explored, which promises further application in display backlights.

Boosting broadband short-wave infrared emission to achieve near-unity quantum efficiency via bridging Cr3+-Ni2+ in spinel solid-solutions towards light-emitting diode applications.

Recently, short-wave infrared (SWIR) phosphor-converted light-emitting diodes (pc-LEDs) have garnered increased attention due to their widespread applications in night vision, biological imaging, and non-destructive testing. Nevertheless, the currently used SWIR phosphors suffer from poor thermal stability and low quantum efficiency. In this study, a finely tuned spinel-based solid solution, Mg0.5Zn0.5Ga2O4, is prepared to host Ni2+ to induce SWIR emission. Cr3+ is codoped as a sensitizer to bridge Cr3+ and Ni2+ ions, significantly enhancing blue light absorption and facilitating energy transfer (ET) to Ni2+ ions. The champion SWIR phosphor exhibits a broadband emission centered at 1304 nm with a full width at half maximum (FWHM) of 250 nm, achieving a near-unity internal quantum efficiency (IQE = 97.7%) and a good thermal stability (70.7%@423 K). The fabricated SWIR pc-LED device delivers a high SWIR output power of 39.9 mW at 360 mA, enabling its application in non-destructive imaging and testing.

Spectrally narrow band-edge photoluminescence from AgInS2-based core/shell quantum dots for electroluminescence applications.

This study presents a facile synthesis of cadmium-free ternary and quaternary quantum dots (QDs) and their application to light-emitting diode (LED) devices. AgInS2 ternary QDs, developed as a substitute for cadmium chalcogenide QDs, exhibited spectrally broad photoluminescence due to intrinsic defect levels. Our group has successfully achieved narrow band-edge PL by a coating with gallium sulfide shell. Subsequently, an intrinsic difficulty in the synthesis of multinary compound QDs, which often results in unnecessary byproducts, was surmounted by a new approach involving the nucleation of silver sulfide followed by material conversion to the intended composition (silver indium gallium sulfide). By fine-tuning this reaction and bringing the starting material closer to stoichiometric compositional ratios, atom economy was further improved. These QDs have been tested in LED applications, but the standard device encountered a significant defective emission that would have been eliminated by the gallium sulfide shells. This problem is addressed by introducing gallium oxide as a new electron transport layer.

Processing of Advanced Materials for Next-Generation Electronics and Photonics - A Review

Advanced materials play a crucial role in the development of next-generation electronics and photonics due to their unique physical and chemical properties. This review highlights recent advances in the processing of advanced materials, including two-dimensional materials, organic semiconductors, and perovskites, for their integration into electronic and photonic devices. Specifically, we discuss the methods of material synthesis, characterization, and device fabrication, as well as their applications in transistors, photovoltaics, light-emitting diodes, and sensors. We also address the challenges and opportunities associated with the development of advanced materials for the future of electronics and photonics.

Exploring color space: an investigation of heteroaryl-substituted benzobis[1,2-d:4,5-d′]oxazoles and their application in organic light-emitting diodes

The color tuning of benzobisoxazole-based OLEDs to achieve white emission with high brightness is reported.

Hole transport layer engineering in high performance quasi-2D perovskite blue light emitting diodes.

Quasi-2D perovskites have emerged as highly promising materials for application in perovskite light-emitting diodes (PeLEDs), garnering significant attention due to their outstanding semiconductor properties. These materials boast an inherent multi-quantum well structure that imparts a robust confinement effect, particularly advantageous for blue emission. However, the development of blue emitters utilizing quasi-2D perovskites encounters challenges, notably colour instability, multipeak emission, and suboptimal fluorescence yield. The hole transfer layer (HTL) on which the perovskite layer is deposited in PeLEDs further affects the performance and efficiency. In this review, we delve into the evolution of blue PeLEDs and elucidate the optical properties of quasi-2D perovskites with the primary focus on HTL materials. We explore different HTL materials like PEDOT:PSS, metal oxides, and conjugated polyelectrolytes as well as ionic liquids, and their role in enhancing the colour stability, minimizing interfacial defects and increasing the fluorescence yield. This review endeavours to provide a holistic perspective of the different HTLs and serve as a valuable reference for researchers navigating the realm of HTL engineering towards the realization of high-performance blue quasi-2D PeLEDs.

Solvent-regulated multicolor-emissive carbon dots and their application in multicolor light-emitting diodes

Multicolor emissive carbon dots are achieved using a solvent regulation strategy, exhibiting multiple emission mechanisms.

The stability of CsPb(BrxCl1-x)3 all-inorganic mixed halide perovskites.

The use of mixed halide perovskites in the preparation of blue light-emitting diodes (LEDs) is considered to be the most effective and direct approach. However, the introduction of chlorine (Cl) element might raise stability issues in the system and lead to low efficiency, thereby impeding the development of deep blue light-emitting diodes with high efficiency and stability. Determining the alloy concentration and the atomic distribution of bromine-chlorine (Br-Cl) mixed systems is essential for further application of deep blue light-emitting diodes. In this work, we have systematically investigated the stability of bromine-chlorine (Br-Cl) mixed alloy systems in various substitution configurations using high-throughput theoretical calculations. Based on this, we have examined the relationship between configuration stability and three aspects: the type of octahedra, the orientation of the octahedra and the Pb-X-Pb distortion angle in the configuration.

Silicon-based peripheral steric donor modifications for a high-efficiency multi-resonance thermally activated delayed fluorescence emitter

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have broad applications in organic light-emitting diodes (OLEDs).

Research Progress of the Application of UV Light-Emitting Diodes for Water Disinfection

With the increasing global demand for safe drinking water, the search for effective and economical water treatment technologies has become an urgent need. Ultraviolet (UV) light sterilization is a proven method for eliminating bacteria in water, but traditional UV systems often rely on mercury lamps, which pose potential environmental and health risks. In recent years, the development of UV-LED technology has offered a new solution for water treatment. This article provides a detailed explanation of the working principles, technological advantages, and applications of UV-LEDs in water treatment. By comparing them with traditional UV systems, UV-LEDs not only demonstrate lower energy consumption and longer lifespan, but also avoid the use of toxic mercury. Despite current challenges in cost and technological maturity, the environmental friendliness and efficiency potential of UV-LED technology indicate a promising market outlook. This article aims to provide a comprehensive review of UV-LED technology for practitioners and researchers in the water treatment industry, and to explore its future development directions.

Design and Synthesis of a Y-Type Thioxanthone-Carbazole for the Application in Blue and Yellow Organic Light-Emitting Diodes

Design and Synthesis of a Y-Type Thioxanthone-Carbazole for the Application in Blue and Yellow Organic Light-Emitting Diodes

Hybrid nanospheres of silica covalently containing yellow-emitting cationic iridium(III) complex: preparation and application in white light-emitting diodes.

A yellow-emitting cationic iridium(III) complex [(dfppy)2Ir(TBD)]PF6 (TBD: N4,N4'-bis(3-(triethoxysilyl)propyl)-[2,2'-bipyridine]-4,4'-dicarboxamide; dfppy: 2-(2,4-difluorophenyl)pyridine) containing hydrolysable alkoxysilanes was synthesized. Then, a series of silica-based hybrid nanospheres with diameters of around 400 nm was prepared via the hydrolysis of this complex together with tetraethyl orthosilicate (TEOS, a silica source). When the amount of the complex used was 5.0 wt%, hybrid nanospheres showed the best photoluminescence (PL) properties, relative to the PL quantum yield of pure solid [(dfppy)2Ir(TBD)]PF6 (12.7%), that of hybrid nanospheres increased to 26.2%. Moreover, the thermal decomposition temperature (Td) of pure solid [(dfppy)2Ir(TBD)]PF6 was 331 °C, the Td of the complex in hybrid nanospheres increased to 447 °C. However, the yellow light emission was almost unchanged and was still located at 500-750 nm with a maximum wavelength (λem,max) of 577 nm. Under the excitation of blue-emitting chips (λem,max ≈ 455 nm), cold/neutral/warm white light-emitting diodes (WLEDs) with good luminous quality can all be fabricated using these hybrid nanospheres as phosphors in epoxy resin at different blending concentrations. Compared with two or three iridium(III) complexes being contained in silica-based particles as phosphors as described in literatures, in this study, silica-based hybrid nanospheres covalently containing only one yellow-emitting cationic iridium(III) complex as phosphors provide a more effective and simpler method for preparation high-performance WLEDs.

Highly efficient platinum(ii) complexes overcoming Pt–Pt interactions and their applications in organic light-emitting diodes

By introducing the methyl substituent acetylacetone and benzyl substituents, Pt(ii) complexes restrain Pt–Pt interactions in pure films and maintain nearly identical PL spectra with dilute solution. The maximum EQE of non-doped OLED reaches 19.6%.

КВАНТОВЫЕ ТОЧКИ ДЛЯ СОЗДАНИЯ ВЫСОКОЭФФЕКТИВНЫХ СВЕТОДИОДОВ: ПЕРСПЕКТИВЫ И ВЫЗОВЫ

Quantum dots (QDs) are a promising material for creating highly efficient light-emitting diodes (LEDs) due to their unique optical and electronic properties. QDs allow achieving high quantum efficiency, narrow emission bandwidth, and precise tuning of the color characteristics of LEDs. This arti-cle reviews the main advantages of using quantum dots in LEDs, such as a wide color gamut and high color fidelity, and discusses key technological challenges, including stability, integration with traditional semiconductor materials, and toxicity of some elements. The prospects for the development and applica-tion of QD LEDs in various industries, including display technology, lighting, and solar cells, are analyzed.