Search Results (175)

Host engineering is one of the most efficient approaches to maximizing the electroluminescent performance of organic light-emitting devices. Herein, two carbazole-based N,N′-Dicarbazolyl-4,4′-biphenyl (CBP) derivatives, (9-(4′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-4-yl)-3-(3-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-9H-carbazole (CBPmBI), and (9-(4′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-4-yl)-9H-carbazol-3-yl)diphenylphosphine oxide (CBPPO), were designed as bipolar hosts for blue phosphorescent devices. By introducing the electron-withdrawing groups to the backbone of CBP, the bipolar hosts exhibited high triplet energy, enhanced thermal stability, and balanced charge transport. The device constructed with the blue guest emitter bis[2-(4,6-difluorophenyl) pyridinato-C2,N]iridium (III) (FIrpic) showed the excellent electroluminescence performance. For instance, the CBPPO-based devices achieved a maximum current efficiency of 28.0 cd/A, a power efficiency of 25.8 lm/W, and an external quantum efficiency of 14.4%. Notably, the external quantum efficiency retained at14.1% under the brightness of 5000 cd/m², featuring the negligible efficiency roll-off. Full article

Perovskite light-emitting diodes (PeLEDs) have garnered significant interest owing to their exceptional color purity, broadly tunable emission spectra, and cost-effective solution processability. However, blue PeLEDs continue to underperform in efficiency and operational stability compared to their red and green counterparts, primarily due to defect-induced non-radiative recombination losses and inefficient exciton management. Herein, we demonstrate a synergistic approach that integrates multi-cation compositional engineering with triplet exciton management by incorporating a high-triplet-energy material, mCBP (3,3-Di(9H-carbazol-9-yl)biphenyl), during film fabrication. Temperature-dependent photoluminescence reveals that mCBP incorporation significantly enhances the exciton binding energy from 49.36 meV to 68.84 meV and reduces phonon coupling strength, indicating improved exciton stability and suppressed non-radiative channels. The corresponding PeLEDs achieve a peak external quantum efficiency of 10.2% and a maximum luminance exceeding 12,000 cd/m², demonstrating the effectiveness of this solution-based triplet management strategy. This work highlights the critical role of scalable, solution-processed triplet exciton management strategies in advancing blue PeLED performance, offering a practical pathway toward high-performance perovskite-based display and lighting technologies. Full article

Quantum-dot light-emitting diodes (QLEDs) have emerged as promising candidates for next-generation display technologies owing to their high color purity and external quantum efficiency. Despite rapid advancements in device performance, operational stability and long-term reliability remain critical challenges, particularly for cadmium-free and blue-emitting QLEDs. This review provides a comprehensive overview of the degradation mechanisms of QLEDs, emphasizing the relationship between environmental factors, such as moisture, oxygen, and thermal stress, and excitonic factors, including charge-injection imbalance, Auger recombination, and interface deterioration. We further highlight the role of nondestructive characterization techniques, including impedance spectroscopy, Fourier transform infrared spectroscopy, transient photoluminescence, transient electroluminescence, transient absorption, and electroabsorption spectroscopy, in probing real-time charge dynamics and material degradation. By integrating the insights from these operando analyses, this review offers a detailed perspective on the origins of device degradation and provides guidance for rational design strategies aimed at enhancing the operational stability and commercialization potential of QLEDs. Full article

The development of a straightforward strategy for preparing organic fluorescent materials, fine-tuning white-light emission, and subsequently constructing white light-emitting diodes (LEDs) is of great significance. Herein, we report on the modulation of white-light emission and the fabrication of white LEDs using polyhedral oligomeric silsesquioxane (POSS)-based fluorescent hybrid porous polymers (HPPs) through simple physical blending. Two HPPs, namely HPP-1 and HPP-2, which emit blue and red light, respectively, were synthesized via the efficient Heck reactions of octavinylsilsesquioxane with 4,4′-dibromobiphenyl and 1,3,6,8-tetrabromopyrene. By physically doping of HPP-1 and HPP-2 in variable ratios in solvent suspensions, it was discovered that white-light emission is significantly influenced by the concentrations of the materials and the excitation wavelength. Similar findings were also observed in the solid-state physical doping. An ideal white light emission with a CIE coordinate of (0.33, 0.33) can be achieved when excited at 380 nm with a mass ratio of HPP-1 to HPP-2 of 1:2. Finally, the two HPPs were dispersed in polysiloxane matrices, and a white LED with a CIE coordinate of (0.42, 0.36) was obtained. The LED exhibited a color rendering index of up to 90 and a correlated color temperature of 2858 K, realizing warm white light emission. This simple and convenient white-light regulation strategy holds great promise for application in the development of novel white LEDs based on organic fluorescent porous materials. Full article

The future development of perovskite light-emitting diodes (LEDs) is significantly limited by the poor stability and low brightness of the pure-blue emission in the wavelength range of 460–470 nm. In this study, the Cl/Br element ratio in CsPbCl_xBr_3−x perovskite nanocrystals (NCs) was modulated to precisely control their blue emission in the 428–512 nm spectral region. Then, the undoped CsPbCl₁Br₂ and the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs were synthesized via the hot-injection method and investigated using variable-temperature photoluminescence (PL) spectroscopy. The PL emission peak of the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs exhibits a blue shift from 475 nm to 460 nm with increasing ZnCl₂ doping concentration. Additionally, the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs show a high photoluminescence quantum yield (PLQY). The variable-temperature PL spectroscopy results show that the ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs have a larger exciton binding energy than the CsPbCl₁Br₂ perovskite NCs, which is indicative of a potentially higher PL intensity. To assess the stability of the perovskite NCs, high-temperature experiments and ultraviolet-irradiation experiments were conducted. The results indicate that zinc doping is beneficial for improving the stability of the perovskite NCs. The ZnCl₂-doped CsPbCl₁Br₂ perovskite NCs were post-treated using didodecylammonium bromide, and after the post-treatment, the PLQY increased to 83%. This is a high PLQY value for perovskite NC-LEDs in the blue spectral range, and it satisfies the requirements of practical display applications. This work thus provides a simple preparation method for pure blue light-emitting materials. Full article

White-light-emitting diodes (wLEDs) are central to next-generation lighting technologies, yet their reliance on critical raw materials (CRMs), such as rare-earth elements, raises concerns regarding sustainability and supply security. In this work, we present a simple, low-cost method to produce photoluminescent carbon-based nanostructures—known as oxidative debris (OD)—via alkaline treatment of graphene oxide (GO) using KOH solutions ranging from 0.04 M to 1.78 M. The resulting OD, isolated from the supernatant after acid precipitation, exhibits strong and tunable photoluminescence (PL) across the visible spectrum. Emission peaks shift from blue (~440 nm) to green (~500 nm) and yellow (~565 nm) as a function of treatment conditions, with excitation wavelengths between 300 and 390 nm. Optical, morphological. and compositional analyses were performed using UV-Vis, AFM, FTIR, and Raman spectroscopy, confirming the presence of highly oxidized aromatic domains. The blue-emitting (S2) and green/yellow-emitting (R2) fractions were successfully separated and characterized, demonstrating potential color tuning by adjusting KOH concentration and treatment time. This study highlights the feasibility of reusing GO-derived byproducts as sustainable phosphor alternatives in wLEDs, reducing reliance on CRMs and aligning with green chemistry principles. Full article

Main-chain conjugated and non-conjugated polyelectrolytes are an important class of materials that have many technological applications ranging from fire-retardant materials to carbon-nanotube composites, nonlinear optical materials, electrochromic materials for smart windows, and optical sensors for biomolecules. Here, we describe a series of poly(pyridinium salt)s-fluorene containing 9,9-bis(4-aminophenyl)fluorene moieties with various organic counterions that were synthesized using ring-transmutation polymerization and metathesis reactions, which are non-conjugated polyelectrolytes. Their chemical structures were characterized by Fourier transform infrared (FTIR), proton (¹H) and fluorine 19 (¹⁹F) nuclear magnetic resonance (NMR) spectrometers, and elemental analysis. They exhibited polyelectrolytic behavior in dimethyl sulfoxide. Their lyotropic liquid-crystalline phases were examined by polarizing optical microscopy (POM) and small angle X-ray scattering (SAXS) studies. Their emission spectra exhibited a positive solvatochromism on changing the polarity of solvents. They emitted greenish-yellow lights in polar organic solvents. They formed aggregates in polar aprotic and protic solvents with the addition of water (v/v, 0–90%), whose λ_em peaks were blue shifted. Full article

Objective: This study aimed to evaluate the photobiomodulatory (PBM) effects of low-power light-emitting diode (LED) irradiation on cultured human umbilical vein endothelial cells (HUVECs), focusing on changes in cellular metabolic activity and morphology. Materials and Methods: HUVECs were cultured and divided into three groups: control (no irradiation), red LED (655 nm), and blue LED (455 nm). Cells were irradiated once with a total energy dose of 4 J over 60 s. Cellular metabolic activity was assessed at 0, 1, 3, and 6 h post-irradiation using the WST-8 assay. Morphological changes were examined 3 h post-irradiation using rhodamine–phalloidin staining and confocal laser scanning microscopy. Results: Red LED irradiation significantly enhanced metabolic activity immediately and at 3 h post-irradiation compared to the control group. Blue LED irradiation showed a non-significant trend toward increased metabolic activity at 1 and 3 h. Morphometric analysis revealed increases in cell area, perimeter, and Feret diameter in both LED-irradiated groups, with more pronounced changes observed in the red LED group. Conclusions: Low-power red LED light (655 nm) effectively promotes metabolic activation and induces morphological changes in vascular endothelial cells, suggesting its potential application in angiogenesis and wound healing. Due to its safety and accessibility, LED-based PBM may serve as a promising therapeutic modality for soft tissue regeneration in both clinical and home-care settings. Full article

Dy³⁺ single-doped and Dy³⁺/Eu³⁺ co-doped ZnO:B₂O₃:WO₃:Nb₂O₅ glass was successfully synthesized using the melt quenching method. The amorphous character of the prepared samples was confirmed by X-ray diffraction (XRD). The glass transition and crystallization temperatures were examined by differential scanning calorimetry (DSC). Raman spectroscopy was applied to investigate the glass microstructure. Physical properties like the density, molar volume, oxygen molar volume and oxygen packing density of the glass were also determined. The photoluminescence excitation (PLE) and emission (PL) spectra of the resultant glass types were measured. The obtained Dy³⁺ single-doped glass was characterized by strong luminescence at 482 and 574 nm, corresponding to the ⁴F_9/2 → ⁶H_15/2 (blue) and ⁴F_9/2 → ⁶H_13/2 (yellow) transitions, respectively, and weak luminescence at 663 nm and 753 nm due to the ⁴F_9/2 → ⁶H_11/2 (red) and ⁴F_9/2 → ⁶H_9/2 + ⁶F_11/2 (red) transitions. The luminescence results indicate that energy transfer from the Dy³⁺ to Eu³⁺ ions occurs in the proposed glass system. The emitted light from the Dy³⁺ single-doped glass was found to be yellow-orange. The Dy³⁺/Eu³⁺ co-doped samples emitted darker orange light. The obtained results show that the investigated types of glass have the potential to be used as orange light-emitting materials. Full article

Two blue fluorescent dopants were designed and successfully synthesized, 5-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho [3,2,1-de]anthracen-7-yl)-5H-benzo[b]carbazole (TDBA-Bz) and 9-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9H-carbazole (TDBA-Cz). Both in solution and the film state, the two emitters demonstrated deep-blue luminescence characteristics. In solution-processed organic light-emitting diodes (OLEDs), TDBA-Bz and TDBA-Cz used as dopant materials showed electroluminescence peaks at 436 nm and 413 nm, respectively. The corresponding CIE color coordinates were determined to be (0.181, 0.114) for TDBA-Bz and (0.167, 0.086) for TDBA-Cz. The solution-processed device using TDBA-Cz as a dopant exhibited a current efficiency (CE) of 7.25 cd/A and an external quantum efficiency (EQE) of 6.45%, demonstrating higher efficiencies compared to the device with TDBA-Bz. In particular, at a luminance of 2000 cd/m², TDBA-Cz maintained an EQE of 4.81%, with only a slight decrease from its maximum EQE. Full article

Quasi-two-dimensional (quasi-2D) perovskites have emerged as a transformative platform for high-efficiency perovskite light-emitting diodes (PeLEDs), benefiting from their tunable quantum confinement, high photoluminescence quantum yields (PLQYs), and self-assembled energy funneling mechanisms. This review systematically explores interfacial energy transfer engineering strategies that underpin advancements in device performance. By tailoring phase composition distributions, passivating defects via additive engineering, and optimizing charge transport layers, researchers have achieved external quantum efficiencies (EQEs) exceeding 20% in green and red PeLEDs. However, challenges persist in blue emission stability, efficiency roll-off at high currents, and long-term operational durability driven by spectral redshift, Auger recombination, and interfacial ion migration. Emerging solutions include dual-cation/halogen alloying for bandgap control, microcavity photon management, and insulator–perovskite–insulator (IPI) architectures to suppress leakage currents. Future progress hinges on interdisciplinary efforts in multifunctional material design, scalable fabrication, and mechanistic studies of carrier–photon interactions. Through these innovations, quasi-2D PeLEDs hold promise for next-generation displays and solid-state lighting, offering a cost-effective and efficient alternative to conventional technologies. Full article

Blue exciplexes, a critical innovative component in organic light-emitting diodes (OLEDs) technology, exhibit substantial potential for enhancing device efficiency, reducing driving voltage, and simplifying structural designs. This article reviews the pivotal role of blue exciplexes in OLEDs, analyzing their unique advantages and challenges as emitters and host materials. Through optimized molecular design, blue exciplexes achieve high color purity and emission efficiency, surpassing conventional fluorescent materials. Additionally, their wide energy bands and high triplet energy provide opportunities to improve the performance of sky-blue, deep-blue, and white OLEDs. However, limitations in deep-blue efficiency, material degradation due to high-energy excitons, and spectral red-shift pose significant challenges to their development. This review offers a comprehensive perspective and research reference on the photophysical mechanisms of blue exciplexes and their applications in display and lighting fields. Full article

Europium(III) β-diketone and organic carboxylic acid complexes are designable, easy to prepare, and easy to modify and have excellent fluorescence properties (narrow emission spectral band, high colour purity, long fluorescence lifetime, high quantum yield, and a spectral emission range covering both the visible and near-infrared regions). These complexes play important roles in popular fields such as laser and fibre-optic communications, medical diagnostics, immunoassays, fluorescent lasers, sensors, anticounterfeiting, and organic light-emitting diodes (OLEDs). In the field of light-emitting materials, europium complexes are especially widely used in OLED lamps, especially because of their high-efficiency emission of red (among the three primary colours); accordingly, these complexes can be mixed with blue and green phosphors to obtain high-efficiency white phosphors that can be excited by near-ultraviolet light. This paper reviews the red-light-emitting europium complexes with β-diketone and organic carboxylic acid as ligands that have been studied over the last five years, describes the current problems, and discusses their future application prospects. Full article

Phosphorescent Pt(II) complexes have garnered significant attention as key components in luminescence-based systems due to their highly efficient emission properties. A notable characteristic of these complexes is their ability to form excimers through strong molecular stacking in concentrated solutions or solid film states. This aggregation-driven emission, primarily arising from metal–metal to ligand charge transfer (MMLCT), is influenced by overlapping d-orbitals oriented perpendicular to the square planar structure of the Pt(II) complexes. Although this property hinders the development of pure blue-emitting Pt(II) complexes, it facilitates the design of materials that emit red- and near-infrared (NIR) light. By employing advanced molecular design techniques, dinuclear Pt(II) complexes have been optimized to significantly enhance red and NIR emissions through the modulation of Pt-Pt interactions and adjustments in ligand electron densities. This review elucidates how the control of Pt-Pt distances and strategic ligand modifications can directly influence the emission spectra toward red and NIR regions. A comparative analysis of recent studies underscores the novelty and effectiveness of double-decker-type dinuclear Pt(II) complexes in achieving efficient emission characteristics in the long-wavelength range. These insights may guide the design of molecular structures for next-generation organometallic phosphorescent materials. Full article

Ultra-weak photon emission (UPE) provides a non-invasive method for assessing the biochemical state of biological materials. In this work, we investigated UPE in fruits of various colours (red, orange, yellow, and green) for potential forensic applications. Firstly, fruits were exposed to natural sunlight for 10 min, after which UPE was measured at 10 min intervals over a three-hour period. The results indicated that, following the initial induced response, all fruit types stabilised to a spontaneous UPE state after approximately 60 min in darkness. Subsequently, we compared UPE responses following exposure to natural sunlight with those obtained under artificial red, green, and blue lights. Under natural sunlight, induced UPE values ranged from 15 to 35 intensity units (IU) and spontaneous UPE from 1 to 25 IU, whereas under artificial lighting, induced UPE ranged from 5 to 30 IU and spontaneous UPE from 1 to 20 IU. Finally, a preliminary comparative study between organic and conventional fruits revealed that organic fruits consistently emitted slightly higher UPE levels than conventional ones, suggesting subtle differences in their biochemical properties. All these findings underscore the potential of UPE as a forensic tool for differentiating plant-based materials, with promising applications in food fraud detection and criminal investigations. Full article