Search Results (659)

Single-molecular white circularly polarized luminescence emitters show promise for use in chiral displays and solid-state lighting, but their design remains challenging because broadband emission, exciton utilization, color balance, and chiroptical activity must be integrated within one molecule. Herein, we report a chiral single-molecular white emitter, DCz-PTZ, constructed through a π-interrupted strategy by combining a rigid spiro framework, an oxygen-bridged carbazole/cyanobenzene segment, and a phenothiazine donor. The interrupted conjugation suppresses excessive charge-transfer (CT) domination and enables dual emissive channels, including short-wavelength locally excited (LE) emission and long-wavelength CT emission. DCz-PTZ exhibits near-ideal white emission in dilute toluene solution with CIE coordinates of (0.33, 0.33), and maintains balanced dual emission in 5 wt% doped films with CIE coordinates of (0.32, 0.34). Photophysical studies support the assignment of the yellow emission to a thermally activated delayed fluorescence (TADF)-active CT state. The enantiomers show mirror-image circularly polarized signals with |g_lum| up to 2.9 × 10⁻³. Optimized white organic light-emitting diodes (WOLEDs) achieve color rendering index (CRI) up to 92 and a maximum external quantum efficiency (EQE_max) of 1.3%. This work demonstrates a π-interrupted molecular strategy for integrating dual emission, TADF exciton utilization, and circularly polarized electroluminescence (CPEL) in a single chiral emitter. Full article

Organic–inorganic hybrid perovskites (OIHPs) have been widely used in fields such as solar cells, photodetectors, and light-emitting diodes due to their simple preparation by solution methods and excellent optoelectronic properties. In recent years, numerous scholars have delved deeply into the magneto-optical properties of perovskites and explored their potential applications in the magneto-optical field. Herein, we present the Faraday rotation characteristics of formamidinium lead bromide (Fabri₃) single crystals within the visible spectrum range. Firstly, FAPbBr₃ single crystals with high transparency and a size of 5.5 × 5.6 × 2 mm³ were prepared using the modified inverse temperature crystallization (MITC) method. The experimental results showed that the Verdet constant of FAPbBr₃ single crystal at 565 nm was up to 531.6 rad/(T·m). Furthermore, the FAPbBr₃ single crystal showed similar or an even higher Verdet constant when compared with the mature magneto-optical material TGG single crystal commonly used in the industry. The thermal simulation results of the FAPbBr₃ single crystal show low temperature dependence which achieves about 90% isolation transparency with a magnetic field of 0.35 T for 625 nm. This study demonstrates the outstanding Faraday rotation properties of FAPbBr₃ single crystals, thereby offering promising prospects for the development of perovskite materials in non-reciprocal devices such as optical isolators and optical circulators. Full article

Organic–inorganic hybrid metal halides (OIMHs), especially zero-dimensional (0D) ones, have been recognized as an excellent class of luminescent materials due to their structural diversity and tunable emission properties. In this work, using the environmentally friendly Zn(II) ion as the central metal and 1,4,7,10-tetraazacyclododecane (Cyclen) as the organic component, we successfully synthesized a novel OIMH, (H₃Cyclen)(ZnBr₄)·Br·H₂O. Single-crystal X-ray diffraction analysis reveals that (H₃Cyclen)(ZnBr₄)·Br·H₂O possesses a 0D structure, in which the [ZnBr₄]²⁻ tetrahedra are uniformly separated by the organic amine cations. This structural feature is expected to enhance the material’s stability and optimize its optoelectronic properties. Under UV lamp irradiation, (H₃Cyclen)(ZnBr₄)·Br·H₂O emits bright blue-green light. Therefore, we systematically investigated its luminescence properties. The emission mechanism was further elucidated using UV–vis absorption spectroscopy and DFT calculations. Finally, (H₃Cyclen)(ZnBr₄)·Br·H₂O was employed as a luminescent material to fabricate a white light-emitting diode (WLED), demonstrating its potential as an excellent phosphor material. Full article

The increasing incidence of traffic accidents involving elderly pedestrians has highlighted the necessity for effective strategies to improve visibility in low-light environments. Conventional safety garments based on retroreflective materials or optical fibers exhibit limitations, including passive operation and low luminance. In this study, a textile-based organic light-emitting diode (OLED) safety garment with automatic light-sensing functionality is proposed to overcome these limitations. The OLED devices were fabricated on an ultrathin polyethylene terephthalate (PET) substrate and transferred onto a textile substrate to maintain flexibility and wearability. A light-emitting module incorporating a LilyPad Arduino and ambient light sensor was implemented to enable automatic illumination under low-light conditions. The fabricated textile-based OLED exhibited a luminance of 550 cd/m² at 4.5 V and maintained stable performance after transfer, with a T₅₀ lifetime of 485 h. Thermal analysis showed a minimal temperature increase of 2.9 °C after 5 h of operation, remaining below body temperature. Moreover, mechanical testing confirmed over 95% luminance retention after 2,000 bending cycles. The fabricated OLED-based luminous safety garment exhibited lightweight wearability with a total weight of 140 g and improved visibility at observation distances of up to 50 m under low-light conditions. These results indicate that the proposed OLED-based luminous safety garment can offer a viable solution for enhancing the safety of elderly pedestrians. Full article

Gas-phase thermal deposition was used to form three organosilane self-assembled monolayers on indium tin oxide (ITO) anodes: amine-terminated (NH₂SAM), methyl-terminated (CH₃SAM), and trifluoropropyl-terminated (F₃SAM). Surface characterisation using water contact angle goniometry, ultraviolet photoelectron spectroscopy, and atomic force microscopy was combined with green organic light emitting diode (OLED) fabrication and J–V–L measurements to determine how terminal group chemistry and deposition time affect device performance. F₃SAM increased the ITO work function from 3.72 to 4.47–4.72 eV, resulting in ultrasmooth surfaces (R_a = 0.20 nm) and a maximum luminescence of ~6000 cd m⁻², eleven times higher than bare ITO (540 cd m⁻²). CH₃SAM enhanced luminescence through surface passivation at 10 min (3374 cd m⁻²), but decreased quickly with extended deposition durations due to multilayer roughening. NH₂SAM reduced the work function to 3.42 eV and gradually decreased hole injection, resulting in a turn-on voltage of 10–11 V after 180 min. These results indicate that terminal group polarity and deposition duration are the two most important parameters in gas-phase SAM engineering of ITO anodes for OLEDs. Full article

Low-refresh-rate driving is an effective way to reduce the power consumption of active-matrix organic light-emitting diode (AMOLED) displays. However, in conventional low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) pixel circuits, leakage current through switching TFTs can disturb the stored gate voltage of the driving TFT during the long emission period. This causes the time-dependent variation in driving current and visible flicker. In this study, a novel pixel circuit for leakage suppression in low-refresh-rate driving is presented. Bias aging was first applied to reduce the leakage current of the LTPS TFT, and a device model was then built from the characteristics measured at 60 °C. Based on this model, the leakage-induced instability of a conventional 7T1C pixel circuit was analyzed. To suppress this effect, a new 8T1C pixel circuit was proposed. The key idea is to reduce the source–drain voltage of the leakage-sensitive switching TFT during the emission period by raising the initial line potential to a level close to the storage node potential. Simulation results show that the proposed circuit greatly reduces the time-dependent variation in both the driving TFT gate voltage and the driving current compared with the conventional 7T1C circuit. Perceptual evaluation based on human visual sensitivity also confirms stable low-refresh-rate operation down to 20 Hz over the practical gray range. These results show that the proposed circuit is an effective solution for moderate low-refresh-rate operation without relying on low-temperature polycrystalline silicon and oxide (LTPO) technology. Full article

In scientific research, the optimization of organic light-emitting diodes (OLEDs) is generally achieved through a lengthy and expensive experimental process as new ideas and configurations are tested on real devices. Electro-optical simulation allows for the rapid evaluation of key performance parameters of device structures, thus reducing manufacturing time and costs. This paper presents an original contribution to the electro-optical modeling and optimization of multilayer OLED devices using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). This optimization explicitly incorporates defect states within the ITO/NPB/Alq₃:C545T/Alq₃/LiF-Al structure. The simulated model is calibrated using experimental data by fitting the trap state distribution. The Pareto front resulting from the multi-objective optimization identifies a set of non-dominated configurations, including an optimal intermediate structure defined by an electron transport layer (ETL) thickness of approximately 42 nm and a hole transport layer (HTL) thickness of approximately 53 nm. This configuration leads to a limited reduction of 1.75–2% in current efficiency (${\eta }_c$) while offering a remarkable improvement of 23–30% in power efficiency (${\eta }_p$) compared to the extreme configurations of the optimal Pareto set. Thus, this solution represents an optimal Pareto trade-off between high current efficiency and improved power efficiency. This paper shows that combining defect modeling and thickness optimization provides a reliable framework for the electro-optical optimization of OLED devices. Future work will extend this approach to spectral and colorimetric analysis. Full article

Organic–inorganic hybrid halide perovskites have attracted extensive attention due to their excellent optoelectronic properties and potential applications in field-effect transistors (FET), light-emitting diodes (LEDs), and photodetectors. However, conventional three-dimensional (3D) perovskites are limited by intrinsic instability and ion migration. Two-dimensional Ruddlesden-Popper (2D RP) perovskites offer improved structural stability, but many systems still suffer from modest photoluminescence efficiency and limited charge-transport performance. In this work, a novel 2D RP perovskite, (C₆H₅NH₃)₂CsPb₂Cl₇, was designed and synthesized, where the anilinium ion (C₆H₅NH₃⁺) serves as the organic spacer. Structural characterization indicates that the material possesses high crystallinity and a smooth surface morphology. Optical measurements reveal a violet emission peak at 411 nm with a single-peak feature and a full width at half maximum (FWHM) of 10 nm. The bandgap is determined to be 3.1 eV. Time-resolved photoluminescence (TRPL) measurements show an average lifetime of 4 ns, and the photoluminescence quantum yield (PLQY) is 29.8%. Based on the measured PLQY and lifetime, the radiative and non-radiative recombination rates were estimated to be K_r ≈ 7.45 × 10⁷ s⁻¹ and K_nr ≈ 1.76 × 10⁸ s⁻¹, respectively, suggesting that radiative recombination is appreciable although non-radiative pathways remain present. FET measurements demonstrate an on/off current ratio of 10⁴ and a carrier mobility of 1.1 cm² V⁻¹ s⁻¹. Without any systematic optimization, (C₆H₅NH₃)₂CsPb₂Cl₇ exhibits relatively favorable emissive behavior and measurable field-effect charge transport performance when compared with structurally similar 2D RP perovskites reported under comparable, non-optimized conditions. This study expands the family of chloride-based 2D perovskites and provides a basis for future improvements in their recombination and field-effect transport properties. Full article

High-performance full-color displays and white lighting require stable and efficient red, green, and blue emitters; however, they are often limited by wide bandgaps, imbalanced carrier injection/transport, complex device structures, and high material costs. To address these challenges, we designed and synthesized a multifunctional deep-blue molecule (PPI-F-PO) integrating a phenanthroimidazole moiety, a 9,9-diphenylfluorene unit, and a phosphine oxide group. The twisted structure of fluorene, featuring a sp³-hybridized carbon, effectively suppresses conjugation extension and aggregation-caused quenching, whereas the electron-withdrawing phosphine oxide group enhances electron transport. Consequently, it exhibits good thermal stability, high solid-state photoluminescence quantum yield (58.8%), and high triplet energy (E_T = 2.54 eV). Non-doped blue OLEDs based on this emitter achieve a maximum external quantum efficiency (EQE) of 2.52% with deep-blue CIE coordinates of (0.16, 0.06). Moreover, using this material as a host, green and orange-red phosphorescent OLEDs exhibit maximum EQEs of 15.4% and 9.7%, respectively, along with low efficiency roll-off. This work demonstrates that a bipolar deep-blue emitter with high triplet energy can act both as a high-efficiency standalone emitter and as a universal host for lower-energy phosphors, thereby simplifying device architecture and reducing material costs for full-color OLEDs. Full article

Two indolocarbazole-based host materials, namely, 5,7-di([1,1′:3′,1″-terphenyl]-5′-yl)-3,9-di-tert-butyl-5,7-dihydroindolo[2,3-b]carbazole (InCz-TP) and 4,4′-(3,9-di-tert-butylindolo[2,3-b]carbazole-5,7-diyl)bis(N,N-diphenylaniline) (InCz-TPA), were designed and synthesized for application in red phosphorescent organic light-emitting diodes (OLEDs). In these systems, bulky substituents possessing tailored electron-donating characteristics were incorporated into the indolocarbazole core. The triplet energy levels were experimentally determined to be 2.81 eV and 2.78 eV, indicating that both materials are appropriate host candidates for red phosphorescent OLEDs. Device evaluations revealed that InCz-TPA delivered superior performance compared to InCz-TP, reaching a maximum external quantum efficiency (EQE) of 8.50%, which corresponds to a 36% enhancement. Both devices exhibited an electroluminescence peak at 628 nm along with nearly identical CIE coordinates of (0.678, 0.317) and (0.680, 0.318), suggesting efficient energy transfer between host and dopant. Full article

Thermally activated delayed fluorescence (TADF) emitters doped in host–guest systems are widely utilized for organic light-emitting diodes (OLEDs), where key rate constants and the fluorescence quantum yield (Φ_F) are strongly influenced by the surrounding environment. However, the multifaceted interactions, i.e., dipole–dipole interaction and conformational restraint between the emitter and environment have been rarely investigated systematically, where excited state charge transfer (CT) and structural relaxation (SR) of emitters should be considered equally. In this study, four representative CT–TADF emitters were selected as model systems and studied in PS/PMMA:TADF:CA host–guest doped films with varied dielectric constants and matrix rigidity. Within D–A and D–A–D configurations, donor substitution from PXZ to DMAC varied CT characteristics, whereas TRZ-based D–A and DPS-based D–A–D emitters provided a relative difference in SR owing to their different rigidity. The total reorganization energy (λ_Total) was introduced as a quantitative measure of these multifaceted interactions and correlated with the rate constants. The results indicate that the dielectric dependence of the nonradiative decay rate (k_nr^S) for D–A–D molecules cannot be explained by the simplified energy gap law, where the vibronic effect plays the role of a game changer. This work provides a quantitative framework and highlights vibrational frequency as a key design parameter for optimizing Φ_F in host–guest doped OLED devices. Full article

Introduction: Type 2 diabetes mellitus predisposes patients to neuropathy, peripheral arterial disease, and diabetic foot ulcers, which may become infected and progress to osteomyelitis, increasing the risk of amputation. The growing prevalence of multidrug-resistant organisms complicates management. Photodynamic therapy (PDT), which combines a photosensitizer with light-emitting diode irradiation to generate reactive oxygen species, has emerged as a potential adjunctive antimicrobial strategy without inducing resistance. Objective: To describe clinical outcomes observed in patients with diabetic foot osteomyelitis treated with adjunctive photodynamic therapy (PDT), with emphasis on wound evolution, limb preservation, and healing time. Methods: This prospective case series included patients with osteomyelitis secondary to infected diabetic foot ulcers treated at a university hospital. Demographic and clinical data were collected from medical records. Serial photographic documentation was used to monitor wound progression and tissue response during therapy. Results: Sixteen patients with diabetic foot osteomyelitis were included. Complete healing was achieved in 13 patients (81.25%), while 2 patients (12.5%) remained under treatment with partial healing and 1 (6.25%) underwent major amputation. Among healed patients, healing time ranged from 19 to 546 days, with a median of 118 days. The number of photodynamic therapy sessions ranged from 2 to 12, depending on the clinical course of each case. Healing time varied among patients, and the hallux was the most frequent site of osteomyelitis. During follow-up, only one patient underwent major amputation, whereas the remaining patients either achieved complete healing or were still under treatment at the time of analysis. Healing time was comparable between insulin-dependent and non-insulin-dependent diabetes, although numerically shorter in the latter. Longer healing periods were associated with more treatment sessions. Conclusions: In this prospective uncontrolled case series, adjunctive PDT was associated with favorable clinical evolution in a subset of patients with diabetic foot osteomyelitis. However, because of the small sample size and the absence of a control group, these findings should be considered preliminary and hypothesis-generating. Full article

The hole injection layer (HIL) plays a critical role in achieving high efficiency and operational stability in organic light-emitting diodes (OLEDs). As a commonly used HIL, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is limited by its intrinsically low electrical conductivity and mismatched work function alignment with the hole transport layer (HTL), leading to inefficient hole injection and carrier imbalance. In this work, a mild citric acid (CA) treatment is used to simultaneously enhance the conductivity of PEDOT:PSS through the partial removal of insulating PSS and tune its work function for improved energy level alignment at the anode interface. This simultaneous optimization effectively enhances the hole transport capability, successfully matching the electron transport capability to realize highly improved charge carrier balance within the device. Consequently, Ir(ppy)₃-based phosphorescent OLEDs featuring the optimally treated PEDOT:PSS HIL deliver a maximum external quantum efficiency of 20.37%, representing a 21% improvement over devices using pristine PEDOT:PSS, along with a twofold extension in operational lifetime. This strategy demonstrates a simple and controllable approach to interfacial engineering, providing practical guidance for the development of high-performance and stable OLEDs. Full article

Organic light-emitting diode (OLED)-based devices continue to grow rapidly in popularity. This work presents a comprehensive thermodynamic study of four nitrogen-containing organic semiconductors: 1,3-bis(9H-carbazol-9-yl)benzene (mCP), 1,3,5-tri(9H-carbazol-9-yl)benzene (TCB), 1,3,5-tris(diphenylamino)benzene (TDAB), and 1,3,5-tris[(3-methylphenyl)phenylamino]benzene (m-MTDAB). A self-consistent set of phase-change thermodynamic parameters in a wide temperature range was obtained using several independent experimental and computational techniques. Vapor pressure measurements above the liquid and crystalline phases of the compounds under study were carried out using the thermogravimetry–fast scanning calorimetry method. Based on the temperature dependence of the measured vapor pressures, vaporization and sublimation enthalpies were derived. Differential scanning calorimetry was employed to determine the heat capacities of the condensed phases and the melting parameters of the studied compounds, as well as to investigate the polymorphism of TCB. Solution calorimetry was used to determine the fusion enthalpies of the compounds at 298.15 K. The obtained values were additionally compared with the literature data and calculated estimates. The results of this study may be used to predict properties for compounds with similar molecular structures. Full article

Previous studies have shown that the external quantum efficiency (EQE) of conventional red Micro-Light emitting diodes(Micro-LEDs) decreases markedly with reducing chip size. This degradation is generally attributed to enhanced non-radiative recombination at sidewall defects, which leads to increased carrier loss in size-scaled LEDs. In this work, AlGaInP quaternary semiconductor epitaxial wafers incorporating multiple quantum wells (MQWs) with different well-layer strain states were grown by metal–organic chemical vapor deposition (MOCVD). Through wafer bonding, photolithography, etching, and metal evaporation, these epitaxial structures were fabricated into Micro-LED arrays with single-pixel pitches of 10, 20, 50, and 100 μm. The experimental results reveal that, with increasing indium (In) composition in the GaInP well layers—corresponding to a gradual increase in lattice mismatch (Δa/a) from 0% to 1%—smaller-sized Micro-LED arrays exhibit superior EQE performance. For devices with a pixel pitch of 10 μm, the EQE of Micro-LED arrays with a 1% lattice mismatch in the well layer is approximately three times higher than that of lattice-matched (0%) counterparts. In contrast, for devices with a pixel pitch of 100 μm, the EQE of lattice-matched (0%) Micro-LED arrays is about 1.3 times higher than that of devices with a 1% lattice mismatch. These results indicate that, to achieve maximum EQE in Micro-LEDs, the strain state of the MQW-layer material must be carefully considered as a priority factor. Optimal device performance requires appropriate matching between LED size and the well-layer growth strain. Full article