Enhanced Luminescence Efficiency Research Articles

An Azaryl-Ketone-Based Thermally Activated Delayed Fluorophore with Aggregation-Induced Emission for Efficient Organic Light-Emitting Diodes with Slow Efficiency Roll-Offs.

Achieving the concurrent manifestation of thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) within a single molecular system is highly sought after for organic light-emitting diodes (OLEDs), yet remains rare. In this study, we present a novel TADF-AIE dye, named PQMO-PXZ, which has been designed, synthesized, and systematically characterized. Our comprehensive investigation, which includes structural analysis, theoretical calculations, and optical studies, evaluates the potential of PQMO-PXZ for integration into OLEDs. Unlike existing azaryl-ketone-based emitters, PQMO-PXZ exhibits red-shifted emission and enhanced luminescence efficiency, due to its rigid structure and strong intramolecular charge transfer characteristics. Significantly, PQMO-PXZ demonstrates pronounced AIE properties and TADF with a short delayed lifetime. When utilized as the emissive core, OLED devices based on PQMO-PXZ achieve a respectable external quantum efficiency of up to 11.8 % with minimal efficiency roll-off, underscoring PQMO-PXZ's promise as a highly efficient candidate for OLED applications.

Carbon Dots and Their Films with Narrow Full Width at Half Maximum Orange Emission.

To obtain carbon dots (CDs) with narrow full width at half maximum (FWHM) and long-wavelength emission, carbon sources with high conjugate sizes and abundant functional groups can be employed to synthesize CDs. In this study, orange-emissive carbon dots (OCDs) were synthesized with phloroglucinol and rhodamine B as precursors. When the molar ratio of them was 30:1, and ethanol was served as the solvent, OCDs with optimized emission wavelength at approximately 580 nm, an FWHM of 30 nm, and a quantum yield (QY) of 27.31% were obtained. Subsequently, the OCDs were incorporated into polyvinyl alcohol (PVA) to fabricate solid-state OCD/PVA fluorescent films, which exhibited an FWHM of 47 nm. The PVA matrix facilitated the dispersion of OCDs, thereby suppressing non-radiative energy transfer among the OCDs and enhancing luminescence efficiency. Consequently, compared with OCDs, the OCD/PVA film exhibited significant luminescent enhancement, and the QY of the composite film was increased to 84.74%. Moreover, OCD/PVA film showed good transmittance and thermal stability. This research offers a solid theoretical and experimental foundation for the potential applications of CDs in the field of solid-state lighting.

Enhanced luminescence efficiency in GaN-based blue laser diodes by H plasma technology

To the best of our knowledge, this paper is the first to report the application of H plasma treatment technology to the treatment of laser diode ridge. Through the H plasma passivation on the ridge of the laser diode, a neutral complexes layer (i.e., Mg-H) is formed on the ridge, which effectively reduces ridge leakage current, thus reducing the threshold current of the laser diode and significantly improving the slope efficiency. The ridge were treated with H plasma using the Oxford Plasmalab System 100 ICP 180. The lasers' leakage current, optical power, emission wavelength, and other parameters were measured using a Cascade150 + B1505A probe station system, along with matched optical power meters and fiber optic spectrometers. Specifically, this study successfully fabricates a GaN-based blue laser diode characterized by a threshold current as low as 0.42 A and a slope efficiency as high as 1.96 W/A. Compared with the traditional silicon oxide-mediated ridge treated laser, the threshold current of the laser passivated by H plasma is reduced by 0.13 A, and the slope efficiency is increased by 0.56 W/A. This research not only enhances the performance of laser diodes but also has the potential to expand their application in multiple fields.

Investigation of optical properties of Ce and Eu-doped Gd2SiO5 insights from GGA + U calculations

Gadolinium silicate, (Gd2SiO5) co-doped with Ce and Eu has been found to exhibit enhanced luminescence efficiency, which makes it a promising material for use in scintillators and phosphors. It has excellent scintillation properties such as high density and high Zeff. In this study, we used density functional theory (DFT) calculations within the Wien2k software to investigate the effect of Ce and Eu concentration and native defects on the electronic structure and optical properties of Ce and Eu co-doped Gd2SiO5. We utilized the DFT + U method to treat the localized 4f electrons of Ce and Eu. Our results indicate that the electronic structure and optical properties of Ce and Eu co-doped Gd2SiO5 are significantly affected by the concentration of the dopants and presence of native defects. We found that increasing the concentration of Ce and Eu dopants leads to a shift in the bandgap to lower energies, resulting in enhanced absorption and emission spectra. Moreover, our calculations reveal that presence of oxygen vacancies and Gd interstitials can induce new defect levels in the bandgap, which may affect the luminescence properties of the material. Our study provides valuable insights into the atomic-level mechanisms that govern the luminescence properties of Ce and Eu co-doped Gd2SiO5 which can aid in the design and optimization of luminescent materials for various applications.

An efficient “hot exciton” fluorophore based on a dicyanophenanthrene-triphenylamine hybrid

The study presents the design, synthesis, and characterization of DCNP-2TPA, a novel “hot exciton” fluorophore featuring a donor-acceptor structure combining dicyanophenanthrene and triphenylamine. Through a comprehensive analysis including structural examination, theoretical modeling, and optical assessments, the suitability of DCNP-2TPA for integration into organic light-emitting diodes (OLEDs) is evaluated. Comparative to existing dicyanophenanthrene-based emitters, DCNP-2TPA demonstrates significantly enhanced luminescence efficiency, by virtue of the incorporation of two triphenylamine moieties with moderate electron-donating strength. Furthermore, DCNP-2TPA exhibits aggregation-induced emission (AIE) properties and showcases hybridized local and charge-transfer (HLCT) excited states, offering an efficient "hot exciton" channel for triplet harvesting. Employing DCNP-2TPA as the emissive core, OLED devices achieve a noteworthy external quantum efficiency of 8.42 %, highlighting the promise of DCNP-2TPA as an efficient candidate for OLED applications.

Perovskite oxide nanoparticles: Dual role as supports for luminescent Eu(III) ions and photocatalysts for bisphenol degradation

Perovskite oxides, such as CaTiO3, SrTiO3, and BaTiO3, have gained significant recognition for their dual role as luminescence supports and photocatalytic materials. In this study, we synthesized perovskite oxide nanoparticles (NPs) using the thermal calcination method and employed them as photocatalysts for the degradation of bisphenol S (BPS) and bisphenol AF (BPAF) under UVC irradiation. The as-synthesized photocatalysts were thoroughly examined for the photocatalytic degradation process and identified secondary products were identified using liquid chromatography in conjunction with high-resolution mass spectrometry. Our observations highlighted the relatively faster photocatalytic degradation of BPS compared to BPAF. Notably, among the perovskite oxide materials, SrTiO3 exhibited the highest catalytic activity for BPS degradation, while BaTiO3 outperformed in the case of BPAF degradation. Perovskite oxide NPs were also utilized as supports for doping with Eu3+ ions to create phosphor supports. Luminescent emissions from the Eu3+ ions, characterized by the 5D0 → 7FJ = 0-4 transitions, were observed and varied depending on the support material. Notably, Eu3+ doped in CaTiO3 nanoparticles exhibited the highest luminescence efficiency. These results highlight the dual functionality of perovskite oxide-based materials in phosphor applications and photocatalysis, offering valuable insights into their potential for both enhancing luminescence efficiency and treating bisphenols.

Theoretical insights on highly efficient X-shaped near-infrared thermal activation delayed fluorescence emitter

The near-infrared (NIR) thermally activated delayed fluorescence (TADF) molecules hold practical application value in various fields, including biological imaging, anti-counterfeiting, sensors, telemedicine, photomicrography, and night vision display. These molecules have emerged as a significant development direction in organic electroluminescent devices, offering exciting possibilities for future technological advancements. Despite the remarkable potential of NIR-TADF molecules in various applications, the development of molecules that exhibit both long-wavelength emission and high efficiency remains a significant challenge. Herein, based on T-type and Y-type TADF molecules BCN-TPA and ECN-TPA, a novel X-type TADF molecule X-ECN-TPA is theoretically designed through a molecular fusion strategy. Utilizing first-principles calculations and the thermal vibration correlation function (TVCF) method, the photophysical properties and luminescent mechanisms of these three molecules in both solvent and solid (doped films) are revealed. A comparison of the luminescent properties of isomeric BCN-TPA and ECN-TPA shows that the enhanced luminescence efficiency of BCN-TPA in the solid states is attributed to higher radiative rates and lower non-radiative rates. Furthermore, compared to BCN-TPA and ECN-TPA, X-ECN-TPA exhibits significant conjugation extension, resulting in a pronounced redshift, reaching 831 nm and 813 nm in solvent and solid states, respectively. Importantly, molecular fusion significantly increases the transition dipole moment density between the donor and acceptor, leading to a substantial increase in radiative transition rates. Additionally, molecular fusion effectively reduces the energy gap between the first singlet excited state (S1) and the first triplet excited state (T1), facilitating the improvement of the reverse intersystem crossing (RISC) process. In addition, the calculation of Marcus formula shows that the triplet energy transfer from CBP to BCN-TPA, ECN-TPA and X-ECN-TPA is very effective. This work not only designs a novel efficient NIR-TADF molecule but also proposes a strategy for designing efficient NIR-TADF molecules. This principle offers unique insights for optimizing traditional molecular frameworks, opening up new possibilities for future advancements.

Recent progress on charge transfer engineering in reticular framework for efficient electrochemiluminescence.

Electrochemiluminescence (ECL) is a luminescence production technique triggered by electrochemistry, which has emerged as a powerful analytical technique in bioanalysis and clinical diagnosis. During ECL, charge transfer (CT) is an important process between electrochemical excitation and luminescent emission, and dramatically affects the efficiency of exciton generation, playing a pivotal role in the light-emitting properties of nanomaterials. Reticular framework materials with intramolecular/intermolecular interactions offer a promising platform for regulating CT pathways and enhancing luminescence efficiency. Deciphering the role of intramolecular/intermolecular CT processes in reticular framework materials allows for the targeted design and synthesis of emitters with precisely controlled CT properties. This sheds light on the microscopic mechanisms of electro-optical conversion in ECL, propelling advancements in their efficiency and breakthrough applications. This mini-review focuses on recent advancements in engineering CT within reticular frameworks to boost ECL efficiency. We summarized strategies including intra-reticular charge transfer, CT between the metal and ligands, and CT between guest molecules and frameworks within reticular frameworks, which holds promise for developing next-generation ECL devices with enhanced sensitivity and light emission.

High‐Performance Ternary Organic Solar Cells with Enhanced Luminescence Efficiency and Miscibility Enabled by Two Compatible Acceptors

AbstractThe ternary strategy has proven to be an effective method for improving the efficiency of organic solar cells (OSCs). However, designing and selecting the third component still pose challenges. In this study, this issue is addressed by focusing on the PBDB‐T:Y18‐F binary system and introducing a new, strong luminescent, asymmetric small‐molecule acceptor (SMA) called L8‐CBIC‐Cl, which shares a similar skeleton with Y18‐F. The similarity in molecular framework facilitates good compatibility between the two acceptors, resulting in the formation of an alloy‐like acceptor phase. Furthermore, the norbornenyl‐modified end group in L8‐CBIC‐Cl contributes to its strong luminescent properties, which in turn leads to a low non‐radiative energy loss and a high open‐circuit voltage. Consequently, the PBDB‐T:L8‐CBIC‐Cl:Y18‐F based ternary devices realize a high power conversion efficiency (PCE) up to 17.01%, which is higher than PBDB‐T:Y18‐F device (14.49%). Importantly, L8‐CBIC‐Cl exhibits a good universality as a guest acceptor in other three binary systems (D18:Y6, D18:BTP‐eC9‐4F, and D18:L8‐BO). The D18:L8‐BO:L8‐CBIC‐Cl device shows an impressive efficiency of 19%. The work demonstrates that employing SMA with a high PLQY and better miscibility with host acceptor as the third component has a great potential for developing high‐efficiency ternary OSCs.

Main Group Elements Activated Near‐Infrared Photonic Materials

AbstractNear‐infrared (NIR) photonic materials find extensive applications across important fields such as telecommunications, laser radar, and atmospheric remote sensing. In particular, photonic materials activated by main group elements, which exhibit unique spectral features including ultra‐broadband tunable luminescence and long lifetime, have become rising stars in NIR emitting dopants. In this review, the energy level characteristics of the p‐electrons to gain insight into the fundamentals of the NIR optical response from the main group elements are first introduced. Next, the NIR luminescence properties of the main group elements are discussed. Then, the strategy for the design of main group elements activated materials with the desired properties based on local chemical environment engineering is proposed. In addition, recent advances in the applications of main group element (excluding bismuth) activated materials are highlighted. Furthermore, the key scientific issues that urgently need to be solved for such materials, such as the detailed luminescence mechanism are highlighted. Anticipation also extends to the future research trends in this exciting field, including the ways for enhancing luminescence efficiency and extending spectral region, and the efforts for implementing these advancements in novel cutting‐edge technologies like photovoltaics and biomedicine.

First-principles calculations for heterostructure studies Involving CsPbI3 perovskite and IV-VI semiconductors

The PbX(X = S, Se, Te)/CsPbI3 heterostructure, formed by lead chalcogenides and halide perovskite CsPbI3, holds promise for optoelectronic devices. Utilizing first-principles calculations with VASP software, this study investigates its structural, electronic, and optical properties. With confirmed appropriate lattice mismatch rates (4.6%, 2.4%, 3.8%) and similar octahedral frameworks, constructing the PbX/CsPbI3 heterostructure is feasible. Calculations of electronic properties reveal mechanisms to improve optical performance. The type-I band alignment at the PbX/CsPbI3 interface(−5.27 eV < PbX < −3.73 eV, −5.34 eV < CsPbI3 < −3.57 eV) reduces electron and hole recombination losses, enhancing energy transfer efficiency. This arrangement facilitates electron and hole transfer from CsPbI3 to PbX, supported by charge density differences. Among the three heterostructures, PbSe/CsPbI3 demonstrates superior charge transfer capabilities, with more pronounced electron clouds. The PbX/CsPbI3 heterostructure extends CsPbI3’s light absorption into the near-infrared via PbX influence. Spectral comparison reveals PbTe/CsPbI3 > PbSe/CsPbI3 > PbS/CsPbI3, with PbSe/CsPbI3 excelling in stability, charge density transfer, and optical properties. Furthermore, under the premise of ensuring stability, different optical absorption characteristics can be achieved by adjusting the composition of Se atoms in PbSe/CsPbI3. This work provides a theoretical basis for the physical mechanisms behind enhancing the performance of PbX/CsPbI3 heterostructures as visible-to-near-infrared optoelectronic materials. It offers a promising avenue for the design of high-performance visible-to-near-infrared optoelectronic materials.

Anomalous intense emission of the 5D0/7F4 transition for reddish-orange light-emitting and fluorescent probe for multiple lattice sites in β-PbF2:Eu3+/K+ oxyfluoride glass ceramics

K+ ions as charge compensating ions doped into the fluorite lattice, vigorously regulating the lattice symmetry around rare earth ions, achieving luminescence efficiency enhancement and spectral broadening of rare earth ions.

Enhanced luminescence efficiency in Eu-doped GaN superlattice structures revealed by terahertz emission spectroscopy

Eu-doped Gallium nitride (GaN) is a promising candidate for GaN-based red light-emitting diodes, which are needed for future micro-display technologies. Introducing a superlattice structure comprised of alternating undoped and Eu-doped GaN layers has been observed to lead to an order-of-magnitude increase in output power; however, the underlying mechanism remains unknown. Here, we explore the optical and electrical properties of these superlattice structures utilizing terahertz emission spectroscopy. We find that ~0.1% Eu doping reduces the bandgap of GaN by ~40 meV and increases the index of refraction by ~20%, which would result in potential barriers and carrier confinement within a superlattice structure. To confirm the presence of these potential barriers, we explored the temperature dependence of the terahertz emission, which was used to estimate the barrier potentials. The result revealed that even a dilutely doped superlattice structure induces significant confinement for carriers, enhancing carrier recombination within the Eu-doped regions. Such an enhancement would improve the external quantum efficiency in the Eu-doped devices. We argue that the benefits of the superlattice structure are not limited to Eu-doped GaN, which provides a roadmap for enhanced optoelectronic functionalities in all rare-earth-doped semiconductor systems.

Tailored Broad‐Spectrum Emission in Hybrid Aggregation Induced Emission (AIE)‐MOFs: Boosting White Light Efficiency in Electrospun Janus Microfibers

AbstractAdvances in energy‐efficient lighting and display technologies demand innovative materials with tailored broad‐spectrum emission properties. Hybrid aggregation‐induced emission metal‐organic frameworks (AIE‐MOFs) offer a promising avenue, combining unique characteristics of organic and inorganic components to yield enhanced luminescence efficiency and robust material stability. The study introduces a spectrum of D (donor)‐A (acceptor) type AIE‐active ligands into MOFs, enabling tunable emission across the visible spectrum, thus underscoring the versatility of these hybridized MOF materials. The emission properties of AIE‐MOFs are further harnessed by integrating them into polymer matrices, resulting in high‐performance electrospun fibers with tunable emission. A significant achievement involves the fabrication of Janus‐type white light‐emitting AIE‐MOF fiber composites via side‐by‐side electrospinning, accomplishing a high quantum yield of 58%, which doubled the performance of homogeneous fibers. Complementing the experimental findings, micro‐Raman and nano‐Fourier transform infrared spectroscopy are employed as local spectroscopic probes, affording a deeper understanding of the material properties and the mechanisms contributing to enhance light emission. In the understanding, this study presents an unconventional implementation of hybrid AIE‐MOFs in Janus‐type structures for white light emission. It significantly improves the efficiency of white light sources in optoelectronics, charting a promising direction for future research in the emergent AIE‐MOF field.

Performance improvement of GaN-based microdisk lasers by using a PEALD-SiO2 passivation layer.

Dry-etching is often utilized to shape GaN-based materials. However, it inevitably causes plenty of sidewall defects as non-radiative recombination centers and charge traps that deteriorate GaN-based device performance. In this study, the effects of dielectric films deposited by plasma-enhanced atomic layer deposition (PEALD) and plasma-enhanced chemical vapor deposition (PECVD) on GaN-based microdisk laser performance were both investigated. The results demonstrated that the PEALD-SiO2 passivation layer largely reduced the trap-state density and increased the non-radiative recombination lifetime, thus leading to the significantly decreased threshold current, notably enhanced luminescence efficiency and smaller size dependence of GaN-based microdisk lasers as compared with the PECVD-Si3N4 passivation layer.

Investigation on Mechanism of Enhanced Luminescence Efficiency of Carbon Quantum Dots Through Thiol-ene Cross-linking

Investigation on Mechanism of Enhanced Luminescence Efficiency of Carbon Quantum Dots Through Thiol-ene Cross-linking

Enhancing Luminescence Efficiency by Controlled Island Formation of CsPbBr3 Perovskite

AbstractCsPbBr3 is an inorganic perovskite material that is promising for light‐emitting applications. Such applications are known to benefit from an island‐type active layer structure, which enhances the device's light emission efficiency. Here, the impact of the environment on the island formation in thermally deposited bilayers of CsPbBr3/LiBr is investigated. It is demonstrated that the island formation occurs only in humid environments, leading to an enhancement of the photoluminescence quantum yield by a factor of 350. Time‐resolved grazing‐incidence wide‐angle X‐ray scattering experiments document the island growth process and reveal that the LiBr has already changed the perovskite crystal orientation prior to the island formation.

Manipulating Charge Transfer and Transport via Intermediary Electron Acceptor Channels Enables 19.3% Efficiency Organic Photovoltaics

AbstractBalancing and improving the open‐circuit voltage (Voc) and short‐circuit current density (Jsc) synergistically has always been the critical point for organic photovoltaics (OPVs) to achieve high efficiencies. Here, this work adopts a ternary strategy to regulate the trade‐off between Voc and Jsc by combining the symmetric‐asymmetric non‐fullerene acceptors that differ at terminals and alkyl side chains to build the ternary OPV (TOPV). It is noticed that the reduced energy disorder and the enhanced luminescence efficiency of TOPV enable a mitigated energy loss and a higher Voc. Meanwhile, the third component, which is distributed at the host donor–acceptor interface, acts as the charge transport channel. The prolonged exciton lifetime, the boosted charge mobility, and the depressed charge recombination promote the TOPV to obtain an improved Jsc. Finally, with synergistically improved Voc and Jsc, the TOPV delivers an optimal efficiency of 19.26% (certified as 19.12%), representing one of the highest values reported so far.

Constraint Mechanism of Power Device Design Based on Perovskite Quantum Dots Pumped by an Electron Beam.

This paper studied the constraint mechanism for power device design based on perovskite quantum dots pumped by an electron beam. Combined with device designing, an experimental system of self-saturation luminescence and aging failure was designed for CsPbBr3 films. On this basis, we further completed the self-saturation luminescence and aging failure experiment and constructed a model of self-saturation luminescence and aging failure for CsPbBr3 device designing. Three constraints were proposed after analyzing and discussing the experimental data. Firstly, too high of a pumping current density makes it difficult to effectively promote the enhancement of luminescence efficiency. Secondly, radiation decomposition and aging failure of CsPbBr3 films are mainly related to the polarized degree of CsPbBr3 nanocrystals. Thirdly, by increasing the pumping electric field, the pumping energy can be effectively and widely delivered to the three-dimensional quantum dots film layer space, and there is a nonlinear relationship between the attenuation of the pumping energy density and the increment of the pumping electric field, which will effectively avoid the local high-energy density of instantaneous optical pumping.

Transition metal(ii) ion doping of CsPb2Br5/CsPbBr3 perovskite nanocrystals enables high luminescence efficiency and stability

A metal-site doping strategy to optimize CsPb2Br5/CsPbBr3 perovskite nanocrystals enables effective elimination of Br vacancies and enhanced luminescence efficiency and stability.