Photoluminescence Performance Research Articles

Formation of Distributed Local Heterojunction to Enhance NIR Emission Due to the Effective Carrier Transfer

AbstractPerovskite light‐emitting devices (PeLEDs) have emerged as a highly promising contender for the next generation of lighting and display technologies. During the nucleation and crystallization process, numerous defects are commonly formed on the surface and grain boundaries as a result of the ionic characteristics of perovskite, especially in an air environment. These defects ultimately contribute to the deterioration of the photoelectron properties. In this study, CsPbI3 nanocrystals (NCs) solution is introduced into ethyl acetate antisolvent as an additive, resulting in the high‐quality perovskite films under ambient conditions. The introduction of CsPbI3 NCs has been found to increase the grain size and improve the uniformity of perovskite films while also effectively passivating defects. More significantly, the utilization of CsPbI3 NCs leads to the formation of a 0D/3D local heterojunction that is distributed throughout the MAPbI3 film. These distributed heterojunctions significantly increase both the carrier concentration and the photoluminescence performance. With the incorporation of doped perovskite films, Silicon (Si) ‐based PeLEDs demonstrate enhanced efficiency, achieving a maximum external quantum efficiency of 12.6% in ambient conditions. Additionally, these devices exhibit a prolonged operational half‐life of 80 minutes. This study presents a novel methodology for fabricating high‐efficiency Si‐based PeLEDs that exhibit exceptional electroluminescence characteristics.

High brightness and low operating voltage CsPbBr3 perovskite LEDs by single-source vapor deposition

In this work, we utilized CsPbBr3 powder as the precursor material for the single-source vapor deposition (SSVD) process to fabricate the CsPbBr3 emitting layer. Due to the high density of grain boundaries and defects in the thin films deposited in the initial stages, non-radiative recombination can occur, reducing the efficiency of perovskite light-emitting diodes (PeLED). To address this issue, we employed a thermal annealing process by subjecting the perovskite films to the appropriate annealing temperature, facilitating the coalescence and growth of different grains, improving lattice integrity, and thereby reducing the presence of defects and enhancing the photoluminescence performance of the films. Furthermore, in this study, we successfully fabricated simple-structured CsPbBr3 PeLED using thermally annealed CsPbBr3 films. Among these components, even without adding the electron and hole transport layers, the best-performing device achieved a maximum brightness of 14,079 cd/m2 at a driving voltage of only 2.92 V after annealing at 350 °C; the brightness is 16.8 times higher than that of CsPbBr3 PeLED without heat treatment, demonstrating outstanding light-emitting performance. The research results show that using SSVD to prepare CsPbBr3 PeLED has broad application potential, providing a simple process option for research on improving the performance of PeLED.

Ultra-Broad-Band-Excitable Cu-Based Halide (C4H10N)4Cu4I8 with High Stability for LED Applications.

Currently, organic-inorganic hybrid cuprous-based halides are receiving substantial attention for their eco-friendliness, distinctive structures, and outstanding photophysical properties. Nevertheless, most of the reported cuprous-based halides demand deep ultraviolet excitation with a narrow excitation range that can meet the commercial requirement. Herein, zero-dimensional (0D) cuprous-based halide (C4H10N)4Cu4I8 single crystals (SCs) were synthesized, with an ultrabroad band excitation ranging 260-450 nm and a greenish-yellow emission band peaking at 560 nm. Excitingly, (C4H10N)4Cu4I8 also features a large Stokes shift of 300 nm, a high photoluminescence quantum yield (PLQY) of up to 84.66%, and a long lifetime of 137 μs. Furthermore, density functional theory calculations were performed to explore the relationship between structure and photophysical properties, and the photoluminescence performance of (C4H10N)4Cu4I8 originates from the electron interactions in [Cu2I4]2- clusters. Taking advantage of broad band excitation and excellent photoluminescent performances, a high luminescence characteristic UV-pumped light-emitting diode (LED) device with remarkable color stability was fabricated by employing the as-synthesized (C4H10N)4Cu4I8 SCs, which present the promising applications of low-dimensional cuprous-based halides in solid-state lighting.

Enhancing photocatalytic destruction of lignin via cellulose derived carbon quantum dots/g-C3N4 heterojunctions

Lignocellulosic biomass exhibits a promising potential for production of carbon materials. Nitrogen and phosphorus co-doped carbon quantum dots (N,P-CQDs) were fabricated via (NH4)2HPO4 assisted hydrothermal treatment of cellulose pulp fibers. The as-prepared N,P-CQDs were characterized by HRTEM, FTIR, fluorescence and UV–vis, and then incorporated into g-C3N4 (CN) through sonication and liquid deposition, forming N,P-CQDs/sonication treated g-C3N4 (C-SCN) composites, which were then explored as photocatalysts. The photocatalytic ability of C-SCN towards model lignin was further analyzed. The results showed that, the fluorescence intensity and photoluminescence performance of N,P-CQDs were much higher than that of CQDs; the heterojunction was successfully constructed between the composites of N,P-CQDs and SCN; the incorporation of N,P-CQDs enhanced the visible light absorption, but reduced the band gap of the composite heterojunction; the resultant photocatalysts exhibited a good photocatalytic ability of model lignin via catalyze the fracture of β–O–4′ ether bond and CC bond, i.e., the photocatalytic degradation ratio reached up to 95.5 %; and the photocatalytic reaction generated some valuable organics such as phenyl formate, benzaldehyde, and benzoic acid. This study would promote the high value-added utilization of lignocellulosic resources especially in the transformation of lignin, conforming the concept of sustainable development.

Ionic liquid-assisted preparation of Ag–Zn–In–S quaternary quantum dot thin films and luminescence performance optimized by machine learning

Machine learning-assisted synthesis of new materials has been an ongoing hot topic. Luminescent Ag–Zn–In–S quaternary semiconductor quantum dot thin films have great application potential in many fields because of their excellent photoelectric performance. In this study, an environmentally friendly ionic liquid-assisted approach was employed to prepare high-performance Ag–Zn–In–S luminescent thin films, and machine learning methods were applied to screen the optimal preparation conditions. The photoluminescence (PL) performance, crystal structure, and morphology of the thin films were also been studied. The initial data set was obtained by high-throughput experiments. By comparing machine learning algorithms of Xgboost, Random Forest, Bagging, SVM, Extra Tree, and Gradient Boosting, the Random Forest achieved the best accuracy (r = 0.84, R2 = 0.847) and was selected to predict the optimal preparation conditions of Ag–Zn–In–S quaternary quantum dot thin films. The machine learning predicted results are in great agreement with the subsequent experimental results, which verifies the accuracy and effectiveness of the machine learning model. This study offers a theoretical foundation for preparing optimal inorganic quantum dot luminescent materials using machine learning.

Surface defect passivation by ligand in polymeric melt encapsulated CsPbBr3 perovskite nanocrystals/PP composite with high X-ray imaging performance

In-situ growth method has been widely used in the preparation of metal halide perovskite nanocrystals/polymer composites. However, the ligand-free process tends to bring surface defects which always deteriorate the photoluminescence. The passivation effect of surface ligands on the defects of nanocrystals, which is of benefit to promote the photoluminescence performance of the composites, is often neglected in the preparation of perovskite nanocrystals/polymers. Here, we report a facile post-passivation treatment of CsPbBr3/polypropylene (PP) composite film with octylamine solution, and surface engineering of CsPbBr3 nanocrystals in PP molecular chain by swelling effect to passivate the surface defects of nanocrystals. The composite film achieves a significant photoluminescence enhancement by 27 times under UV light. In addition, when used as a scintillator material, the passivated CsPbBr3/PP composite film has a enhanced significant light response to X-ray, and the X-ray imaging ability of the metal spring in the capsule is preliminarily realized. Moreover, this post-treatment passivation strategy is easy to apply and expected to be applied to the performance improvement of other perovskite nanocrystals/polymer composites. Overall, this approach has the potential to design a new generation of perovskite nanocrystals/polymer-based scintillator materials.

Tailoring Graphite into Subnanometer Graphene.

Within the intersection of materials science and nanoscience/technology, extremely downsized (including quantum-sized and subnanometer-sized) materials attract increasing interest. However, the effective and controllable production of extremely downsized materials through physical strategies remains a great challenge. Herein, an all-physical top-down method for the production of sub-1nm graphene with completely broken lattice is reported. The graphene subnanometer materials (GSNs) with monolayer structures and lateral sizes of ≈0.5nm are obtained. Compared with their bulk, nanosheets, and quantum sheets, the intrinsic GSNs present extremely enhanced photoluminescence and nonlinear saturation absorption performances, as well as unique carrier behavior. The non-equilibrium states induced by the entirely exposed and broken, intrinsic lattices in sub-1nm graphene can be determinative to their extreme performances. This work shows the great potential of broken lattice and provides new insights toward subnanometer materials.

An efficient and thermally stable source with Cr3+ near-infrared luminescence for non-destructive testing applications

The quest for efficient and heat-resistant near-infrared (NIR) phosphors to create advanced smart NIR lighting sources continues to pose a significant challenge. This study introduces a new fluoride phosphor, Cr3+-doped Cs2NaScF6, wherein the Cs2NaScF6 host provides a weak crystal field suitable for Cr3+ doping. This arrangement allows the production of a broad NIR emission peaking at 797 nm, coupled with a notable internal quantum efficiency of 90.8 % when excited by 446 nm blue light. Meanwhile, due to the relatively mild electron-phonon coupling effect and a high activation energy within this phosphor, the overall NIR emission intensity at 150 °C sustains 81.8 % of its level at room temperature. This highlights exceptional thermal stability in photoluminescence performance. Combining the Cs2NaScF6:Cr3+ phosphor with a commercially available blue InGaN chip to construct a NIR light-emitting diode (LED) device, which exhibits efficient and stable NIR emission, making it suitable for non-destructive testing applications. These findings affirm that the Cs2NaScF6:Cr3+ phosphor can function as a promising candidate to fabricate high-performance device for NIR spectroscopy application.

Photoluminescence and antibacterial performance of sol–gel synthesized ZnO nanoparticles

The hexagonal phase of ZnO NPs was synthesized using sol gel methods and structural properties and correlation with the optical, photoluminescence and antibacterial properties have been investigated.

Enhancing photoluminescence performance of perovskite quantum dots with plasmonic nanoparticles: insights into mechanisms and light-emitting applications.

Perovskite quantum dots (QDs) are considered as promising materials for numerous optoelectronic applications due to their narrow emission spectra, high color purity, high photoluminescence quantum yields (PLQYs), and cost-effectiveness. Herein, we synthesized various types of perovskite QDs and incorporated Au nanoparticles (NPs) to systematically investigate the impact of plasmonic effects on the photoluminescence performance of perovskite QDs. The PLQYs of the QDs are enhanced effectively upon the inclusion of Au NPs in the solutions, with an impressive PLQY approaching 99% achieved. The PL measurements reveal that the primary mechanism behind the PL improvement is the accelerated rate of radiative recombination. Furthermore, we integrate perovskite QDs and Au NPs, which function as color conversion layers, with blue light-emitting diodes (LEDs), achieving a remarkable efficiency of 140.6 lm W-1. Additionally, we prepare photopatternable thin films of perovskite QDs using photocrosslinkable polymers as the matrix. Microscale patterning of the thin films is accomplished, indicating that the addition of plasmonic NPs does not adversely affect their photopatternable properties. Overall, our research not only elucidates the underlying mechanisms of plasmonic effects on perovskite QDs but presents a practical method for enhancing their optical performance, paving the way for next-generation optoelectronic applications, including high-definition micro-LED panels.

A highly efficient lanthanide coordination polymer luminescent material for the multi-task detection of environmental pollutants.

It is challenging to explore novel-structure lanthanide coordination polymers (Ln-CPs) for sensing environmental pollutants. Herein, we designed and synthesized an organic bridging linker 3-(carboxymethoxy)-1-(carboxymethyl) pyrazole-4-carboxylic acid (H3ccpc), and then successfully prepared and characterized a novel Ln-CP, namely [Tb2(ccpc)2(H2O)6]·1.5H2O (ccpcTb). Structural analysis indicates that ccpcTb exhibits a two-dimensional structure, in which Tb ions are in an eight-coordinated environment. The photoluminescence performance of ccpcTb was discussed in detail. The ccpcTb displays bright green luminescence and behaves as a multi-responsive luminescent sensor toward Fe3+ ions, Cr2O72- ions and 2,4,6-trinitrophenol with high selectivity and low detection limits. Furthermore, the possible luminescence sensing mechanisms have been addressed in detail. The luminescence quenching mechanism of sensing Fe3+ and Cr2O72- is attributed to the energy competitive absorption, while that of sensing TNP is due to the synergistic effect of energy competitive absorption and photo-induced electron transfer.

Near-infrared Cr3+-doped lead-free halide perovskite microcrystals for information encryption and temperature thermometry

Lead-free double perovskite materials have attracted lots of interest because they can be doped with luminescence activators to modify their optical characteristics and improve photoluminescence performances.

Fluorescence properties of novel deep-red phosphor LiMg4SbO7:Mn4+ with excellent quantum efficiency and color purity for warm white LEDs.

Red fluorescent materials have important application value in the background light and LED lighting fields of displays. In this work, a novel type of rare earth free deep-red phosphor LiMg4SbO7:Mn4+ was prepared successfully, and its crystal structure, microstructure, fluorescence spectrum, quantum yield, thermal stability, fluorescence lifetime, color coordinates and color purity were studied in detail. The excitation spectra of LiMg4SbO7:Mn4+ phosphors are located at 200-600 nm, which can be matched with ultraviolet, near-ultraviolet, and blue-light chips. The exciting result is that the LiMg4SbO7:0.002Mn4+ phosphor exhibits astonishing quantum efficiency, thermal stability and color purity. Finally, the developed LiMg4SbO7:Mn4+ and the yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce3+) were mixed and coated on a blue light chip (460 nm) to produce a w-LED, which exhibited warm white luminescence with color coordinates of (0.3575, 0.3809), correlated colour temperature (CCT) of 4687 K, and color rendering index (CRI) of 83.6. It is reasonable to consider that LiMg4SbO7:Mn4+ phosphors with excellent photoluminescence performance have great application value in LED lighting fields.

Eu-MOF-Based Fluorescent Ratiometric Sensor by Detecting 3,4,5-Trihydroxybenzoic for Fingerprint Visualization on Porous Objects

Latent fingerprints (LFPs) at the crime scene are served as important clues to locate the trajectory of criminal behavior and portray the characteristics of the suspect. Therefore, visualizing LFPs is of considerable significance. In this work, the europium metal-organic framework (Eu-MOF) sensor was successfully constructed for sensitive detection of gallic acid (3,4,5-trihydroxybenzoic acid, GA) and visualization of the sweat LFPs. The boric-acid-modified Eu-MOF was prepared by using the simple one-pot solvothermal method using Eu as the metal ion center and 3,5-dicarboxybenzeneboronic acid (BBDC) as the organic ligand. The sensor showed desirable photoluminescent performance through the chelating of BBDC with Eu3+. The sensor exhibited the satisfactory linear relationship to GA in the range of 1 nM to 20 nM with a low detection limit of 0.34 nM under the optimized conditions. The prepared sensor with ideal selectivity to GA was successfully applied for visualizing LFPs on porous substrates with the high contrast and superior stability. Given the good performance of the sensor, all fingerprint images obtained from 1 200 samples presented clear friction ridges and met the identification criteria. Notably, the sensor had less impact on the subsequent deoxyribonucleic acid (DNA) detection, displaying a promising perspective for applications in extracting physical evidence of site investigation.

Composition-dependent photoluminescence in nanocrystalline La2Hf2-xZrxO7:Eu phosphor: role of chemical twin Zr/Hf environments around a luminescent center.

Based on chemical intuition, linear trends are anticipated in Eu3+ photoluminescence performance inside a pyrochlore matrix of the chemical twins, Hf and Zr, owing to probable geometrical and chemical similarity around the luminescent center. The present work reports the drastically fluctuating result of doping Eu3+ in nanocrystalline pyrochlore, La2Hf2-xZrxO7 (LHZO), matrix on composition variation; the variation is counter to the anticipation-based chemical brotherhood of Hf and Zr. Zirconium-enriched samples of LHZO improve asymmetry around Eu3+ ion leading to enhanced photoluminescence quantum yield (PLQY). The samples with compositions 0.7Hf and 1.3Zr depict the lowest non-radiative channels with the highest theoretically calculated PLQY of ∼71% and excellent thermal stability (∼91%). Synergistic experimental and theoretical analysis reveals that Eu does not unbiasedly occupy La-sites in the pyrochlore LHZO matrix towards chemical twins of Hf and Zr; rather, it energetically prefers to occupy Zr-rich vicinal sites. When the composition with Zr is in the low-medium range, Eu has a higher probability of occupying Zr-rich vicinal sites depicting higher lifetime and PLQY. When Zr-content goes beyond 70-80%, the other site occupancies start contributing leading to a reduction in both lifetime and quantum yield. This work paves a great strategy and provides a futuristic potential to utilize europium luminescence in separating chemically close Hf-Zr for various technological applications.

Analysis of Structural, Photoluminescence, and Colorimetric Performance of Gd-Incorporated BNT Ceramic.

Structural, optical, photoluminescence and colorimetric analyses of Gd (1-5mol %) doped BNT ceramics synthesized by the solid-state reaction technique are reported. Structural analyses of all the samples are done by the X-ray diffraction method. It is shown that the samples have rhombohedral crystal structures with an R3C space group. The energy band gap of all the phosphors is computed from the UV-visible absorbance spectra. Photoluminescence behaviors are analyzed from the excitation along with the emission spectra of the prepared materials. The critical quenching concentration with the critical energy transfer distance is observed owing to the dipole-dipole interactions between the materials. Colorimetric analyses are carried out with the help of CIE chromaticity. Moreover, the color purity, correlated color temperature, color rendering index, and luminous efficiency of radiation values are evaluated by using the chromaticity coordinates.

Luminescent and Photoredox-Active Molybdenum(0) Complexes Competitive with Isoelectronic Ruthenium(II) Polypyridines.

Ruthenium(II) complexes with chelating polypyridine ligands are among the most frequently investigated compounds in photophysics and photochemistry, owing to their favorable luminescence and photoredox properties. Equally good photoluminescence performance and attractive photocatalytic behavior is now achievable with isoelectronic molybdenum(0) complexes. The zero-valent oxidation state of molybdenum is stabilized by carbonyl or isocyanide ligands, and metal-to-ligand charge transfer (MLCT) excited states analogous to those in ruthenium(II) complexes can be established. Microsecond MLCT excited-state lifetimes and photoluminescence quantum yields up to 0.2 have been achieved in solution at room temperature, and the emission wavelength has become tunable over a large range. The molybdenum(0) complexes are stronger photoreductants than ruthenium(II) polypyridines and can therefore perform more challenging chemical reductions. The triplet nature of their luminescent MLCT states allows sensitization of photon upconversion via triplet-triplet annihilation, to convert low-energy input radiation into higher-energy output fluorescence. This review summarizes the current state of the art concerning luminescent molybdenum(0) complexes and highlights their application potential. Molybdenum is roughly 140 times more abundant and far cheaper than ruthenium, hence this research is relevant in the greater context of finding more sustainable alternatives to using precious and rare transition metals in photophysics and photochemistry.

Luminescent and Photoredox‐Active Molybdenum(0) Complexes Competitive with Isoelectronic Ruthenium(II) Polypyridines

AbstractRuthenium(II) complexes with chelating polypyridine ligands are among the most frequently investigated compounds in photophysics and photochemistry, owing to their favorable luminescence and photoredox properties. Equally good photoluminescence performance and attractive photocatalytic behavior is now achievable with isoelectronic molybdenum(0) complexes. The zero‐valent oxidation state of molybdenum is stabilized by carbonyl or isocyanide ligands, and metal‐to‐ligand charge transfer (MLCT) excited states analogous to those in ruthenium(II) complexes can be established. Microsecond MLCT excited‐state lifetimes and photoluminescence quantum yields up to 0.2 have been achieved in solution at room temperature, and the emission wavelength has become tunable over a large range. The molybdenum(0) complexes are stronger photoreductants than ruthenium(II) polypyridines and can therefore perform more challenging chemical reductions. The triplet nature of their luminescent MLCT states allows sensitization of photon upconversion via triplet‐triplet annihilation, to convert low‐energy input radiation into higher‐energy output fluorescence. This review summarizes the current state of the art concerning luminescent molybdenum(0) complexes and highlights their application potential. Molybdenum is roughly 140 times more abundant and far cheaper than ruthenium, hence this research is relevant in the greater context of finding more sustainable alternatives to using precious and rare transition metals in photophysics and photochemistry.

Yellow Emissive CsCu2I3 Nanocrystals Induced by Mn2+ for High-Resolution X-ray Imaging.

Recently, low-dimensional copper(I)-based perovskite or derivatives have gained extensive attention in scintillator applications because of their environmental friendliness and good stabilities. However, the unsatisfactory scintillation performance and complex fabrication processes hindered their practical applications. Herein, efficient yellow emissive CsCu2I3 nanocrystals (NCs) were successfully prepared via a simple Mn2+-assisted hot-injection method. The added Mn2+ effectively induced the phase transformation from Cs3Cu2I5 to CsCu2I3, leading to the preparation of single-phase CsCu2I3 NCs with few defects and a high fluorescence performance. The as-prepared "optimal CsCu2I3 NCs" exhibited superior photoluminescence (PL) performance with a record-high PL quantum yield (PLQY) of 61.9%. The excellent fluorescence originated from the radiative recombination of strongly localized one-dimension (1D) self-trapped excitons (STEs), which was systematically investigated via the wavelength-dependent PL excitation, PL emission, and temperature-dependent PL spectra. These CsCu2I3 NCs also exhibited outstanding X-ray scintillation properties with a high light yield (32000 photons MeV-1) and an ultralow detection limit (80.2 nGyair s-1). Eventually, the CsCu2I3 NCs scintillator film achieved an ultrahigh (16.6 lp mm-1) spatial resolution in X-ray imaging. The CsCu2I3 NCs also exhibited good stabilities against X-ray irradiation, heat, and environmental storage, indicating their great application potential in flexible X-ray detection and imaging.

Structural, photoluminescence, and photocatalytic performances of Ce3+ -activated orthovanadate oxides M3 (VO4 )2 (M: Mg or Zn) synthesized by solution combustion route.

This paper presents a research investigation into the synthesis of vanadate oxides M3 (VO4 )2 (M: Mg or Zn) using the solution combustion method and investigates their structural, photoluminescence, and photocatalytic properties after introducing cerium (Ce) as a dopant. The resulting synthesized samples all display an orthorhombic crystalline structure with crystallite sizes ranging from 71 to 110 nm. Morphological diversity among the samples is revealed through field-emission scanning electron microscopy (FESEM) imagery. Diffuse reflectance spectroscopy discloses that the introduction of Ce3+ as a dopant leads to an increase in the band gap energy. Notably, when excited at a wavelength of 340 nm, the photoluminescence emission intensity reaches its peak across all samples. This intensity undergoes enhancement due to Ce3+ doping, causing a slight shift toward shorter wavelengths attributable to the augmented band gap resulting from the dopant. Markedly, among the investigated materials, Ce3+ -activated Mg3 (VO4 )2 stands out with the most pronounced emission intensity, positioning it as a highly promising luminescent material. Additionally, the incorporation of Ce3+ has a positive effect on the photocatalytic performance of Mg3 (VO4 )2 , resulting in notable improvement.