Luminous Material Research Articles

Advances in High-Efficiency Blue OLED Materials

Organic light-emitting diode (OLED) technology has rapidly emerged in the display and lighting sectors due to its high contrast ratio, wide viewing angle, and sleek design. Beyond these attributes, OLEDs have also demonstrated crucial applications in medicine, fashion, sports, and more, leveraging their emissive properties and flexible design. As the cornerstone of full-color displays, blue OLEDs, whose performance directly impacts color rendition and saturation, have garnered significant attention from both scientific researchers and industrial practitioners. Despite the numerous advantages of OLED technology, blue OLEDs still confront formidable challenges in terms of luminous efficiency, durability, and material stability. This review examines the evolution of blue OLED materials over recent years, specifically focusing on three generations: fluorescent, phosphorescent, and thermally activated delayed fluorescence (TADF). Through molecular design, device structure optimization, and the application of innovative technologies, remarkable advancements have been achieved in enhancing the luminous efficiency, lifetime, and color purity of blue OLEDs. However, to advance commercialization, future efforts must not only ensure high efficiency and long lifetime but also improve material stability, environmental sustainability, and reduce development costs. Emerging materials such as thermally activated exciton materials and the application of hyperfluorescent (HF) OLED technology represent vital driving forces for the continuous advancement of blue OLED technology. It is anticipated that significant milestones will continue to be achieved in the development of highly efficient blue OLEDs in the future.

Latent fingerprint imaging using irradiated novel mixed metal oxides (MXOY, M=Ba, Zn, Al, Ce) nanophosphor.

Latent fingerprint developed at the site of crime is considered as crucial physical evidence in forensic investigation. The mixed metal oxides (MXOY, M=Ba, Zn, Al, Ce) nanophosphor was synthesised by irradiating the precursor solution with 60Co gamma radiation followed by solution combustion method. The structural, morphological, optical characteristics and fingerprint imaging were studied using X-ray diffraction (XRD), scanning electron microscopy, UV-visible spectroscopy and powder dusting method, respectively. The XRD results revealed that the average crystallite size is found to be 30nm with the estimated bandgap of 3.18eV. The broadband UV exited luminescence of the phosphors was observed at λMax=330nm. The PL spectrum shows three emission bands at 432, 444 and 460nm that corresponds to blue regions, suggesting that the synthesised nanophosphor is a potential luminous material for latent fingerprinting and luminescent devices.

Advantageous occupation of Cu2+ in the B site of double-perovskite Rb2BB'Br6 (B = K; B′ = Bi) framework for white-light-emission

Research on lead-free double perovskite has demonstrated its potential as a solution to the stability and toxicity issues associated with lead-based inorganic perovskite white light-emitting diodes (WLED). This current investigation was designed to fabricate, examine, and compare the photoluminescence (PL) characteristics of Cu2+-activated Rb2BB'Br6 (B = K and B′ = Bi) double-perovskite (DP) [A2BB'Br6] luminous materials. Bi3+ ions are substituted with Cu2+ ions at their B′ sites. These ions are distributed to the equilibrium valence state and demonstrate minimal variation in ion radius. The microstructure and phase purity of Rb2BB'Br6:Cu2+ DP were assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Rietveld refinement was also used to identify the crystal structures, and the resulting samples all exhibit cubic crystal structures. The Fm3m space group in Rb2BB'Br6 DP frameworks is significantly impacted by the B sites. The PL spectra were used to thoroughly examine the associated mechanism of the Cu2+ → Bi3+ energy-transfer process. Cu2+ ions can be successfully doped in the Rb2KBiBr6 host with an optical band gap (Eg) of 2.74 eV (RKBBr: 0.025Cu2+). The Rb2KBiBr6:Cu2+ phosphor exhibits distinct emission bands from 450 to 650 nm upon UV excitation at 366 nm. The Cu2+→ Bi3+ energy transfer design allows for systematic luminescence tuning from blue to white due to spectral overlap between the Cu2+ emission and Bi3+ excitation spectra. It has been established that Cu2+ → Bi3+ energy transfer significantly increases the white emission intensity of Bi3+, with an associated colour temperature of 7892 K and an outstanding colour rendering index of 88.8. As a down-conversion luminous material in solid-state illumination for the upcoming generation of display devices, the discovered Rb2KBiBr6: 0.025Cu2+ phosphor exhibits remarkable promise.

Design and optical waveguide behavior of full-color emitting materials with adjustable band gap

Optical waveguide materials that span the entire visible spectrum is paramount for the efficacious operation of photon transmission devices in many contexts. Notably intriguing is the use of manipulating the band gap to finely modulate chromatic diversity within the luminous material. In this context, we synthesized three distinct organic small molecules, employing carbazole's inherent proclivity as the electron donor, while engaging thiophene, pyrimidine, and fluorenone as adept electron acceptor moieties. Evidently, our investigation unveiled a remarkable metamorphosis in the emitted fluorescence, wherein the chromatic spectrum transitions from blue to green, and subsequently to orange, as the electron acceptor group's capacity for electron absorption diminishes. Interestingly, the three materials manifest an inherent propensity for facile preparation into one-dimensional nanostructures, characterized by smooth surfaces, concurrently exhibiting commendable performance as optical waveguides. Our findings deepen a comprehensive understanding of the design of materials with the full visible spectrum, which might lead to innovations in the design of photonic integrated structures.

Design and performance evaluation of the epoxy-based self-luminous pavement marking

This study aims to prepare the self-luminous pavement marking (SLPM) to enhance driving safety and reduce the risk of traffic accident. Firstly, the composition of the SLPM was determined by the mechanical properties and luminous performance tests. The optimal mass proportions of epoxy resin, toughening agent, curing agent, curing accelerator, luminous powder, reflective powder, glass bead and glass powder was 1.0:0.1:0.3:0.006:0.4:0.3:0.25:0.55. In addition, test results showed that the SLPM has satisfactory mechanical properties, durability and luminous performance, which met the engineering requirements for practical application. The afterglow time was more than 11 h at night in laboratory test. Moreover, it is feasible to prepare different colors of the SLPM according to the RGP principle. The afterglow color and luminous intensity of SLPM strongly depend on the luminous material and its proportions. Overall, this paper provides a reference for designing and applying SLPM materials in road engineering.

Ultralong organic room-temperature phosphorescence, multiple stimulus responsiveness and high-level anti-counterfeiting based on multifunctional carbazolyl imidazolopyridine

Ultralong organic room-temperature phosphorescence materials induced by host−guest doping and the underlying mechanism have become the current research focus. Furthermore, high-level anti-counterfeiting and information encryption require multifunctional luminescent materials. Here, CzIP and L-CzIP with push−pull electronic system are successfully constructed by imidazopyridine units and commercial/self-made carbazole. The comparison experiment results indicate that trace isomer doping not only shows slight influence on crystal stacking and molecular space conformation but also significantly changes fluorescence and phosphorescence spectra and phosphorescence lifetime by boosting intersystem spin–orbit coupling. Non-radiative relaxation of CzIP and L-CzIP can be effectively inhibited by polymethyl methacrylate (PMMA) doping but not for crystallize. PMMA doping further confirms intrinsic phosphorescent characteristic of L-CzIP, whose room-temperature phosphorescence lifetime (84.83 ms) is close to that of CzIP (100.14 ms). Concentration-dependent fluorescent and phosphorescent emission and dynamic phosphorescent emission are also observed for CzIP in PMMA film. More importantly, a new aminopyridine/CzIP-doped system gives room-temperature phosphorescence lifetimes of 657.56 ms and afterglow lifetimes of 4 s. Notably, CzIP also shows high-contrast mechanochromism, selective response and differentiation to HCl, CF3COOH, and CH3COOH, and excellent detection capability to picric acid in aqueous medium and solid state. Finally, various anti-counterfeiting and encryption patterns are successfully constructed based on multifunction of CzIP. This work not only provides a multifunctional luminous material but also more importantly provides a theoretical basis and experimental guidance for designing novel ultralong organic room-temperature phosphorescence materials and achieving high-level anti-counterfeiting and encryption.

Symmetric and disulfide linked reversible fluorescent organic material: A chemosensor for Pb2+ ion and its applications in real world sample analysis

We present an effective, symmetric, and reversible luminous fluorescent organic material based on cystamine. Cysal is a substance that can be produced in a single step by the reaction of salicylaldehyde with cystamine and is characterised by 1H &13C NMR, LCMS mass, and FT-IR spectroscopy. In a buffer solution of CH3CN/H2O (1:1 (v/v), HEPES = 50 mM), cysal displays a modest emissive characteristic. At a physiological pH of 7.4, the yellow-colored sensor Cysal demonstrated a robust emissive response with a high selectivity and sensitivity towards Pb2+ ions among other metal ions examined. The calculated binding constant and detection limit were 3.02 × 104 M−1 and 2.2 × 10−2 µM and 3.02 × 104 M−1, respectively. Real level samples from water, soil, and fairness cream were evaluated for the detection of Pb2+ ions, including the bioimaging method with Ecoli bacterial cells, to show the practical utility of the probe Cysal.

Micro-LEDs Illuminate Visible Light Communication

Visible light communication (VLC), as an interdisciplinary paradigm, spans various technologies from basic device sciences to system engineering. Micro-size light-emitting diodes (micro-LEDs), because of their excellent spatio-temporal capability, are promising candidates for use as transmitters in versatile high-capacity VLC systems. Novel luminous material, fabrication process, and optical structure were successively employed for further increasing the electrical-to-optical (E-O) bandwidth of these micro-LED devices. In addition, multi-color and multi-structured micro-LEDs are enabling multi-modal and heterogeneous VLC systems with clear advantages over previously-studied point-to-point architectures. Herein, we discuss solutions for >1-GHz micro-LEDs. With the deployment of the next-generation VLC system in mind, we then provide perspectives into how micro-LEDs can assist the VLC evolution beyond the fifth-generation/sixth-generation (B5G/6G) era.

Eco-friendly inorganic molecular novel antiperovskites for light-emitting application.

The development of perovskite light-emitting diodes (PeLEDs) has progressed rapidly over the past several years, with high external quantum efficiencies exceeding 20%. However, the deployment of PeLEDs in commercial devices still faces severe challenges, such as environmental pollution, instability and low photoluminescence quantum yields (PLQYs). In this work, we perform high-throughput calculations to exhaustively search the unexplored and eco-friendly novel antiperovskite space (formula: X3B[MN4], with octahedron [BX6] and tetrahedron [MN4]). The novel antiperovskites have a unique structure whereby a tetrahedron can be embedded into an octahedral skeleton as a light-emitting center causing a space confinement effect, leading to the characteristics of a low-dimensional electronic structure, which then makes these materials potential light-emitting material candidates with a high PLQY and light-emitting stability. Under the guidance of newly derived tolerance, octahedral, and tetrahedral factors, 266 stable candidates are successfully screened out from 6320 compounds. Moreover, the antiperovskite materials Ba3I0.5F0.5(SbS4), Ca3O(SnO4), Ba3F0.5I0.5(InSe4), Ba3O0.5S0.5(ZrS4), Ca3O(TiO4), and Rb3Cl0.5I0.5(ZnI4) possess an appropriate bandgap, thermodynamic and kinetic stability, and excellent electronic and optical properties, making them promising light-emitting materials.

FA+ and Mn2+ codoped CsPbCl3 perovskite quantum dots with super thermal stability

As a new generation of luminous material, perovskite quantum dots (PQDs) possess many excellent properties. However, PQDs suffer from dramatic decrease of optical performance when affected by high temperature. In this paper, methamidine acetate (FA + ) and manganese divalent cation (Mn 2+ ) codoped CsPbCl 3 quantum dots (QDs) were synthesized. The introduced FA + and Mn 2+ were designed to substitute Cs + (A sites) and Pb 2+ (B sites), respectively. By comparison with CsPbCl 3 :Mn 2+ QDs, the results show that the CsPbCl 3 :FA + ,Mn 2+ QDs improve the blue exciton luminescence by 15% and the red Mn 2+ ions luminescence by 37%. Furthermore, CsPbCl 3 :FA + ,Mn 2+ QDs demonstrate super thermal stability by maintaining 97% of Mn 2+ emission when the temperature is raised to 70 °C even after 6 thermal cycles. Simultaneously, the UV light and water stability of CsPbCl 3 :FA + ,Mn 2+ QDs have also been obviously enhanced. The powder of the coped PQDs have been fabricated into a white LED which exhibits Color Rendering Index (CRI) of 88.2 and Correlated Color Temperature (CCT) of 5745 K. It shows that CsPbCl 3 :FA + ,Mn 2+ QDs not only reduce the Pb 2+ ions toxicity problem but also boost the thermal stability and thermal cyclability, which may open up more possibilities for the applications in optoelectronic devices.

Preparation and Characterization of a Red-Emitting, Long-Lasting, Stable, and Multi-Structure Luminous Material: SiO₂/RhB@SAOED/SMSOED

In our previous study, it is found that Rhodamine B@SrAl2O4:Eu2+, Dy3+/Sr2MgSi2O7:Eu2+, Dy3+ can achieve the red shift of luminescence color, in order to improve the stability of the luminous material and reduce the loss of red luminescence emission in the subsequent application, the Rhodamine B@SrAl2O4:Eu2+, Dy3+/Sr2MgSi2O7:Eu2+, Dy3+ was coated with SiO2, and SiO2/RhB@SrAl2O4:Eu2+, Dy3+/Sr2MgSi2O7:Eu2+, Dy3+ was successfully synthesized by sol-gel method. The microstructure, surface structure, luminescence properties, afterglow properties, the coating effect and stability of the sample were studied by changing the SiO2 coating ratio and temperature during the coating process. The results showed that when the proportion of SiO2 coating is 30% and the temperature is 60 °C, the effect of SiO2 coating was best. As the proportion of SiO2 more than 30%, the absorption and release of light by the sample were greatly affected, and the afterglow performance decreased.

Upconverted persistent luminescent Zn3Ga2SnO8: Cr3+, Yb3+, Er3+ phosphor for composite anti-counterfeiting ink.

Herein, a novel colorless anti-counterfeiting luminous ink composite material, to the best of our knowledge, was prepared by incorporating upconverted persistent luminescent Zn3Ga2SnO8:1%Cr3+, 5%Yb3+, 0.5%Er3+ (ZGSO: Cr,Yb,Er) phosphors into a resin solution, followed by stirring. Owing to its small particle size and uniform distribution, ZGSO: Cr, Yb, Er exhibits long-lasting, persistent near-infrared emission at 696 nm following the stoppage of excitation by a 274 nm ultraviolet light and a 980 nm excitation. ZGSO: Cr, Yb, Er composites were prepared and exhibited characteristic peaks corresponding to upconversion and an afterglow curve following excitation at 980 nm. With various special luminescent modes, sharp emission peaks, and emission intensity varying over time, the emission light of composite ink is easy to detect and not easily confused. Furthermore, the prepared composite ink can be calligraphic, visualized, and observable, and has good light-emitting performance following UV excitation. Our work provides a meaningful way to fabricate multifunctional anti-counterfeiting luminous ink composites with an intense persistent luminescence for use in anti-counterfeiting signs, inspection imaging, and other complex industrial applications.

Exciton Up-Conversion by Well-Distributed Carbon Quantum Dots in Luminescent Materials for an Efficient Organic Light-Emitting Diode.

In this work, we proposed an efficient and straightforward up-conversion process to enhance the external quantum efficiency in a red-emission organic light-emitting diode (OLED). The carbon quantum dots in the luminescent materials initiated the up-conversion by doping the (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) in an amount of 0.001 wt. %, and the external quantum efficiency (EQE) increased from approximately 80% to 9.27% without spectrum change. The time-resolved photoluminescence was applied to understand the mechanism of EQE enhancement in the PCBM-doped OLED. Two decay-time constants fit the TRPL. After PCBM doping, the extended PL intensity indicated increased time constants. The time constants increased from 1.06 and 4.02 ns of the reference sample to 3.48 and 11.29 ns of the PCBM-doped material, respectively. The nonradiative energy transfer (NRET) mechanism was proposed responsible for the decay-time enhancement. The excitons in the PCBM, either by excitation or injection, will transfer to the phosphorescent material nonradiatively. As the PCBM has lower energy levels than the luminous material for electrons, the backward exciton transfer is a kind of up-conversion. With the increased amounts of excitons in the luminescent material, the luminescent external quantum efficiency and the decay-time increased. This up-conversion method is not limited to the red-emission OLED; it could also be applied to blue or green emission.

Application on the Luminescence Characteristics of Nanoaluminate Rare Earth Long‐Lasting Luminescent Composite Materials in the Field of Ethnic Clothing

In the changing process of garment development, nanoaluminate rare earth material has unique advantages as a new garment material, such as easier preservation and brighter color, changing the visual beauty of traditional clothing. In order to in‐depth study the role of nanoaluminate rare earth long afterglow luminescent composite materials applied to ethnic costumes, this article uses material preparation methods, numerical analysis adjustment methods, and equipment parameter introduction methods to analyze nanoaluminate rare earths and simplify them and create a luminous composite material that can be used in the field of ethnic minority clothing. To study the luminescence characteristics of the composite material, CXHP samples with different doping concentrations of Cr ions were irradiated with an ultraviolet lamp with a center wavelength of 225 nm for 4.5 minutes, and after 12 minutes attenuation, the afterglow emission spectrum was studied. The results show that the sample has near‐infrared afterglow emission ranging from 645 nm to 740 nm, and the two emission peaks are located at 680 nm and 700 nm, respectively. The performance of its application on clothing was studied again. The water consumption in the experiment was 1500 ml, and the grams of composite material added for the three times were 0.6 g, 1.2 g, and 1.8 g, respectively. The hanging dyeing method was adopted during the experiment. Through experiments, it can be obtained that when the composite material is 1.8 grams, the visual effect is more similar to the hue, brightness, purity, and other aspects of the clothing. This way, when combined with the composite material for secondary design, a better visual effect will be achieved. From the practical application level, it has been verified that composite materials can be used in ethnic costumes.

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Discovery of an Environmentally Friendly Water-Soluble Luminous Material with Interstitial Site Occupancy

As an essential precursor, K2MnF6 plays an important role in the preparation of Mn4+-activated fluoride materials, but its deterioration in pure water hampers development of a green route. Herein, ...

A Highly Sensitive "on-off" Time-Resolved Phosphorescence Sensor Based on Aptamer Functionalized Magnetite Nanoparticles for Cadmium Detection in Food Samples.

Cadmium contamination is a severe threat to food safety. Therefore, the development of sensitive and selective cadmium detection strategies is urgently required. The elimination of background autofluorescence generated from the food matrix is critical to the optical assay for cadmium detection. Herein, a time-resolved phosphorescence sensor based on an “on-off” strategy was developed for cadmium determination in food samples. The phosphorescence nanoparticles were used as a luminous material to minimize the interference of background autofluorescence. The cadmium-binding aptamer was immobilized onto the magnetic beads and combined with a black hole quencher 1 (BHQ1) with complementary DNA as the target recognition element. With the presence of cadmium, the cadmium-binding aptamer bound to cadmium specifically and resulted in the release of BHQ1. The free BHQ1 remained in the solution after magnetic separation and quenched the phosphorescence. The phosphorescence intensity was negatively related to the concentration of cadmium. Under optimal conditions, the time-resolved phosphorescence sensor showed a linear response to cadmium concentration within a range from 0.05 to 5 ng mL−1 and with a detection limit of 0.04 ng mL−1. This “on-off” time-resolved phosphorescence sensor was successfully applied for cadmium detection in spring water and clam samples, which provided a rapid and straightforward method.

Preparation and photochromic properties of phosphomolybdic acid/rare earth strontium aluminate luminous fiber

In this study, we intend to obtain a novel luminous fiber with colour-tuned luminescence via the photoelectron transfer of a phosphomolybdic acid pigment (PAP). The luminous fiber include the SrAl2O4: Eu2+, Dy3+ materials as the luminescence sources, a solid solution of PAP and polyvinyl alcohol as the photoinitiator, amino silicone resin (ASR) as the surface-modified film-forming material and polypropylene (PP) as the matrix, which are prepared by the melt spinning method. The surface morphology was characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV–vis) spectroscopy, photoluminescence emission spectroscopy, and CIE-1931 chromaticity coordinates. Thus, promising results were obtained, which denoted that the luminescence colour of the luminous fibers could transform from yellow–green to blue by adjusting the PAP concentration. The PL emission spectra of these luminous fibers consisted of two emission peak regions in the range of 430–530 nm. The intensity of the two emission peaks in the fiber reaches the maximum when the concentration of the PAP was 50%. Further, the fibers gradually turned blue with luminescence decay when the fiber was placed in a dark place. The existence of photosensitive discoloration was found to be directly related to the amino groups embedded in the silicone resin coated with the luminous surface material, which reacted with PAP to develop phosphorous molybdenum blue via the photo-reduction process. These findings provide valuable insights toward developing next-generation luminescent materials and multicolor luminous fibers.

Trichromophore-doped cassava-based biopolymer as low-cost and eco-friendly luminous material for bio hybrid white-light-emitting diodes by dual-FRET process

White-light-emitting diodes (WLEDs) are promoted as environmentally friendly because they are energy saving-features and mercury-free aspects, but, rare-earth-free, metal-free, cost-competitive, and eco-friendly for brighter WLEDs are attractive but quite challenging in practice. This paper reports a new methodology using biopolymer luminous material in bio hybrid white-light-emitting diodes (Bio-HWLEDs) based on a trichromophore-doped cassava crystalline thick film that emits bright white light emission through a dual Fӧrster resonance energy transfer (FRET) process. The dual-FRET takes place from coumarin to sulforhodamine via the curcumin chromophore. The Bio-HWLED showed color co-ordinates (0.33, 0.32) that exactly matched with pure white light emission. The effect of temperature on luminescence and the activation energy for thermal quenching were determined using the temperature-dependent photoluminescence measurements. Moreover, Bio-HWLED showed a low luminous drop rate of 0.00069 s−1 to overcome the aggregation-induced quenching effect. These results pave the way towards the realization of commercially viable, large-scale and high-contrast bio hybrid light applications that are environmentally friendly.

Disassembly of Alzheimer’s amyloid fibrils by functional upconversion nanoparticles under near-infrared light irradiation

Alzheimer's disease (AD) is a common neurodegenerative disease characterized by cognitive and memory function impairment. Studies have shown that the overproduction and further misfolding of amyloid polypeptide (Aβ) are the main causes of AD. Therefore, how to reduce Aβ species, especially to disassemble the preformed amyloid aggregates, has become the focus of related research. Photodynamic therapy (PDT) using normal photosensitizers eg. porphyrins, is a traditional way of inhibiting amyloid aggregation or degrading the amyloid aggregates, but UV light irradiation presents a side effect for the damage of normal tissue, which limits its medical application. Upconversion nanoparticles (UCNPs) is a luminous material which can be modified by photodynamic agent to form the complex generating reactive oxygen species (ROS) with noninvasive light irradiation. It presents a good advantage in the disassembly of amyloid aggregates via ROS in noninvasive light irradiation. Herein, we prepared β-NaYF4:Yb/Er@SiO2@RB by combing UCNPs with photosensitizer to disassemble preformed Aβ aggregates under near-infrared light. The results displayed upconversion nanomaterials could degrade Aβ1–42 fibrils effectively by photo-generating ROS, which demonstrated that the functional UCNPs may have potential applications in the treatment of amyloid diseases in future.