High Photoluminescence Quantum Yield Research Articles

All‐Inorganic Cs2YbCl5·H2O Perovskite with Luminescence Response to Methanol for Anti‐Counterfeiting

AbstractStimuli‐responsive luminescent materials have attracted much research attention due to their wide application potential in various fields. Typically, the family of hydrated double perovskite A2MIIIX5·H2O shows unique emission color transformation between hydrated and dehydrated complexes, highlighting the application potential in advanced anti‐counterfeiting. Herein, two zero‐dimensional perovskites of Cs2YbCl5·H2O and Cs3YbCl6, are reported and broad‐band self‐trapped exciton recombination emission can be realized via external Sb3+ doping. Intriguingly, the Cs2YbCl5·H2O can be transformed to the dehydrated counterpart of Cs3YbCl6 through a facile methanol treatment at room temperature, leading to the emission color transformation from yellow to green. Notably, the green‐emissive Cs3YbCl6:Sb3+ delivers a high photoluminescence quantum yield of 67.3%. Leveraging the advantages of obvious methanol‐induced emission color transformation between Cs2YbCl5·H2O and Cs3YbCl6 at room temperature, Cs2YbCl5·H2O can be used in the field of high‐security‐level anti‐counterfeiting.

Efficient Perovskite Nanograin Light-Emitting Diodes in Green-to-Blue Gamut with Co-Additive Engineering.

Perovskite nanograins exceeding the Bohr exciton diameter show great potential for high-performance light-emitting diodes (LEDs) owing to their bandgap homogeneity, spatial charge confinement, and nonlocal interaction. However, it is challenging to directly synthesize proper nanograins along with reduced crystal defects on functional substrate, and the corresponding high-efficiency perovskite LEDs (PeLEDs) have rarely been reported. In this study, crystallization modulation for perovskites with an effective co-additive system, including lithium bromide, p-fluorophenethylammonium bromide, and 18-crown-6, is performed. Furthermore, it is demonstrated that the proposed co-additive system can synergistically retard perovskite crystallization and reduce crystal defects. Consequently, high-quality perovskite nanograin solids (≈22.8nm) are obtained with a high photoluminescence quantum yield (≈88%). These superior optical properties contribute to developing efficient green PeLEDs with a champion external quantum efficiency (EQE) of 28.4% and an average EQE of 27.1%. The co-additive system can be universally applied to mixed-halide perovskite nanograin LED, presenting a maximum EQE of 24.4%, 21.6%, 17.5%, and 11.1% for the blue device at 496, 488, 478, and 472nm, respectively, along with a narrow spectral linewidth (17-14nm) and stable color. These results supplement the research on high-efficiency perovskite nanograin LEDs for multicolor displays and lighting.

Well-type thick-shell quantum dots combined with double hole transport layers device structure assisted realization of high-performance quantum dot light-emitting diodes

Quantum dot (QD) light-emitting diodes (QLEDs) are promising for next-generation lighting and displays. Considering the optimization design of both the QD and device structure is expected to improve the QLED's performance significantly but has rarely been reported. Here, we use the thick-shell QDs combined with a dual-hole transport layer device structure to construct a high-efficiency QLED. The optimized thick-shell QDs with CdS/CdSe/CdS/ZnS seed/spherical quantum well/shell/shell geometry exhibit a high photoluminescence quantum yield of 96% at a shell thickness of 5.9 nm. The intermediate emissive CdSe layer with coherent strain ensures defect-free growth of the thick CdS and ZnS outer shells. Based on the orthogonal solvents assisted Poly-TPD&PVK dual-hole transport layer device architecture, the champion QLED achieved a maximum external quantum efficiency of 22.5% and a maximum luminance of 259955 cd m-2, which are 1.6 and 3.7 times that of thin-shell QDs based devices with single hole transport layer, respectively. Our study provides a feasible idea for further improving the performance of QLED devices.

Flexible, photoluminescent 0D Cs4PbX6 (X = Br, Br/I)–PMMA composite films for white LED via water-induced recrystallization

3D CsPbX3 inorganic perovskite materials have attracted much attention in optoelectronic devices because of their strong absorbance, high photoluminescent quantum yield, tunable band gap, and narrow emission bandwidth. However, their practical usefulness is limited due to their poor stability in ambient conditions. Here, we created photoluminescent 0D Cs4PbX6 (X = Br, Br/I) suspensions in toluene by adding a small amount of water. The photoluminescent 0D Cs4PbX6 perovskite was mixed with polymethylmethacrylate (PMMA) forming 0D Cs4PbX6/PMMA composite films with higher PL, stability, transparency, and transmittance than that of the 3D CsPbX3/PMMA composite films prepared separately. Moreover, the PL intensity maintains 90% of the initial value after 30 days in water, showing excellent water stability. The flexible white-light LED device prepared by the composite films illustrated good luminescence performance with color rendering index 74.77, chromaticity coordinates (0.32, 0.33), and color temperature 6997 K.Graphical abstract

Ternary Eu3+ crystalline complexes with photoluminescence and triboluminescence for dynamic stress visualization

Investigation of photoluminescence (PL) and fracture-induced triboluminescence (TL) is necessary for the development of both fundamental theories and practical applications in mechanical energy conversion; however, most known PL/TL-emitting materials are confined to inorganic systems. In this study, a novel lanthanide-based crystalline complex (LnCC), Eu(DBM)3DETA was synthesized via the synergistic coordination of Eu3+ with DBM (Dibenzoylmethane) and DETA (Diethylenetriamine) units, leading to the formation of brighter LnCC with bright red emission, high PL quantum yields (57.19 %) and unique TL characteristics. The key to success in obtaining Eu(DBM)3DETA is the utilization of DETA molecule as synergistic ligand, presenting block crystals with higher coordination number of Eu3+ ions via recrystallization. Due to the dense accumulation of cross-linked three-dimensional frameworks through van der Waals interactions, the fracture-induced piezoelectric effect results in charge separation and excitation through the resultant electric field and discharge, triggering a fast TL response of Eu(DBM)3DETA and expanding the possibilities of the quantitative stress sensing. Importantly, amorphous powders can still recover to their original PL and TL emission intensities after recrystallization in cyclic crystal-to-amorphous phase transitions. The unique PL and TL characteristics of Eu(DBM)3DETA provide promising opportunities to display stress visualization differences of electronic signatures under different forces.

Facile Synthesis and Photoluminescent Properties of Asymmetric Perylene Diimides Capable of Tuning Emission Colors in Polymeric Matrices.

We report the facile synthesis of asymmetric perylene diimides (asym-PDIs) using readily available reagents, demonstrating their distinct photoluminescent properties. In CHCl3, asym-PDIs exhibit higher solubility compared to traditional perylene dyes, of which solubilities can be varied by substituent selections. Among them, UV-vis absorption spectra of CPE in CHCl3 solution displayed no aggregate peaks in the ground state, maintaining high photoluminescent quantum yields. Also, CPE can be readily dispersed into poly(methyl methacrylate) PMMA (CPE-PMMA), forming thin films without aggregate formation. Importantly, the emission color of CPE-PMMA thin films significantly changes with the addition of polycyclic aromatic hydrocarbons (PAHs). These color changes should be strongly correlated with the HOMO level of the added PAHs.

Mn derived growth of CsPbBr3 nanoplatelets for stable and bright orange emission

Abstract Mn-doped perovskites have been extensively studied in optics, magnetism, and electronics due to their orange emission. However, successful Mn doping required a high Mn/Pb feed ratio. In this paper, Mn-doped CsPbBr3 nanoplatelets (NPLs) with bright orange emission were prepared by a two-step slow thermal injection synthesis. The slow injection of precursors effectively slow-down the crystal growth kinetic process and controls the growth of undoped CsPbBr3 NPLs. This process also significantly improves Mn doping efficiency. Mn doping induced the generation of numerous precursor clusters during the growth of CsPbBr3 NPLs, and the formation of these clusters was crucial for enhancing the doping efficiency. The maximum amount of Mn precursor in CsPb0.83Mn0.17Br3 was 50% of Pb precursors. The photoluminescence quantum yields (PLQYs) of CsPb0.94Mn0.06Br3 NPLs reached up to 80.6%, which was 3.1 times of that of CsPbBr3 NPLs. The PL properties of Mn-doped CsPbBr3 NPLs were significantly enhanced compared with pure CsPbBr3 NPLs. The growth process and luminescence mechanism of Mn-doped CsPbBr3 NPLs were discussed. High PLQYs and efficient Mn doping supplied an ideal approach for the preparation of various CsPbX3 (X = Cl, Br, and I) NCs for commercial applications.

Ultrasensitive Piezochromic Molecular Crystals: Mechanical Pressure‐Induced Controlled Regulation of TADF and RTP

AbstractConsidering that regulation of thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) is necessary for a fluorophore to survive and properly show its characteristic features, it is successfully shown herein that a carefully designed novel pyrene derivative can exhibit remarkable aggregation‐induced emission (AIE) overcoming the characteristic fast excitonic decay of pyrene compounds. Moreover, it is established that J‐aggregation in the red‐emitting molecular crystals of the compound reduces the singlet‐triplet energy gap (∆EST), allowing TADF with a very high photoluminescence quantum yield (PLQY) of 72%. Whereas, anisotropic grinding of the same crystals generates well‐defined microcrystals that show RTP as the nature of aggregation changes. Impressively, under isotropic hydrostatic pressure, the crystals show near‐infra‐red (NIR) emission with a very high piezochromic luminescence sensitivity of 46.2 nm GPa−1. The results have established that formation of stable H‐aggregates in the microcrystals is responsible for the ultra‐long RTP. A highly sophisticated full‐spectrum Mueller‐matrix analysis is used for the first time in such systems to demonstrate the details of the effect of perturbation (pressure) on molecular conformation.

Targeted synthesis of a 3D covalent organic framework with fjh topology exhibiting high photoluminescence: A robust platform for sensitive detection of furantoin

The inappropriate use of antibiotics poses significant risks to both the environment and human health, necessitating the development of accurate and sensitive detection methods. Fluorescence detection, particularly utilizing three-dimensional (3D) covalent organic frameworks (COFs), stands out as a promising avenue. Unlike two-dimensional COFs, 3D COFs can mitigate fluorescence quenching resulting from non-radiative energy loss, primarily attributed to π-π interlayer stacking. In this study, by carefully selecting and designing the building blocks, we synthesized a 3D COF named PyTTA-TTFB-COF with fjh topology and remarkable photoluminescence. This was achieved through the combination of a 4-connected square chromophore, 1,3,6,8-Tetrakis(4-aminophenyl) pyrene, with a 3-connected triangle, 1,3,5-trimethyl-2,4,6-tris(4-formylphenyl) benzene, possessing a specific stereo conformation. Significantly, PyTTA-TTFB-COF exhibits a high photoluminescence quantum yield, notably reaching 60.1% in acetonitrile. Moreover, it displays substantial fluorescence quenching when exposed to furantoin, surpassing the performance observed with other antibiotics. Competitive experiments have confirmed that PyTTA-TTFB-COF can serve as a specific fluorescent probe for the interference-free detection of furantoin.

Green‐Emissive Carbon Dots with a High Quantum Yield Applied for Photoconversion Film to Prevent from Blue Light Damage

AbstractHigh‐energy blue light is highly detrimental to health as it can penetrate the lens into the retina, potentially causing atrophy or even death of retinal pigment epithelial cells. To prevent the harmful effects of high‐energy blue light on our health, here the preparation of a photoconversion film specifically designed to block high‐energy blue light is reported, which is composed of green‐emissive carbon dots (G‐CDs) with a high photoluminescence quantum yield (PLQY = 95%) dispersed in polyvinyl alcohol (PVA) matrix. Notably, such a film (named as G‐CDs@PVA) not only converts an incident laser light with a short wavelength into a fluorescence with a longer wavelength, but also exhibits concentration‐dependent (0, 10, 20, and 30 wt.%) blue light barrier rate and green‐emissive intensity. With the increase of the concentration of G‐CDs in the film, the blue light barrier rate of the film as well as the maximum intensity of the green emission are also increased. When the concentration of G‐CDs reaches 30 wt.%, the blue light barrier rate of G‐CDs@PVA achieves up to 97%. Furthermore, G‐CDs@PVA film is attached to a blue light‐emitting diode (LED) chip to explore its practical application in the field of blocking blue light damage.

Modulating the Locally Excited States with a Regulating Substituent for Highly Efficient Red/Near‐Infrared Thermally Activated Delayed Fluorescence Emitters

AbstractDeveloping highly efficient red/near‐infrared (NIR) thermally activated delayed fluorescence (TADF) materials is important for organic light‐emitting diodes (OLEDs). Here, two TADF emitters, APTT and APTI, which have the same D/A backbone but different attaching groups at acenaphtho‐[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC) core, are reported. The appended regulating groups can not only suppress the D/A rotation due to the space confinement effects but also modulate the locally excited triplet state (3LE). The improved molecular rigidity suppresses the non‐radiative process, accounting for the improved photoluminescence quantum yields (PLQYs), while the modulated 3LE promotes the reverse intersystem crossing (RISC) process due to the high utilization efficiency of triplets. Consequently, both APTT and APTI demonstrate high PLQY and fast RISC process, thereby enhancing TADF efficiency. The doped devices based on APTT and APTI achieve maximum external quantum efficiency (EQEmax) values of 20.5% and 25.4% with emission peaks at 664 and 670 nm, respectively. The non‐doped devices of APTT and APTI achieve the EQEmax of 2.8% and 2.9% with emission peaks at 788 and 794 nm, respectively. Encouragingly, the non‐doped devices of APTI have set new records for near‐infrared TADF OLEDs based on the APDC core. This study provides an efficient approach to modulating the optoelectronic properties of highly efficient NIR TADF OLEDs.

Synthesis, characterization, and optical studies of lead-free perovskite, Cs3M2Br9 (M = Bi, Sb) nanocrystals

In recent years, there has been a surge in research interest surrounding all inorganic lead perovskite nanocrystals (NCs) owing to their exceptional performance in various optoelectronic devices. Nevertheless, the presence of lead and concerns regarding its toxicity and stability have cast a shadow over their potential wide-ranging applications. In this study, we present the synthesis of two lead-free all-inorganic perovskite materials, Cs3M2Br9 (where M = Bi or Sb), in bulk form, using an aqueous halide acid medium. Additionally, we describe a top-down approach for the fabrication of two lead-free all-inorganic perovskite, Cs3M2Br9 (M = Bi or Sb) NCs. The Cs3Sb2Br9 NCs display a sheet-like morphology, while Cs3Bi2Br9 NCs exhibit a cubic structure. The PL spectra of Cs3Sb2Br9 and Cs3Bi2Br9 NCs exhibit distinct emission peaks at 476 nm and 472 nm, respectively, with relatively narrow full width at half maximum (FWHM) of 44 nm and 38 nm, respectively. Cs3Sb2Br9 and Cs3Bi2Br9 NCs demonstrate excellent thermal stability up to 320 °C and 470 °C, respectively. Notably, the high photoluminescence quantum yield (PLQY) of these NCs, Cs3Sb2Br9 NCs (31 %) and Cs3Bi2Br9 NCs (36 %) are highly beneficial for optoelectronic applications is observed.

From Dopant to Host: Solution Synthesis and Light‐Emitting Applications of Organic‐Inorganic Lanthanide‐Based Metal Halides

The rich and unique energy level structure arising from 4fn inner shell configuration of trivalent lanthanide ions (Ln3+) renders them highly attractive for light‐emitting applications. Currently, research primarily focuses on Ln3+ doping in either traditional garnets or the recently developed perovskite phosphors. However, there have been few reports on stable phosphors crystallized with pure lanthanide elements. Herein, a universal solution‐based route to eight Ln3+‐based metal halides from the organic‐inorganic A4LnX7 family is described, where A+ = 4,4‐difluoropiperidinium (DFPD+), Ln3+ = Nd3+, Eu3+, Ho3+, Sm3+, Tm3+, Tb3+, Yb3+, Er3+, and X− = Cl−, Br−. Visible photoluminescence (PL) is observed from Tb3+‐, Eu3+‐, Ho3+‐, and Sm3+‐based compounds with Tb and Eu compositions exhibiting high PL quantum yields of 90–100%; Nd3+‐, Tm3+‐, Yb3+‐, and Er3+‐based crystals show fascinating near‐infrared emission. Light‐emitting diodes (LEDs) fabricated with (DFPD)4TbCl7 yield characteristic emission of Tb3+, representing the first demonstration of electroluminescence from these organic‐inorganic Ln3+‐based metal halides. Moreover, these materials exhibit distinct excitation wavelength‐dependent emission after alloying with different Ln3+ ions, making them interesting for multicolor display and multilevel information encryption applications. It is foreseen that this study will open up the way to a possible design of robust optoelectronic devices based on lanthanide metal halides.

Ultrastable Copper Iodide Hybrid with Intrinsic Greenish White-Light Emission by Incorporating an Anionic Inorganic Functional Unit into an Extended Structure.

Incorporating a functional unit into the multidimensional coordination polymer skeleton is an efficient way to improve the stability of materials and expand their application. In this paper, anionic copper iodide inorganic functional modules are incorporated into one-dimensional extended chains by using a unique bidentate cationic organic ligand. Benefiting from the ionic extended structure, the resulting hybrid possesses a remarkable stability with a decomposition temperature as high as 300 °C. Meanwhile, the hybrid material exhibits intrinsic greenish white-light emission with a high photoluminescent quantum yield of 70%. The emission was investigated by temperature-dependent emission spectra, which proved to be the result of the synergistic effect of two energy states. The novel synthetic strategy provides an efficient route for the development of functional organic metal halides.

Efficient Deep-Blue Multiple-Resonance Emitters Based on Azepine-Decorated ν-DABNA for CIEy below 0.06.

Ultrapure deep-blue emitters are in high demand for organic light-emitting diodes (OLEDs). Although color coordinates serve as straightforward parameters for assessing color purity, precise control over the maximum wavelength and full-width at half-maximum is necessary to optimize OLED performance, including luminance efficiency and luminous efficacy. Multiple-resonance (MR) emitters are promising candidates for achieving ideal luminescence properties; consequently, a wide variety of MR frameworks have been developed. However, most of these emitters experience a wavelength displacement from the ideal color, which limits their practical applicability. Therefore, a molecular design that is compatible with MR emitters for modulating their energy levels and color output is particularly valuable. Here, it is demonstrated that the azepine donor unit induces an appropriate blue-shift in the emission maximum while maintaining efficient MR characteristics, including high photoluminescence quantum yield, narrow emission, and a fast reverse intersystem crossing rate. OLEDs using newly developed MR emitters based on the ν-DABNA framework simultaneously exhibit a high quantum efficiency of ≈30%, luminous efficacy of ≈20lm W-1, exceptional color purity with Commission Internationale de l'Éclairage coordinates as low as (0.14, 0.06), and notably high operational stability. These results demonstrate unprecedentedly high levels compared with those observed in previously reported deep-blue emitters.

Elimination of Intragrain Defect to Enhance the Performance of FAPbI3 Perovskite Solar Cells by Ionic Liquid.

Ionic liquids have been widely used to improve the efficiency and stability of perovskite solar cells (PSCs), and are generally believed to passivate defects on the grain boundaries of perovskites. However, few studies have focused on the relevant effects of ionic liquids on intragrain defects in perovskites which have been shown to be critical for the performance of PSCs. In this work, the effect of ionic liquid 1-hexyl-3-methylimidazolium iodide (HMII) on intragrain defects of formamidinium lead iodide (FAPbI3) perovskite is investigated. Abundant {111}c intragrain planar defects in pure FAPbI3 grains are found to be significantly reduced by the addition of the ionic liquid HMII, shown by using ultra-low-dose selected area electron diffraction. As a result, longer charge carrier lifetimes, higher photoluminescence quantum yield, better charge carrier transport properties, lower Urbach energy, and current-voltage hysteresis are achieved, and the champion power conversion efficiency of 24.09% is demonstrated. These observations suggest that ionic liquids significantly improve device performance resulting from the elimination of {111}c intragrain planar defects.

The deposition and the optical characteristics of Cu-based metal halide Cs3Cu2I5 thin film via mist deposition

Cu-based metal halides, such as Cs3Cu2I5, are promising materials for LEDs, photodetectors, and scintillators because of their excellent optical properties, nontoxicity, and high air stability. In this study, we demonstrated the deposition of high-coverage Cs3Cu2I5 thin films using solution-based mist deposition. By adjusting the substrate temperature appropriately, continuous Cs3Cu2I5 thin films were formed. The Cs3Cu2I5 thin films exhibited blue emission under ultraviolet irradiation, with a large Stokes shift of 1.40 eV. Furthermore, they exhibited a high photoluminescence quantum yield of over 80%.

Stretchable Metal Halide Perovskite Color Conversion Layers with Block Copolymer Dispersant

AbstractStretchable luminescent nanocomposites with metal halide perovskite (MHP) emitters are in high demand as deformable color‐conversion layers (CCLs) for vivid‐colored form‐factor free displays. However, the immiscibility of the MHP crystals with an elastomeric polymer matrix induces particle aggregation with resultant luminescence quenching, hindering the development of MHP‐based CCLs. Herein, a simple method is proposed to produce highly luminescent MHP nanoparticles (NPs) and stably disperse them in an elastomeric poly(dimethylsiloxane) (PDMS) polymer matrix with block copolymer (BCP) dispersant. The nanocomposites are developed through sequential steps of synthesis of MHP‐NP dispersion solution with BCP and blending with PDMS followed by thermal curing. It is revealed that Lewis basic poly(2‐vinylpyridine)‐block‐poly(dimethylsiloxane) (P2VP‐b‐PDMS) BCP added in the synthesis step promotes crystallization of the MHPs as nanocrystals with an average diameter of 5.9 ± 1.2 nm, whereas MHPs with hundreds of nm are produced without BCP. The resultant MHP‐NPs with P2VP‐b‐PDMS exhibit excellent photophysical properties, such as narrow band emission, high photoluminescence (PL) quantum yield, and long PL lifetime. The MHP‐NPs are stably dispersed in the PDMS matrix by P2VP‐b‐PDMS without particle aggregation, leading to highly deformable and stretchable nanocomposites with stable PL emission upon repetitive stretching, and excellent environmental stability.

Syntheses and efficient phosphorescence of ionic silver(I) complexes based on benzothiazole-phosphine ligands

Two ionic mononuclear silver(I) complexes (1 and 2) with formula of [Ag(N^P)(Xantphos)]SbF6, where N^P = 2–(benzo[d]thiazol)–2–yl) diphenylphosphine derivatives, Xantphos = 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene, have been synthesized and characterized. Single crystal analysis reveals that the geometries around Ag(I) centers adopt distorted tetrahedron (1) and trigonal planar (2). In powder at 298 K, these complexes exhibit bright emissions with high photo-luminescent quantum yields of 55.2 % (1) and 46.7 % (2) and lifetimes of 0.426 ms (1) and 1.87 ms (2), respectively. The results suggested that these complexes containing bulky benzothiazole phosphine can realize efficient long-lived phosphorescence.

Ir(III) Metal Emitters with Cyano-Modified Imidazo[4,5-b]pyridin-2-ylidene Chelates for Deep-Blue Organic Light-Emitting Diodes.

Ir(III) carbene complexes have been explored as one of the best blue phosphors for their high performance. Herein, the authors designed and synthesized a series of blue-emitting Ir(III) phosphors (f-ct9a-c), featuring fac-coordinated cyano-imidazo[4,5-b]pyridin-2-ylidene cyclometalates. These Ir(III) complexes exhibit true-blue emission with a peak maximum spanning 448-467 nm, with high photoluminescence quantum yields of 81-88% recorded in degassed toluene. Moreover, OLED devices bearing phosphors f-ct9a and f-ct9b deliver maximum external quantum efficiencies (EQEmax) of 25.9% and 30.3%, together with Commission Internationale de L'Eclairage (CIEx,y) coordinates of (0.157, 0.225) and (0.142, 0.169), respectively. Remarkably, the f-ct9b-based device displays an incredible EQE of 29.0% at 5000 cd·m-2. The hyper-OLED device based on f-ct9b and ν-DABNA exhibits an EQEmax of 34.7% and CIEx,y coordinates of (0.122, 0.131), affirming high potentials in achieving efficient blue electroluminescence.