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Four new AIE-active Ir(iii) complexes were synthesized. MFIrqa, SFIriqa and SFIrqa based NPs are shown to be good PSs in vitro for PDT through Type I ˙OH generation mechanism.

Nondoped organic light-emitting diodes (OLEDs) are of paramount importance for display and lighting applications owing to their advantages of facile fabrication and outstanding stability. However, nondoped OLEDs achieving extraordinary electroluminescence (EL) performance and low turn-on voltage (

The prominent pathological feature of fatty liver disease lesions is excessive fat accumulation in lipid droplets in hepatocytes. Thus, developing fluorescent lipid droplet-specific probes with high permeability and a high imaging contrast provides a robust tool for diagnosing fatty liver diseases. Herein, we rationally developed a novel donor-acceptor lipophilic fluorescent probe ANI with high photostability for wash-free visualization of lipid droplets and fatty liver disease characteristics. ANI showed a typical twisted intramolecular charge transfer effect with very faint fluorescence in high-polar solvents, but dramatically boosted emissions in low-polar environments. The solvatochromic probe can selectively light up lipid droplets with a high contrast in a wash-free manner. Further use of ANI to reveal the excessive accumulation of lipid droplets with a significantly large size in the liver tissues from the fatty liver disease model mice was successfully demonstrated. The remarkable imaging performances rendered ANI an alternative tool for accurately evaluating fatty liver disease in intraoperative diagnosis.

Constructing high-quality white organic light-emitting diodes (WOLEDs) remains a big challenge because of high demands on the electroluminescence (EL) performance including high efficiency, excellent spectral stability, and low roll-off simultaneously. To achieve effective energy transfer and trap-assisted recombination in the emissive layer, herein, four Ir(III) phosphors, namely

A feasible strategy through synergistic heavy-atom effect and methylation approach to suppress non-radiative pathway and accelerate ISC processes is demonstrated. As a result, efficient and long-lived phosphorescence is realized.

Stable one-dimensional coordination polymer is used as a highly selective sensor for the detection of TNP.

Molecular isomeric engineering is employed to construct efficient orange-red Ir(iii) complexes for WOLEDs and understand the intrinsic structure–property relationship.

An unprecedented fully reduced {MoV60} POM served as a cheap and robust molecular light-absorber model possessing wide light absorption and was applied to build a co-sensitized solar cell photoelectronic device.

Near-infrared (NIR) photosensitizers with rapid reactive oxygen species (ROS) production ability are in great demand owing to their promising performance toward boosting photodynamic therapy (PDT) and deep-tissue imaging, but molecular design guidelines for efficient photosensitizers are rarely elucidated. Herein, three AIEgens named DBP, TBP, and TBP-SO3 are designed and synthesized by precise donor-acceptor (D-A) molecular engineering to deeply understand the structure-property-application relationships. All the compounds exhibit AIE characteristics with strong long-wavelength emission in the aggregated state and are capable of efficiently producing ROS under white light irradiation. By controlling the ability of the D-A units, TBP-SO3 realizes NIR emission and more rapid ROS generation ability due to the promoted intersystem crossing processes compared with those of DBP and TBP. In addition, NIR-emitting TBP-SO3 is capable of specific endoplasmic reticulum targeting and excellent PDT treatment ability of cancer cells and bacteria. This successful example of molecular engineering paves a valuable way for developing advanced PSs with AIE properties, efficient ROS generation ability, and intense emission for fluorescence imaging PDT.

A TPE-based fluorescent porous covalent organic polymer (COP-3) was designed and synthesized. The COP-3 exhibits excellent performance in sensing Fe3+ with high anti-interference, recyclability and a low limit of detection (LOD) of 0.191 μM (10.696 ppb), which is much lower than those of the reported metal-free porous polymers.

Switchable multimode microlasers are of great significance to the development of photonic devices with high integration levels. Herein, we demonstrate an acid/alkaline gas-responsive multimode AIEgen@starch microsphere-based microlaser. The aggregation-induced emission (AIE) active fluorescent dye ASCPI was used as the gain medium in this study. ASCPI was weakly emissive in water but became highly emissive when introduced to a starch microsphere as a guest molecule. The resultant ASCPI@starch microsphere worked well as a typical whispering-gallery-mode microlaser. The laser mode wavelengths were size-dependent. Due to the sensitivity of ASCPI to pH, the output of the microlaser could be switched to a shorter wavelength by acetic acid vapor treatment or a longer wavelength by NH3 vapor treatment. This work will provide useful enlightenment for the rational design of effective switchable lasers using AIE materials with simple preparation procedures.

Density functional theory (DFT) calculations have been carried out to investigate two synthesized iridium(III) complexes with substituted Phbd (1-phenyl-2-(pyridin-2-yl)-1H-benzo[d]imidazole) and Crbd (9-(4-(2-(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl)phenyl)-9H-carbazole) as ancillary ligands. The aim of this paper is to study the effect of the substituent on the geometrical structures, electronic and second-order nonlinear optical (NLO) properties, and UV-vis absorption spectra. It is found that the first hyperpolarizabilities can be easily modulated by the introduction of Phbd and Crbd units. The complex with Phbd possesses larger first hyperpolarizability values compared to the complex with Crbd as an ancillary ligand. Significantly, the changes in the first hyperpolarizabilities can be qualitatively explained by means of the charge transfer pattern. It is anticipated that the theoretical investigation of these iridium(III) complexes will be helpful for designing high performance and versatile NLO materials.

Phosphorescent organic light-emitting diodes (OLEDs) with high electroluminescence (EL) efficiency and low efficiency roll-off are urgently required to meet the continuously increasing market need ...

The direct usage of CO

Fully reduced polyoxometalates are predicted to give rise to a broad and strong absorption spectrum, suitable energy levels, and unparalleled electronic and optical properties. However, they are not available to date. Here, an unprecedented fully reduced polyoxomolybdate cluster, namely Na

Visually identifying pathogens favors rapid diagnosis at the point-of-care testing level. Here, we developed a microenvironment-sensitive aggregation-induced emission luminogen (AIEgen), namely IQ–Cm, for achieving fast discrimination of Gram-negative bacteria, Gram-positive bacteria and fungi by the naked-eye. With a twisted donor–acceptor and multi-rotor structure, IQ–Cm shows twisted intramolecular charge transfer (TICT) and AIE properties with sensitive fluorescence color response to the microenvironment of pathogens. Driven by the intrinsic structural differences of pathogens, IQ–Cm with a cationic isoquinolinium moiety and a membrane-active coumarin unit as the targeting and interacting groups selectively locates in different sites of three pathogens and gives three naked-eye discernible emission colors. Gram-negative bacteria are weak pink, Gram-positive bacteria are orange-red and fungi are bright yellow. Therefore, based on their distinctive fluorescence response, IQ–Cm can directly discriminate the three pathogens at the cell level under a fluorescence microscope. Furthermore, we demonstrated the feasibility of IQ–Cm as a visual probe for fast diagnosis of urinary tract infections, timely monitoring of hospital-acquired infection processes and fast detection of molds in the food field. This simple visualization strategy based on one single AIEgen provides a promising platform for rapid pathogen detection and point-of-care diagnosis., A simple AIEgen with three emission colors achieves rapid identification of Gram-negative bacteria, Gram-positive bacteria and fungi.

Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room-temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K+ was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10-fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials.

Recently, solution-processable PhOLEDs have been attracting great interest for their low cost and high productivity relative to the vacuum-deposited devices. Similar to vacuum-deposited OLEDs, however, they usually suffer from serious efficiency roll-offs, especially in high brightness. Finding a feasible way and/or designing novel materials to increase efficiencies and reduce roll-offs simultaneously are highly desired. Herein, a new family of solution-processable cyclometalated iridium(III) phosphors with carbazole (

Antibacterial photodynamic therapy (PDT) is one of the emerging methods for curbing multidrug-resistant bacterial infections. Effective fluorescent photosensitizers with dual functions of bacteria imaging and PDT applications are highly desirable. In this study, three cationic and heteroleptic cyclometalated Ir(III) complexes with the formula of [Ir(CˆN)2 (NˆN)][PF6 ] are prepared and characterized. These Ir(III) complexes named Ir(ppy)2 bP, Ir(1-pq)2 bP, and Ir(2-pq)2 bP are comprised of three CˆN ligands (i.e., 2-phenylpyridine (ppy), 1-phenylisoquinoline (1-pq), and 2-phenylquinoline (2-pq)) and one NˆN bidentate co-ligand (bP). The photophysical characterizations demonstrate that these Ir(III) complexes are red-emitting, aggregation-induced emission active luminogens. The substitution of phenylpyridine with phenylquinoline isomers in the molecules greatly enhances their UV and visible-light absorbance as well as the photoinduced reactive oxygen species (ROS) generation ability. All three Ir(III) complexes can stain both Gram-positive and Gram-negative bacteria efficiently. Interestingly, even though Ir(1-pq)2 bP and Ir(2-pq)2 bP are constitutional isomers with very similar structures and similar ROS generation ability in buffer, the former eradicates bacteria much more effectively than the other through white light-irradiated photodynamic inactivation. This work will provide valuable information on the rational design of Ir(III) complexes for fluorescence imaging and efficient photodynamic inactivation of bacteria.

Photosensitizers (PSs) with multiple characteristics, including efficient singlet oxygen (1O2) generation, cancer cell-selective accumulation and subsequent mitochondrial localization as well as near-infrared (NIR) excitation and bright NIR emission, are promising candidates for imaging-guided photodynamic therapy (PDT) but rarely concerned. Herein, a simple rational strategy, namely modulation of donor–acceptor (D–A) strength, for molecular engineering of mitochondria-targeting aggregation-induced emission (AIE) PSs with desirable characteristics including highly improved 1O2 generation efficiency, NIR emission (736 nm), high specificity to mitochondria, good biocompatibility, high brightness and superior photostability is demonstrated. Impressively, upon light irradiation, the optimal NIR AIE PS (DCQu) can generate 1O2 with efficiency much higher than those of commercially available PSs. The excellent two-photon absorption properties of DCQu allow two-photon fluorescence imaging of mitochondria and subsequent two-photon excited PDT. DCQu can selectively differentiate cancer cells from normal cells without the aid of extra targeting ligands. Upon ultralow-power light irradiation at 4.2 mW cm−2, in situ mitochondrial photodynamic activation to specifically damage cancer cells and efficient in vivo melanoma ablation are demonstrated, suggesting superior potency of the AIE PS in imaging-guided PDT with minimal side effects, which is promising for future precision medicine., Mitochondria-targeted photosensitizers with highly efficient singlet oxygen generation, bright near-infrared AIE and good two-photon absorption are obtained through ingenious molecular engineering for cancer cell-selective photodynamic therapy.

Mechanochromic luminescent (MCL) materials are promising in pressure sensors, security papers, photoelectric devices and optical data recording. Although some kinds of MCL-active iridium(III) complexes with various soft substituent functional ligands (e.g., dendritic carbazole, flexible chains, and Schiff base ligands) were reported, the MCL mechanism is still not clear and mainly ascribes to the physical phase transformations from crystalline state to amorphous state in response to force stimulus at present stage, and deserves further study in order to obtain more intelligent MCL materials. Herein, two new iridium(III) complex isomers are tactfully constructed and show distinctly opposite MCL properties in spite of the same physical phase transformations happening on them. The absolutely out of the ordinary MCL mechanism has been presented on account of molecular level for the first time via the comparative study of photophysical properties based on isomers

Inkjet printing technology is one of the most attractive methods for the realization of full-color patterning for displays. In this work, we successfully introduce this technology into fabricating pixelated light-emitting electrochemical cells (LECs). By carefully controlling the poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate), and cationic Ir(III) complexes ink formulation, as well as their inkjet printing properties, patterned LEC pixels in ultrahigh definition TV format was fabricated, leading to a resolution of 73 pixels per inch. The as-resulted inkjet-printed LEC exhibits a maximum luminance and a current efficiency of 3402 cd/m2, and 7.5 cd/A, respectively, which is close to that of the spin-coated one. This work paves a new way for the fabrication of low-cost material-efficient, pixelated light-emitting electrochemical cells.

In clinical studies, thiol measurement in the whole blood is of diagnostic and prognostic significance. In addition, the detection of mitochondrial thiol is very important for investigating cellular functions or dysfunctions. Here, a ratiometric aggregation-induced emission luminogen (AIEgen) called TPE-PBP for thiol detection was developed by introducing a

Organic compounds with bright solid-state emission are emerging as versatile materials in many fields. However, traditional fluorescent dyes generally show high-emissive fluorescence in solution but faint or quenched emission in the solid state. Therefore, it remains a great challenge to develop bright solid-state emissive materials based on traditional fluorescent dyes. Herein, we report several solid-state emissive meso-substituted BODIPYs (PhMe3-BODIPY, PhMe-BODIPY, Ph-BODIPY and Me-BODIPY) obtained by using a simple two-step synthesis. Interestingly, these BODIPYs exhibit bright dual-state emission (DSE) with green fluorescence (512–520 nm, fluorescence quantum yield ΦF is up to 85%) in THF and solid-state red emission (601–632 nm, ΦF is up to 32.2%) in the crystalline state. The highly emissive fluorescence in the crystalline state is demonstrated to be due to the formation of J-aggregation. More importantly, the single crystals of the meso-aryl-substituted BODIPYs exhibit an unusual high-contrast mechanochromic property, which displays remarkable fluorescence color changes from red to yellow upon gentle grinding due to the transition from single crystals to microcrystals. Furthermore, strong grinding completely destroys the J-aggregation and leads to the transformation from microcrystals to a free state, hence the fluorescence color becomes green after strong grinding.

Two novel orange-emitting iridium (III) complexes (nbi)2Ir (bisq) (1) and (nbi)2Ir (dmbisq) (2) utilizing 2-naphthalen-1-yl-phenyl-1H-benzimidazole as cyclometalated ligands were successfully synthesized and characterized. The effect of substituent groups in the ancillary ligands on their emission properties was systematically investigated. The experimental results indicate that complex 2 modified by introduction of methyl groups into its ancillary ligand exhibited higher photoluminescence and electroluminescence efficiencies than 1 without methyl groups. Such improved emission efficiencies were tentatively attributed to the suppressed intermolecular interactions in the solid state caused by the introduction of the methyl groups. Although the obtained efficiencies herein are not high, this work enlightens us to manipulate the photoluminescence and electroluminescence properties of iridium (III) complexes via reasonable modification in the ancillary ligand.

Two o-carborane derivatives 1 and 2 exhibiting both aggregation induced emission (AIE) and thermally activated delayed fluorescence (TADF) properties were investigated by combining density functional theory with molecular dynamics simulation. The reason for their TADF property was explored. Besides, taking 1 as an example, the AIE phenomenon was also probed by simulating the aggregation process and comparing the photophysical properties of the molecules in different aggregation states (including crystals, water, and films) with the isolated molecule. The results manifest that the separated orbital occupations of the HOMO and LUMO at the respective donor and acceptor units result in a small singlet–triplet energy gap and a favorable TADF feature, which is similar to many typical TADF molecules. In the AIE phenomenon, a much smaller structural change of donor and acceptor units between S1 and S0 states was experienced for the molecules in all aggregate states compared with that for the isolated molecule, decreasing the energy dissipation substantially and enhancing the luminescence efficiency. In addition, o-carborane is conjectured to help in the free rotation of donor and acceptor units for the isolated molecule, which may contribute to AIE. What's more, on the basis of 1 and 2, we designed 3–6 by means of replacing the triphenyltriazine group with other electron-withdrawing groups having lower LUMO energy levels, aiming to obtain this kind of red light emitting material. The results indeed proved our assumption that 3–6 not only present the feature of red light emission but also have both TADF and AIE properties in films.

Dinuclear Ir(III) complexes have recently emerged with great promise for organic electroluminescent devices owing to their unique merits such as increased spin–orbit coupling and adjustable photophysical properties. However, most of them require sophisticated doping processes for their engineering, resulting in high production costs. Herein, we developed novel dinuclear Ir(III) complexes, which become weak phosphors in solution but exhibit intensified emission in the solid state. The intermolecular interaction-caused quenching was suppressed perfectly, and the carrier transport abilities were modulated simultaneously, leading to high emission efficiencies in the neat film and balanced charge carrier transport. The green-emitting single-layer nondoped device achieved promising efficiencies with an external quantum efficiency (EQE) of 11.6% and current efficiency (CE) of 40.0 cd A−1. The orange-emitting device realized an EQE of 12.9% and CE of 38.4 cd A−1, which are the highest efficiencies reported to date for solution-processed single-layer nondoped devices and even comparable to that of most reported multilayer doping devices.

A newly prepared tetraphenylethylene-based (TPE-based) covalent organic polymer (COP) named COP-1 exhibits high selectivity for sensing Fe3+ and the limit of detection (LOD) for Fe3+ is 0.42 μM, which is lower than the reported metal-free porous polymers. Furthermore, a WLED is fabricated and the CIE coordinates are (0.32, 0.33), very close to pure white light. The COP-1 shows potential applications in biosensors of Fe3+ and preparation of WLEDs.

In contrast to the traditional view that the small organic molecules emit fluorescence, more and more experiments manifest their special luminescence types, such as the thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence. Why the similar organic molecules exhibit different luminescence types is focused on in this work on the basis of density functional theory/time-dependent density functional theory calculations on a series of small organic molecules with phenoxazine or carbazole as a donor and diphenyl-triazine as an acceptor. The deep analysis of the geometrical and electronic structures shows how the structure, especially for the donor–acceptor dihedral angle, determines the singlet–triplet energy gap and the property of excited states. The explorations on the electron–hole pairs of natural transition orbitals and the contribution of the key heteroatom (N) to different molecular orbitals reveal the distinct electron transition processes of excitation to singlet and trip...

The mercury ions in waste water have threatened public health and environmental protection. In this sense, novel materials with outstanding performances for removal of Hg

Highly efficient light-emitting electrochemical cells (LECs) have attracted tremendous interest because of their simple structures and low-cost fabrication processing, showing great potential for full-color displays and solid-state lighting. In this work, we rationally designed and synthesized two red-emitting cationic Ir(III) complexes, [Ir(tBuPBI)

Advanced 1.5-µm emitting materials that can be used to fabricate electrically driven light-emitting devices have the potential for developing cost-effective light sources for integrated silicon photonics. Sensitized erbium (Er3+) in organic materials can give bright 1.5-µm luminescence and provide a route for realizing 1.5-µm organic light emitting diodes (OLEDs). However, the Er3+ electroluminescence (EL) intensity needs to be further improved for device applications. Herein, an efficient 1.5-µm OLED made from a sensitized organic Er3+ co-doped system is realized, where a “traditional” organic phosphorescent molecule with minimal triplet–triplet annihilation is used as a chromophore sensitizer. The chromophore provides efficient sensitization to a co-doped organic Er3+ complex with a perfluorinated-ligand shell. The large volume can protect the Er3+ 1.5-µm luminescence from vibrational quenching. The average lifetime of the sensitized Er3+ 1.5-µm luminescence reaches ~0.86 ms, with a lifetime component of 2.65 ms, which is by far the longest Er3+ lifetime in a hydrogen-abundant organic environment and can even compete with that obtained in the fully fluorinated organic Er3+ system. The optimal sensitization enhances the Er3+ luminescence by a factor of 1600 even with a high concentration of the phosphorescent molecule, and bright 1.5-µm OLEDs are obtained., Light emission: Erbium and iridium make a powerful combination Light emission from ions of the element erbium, for use in electrically driven light-emitting devices, can be significantly enhanced by adding sensitizer materials containing iridium ions. The potential of erbium for cost-effective light emission in photonics applications is well-recognized, but methods to increase the power efficiency of the devices are keenly sought. Hong-Fei Li and colleagues at Queen Mary University of London, UK, and Northeast Normal University in Changchun, China, found that a phosphorescent iridium complex enhanced the emission from an erbium complex by a factor of up to 1600. The dramatic effect of the iridium sensitizer was demonstrated in an organic (carbon-based) light-emitting diode. This innovation emphasizes the potential advantages of exploring combinations of molecular complexes in light-emitting devices, rather than seeking a single light-emitting molecule possessing all of the properties required.

A newly prepared tetraphenylethylene-based (TPE-based) covalent organic polymer (COP) named COP-1 exhibits high selectivity for sensing Fe3+ and the limit of detection (LOD) for Fe3+ is 0.42 μM, which is lower than the reported metal-free porous polymers. Furthermore, a WLED is fabricated and the CIE coordinates are (0.32, 0.33), very close to pure white light. The COP-1 shows potential applications in biosensors of Fe3+ and preparation of WLEDs.

A sublimable cationic Ir(iii) complex using chlorine as a counterion was synthesized to fabricate high-performance WOLEDs via a vacuum-deposition process for the first time.

A clear relationship between structures and desired properties is a crucial factor for further material design with diverse structure and performance optimization. Herein, a new design strategy to achieve efficient mechanochromism of Ir(III) complexes has been described by deeply exploring the photophysical properties of a series of cationic Ir(III) phosphors that contain the same main ligands but easily tunable donor–acceptor type ancillary ligands. All designed phosphors exhibit intense emissions in solid states due to intrinsic aggregation-induced emission (AIE) characteristics. By simply tuning the donor moieties on ancillary ligands, controllable and naked-eye visible mechanochromic luminescence behavior has been successfully realized. Compared with previous works, this design strategy reported herein is more simple and feasible. Subtle modification of the donor groups on ancillary ligands leads to obvious changes in the dipole moments. The larger the dipole moments, the more efficient is the mechanochromism for such a studied system. Benefiting from the prominent and reversible mechanochromism as well as intense emission in the aggregation state, an efficient data encryption device and a sensitive explosive probe towards 2,4,6-trinitrophenol (TNP) are achieved.

As is well known, carbon dioxide (CO2) reduction reaction (CO2 RR) by photocatalytic technology is a means with great promise to alleviate the crises on the global energy and the environmental fronts. It is critical to design and construct photocatalysts with high performance as catalysts are the core of the photocatalytic process. Recently, polyoxometalates (POMs) have aroused wide research interest as CO 2 photoreduction-related catalysts because they possess tunable compositions, thermal stability, redox reaction and tailorable light-absorption capabilities. This review has discussed the recent progress of POMs and POM-based photocatalysts for CO 2 reduction focusing on the roles of POMs as photocatalysts, cocatalysts, photocatalytic hosts (photosensitizers), and multi-electron donors in systems of CO2 photoreduction, which can provide important guides for the design of high-efficiency photocatalysts. In the end, based on summarizing the previous work, we make a prospect to the future research direction, key challenges, and possible solutions in this field.

The emission color is a crucial parameter to evaluate the performances of luminescent materials, thus seeking out the effective control method for illuminating color is an important issue. To further explore the relationship between emission colors and structure of aggregation-induced emission (AIE)-active phosphors, cationic Ir(III) complexes comprising the same ancillary ligand but different 1-phenyl-1H-pyrazole derivatives as cyclometalated ligands, were designed and synthesized. The experimental results show that all complexes exhibit outstanding AIE characters and their emission colors can be adjusted by simply changing their cyclometalated ligands. However, different from previous strategy, modifying main ligands only changes the energy level of lowest unoccupied molecular orbital rather than that of highest occupied molecular orbital. Combining this result and our reported approach, a strong blue-emitting AIE-active Ir(III) complex is successfully constructed. In addition, we observed that all complexes upon mechanical grinding exhibit remarkable and reversible mechanochromic luminescence behavior.

Restricted by the energy-gap law and π-π stacking, developing highly efficient red emitting materials and corresponding organic light-emitting diodes (OLEDs) having the emission over 600 nm is a formidable challenge. Three red emitters, namely DPABz-TPA, 2DPABz-TPA, and 3DPABz-TPA, are developed bearing mono-, bis-, and tri-[2,1,3]benzothiadiazole (Bz) substituted triphenylamine (TPA) as the emissive core and bulky diphenylamine (DPA) as the steric protection units. All compounds display strong red emission with peaks at 645 nm and high efficiency up to 38%. Compared with reference molecule DPABz-TPA, both 2DPABz-TPA and 3DPABz-TPA exhibit higher radiative transition rate and thermal stability. The OLEDs based on 2DPABz-TPA and 3DPABz-TPA thus show superior EL efficiencies of the maximum current efficiency of 2.5 and 2.4 cd A−1, and external quantum efficiency of 2.9% and 3.2% compared with those of DPABz-TPA (1.9 cd A−1 and 2.1%). More importantly, the efficiency roll-off of OLED based on sterically protected 3DPABz-TPA obviously decreases owing to limited intermolecular packing. These results indicate that the strategy combined multiple donor-acceptor units and steric hindrance effect is favorable for constructing robust red emitters for efficient OLEDs.

Light-emitting electrochemical cells (LECs) have the advantages of simple structure, low driving voltage, and low packaging requirements. However, due to the different mobility of electrons and holes in emission layer, exciton quenching is inevitable caused by carrier imbalance. In this work, a red light cationic Ir(Ⅲ) complexes [Ir(tBuPBI)2(qibi)]PF6 (R) was used as the luminescent materials for the LECs, and we use the doping of MoOx into poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) layer to lower the energy barrier between complexes R and anode. In combination with the introduction of Al/LiF composite cathode, the carrier injection efficiency of the LECs is significantly improved, leading to the enhanced balance of carrier injection. In particular, high electron injection efficiency would significantly contribute to the device improvement based on the complexes with hole-preferred transporting characteristic. With enhanced carrier injection, the recombination region of the carrier is located near the center of emission layer, and the exciton quenching near the electrode will be significantly alleviated. The maximum external quantum efficiency of the LEC device is as high as 11.77%, which is 1.3 time that of the standard device. The half-lifetime of the device is 690 min, which is about 1.37 times of that of the standard device.