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Highly efficient near‐infrared (NIR) emitters have significant applications in medical and optoelectronic fields, but the development stays a great challenge due to the energy gap law. Here, we report two NIR phosphorescent Ir(III) complexes which display emission peaks around 730 nm with a narrow full width at half maximum of only 43 nm. Therefore, pure NIR luminescence can be obtained without having a very long emission wavelength, thus alleviating the restriction of the energy gap law, and obtaining impressively high photoluminescence quantum yield up to 0.70. More importantly, the pure NIR organic light‐emitting diode (OLED) fabricated by the solution‐processed mothed shows outstanding device performance with the highest external quantum efficiency of 16.43 %, which sets a new record for solution‐processed NIR‐OLEDs based on different emitters. This work sheds light on the development of Ir(III) complexes with narrowband emissions as highly efficient pure NIR‐emitters. [ABSTRACT FROM AUTHOR]

Highly efficient near‐infrared (NIR) emitters have significant applications in medical and optoelectronic fields, but the development stays a great challenge due to the energy gap law. Here, we report two NIR phosphorescent Ir(III) complexes which display emission peaks around 730 nm with a narrow full width at half maximum of only 43 nm. Therefore, pure NIR luminescence can be obtained without having a very long emission wavelength, thus alleviating the restriction of the energy gap law, and obtaining impressively high photoluminescence quantum yield up to 0.70. More importantly, the pure NIR organic light‐emitting diode (OLED) fabricated by the solution‐processed mothed shows outstanding device performance with the highest external quantum efficiency of 16.43 %, which sets a new record for solution‐processed NIR‐OLEDs based on different emitters. This work sheds light on the development of Ir(III) complexes with narrowband emissions as highly efficient pure NIR‐emitters. [ABSTRACT FROM AUTHOR]

Aggregation‐induced emission (AIE)‐active phosphorescent emitters have intrinsic advantages in time‐gated imaging/sensing and improving the electroluminescent efficiencies of organic light‐emitting devices (OLEDs). However, compared with the very prosperous and fruitful developments of AIE‐active fluorescent emitters and related working mechanisms, the progresses on AIE‐active phosphorescent emitters and associated AIE mechanisms are still relatively slow. Herein, the AIE properties of a series of phosphorescent Pt(II) complexes with two monodentate ligands are reported. Compared with the conventional rigid Pt(II) complexes bearing two bidentate ligands or one tri‐/tetradentate ligand, the incorporation of two monodentate ligands provides the resulting Pt(II) complexes with more room to deform their coordination skeletons from the square‐planar geometry in the ground state to the quasi‐tetrahedral configuration in the excited state, causing poor solution emissions. In doped films and aggregate states, intense emissions are observed for these Pt(II) complexes. The as‐fabricated solution‐processed OLED exhibits an impressively high external quantum efficiency of 21.7%. This study provides an effective way to develop excellent AIE‐active phosphorescent emitters. [ABSTRACT FROM AUTHOR]

Phosphorescent organic light-emitting devices (OLEDs) have attracted increased attention from both academic and industrial communities due to their potential practical application in high-resolution full-color displays and energy-saving solid-state lightings. The performance of phosphorescent OLEDs is mainly limited by the phosphorescent transition metal complexes (such as iridium(iii), platinum(ii), gold(iii), ruthenium(ii), copper(i) and osmium(ii) complexes, etc.) which can play a crucial role in furnishing efficient energy transfer, balanced charge injection/transporting character and high quantum efficiency in the devices. It has been shown that functionalized main-group element (such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur and fluorine, etc.) moieties can be incorporated into phosphorescent emitters and their host materials to tune their triplet energies, frontier molecular orbital energies, charge injection/transporting behavior, photophysical properties and thermal stability and hence bring about highly efficient phosphorescent OLEDs. So, in this review, the recent advances in the phosphorescent emitters and their host materials functionalized with various main-group moieties will be introduced from the point of view of their structure–property relationship. The main emphasis lies on the important role played by the main-group element groups in addressing the key issues of both phosphorescent emitters and their host materials to fulfill high-performance phosphorescent OLEDs. [ABSTRACT FROM AUTHOR]

A series of tris-heteroleptic phosphorescent cyclometalated IrIII complexes with two different cyclometalating ligands and one ancillary ligand was synthesized. Through manipulation of the electronic features of individual cyclometalating ligands, not only the emission color and electrochemical properties of these IrIII complexes can be tuned, but also unique charge carrier injection and transport traits can be conferred to them. Owing to the enhanced electron injection/transport and ambipolar characters associated with these tris-heteroleptic structures, these IrIII emitters showed very impressive electroluminescent performance with a maximum external quantum efficiency of 20.20 %, luminance efficiency of 69.41 cdA-1 and power efficiency of 35.15 LmW-1. These results provide a new outlet to design and synthesize highly efficient electrophosphors for phosphorescent organic light-emitting diodes. [ABSTRACT FROM AUTHOR]

Simple trifunctional IrIII ppy-type asymmetric phosphorescent emitters with ambipolar character are reported, which afford highly efficient OLEDs. [ABSTRACT FROM AUTHOR]

The first example of phosphorescent I− ion sensors based on borylated PtII ppy-type phosphors (Hppy = 2-phenylpyridine) was reported, which shows good selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

Phosphorescent near‐infrared (NIR) organic light‐emitting devices (OLEDs) have drawn increasing attention for their promising applications in the fields such as photodynamic therapy and night‐vision readable displays. Here, three simple phosphorescent Pt(II) complexes are synthesized, and their intermolecular interactions are investigated in crystals and neat films by X‐ray single crystal diffraction and grazing‐incidence wide‐angle X‐ray scattering, respectively. The photophysical properties, molecular aggregation (including Pt–Pt interaction), molecular packing orientation, and electron transport ability are all influenced by the strong intermolecular hydrogen bonds. Consequently, the nondoped OLEDs based on tBu‐Pt and F‐Pt show electroluminescent emissions in NIR region with the highest external quantum efficiencies of 13.9% and 16.7%, respectively. [ABSTRACT FROM AUTHOR]

Color‐tuning for phosphorescent emitters in organic light‐emitting diodes (OLEDs) across the entire visible spectrum is prerequisite to fulfil flexible full‐color displays and white solid‐state lighting. Heteroleptic 2‐phenylpyridine‐type (ppy‐type) Ir(III) and Pt(II) complexes as phosphorescent emitters have been well exploited in the electroluminescence (EL) field due to their outstanding EL performance. Furthermore, the photophysical characters of these heteroleptic Ir(III) and Pt(II) complexes are generally dominated by the nature of cyclometalating ppy‐type ligands. Accordingly, either sophisticated modification or judicious combination of different cyclometalating ppy‐type ligands will provide a wonderful platform to tune their emission color. In this personal account, we put a special emphasis on our contributions to the novel color‐tuning strategies in these heteroleptic ppy‐type Ir(III) and Pt(II) complexes. In addition, afforded by our novel color‐tuning strategies, ambipolar character or enhanced electron injection/transport (EI/ET) features can be furnished to bring high EL performances. [ABSTRACT FROM AUTHOR]

A series of four-coordinated PtII(C^N)(N-donor ligand)Cl-type complexes have been synthesized through a combination of long-size C^N-type and N-donor ligands. In addition, by varying the coordinating site in the N-donor ligand, a distorted molecular configuration has been constructed in these complexes. Their photophysical features, aggregation-induced phosphorescence emission (AIPE) behaviors, electrochemical properties and electroluminescence (EL) performance have been investigated in detail. It has been found that their AIE behaviors can be enhanced by both employing long-size ligands, especially the N-donor ligand, and adopting a distorted molecular configuration, furnishing a high AIE factor (αAIE) of ca. 13.8. Critically, benefitting from their long-size C^N-type and N-donor ligands, these PtII(C^N)(N-donor ligand)Cl-type complexes can exhibit very sensitive AIE behaviors in a mixture of THF–H2O, indicated by their noticeable emission increase with a low H2O volumetric fraction (fw) of ca. 0.1 in their THF solution. In solution-processed organic light-emitting diodes (OLEDs), they can achieve a luminance of 6743 cd m−2 at 13.5 V, a maximum external quantum efficiency (ηext) of 13.8%, a maximum current efficiency (ηL) of 42.4 cd A−1 and a maximum power efficiency (ηP) of 34.4 lm W−1, respectively. Hence, this research can provide key information for developing phosphorescent complexes with a highly sensitive AIE response and impressive EL ability. [ABSTRACT FROM AUTHOR]

To date, it is still a great challenge to realize high optical power limiting (OPL) ability with excellent visible light transmittance at the same time for organic OPL materials. For example, the carbazole-based Pt(II) polyynes usually showed good visible light transmittance but weak OPL ability. In this work, we designed and synthesized two high performance OPL materials by introducing OPL-active metal alkynyl segments into the side chain of carbazole-based Pt(II) polyynes for the first time. Arranging metal alkynyl in side chains could effectively disrupt the π-conjugation between the polymer backbones and side chains, thus the developed polymers showed excellent visible light transmittance. In addition, with more OPL-active metal alkynyl groups in the side chain, the developed polymers were expected to show good OPL performance at the same time. To further improve the OPL performance, we utilized the triphenylamine and triarylboron groups to manipulate the involvement of the Pt(II) center in transition processes, which could effectively influence the intersystem crossing to enhance the population of triplet states. As a result, the Pt(II) polyyne CzTPA with the triphenylamine group linked to OPL-active metal alkynyl groups in side chains displayed the best OPL performance with the figure of merit σ ex /σ o of up to 7.17, which was much higher than that of state-of-the-art OPL material C 60. Therefore, this work demonstrates a promising strategy to develop high performance OPL materials possessing both strong OPL ability and impressively high visible light transmittance at the same time. [Display omitted] • Two Pt(II) polyynes were synthesized to show strong room temperature phosphorescence. • High transmittances in visible region was achieved duo to effective conjugation-breaker. • Triphenylamine- and triarylboron-based were linked to the sidechain to optimize the OPL properties. [ABSTRACT FROM AUTHOR]

Tris(cyclometalated) iridium(III) phosphorescent emitters with 2-phenylthiazole-type ligands have been designed and synthesized. Their photophysical properties, electrochemical behavior and electroluminescent (EL) performance can be influenced by introducing fluorine atoms to the phenyl moiety of the thiazole-based ligands. The phosphorescent emission maxima can be shifted from 546 nm to 517 nm by increasing the number of the fluorine atoms attached to the ligands of the iridium(III) complexes. Furthermore, the HOMO levels for these phosphorescent complexes exhibit a gradual decrease from -5.28 eV to -5.59 eV with the introduction of fluorine atoms. Owing to the character of their electronic structures, the phosphorescent emitters are preferentially excited by means of a host-guest energy-transfer process in the organic light-emitting diodes (OLEDs). Accordingly, their EL performance is strictly restricted by the triplet energy level difference between the phosphorescent dopant and the host materials. The thiazole-based cyclometalated iridium(III) triplet emitters can exhibit maximum EL efficiencies with ηext = 7.87 %, ηL = 23.62 cd A-1 and ηp = 13.46 lm W-1. [ABSTRACT FROM AUTHOR]

A series of (C^N)Pt(acac)-type complexes has been successfully synthesized with a benzo[b]furan, benzo[b]thiophene, benzo[b]selenophene, or benzo[b]tellurophene group in the benzoaryl-pyridine ligand. Using X-ray crystallography, the chemical structures of the complexes with benzo[b]selenophene and benzo[b]tellurophene groups have been clearly revealed. The photophysical, electrochemical, and electroluminescent (EL) behaviors of these (C^N)Pt(acac)-type complexes have been fully characterized. Furthermore, both time-dependent functional theory (TD-DFT) and natural transition orbital (NTO) theoretical results have been obtained to gain insight into the absorption and emission features. It has been shown that both the absorption bands with the lowest energy and the phosphorescence emission behaviors are dominated by the benzoaryl-pyridine cyclometalating ligand. Importantly, the effects of the group VIA atoms on the properties of these (C^N)Pt(acac)-type complexes have been revealed. Owing to the rareness of (C^N)Pt(acac)-type complexes with benzo[b]selenophene and benzo[b]tellurophene groups, their EL abilities have been characterized using solution-processed organic light-emitting diodes (OLEDs). The optimized red OLEDs with the complex bearing a benzo[b]selenophene unit show a maximum external quantum efficiency (ηext) of 6.3%, current efficiency (ηL) of 10.5 cd A−1, and power efficiency (ηP) of 9.1 lm W−1, while the EL device with the complex bearing a benzo[b]tellurophene unit can give deep-red emission at ca. 636 nm with ηext of 6.3%, ηL of 6.5 cd A−1, and ηP of 5.8 lm W−1. This research not only provides novel (C^N)Pt(acac)-type complexes, but also furnishes critical information regarding the photophysical and EL behavior of these new complexes. [ABSTRACT FROM AUTHOR]

A new 2-phenylpyridine-type (ppy-type) ligand with the dithieno[3,2-b:2′,3′-d]phosphole oxide (DTPO) group has been successfully synthesized. Based on this novel ligand, three cyclometalated iridium(III) complexes (P–Ir–P, P–Ir–T and P–Ir–C) are synthesized with symmetrical and unsymmetrical structures. Photophysical results reveal that these cyclometalated iridium(III) complexes can show weak near-infrared (NIR) phosphorescence emission with wavelengths of 739 nm for P–Ir–P, 750 nm for P–Ir–T and 746 nm for P–Ir–C. Importantly, transient absorption characterization shows that these cyclometalated iridium(III) complexes can exhibit strong excited state absorption in the range of ca. 520 to 700 nm, indicating their optical power limiting (OPL) potential in this wavelength range. Open-aperture Z-scan against a 532 nm laser shows their OPL ability in the order of P–Ir–P > P–Ir–C > P–Ir–T. Complex P–Ir–P shows an even better OPL ability than the state-of-the-art OPL material C60, indicating the important potential application of these cyclometalated iridium(III) complexes as new OPL materials. [ABSTRACT FROM AUTHOR]

• A three-ligand molecular framework for developing Pt(II) complex is proposed. • The crystal structures of new three-ligand Pt(II) complexes are clarified. • The effect of each ligand on the properties of the complex is carefully studied. • Solution-processed pure yellow OLED achieves a record EQE of 24.2%. Cyclometallated Pt(II) complexes are one of the most competitive light-emitting materials for fabricating high-performance OLEDs. The properties of cyclometallated Pt(II) complexes can be conveniently manipulated by altering the ligand structures. However, because of the typical design fashion which leads to Pt(II) complexes with one or two ligands, the conventional cyclometallated Pt(II) complexes always have a rigid planar structure and are prone to form close packing, resulting in a change in the emission spectrum and a decrease in the color purity. Besides, it is also relatively difficult or cumbersome to simultaneously introduce electron-withdrawing and electron-donating groups into one molecule to improve the balance of electron and hole injection/transport process. In this work, we propose a new molecular framework which consists of one bidentate ligand and two independent monodentate ligands. Based on this three-ligand molecular framework, nineteen Pt(II) complexes are synthesized to investigate the influence of each ligand on the emission as well as the charge injection/transport properties. Some of these three-ligand Pt(II) complexes display impressive aggregation-induced emission properties, high photoluminescent quantum yields and improved balance of hole and electron injection/transport ability. Consequently, solution-processed phosphorescent OLEDs exhibit very pure yellow emissions with a remarkably high external quantum efficiency (EQE) reaching up to 24.2%, which is the highest EQE reported for pure yellow OLEDs fabricated with the solution-processed method. This study proposes a new molecular framework, demonstrates its promising potential for developing high-performance electroluminescent materials and provides clear clues on how to engineer molecular structure for desired properties. [ABSTRACT FROM AUTHOR]

A series orange phosphorescent copolymers with platinum(II) polymetallayne-based backbone have been successfully prepared through Sonogashira cross-coupling among bicarbazole moieties, 2-(naphthalen-2-yl)pyridine-based Ir III phosphorescent units, and trans -[PtCl 2 (PBu 3 ) 2 ]. The photophysical investigations have indicated highly efficient energy-transfer from both the singlet and high energy triplet states from the polymetallayne segments to the phosphorescent units in the copolymer backbone due to the proper energy-level matching fulfilled by the 2-(naphthalen-2-yl)pyridine-type ligands in the Ir III phosphorescent units. Benefiting from these advantages, the phosphorescent polymers can furnish solution-processed phosphorescent OLEDs (PHOLEDs) with high EL efficiencies with current efficiency ( η L ) of 8.35 cd A −1 , external quantum efficiency ( η ext ) of 3.79% and power efficiency ( η P ) of 2.25 lm W −1 , representing the very decent electroluminescent performances ever achieved by the orange phosphorescent copolymers. This work herein might not only provides a further study about the novel phosphorescent copolymers with platinum(II) polymetallaynes as backbone, but also provide valuable information for the design and synthesis of highly efficient phosphorescent copolymers. [ABSTRACT FROM AUTHOR]

Two red-emitting IrIII(C^N) 2 (P-donor ligand)Cl-type complexes bearing C^N ligands with carbazole functional group have been successfully prepared with different P-donor ligands of triphenylphosphine and triethylphosphine, respectively. The investigation of their phosphorescent behavior in the mixture of THF and water to reveal their aggregation induced phosphorescent emission (AIPE) ability, which is also indicated by their much higher phosphorescent quantum yield (Φ P) in doped film than those in the dilute solution. Mainly, their AIPE are induced by the blocked stretching motion of aromatic segments in C^N ligand and restrained the deformation of their coordinating skeletons. The AIPE complexes can possess AIE factor (α AIE) of ca. 7.4. In addition, the carbazole group can effectively promote hole transporting ability of the concerned AIPE emitters, which can benefit their electroluminescent ability. Hence, the IrIII(C^N) 2 (P-donor ligand)Cl-type complexes can show decent EL efficiencies in the solution-processed red-emitting organic Light-emitting diodes (OLEDs) with a maximum external quantum efficiency (η ext) of 8.5%, a maximum current efficiency (η L) of 22.0 cd A−1 and a maximum power efficiency (η P) of 15.9 lm W−1. Furthermore, as long-wavelength emitter, solution-processed white OLEDs (WOLEDs) have been constructed based on the red-emitting AIPE IrIII(C^N) 2 (P-donor ligand)Cl-type complexes, which can play critical role in achieving stable white electroluminescent spectra at high luminescence. The concerned WOLEDs can show attractive EL efficiencies of 6.6%, 23.7 cd A−1 and 16.0 lm W−1. All these results can provide valuable information for developing new AIPE materials with high EL ability. [Display omitted] • AIPE-active IrIII(C^N)(P-donor ligand)Cl-type complexes were prepared with different phosphine ligands. • Solution-processed red-emitting OLED showed a peak CE of 22.0 cd A−1. • Solution-processed white OLED showed a peak CE of 24.8 cd A−1 with CIE (0.31, 0.38). [ABSTRACT FROM AUTHOR]

• Novel polymeric hosts adopting cardo-type backbones were developed using palladium-free catalyst. • The triplet energy-levels (E T s) of the novel polymeric hosts can cover the range from 1.92 to 2.83 eV. • Solution-processed blue, green and red OLEDs can show maximum EQE of 11.3%, 19.5% and 15.5%, respectively. A series of polymeric hosts with cardo-type backbone have been successfully developed with cheap palladium-free catalyst through controlling the special orientation of different monomers. By engineering the configuration of polymer backbones with different number and kind of the functional groups attached to the monomers, the triplet energy-levels (E T s) of these new polymeric hosts can be precisely controlled from 1.92 to 2.83 eV. Importantly, the functional groups on the monomers can afford improved and balanced charge carrier injection/transporting ability to these polymeric hosts. In addition, these polymeric hosts can show good thermal property with decomposition temperatures (T d) higher 410 °C and glass transition temperatures (T g) higher than 170 °C. Benefitting from all these advanced properties, solution-processed phosphorescent organic light-emitting devices (PhOLEDs) based on these polymeric hosts can show impressive electroluminescence (EL) performances. The optimized blue device B2 possesses a maximum luminance efficiency (η L) of 25.5 cd A−1, corresponding to a power efficiency (η P) of 19.9 lm W−1 and an external quantum efficiency (η ext) of 11.3%. The maximum η L , η P and η ext for the optimized green device G2 are 66.9 cd A−1, 62.8 lm W−1 and 19.5%, respectively, while EL efficiencies of the optimized red device R2 can reach 11.0 cd A−1, 9.4 lm W−1 and 15.5%. All of the promising EL data achieved by these polymeric hosts show their great potential application in developing high performance polymer-based OLEDs. [ABSTRACT FROM AUTHOR]