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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]

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]

Abstract: Although phosphorescent and thermally activated delayed fluorescence (TADF) emitters can break through the spin statistics rules and achieve nearly 100% radiative exciton production (ηr), the swift efficiency roll‐off as luminance increases due to the accumulation of lowest triplet excited states with relatively long lifetime is the fatal bottleneck for their lighting application. How to achieve high ηr and low efficiency roll‐off simultaneously is still a challenge. To address this issue, two metal‐free organic molecules are reported with a highly twisted donor–bianthracene–acceptor structure involving high‐lying twisted intramolecular charge transfer (TICT) intermediate excited states, by which electroluminescent (EL) devices with both high ηr and extremely low efficiency roll‐off could be realized. Significant low efficiency roll‐off is achieved with about 99.1% of the maximum external quantum efficiency (EQE) maintained even at a high current density of 100 mA cm−2, corresponding to luminance of 23615 cd m−2, along with maximum EQE of 7.13% (ηr of 64.82%) in a doped green EL device with 9‐(4‐{10′‐[4‐(4,6‐diphenyl‐[1,3,5]triazin‐2‐yl)‐phenyl]‐[9,9′]bianthracenyl‐10‐yl}‐phenyl)‐9H‐carbazole as a host. The state‐of‐the‐art low efficiency roll‐off and enhanced ηr would be attributed to spin mixing of high‐lying TICT singlet and triplet intermediate excited states, proving the great potential of such a host design strategy for their practical lighting application. [ABSTRACT FROM AUTHOR]

Functional PtII ppy-type complexes (ppy = 2-phenylpyridine anion) with pyridine and chloride monodentate ligands are prepared, which show high electroluminescence efficiencies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Near-ultraviolet fluorescence with atypical planar structures. • Atypical planar structure can promote the emission blue-shift. • The enhancing rigidity of molecule can obtain high PLQY. • TPhPO moiety can reduce the LUMO energy level to bring near-ultraviolet emission. • Doped device of DPhPO-Ad achieved the highest maximum η ext of 4.58%. In this work, three D-A-locked near-ultraviolet (NUV) emitters (DPhPO-Oz , DPhPO-Ad and DPhPO-Tz) with atypical planar structures were synthesized by an intramolecular-locked of donor and acceptor (D and A) units. They adopt triphenylphosphine oxide (TPhPO) moiety as accepter, which can improve the electron injection and transportation, reduce the LUMO energy level to widen the bandgap and limit the emission red-shift. By locking the D and A units got D-A-locked emitters with atypical planar structure. This atypical planar structure can increase molecular rigidity and reduce the non-radiative decay of the D-A-locked emitters. It also can increase the PLQY and decrease the intermolecular π–π stacking. The highest PLQY of the D-A-locked emitters is 0.64. Due to their atypical planar structure, all of the three emitters show blue-shifted emission and narrower FHWM with the Commission Internationale de L'Eclairage (CIE y) ≤ 0.03 in toluene solution. In order to further investigate the effect of the atypical planar configurations of the molecules on their emissions. Three additional d -locked emitters (TPhPO-Oz , TPhPO-Ad and TPhPO-Tz) with distinct D-A structures were synthesized. Although the d -locked emitters can also show near-ultraviolet emission with narrow FHWM in toluene, they still exhibit red-shift and wider FHWM in their emission spectra with respect to the D-A-locked emitters. These results indicate that the shorter emission wavelength in the D-A-locked emitters with narrow FHWM should be due to their atypical planar structure. As the above consequence, the NUV organic light-emitting diodes based on DPhPO-Ad can achieve forward-viewing maximum external quantum efficiency (η ext) of 4.58 % with electroluminescence (EL) at 404 nm, CIE y coordinate at 0.05 and narrow FHWM (54 nm). [ABSTRACT FROM AUTHOR]

Phosphorescent dendrimers together with dendritic host materials have inherent advantages in achieving highly efficient phosphorescent organic light-emitting diodes (PHOLEDs) with low-cost, solution-processed device fabrication. Recently, much research effort has been devoted to developing these dendritic materials in the field of electroluminescence (EL). In this Focus Review, the major advances in this line of research are summarized and discussed. The crucial roles played by these dendritic organic electronic materials in coping with the key issues in the field of PHOLEDs have been specially emphasized. These include alleviating the triplet-triplet annihilation effect through the site-isolation effect associated with the dendritic structures, promoting charge-carrier injection/transporting ability and ambipolar properties through functionalized dendrons, fulfilling simple PHOLEDs with high EL efficiencies, obtaining self-hosting phosphorescent emitters, and avoiding undesired energy transfer process from phosphorescent cores to the dendrons. In addition, the future perspectives and ongoing challenges of this research frontier are also highlighted. [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]

A series of novel red phosphorescent polymers is successfully developed through Suzuki cross-coupling among ambipolar units, functionalized IrIII phosphorescent blocks, and fluorene-based silane moieties. The photophysical and electrochemical investigations indicate not only highly efficient energy-transfer from the organic segments to the phosphorescent units in the polymer backbone but also the ambipolar character of the copolymers. Benefiting from all these merits, the phosphorescent polymers can furnish organic light-emitting diodes (OLEDs) with exceptional high electroluminescent (EL) efficiencies with a current efficiency ( ηL) of 8.31 cd A−1, external quantum efficiency ( ηext) of 16.07%, and power efficiency ( ηP) of 2.95 lm W−1, representing the state-of-the-art electroluminescent performances ever achieved by red phosphorescent polymers. This work here might represent a new pathway to design and synthesize highly efficient phosphorescent polymers. [ABSTRACT FROM AUTHOR]

In this research, we have developed a series of PtII(C^N)(N-donor ligand)Cl-type phosphorescent complexes with the four-coordinate organoboron unit in the C^N ligand. Through shifting the coordinating position of the Pt(II) center from phenyl ring to pyridyl ring of the 2-phenylpyridine-type (ppy-type) four-coordinate organoboron unit, the variation of >50 nm in charge-transfer (CT) absorption band and >40 nm in phosphorescent wavelength can be observed in the synthesized PtII(C^N)(N-donor ligand)Cl-type complexes, indicating effective tuning of their photophysical properties incurred by the four-coordinate organoboron unit. In addition, based on the cyclic voltammetry result, obvious variation of electron density on the Pt(II) center of these PtII(C^N)(N-donor ligand)Cl-type phosphorescent complexes can also be observed. Critically, these PtII(C^N)(N-donor ligand)Cl-type complexes with the ppy-type four-coordinate organoboron unit can exhibit aggregation enhanced phosphorescent emission (AEPE) behavior. It seems that the hydrogen bonding among the N-donor ligands and water molecules can affect their AEPE response greatly, representing a new way to tune the AEPE behavior in the PtII(C^N)(N-donor ligand)Cl-type complexes. In the solution-processed organic light-emitting diodes (OLEDs), peak electroluminescent (EL) efficiencies of 15.3%, 10.3 cd A−1 and 9.8 lm W−1 have been achieved with EL at ca. 648 nm. These impressive results have provided key information for tuning optoelectronic properties of the PtII(C^N)(N-donor ligand)Cl-type complexes by the four-coordinate organoboron unit and N-donor ligand. Optoelectronic properties and AEPE behavior tuned by hydrogen bonding of the PtII(C^N)(N-donor ligand)Cl-type complexes with the four-coordinate organoboron unit. [Display omitted] • Pt(II) complexes with four-coordinate organoboron unit showing aggregation enhanced phosphorescent emission (AEPE) behavior. • Tuning AEPE behavior of Pt(II) complexes through hydrogen bonding interaction. • High electroluminescent efficiencies achieved in deep-red solution-processed OLEDs with AEPE emitter. [ABSTRACT FROM AUTHOR]

• •4-Position substitution of dibenzo[ b,d ]thiophene- S,S -dioxide/dibenzo[ b,d ]thiophene. • •Ir(III) complexes with dibenzo[ b,d ]thiophene- S,S -dioxide/dibenzo[ b,d ]thiophene unit. • •High efficient solution-processed OLEDs based on unsymmetric Ir(III) complexes. Through attaching pyridyl ring to 4-position of dibenzo[ b,d ]thiophene- S,S -dioxide and dibenzo[ b,d ]thiophene, two ppy-type ligands have been developed. With the obtained ligands in one-pot reaction, three Ir(III) complexes have been synthesized as symmetric Ir-1 with two dibenzo[ b,d ]thiophene- S,S -dioxide units, unsymmetric Ir-2 with both dibenzo[ b,d ]thiophene- S,S -dioxide and dibenzo[ b,d ]thiophene units and symmetric Ir-3 with two dibenzo[ b,d ]thiophene units. Photophysical results show that their phosphorescent wavelengths fall in the order of Ir-2 (585 nm) ˃ Ir-1 (567 nm) ˃ Ir-3 (543 nm) in solution and their phosphorescent quantum yields (Φ p) fall in the same order with ca. 0.83 for Ir-2 , 0.68 for Ir-1 and 0.53 for Ir-3 , indicating the advantage of constructing unsymmetric Ir(III) complexes. Solution-processed OLEDs based on the unsymmetric complex Ir-2 can show the highest electroluminescent (EL) efficiencies with the external quantum efficiency (η ext) of 16.6%, a maximum current efficiency (η L) of 51.1 cd A −1 and a maximum power efficiency (η P) of 38.7 lm W −1, indicating its great potential in the EL field. These encouraging results can provide critical information for developing highly efficient phosphorescent emitters based on dibenzo[ b,d ]thiophene- S,S -dioxide and dibenzo[ b,d ]thiophene groups. [Display omitted] [ABSTRACT FROM AUTHOR]

Three organic ligands with 9-phenyl-9-phosphafluorene oxide (PhFlPO) group have been synthesized via successive nucleophilic aromatic substitution (S N Ar) reactions between dibenzothiophene dioxides and PhPH 2 -KOH under mild reaction conditions at room temperature. In this way, the novel PhFlPO-type organic ligands can be easily obtained without either highly sensitive Grignard or organolithium reagents of noble metal catalysts. Using these PhFlPO-type organic ligands, cyclometalated Ir(III) phosphorescent complexes with PhFlPO groups have been developed through well-accepted two-step strategy. To the best of our knowledge, these complexes represent the unprecedented examples of symmetric cyclometalated Ir(III) phosphorescent complexes bearing PhFlPO group. It has been found that electron-density on the coordinated carbon atom in the PhFlPO unit can exert a significant influence on the metal-to-ligand charge transfer transition (MLCT) processes and phosphorescent emission behavior of these cyclometalated Ir(III) phosphorescent complexes. In addition, the electroluminescent potential of these new cyclometalated Ir(III) phosphorescent complexes with PhFlPO groups has been characterized in solution-processed organic light-emitting diodes (OLEDs). They can show very impressively high external quantum efficiency (η ext), current efficiency (η L) and power efficiency (η P) of 20.0%, 71.7 cd A−1 and 56.1 lm W−1, respectively. These encouraging research results can furnish critical information for developing new PhFlPO-based Ir(III) phosphorescent emitters. Phosphorescent Ir(III) complexes with 9-Phenyl-9-phosphafluorene oxide organic ligands for highly efficient solution-processed OLEDs. [Display omitted] • Synthesis of ligands with 9-phenyl-9-phosphafluorene oxide group by successive nucleophilic aromatic substitution reactions. • Organic ligands with pyridyl group substituted on different position on the 9-phenyl-9-phosphafluorene oxide unit. • Symmetric Ir(III) phosphorescent complexes with 9-phenyl-9-phosphafluorene oxide group showing high EL efficiencies. [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]

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]