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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]

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]

Ideal hole transporting polymers used in quantum dot (QD) light‐emitting diodes (QLEDs) should possess the features such as high conductivities and stabilized highest occupied molecular orbitals (HOMOs). Herein, an efficient polymer (named CNPr‐TFB) is achieved by rationally adding a relatively weak electron‐withdrawing group (2‐cyanopropan‐2‐yl, CNPr) on a TFB like hole transporting polymer. CNPr‐TFB exhibits a superior hole conductivity and much more stabilized HOMO in comparison with TFB. Therefore, much more holes are delivered into the QD emissive layers and a balanced recombination of electron and hole in the QLEDs is achieved. The external quantum efficiencies of the red, green, blue, and white QLEDs made by CNPr‐TFB as the hole transporting layer (HTL) are 20.7%, 16.6%, 11.3%, and 15.0%, respectively, which are increased by 1.4–2.3 times in comparison with those of devices based on the commonly used TFB HTL. Meanwhile, the CNPr‐TFB‐based QLEDs also exhibit longer operation lifetimes than those of devices using the TFB HTL. These results confirm that CNPr‐TFB with the features of high conductivity and stabilized HOMO can be an excellent HTL material for the QLED applications [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]

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]

[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]

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]

• •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]

• 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]

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]

Highly efficient phosphors are critical in solution-processed organic light-emitting devices (OLEDs). Multinuclear Ir(III) complexes containing more than one metal center have showed great potential in fabricating high performance OLEDs, yet the electroluminescent (EL) properties of multinuclear Pt(II) complexes are rarely studied. In this work, two neutral trinuclear Pt(II) complexes are synthesized based on the triphenylamine core bearing three bidentate ligand arms. Both the yellow emitter (PyTPt) and deep-red emitter (IqTPt) exhibit improved photoluminescent quantum yields (PLQYs) compared with their corresponding mononuclear Pt(II) complexes. Furthermore, the PLQYs of PyTPt and IqTPt doped films are increased to 0.63 and 0.47, respectively. The solution-processed pure yellow-emitting device based on PyTPt achieves impressively high external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 16.92%, 56.74 cd/A and 29.09 lm W−1, respectively, which are among the best performance reported for the OLEDs employing multinuclear Pt(II) complexes. The solution-processed device based on IqTPt shows pure red emission with the peak EQE approaching 9.0%. Both PyTPt and IqTPt display much higher EL efficiencies than their corresponding mononuclear Pt(II) complexes. This work demonstrates that it is an attritive strategy to develop multinuclear Pt(II) complexes for high-performance OLEDs. Image 1 • Efficient trinuclear Pt(II) complexes were developed using the triphenylamine core. • Solution-processed yellow OLED showed a peak EQE of 16.92%. • Solution-processed deep-red OLED showed a peak EQE of 8.91% with CIE (0.66, 0.29). [ABSTRACT FROM AUTHOR]

Employing complimentary color phosphorescent emitters of the well-known FIrpic and new unsymmetrical orange emitter Ir-POB with 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety, solution-processed white organic lighting-emitting diodes (WOLEDs) had been fabricated to cope with the variation of EL spectra at different working voltage through excitation of both FIrpic and Ir-POB with the same mechanism in the device. Through constructing a thin exciton formation zone by the energy level layout between host 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA) and 1,3,5-tris-(N -(phenyl)-benzimidazole)-benzene (TPBi), both FIrpic and Ir-POB in the single emission layer can be excited by energy-transfer mechanism to bring stable white EL spectra in wide range of driving voltages with small CIE coordinate variation of Δx = 0.0044 and Δy = 0.0197. Furthermore, in order to overcome the disadvantage associated with energy-transfer mechanism, both FIrpic and Ir-POB have been excited by direct charge-trapping mechanism in WOLEDs by judiciously controlling the energy level layout between phosphorescent emitters and co-hosts polyvinyl carbazole (PVK) and 1,3-bis(5-(4-(tert -butyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene (OXD-7). The concerned WOLEDs not only maintain stable white EL in even wider driving voltage rang with CIE coordinate variation of Δx = 0.0078 and Δy = 0.0053, but also furnish much higher EL efficiencies of maximum external quantum efficiency (η ext) of 22.4%, a maximum current efficiency (η L) of 58.4 cd A−1 and a maximum power efficiency (η P) of 41.3 lm W−1. Hence, by unifying excitation mechanism of the phosphorescent emitters, optimized trade-off between white EL stability and high EL efficiencies have been successfully achieved. Definitely, these results can provide crucial information for developing WOLEDs with high performances. Image 1 • Stable white EL has been achieved by unifying excitation mechanism of the phosphorescent emitters. • Functional orange phosphorescent emitter with 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety has been employed for WOLEDs. • Optimized trade-off between stable white EL spectra and efficiencies has been fulfilled in solution-process WOLEDs. [ABSTRACT FROM AUTHOR]