Highly efficient thermally activated delayed fluorescence (TADF) molecules are in urgent demand for solid‐state lighting and full‐color displays. Here, the design and synthesis of three triarylamine‐pyridine‐carbonitrile‐based TADF compounds, TPAPPC, TPAmPPC, and tTPAmPPC, are shown. They exhibit excellent photoluminescence quantum yields of 79−100% with small ΔEST values, fast reverse intersystem crossing (RISC), and high horizontal dipole ratios (Θ// = 86−88%) in the thin films leading to the enhancement of device light outcoupling. Consequently, a green organic light‐emitting diode (OLED) based on TPAmPPC shows a high average external quantum efficiency of 38.8 ± 0.6%, a current efficiency of 130.1 ± 2.1 cd A–1, and a power efficiency of 136.3 ± 2.2 lm W–1. The highest device efficiency of 39.8% appears to be record‐breaking among TADF‐based OLEDs to date. In addition, the TPAmPPC‐based device shows superior operation lifetime and high‐temperature resistance. It is worth noting that the TPA‐PPC‐based materials have excellent optical properties and the potential for making them strong candidates for TADF practical application.

Near‐infrared organic light‐emitting diodes (NIR OLEDs) enable many unique applications ranging from night‐vision displays and photodynamic therapies. However, the development of efficient NIR OLEDs with a low efficiency roll‐off is still challenging. Here, a series of new heteroleptic Pt(II) complexes (1–4) flanked by both pyridyl pyrimidinate and functional azolate chelates are synthesized. The reduced ππ* energy gap of the pyridyl pyrimidinate chelate, and strong intermolecular interaction and high crystallinity in vacuum‐deposited thin films engender strong intermolecular charge transfer transition including metal–metal‐to‐ligand charge transfer; thereby, exhibiting efficient photoluminescence within 776–832 nm and short radiative lifetimes of 0.52–0.79 µs. Consequently, nondoped NIR‐emitting OLEDs based on these Pt(II) complexes are fabricated, to which Pt(II) complexes 2 and 4 give record high maximum external quantum efficiency of 10.61% at 794 nm and 9.58% at 803 nm, respectively. Moreover, low efficiency roll‐off is also observed, among which the device efficiencies of 2 and 4 are at least four times higher than that of the best NIR‐emitting OLEDs recorded at current density of 100 mA cm−2.

Up to now, the most efficient blue phosphorescent organic lightemitting diode (PhOLED) was achieved with a maximum external quantum efficiency (η ext ) of 34.1% by using an exciplex cohost. It still remains a challenge to obtain such high efficiencies using a single-host matrix. In this work, a highly efficient sky-blue PhOLED is successfully fabricated using a newly developed bipolar host material, namely 5-(2-(9H-[3,9′-bicarbazol]-9-yl)phenyl)nicotinonitrile (o-PyCNBCz), which realizes a η ext of 29.4% at a practical luminance of 100 cd m −2 and a maximum η ext of 34.6% (at 23 cd m −2 ). The present device is characterized by simple configuration with a single host and single emitting layer. o-PyCNBCz also reveals high efficiency of 28.2% (94.8 cd A −1 ) when used as the host for green PhOLED. Under identical conditions, o-PyCNBCz always outperforms than its isomer 3-PyCNBCz (5-(9-phenyl-9H-[3,9′-bicarbazol]-6-yl)nicotinonitrile) in terms of more balanced charge transportation, higher photoluminescent quantum yields of over 90%, and higher horizontal orientation ratio of the emitting dipole for the host-dopant films, which finally lead to its superior performance in PhOLEDs. It is observed that all these merits of o-PyCNBCz benefit from its ortho-linking style of carbazole (p-type unit) and cyanopyridine (n-type unit) on the phenylene bridge and the resultant molecular conformation.

For the application of organic light-emitting diodes (OLEDs) in lighting and panels, the basic requirement is to include a full spectrum color range. Compared with the development of blue and green luminophores in thermally activated delayed fluorescence (TADF) technology, the progress of orange-to-red materials is slow and needs further investigation. In this study, three diboron compound-based materials, dPhADBA, dmAcDBA, and SpAcDBA, were designed and synthesized by nucleophilic arylation of three amine donors on 9,10-diboraanthracene (DBA) in a two-step reaction. With increasing electron-donating ability, they show orange-to-red emission with TADF characteristics. The electroluminescence of these diboron compounds exhibits emissions λ max at 613, 583, and 567 nm for dPhADBA, dmAcDBA, and SpAcDBA, respectively. It is noteworthy that the rod-like D-A-D structures can achieve high horizontal ratios (84−86%) and outstanding device performance for orange-to-red TADF OLEDs: the highest external quantum efficiencies for dPhADBA, dmAcDBA, and SpAcDBA are 11.1 ± 0.5, 24.9 ± 0.5, and 30.0 ± 0.8%, respectively. Therefore, these diboron-based molecules offer a promising avenue for the design of orange-to-red TADF emitters and the development of highly efficient orange-to-red OLEDs.

Pt(II) metal complexes are known to exhibit strong solid-state aggregation and are promising for realization of efficient emission in fabrication of organic light emitting diodes (OLED) with nondoped emitter layer. Four pyrimidine-pyrazolate based chelates, together with four isomeric Pt(II) metal complexes, namely: [Pt(pm2z) 2 ], [Pt(tpm2z) 2 ], [Pt(pm4z) 2 ], and [Pt(tpm4z) 2 ], are isolated and systematically investigated for their structure-property relationships for practical OLED applications. Detailed single molecular and aggregated structures are revealed by photophysical and mechanochromic measurements, grazing-incidence X-ray diffraction, and theoretical approaches. These results suggest that these Pt(II) emitters pack like a deck of playing cards under vacuum deposition, and their emission energy is not only affected by the single molecular designs, but notably influenced by their intermolecular packing interaction, i.e., Pt···Pt separations that are arranged in the order: [Pt(tpm4z) 2 ] > [Pt(pm4z) 2 ] > [Pt(tpm2z) 2 ] > [Pt(pm2z) 2 ]. Nondoped OLED with emission ranging from green to red are prepared, to which the best performances are recorded for [Pt(tpm2z) 2 ], giving maximum external quantum efficiency (EQE) of 27.5% at 10 3 cd m −2 , maximum luminance of 2.5 × 10 5 cd m −2 at 17 V, and with stable CIE x,y of (0.56, 0.44).computers, notepads, and cell phones. Their efficiencies have been improved during the past two decades using suitable third-row transition-metal phosphors as emitters. Among these emitters, Pt(II) metal complexes have been attracting intensive studies owing to their higher stability and intense luminescence at room temperature (RT). [1] However, in contrast to the Ir(III) emitters with d 6 -electronic configuration and octahedral coordination structure, [2] the Pt(II) emitters possesses distinctive d 8 -configuration and square planar geometry, which induced a greater tendency in forming π-π-stacking interaction between adjacent molecules in solid state. As for application, this aggregation is capable of tuning emission to lower energy region of the visible spectra and even further into the near-infrared (NIR), which allows versatile prospective in applications for this class of emitters.Many aggregated Pt(II) complexes have been synthesized, for which their structures can be differentiated into two classes. One is best represented by those bearing a linear Pt n architecture and with Pt···Pt distance of less than 3.4 Å; the latter is the sum of van del wall radii of

Two isomeric host materials (Sy and Asy) comprising carbazole (donor) and CN-substituted pyrimidine (acceptor) were synthesized, characterized, and utilized as host materials for green and blue thermally activated delayed fluorescence (TADF) organic light emitting diodes (OLEDs). Both molecules have high triplet energy and small energy difference between singlet and triplet states, leading to feasible TADF. The different linking topologies of carbazole and CN groups on the pyrimidine core provide distinct photophysical properties and molecular packing manners, which further influence the efficiency as they served as hosts in TADF OLEDs. As compared to Asy-based cases, the Sy-hosted TADF OLED device gave higher maximum external quantum efficiencies (EQE) of 24.0% (vs 22.5%) for green (4CzIPN as a dopant) and 20.4% (vs 15.0%) for blue (2CzTPN as a dopant) and low efficiency roll-off. The high horizontal dipole ratio (Θ ≈ 88%) for both emitters dispersed in Sy and Asy hosts accounts for the high device efficiency. A clear molecular structure-physical property-device performance relationship has been established to highlight the importance of symmetrical structure in TADF host material design.

TADF molecules with various dipyridylpyrimidine acceptors are synthesized and exhibited a max. EQE of 14.1% for a non-doped OLED device architecture.

Both the monoanionic dicarbene pincer chelate and dianionic azole-pyridine-carbazole cyclometalate were successfully employed in the preparation of respective bis-tridentate Ir(III) metal complexes (Cz6 ‒ 9) in moderate yields. Tuning of...