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Metal-TADF (thermally activated delayed fluorescence) emitters hold promise in the development of next generation light-emitting materials for displaya nd lighting applications,examples of which are,however,largely confined to Cu I and recently Au I ,A g I ,a nd Au III emitters.H erein is described the design strategy for an unprecedented type of metal-TADF emitter based on inexpensive tungsten metal chelated with Schiff base ligand that exhibit high emission quantum yields of up to 56 %insolutions and 84 %inthin-film (5 wt %i n1 ,3-bis(N-carbazolyl)benzene,m CP) at room temperature.F emtosecond time-resolved emission (fs-TRE) spectroscopya nd DFT calculations were undertaken to decipher the TADF properties.S olution-processed OLEDs fabricated with the W-TADF emitter demonstrated external quantum efficiency (EQE) and luminance of up to 15.6 %and 16890 cd m À2 ,r espectively.

Luminescent iridium(iii) porphyrin NHC complexes are efficient singlet oxygen generators and antitumor agents.

The realization of high-efficiency solution-processed organic light-emitting diodes (OLEDs) using phosphorescent tetradentate Pt­(II) emitters and bipolar organic hosts is demonstrated in this work. To investigate the effect of organic host on the platinum dopant, the performances of solution-processed Pt-OLEDs with various combinations between four tetradentate Pt­(II) emitters, including two newly developed tetra-Pt-S2 and tetra-Pt-S3 and three bipolar organic hosts m-TPAPy, o-TPAPy, and o-CzPy, have been analyzed and compared. Among the tetradentate Pt­(II) complexes studied in this work, tetra-Pt-S3 exhibited the best electroluminescent performance attributable to its bulky molecular scaffold structure, high emission quantum yield, and good solubility in common organic solvents. High external quantum efficiencies (EQEs) of up to 22.4% were achieved in the solution-processed OLED with tetra-Pt-S3 emitter and m-TPAPy host at the dopant concentration of 4 wt %. At a high luminance of 1000 cd m–2, the EQE of this device decreased slightly to 21.0%.

Voltage‐dependent, color‐tunable organic light‐emitting diodes (OLEDs) are appealing tools that can be used for the visualization of electronic output signal of sensors. Nonetheless, the literature‐reported color‐tunable OLEDs that have a simple single‐cell device structure suffer from relatively low efficiency, pronounced efficiency roll‐off, color‐aging, and short operation lifetime, all of which limit their practical applications. Here, a novel co‐host‐in‐double‐emissive‐layer (CHIDEL) device, designed to enhance the performance of color‐tunable OLEDs with the use of a single tetradentate Pt[O^N^C^N] emitter, is described. When Pt‐X‐2 is used as a single emitter in an optimized CHIDEL device, a white OLED with tunable Commission International de I'Eclairage (CIE) coordinates from (0.47, 0.44) at 3 V to (0.36, 0.48) at 11 V, a high color rendering index of 82, and high external quantum efficiency (EQE) of up to 20.75% can be achieved. By using Pt‐X‐4 as a single emitter, the voltage‐dependent color‐tunable CHIDEL device, with CIE coordinates shifted from (0.56, 0.43) at 3 V to (0.42, 0.55) at 11 V, demonstrates a high luminance of beyond 90 000 cd m−2 and a high EQE of 23.23% at a luminance of 1300 cd m−2. A long‐lifetime time to 90% of the initial luminance (LT90) of almost 20 000 h is demonstrated for the color‐tunable OLED with Pt‐X‐4 emitting dopant.

Acceleration of singlet-triplet intersystem crossings (ISC) is instrumental in bolstering triplet exciton harvesting of multi-resonance thermally activated delayed fluorescent (MR-TADF) emitters. This work describes a simple gold(I) coordination strategy to enhance the spin-orbit coupling of green and blue BN(O)-based MR-TADF emitters, which results in a notable increase in rate constants of the spectroscopically observed ISC process to 3 × 10 9 s À 1 with nearly unitary ISC quantum yields. Accordingly, the resultant thermally-stable Au I emitters attained large values of delayed fluorescence radiative rate constant up to 1.3 × 10 5 /1.7 × 10 5 s À 1 in THF/PMMA film while preserving narrowband emissions (FWHM = 30-37 nm) and high emission quantum yields (ca. 0.9). The vapor-deposited ultrapure-green OLEDs fabricated with these Au I emitters delivered high luminance of up to 2.53 × 10 5 cd m À 2 as well as external quantum efficiencies of up to 30.3 % with roll-offs as low as 0.8 % and long device lifetimes (LT 60 ) of 1210 h at 1000 cd m À 2 .

Double-host OLEDs with three bulky tetradentate [Pt(O^N^C^N)] emitters achieve a high EQEmax of >20%, a PEmax of >100 lm W−1, and low efficiency roll-off within 10 000 cd m−2.

A critical step in advancing the practical application of copper-based organic light-emitting diodes (OLEDs) is to bridge the large gap between device efficiency and operational stability at practical luminance. Described is a panel of air-and thermally stable two-coordinate Cu I emitters featuring bulky pyrazine-(PzIPr) or pyridine-fused N-heterocyclic carbene (PyIPr*) and carbazole (Cz) ligands with enhanced amide-Cu-carbene bonding interactions. These Cu I emitters display thermally activated delayed fluorescence (TADF) from the 1 LL'CT(Cz!PzIPr/PyIPr*) excited states across the blue to red regions with exceptional radiative rate constants of 1.1-2.2 × 10 6 s À 1 . Vapourdeposited OLEDs based on these Cu I emitters showed excellent external quantum efficiencies and luminance up to 23.6 % and 222 200 cd m À 2 , respectively, alongside record device lifetimes (LT 90 ) up to 1300 h at 1000 cd m À 2 under our laboratory conditions, highlighting the practicality of the Cu I -TADF emitters.