Chiral boron/nitrogen doped multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters are promising for highly efficient and color‐pure circularly polarized organic light‐emitting diodes (CP‐OLEDs). Herein, we report two pairs of MR‐TADF materials (Czp‐tBuCzB, Czp‐POAB) based on planar chiral paracyclophane with photoluminescence quantum yields of up to 98 %. The enantiomers showed symmetric circularly polarized photoluminescence spectra with dissymmetry factors |gPL| of up to 1.6×10−3 in doped films. Meanwhile, the sky‐blue CP‐OLEDs with (R/S)‐Czp‐tBuCzB showed an external quantum efficiency of 32.1 % with the narrowest full‐width at half‐maximum of 24 nm among the reported CP‐OLEDs, while the devices with (R/S)‐Czp‐POAB displayed the first nearly pure green CP electroluminescence with |gEL| factors at the 10−3 level. These results demonstrate the incorporation of planar chirality into MR‐TADF emitter is a reliable strategy for constructing of efficient CP‐OLEDs.

Monolayer transition metal dichalcogenides (TMDs) have emerged as widely accepted 2D gain materials in the field of light sources owing to their direct bandgap and high photoluminescence quantum yield. However, the monolayer medium suffers from weak emission because only a single layer of molecules can absorb the pump energy. Moreover, the material degradation when transferring these fragile materials hinders their cooperation with the optical cavity further. In this study, for the first time, a high‐quality monolithic structure is developed by directly growing single‐domain tungsten diselenide (WSe2) bilayers on single silica microsphere (MS) cavities. Such a completely wrapped structure guides the indirect‐to‐direct bandgap transition of WSe2 bilayers, leading to a significantly improved photoluminescence intensity by about 60‐fold. Moreover, the high‐quality monolithic structure enhances the confinement factor of the cavity by more than 20‐fold. Based on the above advantages, a bilayer WSe2/MS microlaser is realized with an ultralow threshold of 0.72 W cm−2, nearly an order of magnitude lower than the existing records. The results demonstrate the possibility of using multilayer TMD materials as 2D gain media and provide insights into a new ultracompact monolithic platform of TMD material/cavity for lasing devices.

In this study, two cyclometalated iridium(III) complexes named (4tfptp)2Ir(tpip) and (4tfptp)2Ir(Stpip), with 4-(4-(trifluoromethyl)phenyl)thieno[2,3-d]pyrimidine (4tfptp) as main ligand and bis(diphenylphosphoryl)amide (tpip) or bis(diphenylphorothioyl)amide (Stpip) as ancillary ligand, were synthesized for organic...

Phosphorescent iridium(III) complexes have been widely researched for the fabrication of efficient organic light-emitting diodes (OLEDs). In this work, three red Ir(III) complexes named Ir-1, Ir-2, and Ir-3, with Ir-S-C-S four-membered framework rings, were synthesized efficiently at room temperature within 5 min using sulfur-containing ancillary ligands with electron-donating groups of 9,10-dihydro-9,9-dimethylacridine, phenoxazine, and phenothiazine, respectively. Due to the same main ligand of 4-(4-(trifluoromethyl)phenyl)quinazoline, all Ir(III) complexes showed similar photoluminescence emissions at 622, 619, and 622 nm with phosphorescence quantum yields of 35.4%, 50.4%, and 52.8%, respectively. OLEDs employing these complexes as emitters with the structure of ITO (indium tin oxide)/HAT-CN (dipyra-zino[2,3-f,2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile, 5 nm)/TAPC (4,4′-cyclohexylidenebis[N,N-bis-(4-methylphenyl)aniline], 40 nm)/TCTA (4,4″,4″-tris(carbazol-9-yl)triphenylamine, 10 nm)/Ir(III) complex (10 wt%): 2,6DCzPPy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(mpyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) achieved good performance. In particular, the device based on complex Ir-3 with the phenothiazine unit showed the best performance with a maximum brightness of 22480 cd m−2, a maximum current efficiency of 23.71 cd A−1, and a maximum external quantum efficiency of 18.1%. The research results suggest the Ir(III) complexes with a four-membered ring Ir–S–C–S backbone provide ideas for the rapid preparation of Ir(III) complexes for OLEDs.