Multi-resonance TADF (MR-TADF) emitters are promising for high-resolution OLEDs, but the concurrent optimization of excited-state dynamics and color purity remains a tough challenge. Herein, three deep-blue MR-TADF compounds (BN1-BN3) featuring gradually enlarged ring-fused structures and increased rigidity are accessed by lithiumfree borylation in high yields from the same precursor, with all the emitters possessing CIE y coordinates below 0.08. Structure-property investigations demonstrate a strategic improvement of the oscillator strength (f osc ) and acceleration of the reverse intersystem crossing (RISC) process by extending the π-skeleton, where BN3 realizes a maximum external quantum efficiency (EQE) of 37.6 % and reduced roll-off, thus showing the best efficiency reported for deep-blue TADF OLEDs. The internal regulation of the efficiency and color purity of these compounds validate the general effectiveness to achieve advanced deep-blue narrowband emitters with higher-order boron/nitrogen-based MR motifs.

Scheme 1. Molecular design strategy for narrowband emission circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters.

AIE-active organic intelligent luminescent materials exhibit both multicolor tunable and high-contrast beyond 100 nm mechanochromism and acidochromism.

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Multi‐resonance TADF (MR‐TADF) emitters are promising for high‐resolution OLEDs, but the concurrent optimization of excited‐state dynamics and color purity remains a tough challenge. Herein, three deep‐blue MR‐TADF compounds (BN1–BN3) featuring gradually enlarged ring‐fused structures and increased rigidity are accessed by lithium‐free borylation in high yields from the same precursor, with all the emitters possessing CIEy coordinates below 0.08. Structure–property investigations demonstrate a strategic improvement of the oscillator strength (fosc) and acceleration of the reverse intersystem crossing (RISC) process by extending the π‐skeleton, where BN3 realizes a maximum external quantum efficiency (EQE) of 37.6 % and reduced roll‐off, thus showing the best efficiency reported for deep‐blue TADF OLEDs. The internal regulation of the efficiency and color purity of these compounds validate the general effectiveness to achieve advanced deep‐blue narrowband emitters with higher‐order boron/nitrogen‐based MR motifs.

In this work, we demonstrate dibenzothiophene sulfoximine derivatives as building blocks for constructing emitters featuring both thermally activated delayed fluorescent (TADF) and aggregation-induced emission (AIE) properties, with multiple advantages including high chemical and thermal stability, facile functionalization, as well as tunable electron-accepting ability. A series of phenoxazine-dibenzothiophene sulfoximine structured TADF emitters were successfully synthesized and their photophysical and electroluminescent properties were evaluated. The electroluminescence devices based on these emitters displayed diverse emissions from yellow to orange and reached external quantum efficiencies (EQEs) of 5.8% with 16.7% efficiency roll-off at a high brightness of 1000 cd·m−2.

Highly efficient circularly polarized luminescence (CPL) emitters with narrowband emission remain a formidable challenge for circularly polarized OLEDs (CP‐OLEDs). Here, a promising strategy for developing chiral emitters concurrently featuring multi‐resonance thermally activated delayed fluorescence (MR‐TADF) and circularly polarized electroluminescence (CPEL) is demonstrated by the integration of molecular rigidity, central chirality and MR effect. A pair of chiral green emitters denoted as (R)‐BN‐MeIAc and (S)‐BN‐MeIAc is designed. Benefited by the rigid and quasi‐planar MR‐framework, the enantiomers not only display mirror‐image CPL spectra, but also exhibit TADF properties with a high photoluminescence quantum yield of 96 %, a narrow FWHM of 30 nm, and a high horizontal dipole orientation of 90 % in the doped film. Consequently, the enantiomer‐based CP‐OLEDs achieved excellent external quantum efficiencies of 37.2 % with very low efficiency roll‐off, representing the highest device efficiency of all the reported CP‐OLEDs.