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A unique molecular design paradigm aimed at developing solution-processed multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) materials is proposed here, the solution processing ability could be enhanced by integrating three MR-building blocks. When utilized as an emitter in solution-processed organic light-emitting diodes (sOLEDs), the synthesized TriBNCz molecule demonstrates a narrow emission spectrum with full width at half maximum (FWHM) of 27 nm. Furthermore, through a sensitization strategy, the sOLED device achieves impressive maximum external quantum efficiency (EQE) of 28.8 % and maintains 26.1 % at 1000cd/m−2, with an FWHM of 30 nm and Commission Internationale de I'Éclairage (CIE) coordinates of (0.103, 0.497). [Display omitted] • A novel narrowband multiple resonance delayed fluorescence emitter is developed through the integration of MR-building blocks; • A higher k RISC has been achieved owing to the mixed SRCT and LRCT characteristic of excited states as well as multiple charge transfer channels; • Quite high maximum EQE of 28.8 % and a high-level EQE of 26.1 % at 1000 cd/m2, with an FWHM of 30 nm have been realized. Solution-processed organic materials that exhibit both high emission efficiency and narrowband emission characteristics are rare, and the performance of corresponding solution-processed organic light-emitting diodes (sOLEDs) remains inadequate for practical applications. This study proposes a proof-of-concept design aimed at enhancing both solution processing capability and emission efficiency in multiple-resonance induced thermally activated delayed fluorescence (MR-TADF) materials through the integration of multiple emitting units. A unique emitter named TriBNCz is synthesized and characterized, incorporating three MR-building blocks onto a single phenyl ring, resulting in sky-blue emission with a peak at 490 nm and a small full width at half maximum (FWHM) of 25 nm. Significant improvements in solution processing attributes, including solubility and film-forming properties, are achieved. Moreover, except for the MR effect of the excited states, long-range charge transfer properties of excited states are also obtained. The multiple charge transfer channels contribute to higher rate of reverse intersystem crossing (k RISC). The optimized sOLED device exhibits a maximum external quantum efficiency (EQE max) of 17.8 %. Furthermore, by employing 5TCzBN as a sensitizer, the sensitized sOLED achieves an EQE max of 28.8 % and a high-level EQE of 26.1 % at 1000 cd m−2, with an FWHM of 30 nm and Commission Internationale de I'Éclairage (CIE) coordinates of (0.103, 0.497), representing one of the best results among narrowband emission sOLEDs. This research opens a new avenue to develop high-performance solution-processed organic materials and sOLED devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • PYHB and PYHP deliver excellent thermal stability and morphological stability. • PYHB and PYHP can inherit the narrowband blue emission and HLCT characteristics. • PYHB and PYHP remove the limitations of traditional polymer luminescent materials. • PYHB and PYHP outperform previously reported polymer luminescent materials. • Our strategy provides a promising platform for PIs as a photoelectric material. Blue light-emitting materials with excellent film-forming ability, superior morphological stability, outstanding color purity, and high device efficiency are in urgent demand for new-generation display and solid-state lighting devices fabricated by low-cost wet processing. However, their current performances are far from satisfactory. Herein, two polyimide (PI)-based blue polymers are first precisely constructed and synthesized through a "Hinge-type Linking" strategy. A small molecular is introduced into the PI backbone via non-conjugated aliphatic imide ring linker. These polymers not only show superb thermal stability and morphological stability, but also maintain narrowband blue emission. Furthermore, PIs are prepared by polycondensation method, precipitated and purified in ethanol solvent, which avoids the use of metal catalysts. The resulting solution-processable devices achieve high performance with a maximum external quantum efficiency (EQE) of 9.94 % and maximum emission peak at 460 nm. To the best of our knowledge, this is the first time that solution-processable polymer light-emitting diodes (PLEDs) based on the "hot exciton" mechanism achieving splendid performance with maximum EQE close to 10 %. The superior performance is attributed to the validity of the "Hinge-type Linking" strategy in PLEDs, opening up a new avenue for PLED development and application. [ABSTRACT FROM AUTHOR]

Boron, sulfur-doped polycyclic aromatic hydrocarbon emitters with multiple-resonance-dominated lowest excited states are developed by tuning energy level alignment between 5,9-dithia-13b-boranaphtho[3,2,1- de ]anthracene skeleton and peripheral arylamine moieties, which reveal narrowband deep-blue electroluminescence with full-width at half maximum of 29 nm, Commission Internationale de l'Éclairage color coordinates of (0.13, 0.09) and maximum external quantum efficiency of 21.8%. [Display omitted] • Novel B,S-doped polycyclic aromatic multiple resonance emitters are developed. • Sulfur atoms enhance spin-orbital coupling and reverse intersystem crossing. • The lowest excited state characteristics are regulated by arylamine substituents. • The emitters exhibit narrowband deep-blue electroluminecence with EQE of 21.8%. Different from boron, nitrogen-based multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters, boron (B), sulfur (S)-doped polycyclic aromatic hydrocarbons (PAHs) containing 5,9-dithia-13b-boranaphtho[3,2,1- de ]anthracene (BSS) skeleton and arylamine moieties in para -positions of boron atoms are developed as a novel kind of MR-TADF emitters for narrowband deep-blue electroluminescence. The molecular design not only utilizes heavy-atom effect of sulfur atoms in BSS skeleton to enhance spin-orbital coupling and promote reverse intersystem crossing, but also uses arylamines as peripheral substituents to modify excited state characteristics. By decreasing electron-donating ability and downshifting HOMO level of arylamines, the lowest excited state for resultant emitter is converted from intersegmental charge transfer state to multiple resonance state localized on BSS skeleton, leading to blue-shifted and narrowed emissions. The B,S-doped PAH emitter bearing carbazole moiety exhibits deep-blue electroluminecence with full-width at half maximum of 29 nm, Commission Internationale de l'Éclairage color coordinates of (0.13, 0.09), and the maximum external quantum efficiency of 21.8 %, representing a new approach toward efficient narrowband deep-blue emission beyond boron, nitrogen-based MR-TADF emitters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Deep Blue MR-TADF emitters were designed by incorporating rigid DOBNA into MR skeletons. • Both emitters possess narrowband deep blue emission with FWHM of 19 nm. • Small ΔE ST (0.05 eV) and high PLQY are realized in the emitters. • MR-TADF OLEDs demonstrate high EQEs (>30 %) with CIE y coordinate below ≤ 0.07. The simultaneous achievement of high efficiency and deep blue narrowband emission in multi resonant thermally activated delayed fluorescence (MR-TADF) materials are crucial and challenging. Herein we report two deep blue MR-TADF emitters, namely, TPD4PA and tBu-TPD4PA , using double boron, three nitrogen and two oxygen atoms. The design is based on amalgamating the high charge transfer (CT) characteristic moiety into MR-type fragments towards efficient MR-TADF emitters with improved CT characteristics. Both the materials show deep blue photo luminescent emissions of ∼450 nm with a high photoluminescence quantum yield (PLQY) of ∼90 %. These materials showed very small singlet–triplet gap (≤0.06 eV) and a high rate of reverse intersystem crossing of ∼2.5 × 105 s−1. The TADF devices based on TPD4PA and tBu-TPD4PA showed maximum external quantum efficiencies of 30.7 and 32.5 %, respectively. Furthermore, both devices exhibited narrow band deep blue emissions and corresponding CIE y coordinates 0.06 and 0.07, which match near NTSC and BT2020 blue color requirements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel host materials with dendritic architectures are developed for MR-TADF OLEDs. • Alkoxy-capping groups up-shift HOMO levels to realize barrier-free hole injection. • Adamantane core interrupts conjugation of four carbazole dendrons to keep high E T. • EQE of 24.2% is realized for solution-processed narrowband OLEDs using dendritic host. Narrowband electroluminescence from multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have attracted much attention owing to their potential in developing high-resolution organic light-emitting diode (OLED) displays. However, host materials used for MR-TADF emitters are mainly focused on small molecules that are relying on vacuum deposition for device fabrication. Here, we demonstrate the design of novel host materials with dendritic structures consisting of a non-conjugated adamantane core and four alkoxy-capped carbazole dendrons in periphery for solution-processed MR-TADF OLEDs with highly efficient narrowband electroluminescence. By introducing electron-donating n -butoxy capping groups to carbazole units and using the second-generation dendrons instead of the first-generation ones, triplet energies for the dendritic hosts are kept at higher than 2.80 eV, but the highest occupied molecular orbital (HOMO) levels can be considerably elevated from −5.51 to −5.19 eV, leading to barrier-free hole injection from anode to emissive layer. Solution-processed OLEDs based on the alkoxy-capped dendritic host and B,N-containing MR-TADF emitter reveal narrowband emission with full-width at half-maximum of 42 nm, together with low turn-on voltage of 2.8 V, maximum external quantum efficiency of 24.2% and power efficiency of 95.0 lm W−1, which represent the promising device efficiencies for narrowband electroluminescence by solution process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Newly synthesized diboron embedded deep blue MR-TADF emitters. • Narrow spectra with FWHM of 14 nm and CIE y coordinate below 0.10. • Small △E ST (≤0.07 eV), high PLQY, and good TADF performances. • All these materials show high EQEs (>33%) We report three deep blue multiple resonant TADF emitters, m-ν-DABNA, 4F-ν-DABNA, and 4F-m-ν-DABNA by incorporating methyl groups and fluorine atoms in diboron based ν-DABNA core. The introduction of methyl groups at para positions to the boron atoms and fluorine atoms at ortho positions to the nitrogen atoms resulted in bandgap enhancement by electron donating and electron withdawing effects. All three emitters exhibit pure blue emissions with high photoluminescence quantum yield around ∼ 90%, small ΔE ST (≤0.07 eV) values, and fast reverse intersystem crossing rate (k RISC). Fabricated OLEDs with these emitters show excellent external quantum efficiency over 33%. Among three materials, 4F-ν-DABNA and 4F-m-ν-DABNA exhibit the CIE y coordinate of 0.08 and 0.06, respectively. Our current material design approach guides a path for the development of deep blue TADF emitters for highly efficient narrowband OLEDs. [ABSTRACT FROM AUTHOR]