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The insolubility and severe self-aggregation tendency of hybridized localized and charge-transfer (HLCT) small molecular emitters have limited their application in solution-processed organic light-emitting diodes (OLEDs), particularly in red OLEDs. Herein, a series of solution-processable novel red hyper-structured molecular (HSM) HLCT emitters, CRA–MTBP(X)–mCP(8−X) (X = 8, 7, 6, 4, 2, 1 or 0), are designed. The benzothiadiazole/triphenylamine-based HLCT unit (MTBP) and the host unit (mCP) at different molar ratios were hooked up to the inactive calix[4]resorcinarene (CRA) core via efficient "Click" reactions, respectively. CRA–MTBP(X)-mCP(8−X) exhibited good thermal stability with a glass transition temperature (Tg) of above 120 °C and a decomposition temperatures (Td) exceeding 363 °C. UV-Vis, PL, and CV results demonstrated that these HSMs inherit the photophysical and electrochemical properties of the corresponding functional units. Spin-coating CRA–MTBP(X)–mCP(8−X) as light-emitting layers, all the non-doped diodes showed orange to red emission. Among them, a CRA–MTBP(8)–mCP(0)-based device emitted red light, with an EL emission peak (λEL) at 651 nm and CIE coordinates of (0.63, 0.36), a maximum external quantum efficiency (EQEmax) of 1.35% with low roll-off and a maximum luminance (Lmax) of 2831 cd m−2. Furthermore, the doped device based on CRA–MTBP(8)–mCP(0) using CBP as the host emitted bright red light with a λEL at 612 nm, an EQEmax of 3.27%, and a Lmax of 4362 cd m−2. These results indicate that the construction of HSMs by introducing red HLCT units could be an effective strategy for structuring solution-processable HLCT red emitters. [ABSTRACT FROM AUTHOR]

Due to the challenges of a fluorescence spectral red-shift and broadening, the development of ultraviolet (UV) organic light-emitting diodes (OLEDs) remains a significant challenge. Herein, we report four narrowband UV/deep-blue fluorescence thermally activated delayed fluorescence (TADF) molecules based on the boron oxygen polycyclic aromatic hydrocarbon (DOBA) multiple-resonance (MR) structures, namely TDBA-Cz, TDBA-α-Cb, TDBA-β-Cb, and TDBA-γ-Cb. There is a significant twisted structure between the donor (D) of carbazole or carboline and the DOBA acceptor (A), which can weaken the intermolecular interaction of DOBA and improve the luminescence efficiency. OLED devices based on TDBA-Cz, TDBA-α-Cb, and TDBA-γ-Cb exhibit ultraviolet emission (λem: 397 nm, 397 nm, and 393 nm). It is worth noting that their full-width at half-maxima (FWHM) are all less than 31 nm, which is one of the narrowest values in the ultraviolet region (λem < 400 nm). The maximum external quantum efficiency (EQE) is 3.55%, 3.54%, and 3.81%, respectively. A sky-blue device was further constructed with TDBA-α-Cb as the host material and DSA-Ph as the doped material, with a maximum EQE, current efficiency (CE), and power efficiency (PE) of 5.06%, 10.20 cd A−1, and 7.50 lm W−1, respectively. The above results indicate that DOBA-based carbazole or carboline systems can be used not only as doping materials but also as host materials. This dual-purpose molecule enriches the molecular library for constructing ultraviolet and blue OLEDs. [ABSTRACT FROM AUTHOR]

Recently, an ever‐growing interest has been paid on organic single‐molecule white light‐emitting materials for effective white organic light‐emitting diodes (WOLEDs). However, subject to Kasha's rule, photons can only be emitted from the lowest excited state and thus panchromatic or dual emissions are extremely forbidden, which results in a certain challenge in achieving white emission. Herein, a strategy of synergetic carbonyl and heptagonal structure is proposed for organic single‐molecule white light emission and demonstrated by TAO/TABO/TA2O organic luminescent materials that are modified on aryl ketones/amine fragments. Among them, due to the robust intermolecular interactions triggered by synergetic carbonyl and heptagonal structure, TA2O exhibits vibrant monomer and dimer photoluminescence with dual thermally activated delayed fluorescence (TADF) characteristics. As a result, the first single‐molecule dual‐TADF WOLED based on the synergetic system is successfully fabricated with an external quantum efficiency of 7.2%. This study not only expands the scope of carbonyl and heptagonal structure for novel optoelectronic properties and applications but also opens new avenues for the development of efficient single‐molecule WOLEDs with dual TADF mechanisms. [ABSTRACT FROM AUTHOR]

The large‐scale fabrication of long‐lived and sustainable room‐temperature phosphorescence (RTP) materials with color‐tunable afterglow is of considerable practical importance in diverse optoelectronic applications but remains challenging. Herein, based on a process for the mass production of cellulose acetoacetate filaments, large‐scale RTP filaments are synthesized by introducing amino‐bearing luminophores via a mild enamine reaction. Attributed to efficient intersystem crossing facilitated by acetoacetyl and benzoyloxy groups alongside a rigid environment provided by multiple hydrogen bonding, the resulting filaments exhibit impressive RTP with a lifetime of 772 ms and a phosphorescence quantum yield of 45.06%. Furthermore, the afterglow color of RTP filaments is rationally modulated from blue to greenish‐yellow to rosy‐red through triplet‐to‐singlet Förster resonance energy transfer. Meanwhile, the formation of diverse clusters with comparable but different lifetimes leads to interesting excitation‐dependent afterglows. This work not only provides an effective strategy to construct long‐lived, color‐tunable, sustainable afterglows but also establishes large‐scale and continuous preparation routes for functional cellulose filaments. [ABSTRACT FROM AUTHOR]

In the development of organic light‐emitting diodes (OLEDs) with high efficiency and minimal efficiency roll‐off, fast reverse intersystem crossing (RISC) in multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials is critical. The RISC process is typically hindered by insufficient spin‐orbital coupling (SOC). Incorporating heavy atom selenium into the MR‐TADF structure has the potential to enhance SOC through the heavy atom effect. However, the specific placement of selenium within the molecule results in different enhancements of SOC, with the detailed interplay between these factors yet to be elucidated. The introduction of a selenium‐containing moiety, phenoxaselenine, into the MR‐TADF structure at different substituted positions is undertaken, revealing that the molecule with 3‐substituted phenoxaselenine exhibits faster RISC transition and a significant increase in SOC between higher triplet excited states and S1 state, compared to the molecule with 2‐substituted phenoxaselenine. Significantly reduced efficiency roll‐off is achieved for the narrow‐band emission OLEDs based on the molecule with 3‐substituted phenoxaselenine owing to the enhanced heavy atom effect, giving an impressive external quantum efficiency above 20% even under 10 000 cd m−2 in the corresponding OLED device. These results underscore the potential of strategic heavy atom effect manipulation in MR‐TADF materials for efficient spin‐flipping. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) based on multiple resonance‐thermally activated delayed fluorescence (MR‐TADF) have the advantages of high exciton utilization and excellent color purity. However, the large conjugated planarity of general MR‐TADF emitters makes them easily aggregate in the form of π–π stacking, resulting in aggregation‐caused quenching (ACQ) and the formation of excimers, which reduce exciton utilization efficiency and color purity. To address these issues, large shielding units can be incorporated to prevent interchromophore interactions, whereas the majority of reported molecules are limited to blue‐green light emissions. This work proposes a strategy of incorporating steric hindrance groups at different sites of the B/N core to suppress interactions between chromophore, contributing to blue MR‐TADF emitters with high photo‐luminance quantum yields (PLQYs ≥ 95%) and narrow full width at half maximum (FWHM), and importantly, great suppression of the ACQ effect. Therefore, blue OLEDs achieve high external quantum efficiencies up to 34.3% and high color purity with FWHM of about 27 nm and CIE around (0.12, 0.15), even at a high doping concentration of 20 wt%. [ABSTRACT FROM AUTHOR]

Herein, we propose a regional functionalization molecular design strategy that enables independent control of distinct pivotal parameters through different molecule segments. Three novel multiple resonances thermally activated delayed fluorescence (MR‐TADF) emitters A‐BN, DA‐BN, and A‐DBN, have been successfully synthesized by integrating highly rigid and three‐dimensional adamantane‐containing spirofluorene units into the MR framework. These molecules form two distinctive functional parts: part 1 comprises a boron‐nitrogen (BN)‐MR framework with adjacent benzene and fluorene units forming a central luminescent core characterized by an exceptionally rigid planar geometry, allowing for narrow FWHM values; part 2 includes peripheral mesitylene, benzene, and adamantyl groups, creating a unique three‐dimensional "umbrella‐like" conformation to mitigate intermolecular interactions and suppress exciton annihilation. The resulting A‐BN, DA‐BN, and A‐DBN exhibit remarkably narrow FWHM values ranging from 18 to 14 nm and near‐unity photoluminescence quantum yields. Particularly, OLEDs based on DA‐BN and A‐DBN demonstrate outstanding efficiencies of 35.0 % and 34.3 %, with FWHM values as low as 22 nm and 25 nm, respectively, effectively accomplishing the integration of high color purity and high device performance. [ABSTRACT FROM AUTHOR]

Realizing highly efficient organic light‐emitting diodes (OLEDs) based on "hot exciton" emitters is crucial for the widespread use of purely organic electroluminescence. Herein, it is demonstrated that the radiative decay rate, modulated by molecular configuration, plays a vital role in determining the optoelectronic properties of hot exciton materials. The proof‐of‐concept isomers, TPA‐1IPCN and TPA‐3IPCN, and TPA‐1IANCN and TPA‐3IANCN are intentionally designed and successfully synthesized. By employing a novel donor–acceptor–acceptor (D–A'–A) molecular architecture, implementing a molecular isomerization strategy, incorporating diverse steric hindrance moieties, and strategically manipulating the positioning of functional groups, precise modulation of the molecular configuration can be achieved to enable accurate regulation of the radiative decay rate. Consequently, various optoelectronic properties, including photoluminescent wavelength, photoluminescence quantum yield, fluorescence lifetime, packing mode in aggregated state, and molecular horizontal dipole ratios in films, undergo significant modifications. As a result, non‐doped blue OLED based on TPA‐1IPCN exhibits outstanding maximum external quantum efficiency (EQE) of 10.3% with minimal efficiency roll‐off—one of the highest reported values for blue OLEDs based on hot exciton materials. [ABSTRACT FROM AUTHOR]