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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] more...

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] more...

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] more...

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] more...

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] more...

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] more...

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] more...

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] more...

In this study, two isomers BP1 and BP2, featuring diindolophenthiazine as the donor and benzophenone as the acceptor, are designed and synthesized for the first time. Both compounds exhibit dual conformations and thus dual emissions of fluorescence and thermally activated delayed fluorescence in films to achieve single molecular white-light emissions. Owing to the dual conformations and the changes of their corresponding compositions in amorphous and crystalline states, machanochromism is observed in both compounds. Additionally, white photoluminescence with Commission Internationale de L'Eclairage (CIE) coordinates of (0.31, 0.33) are achieved for BP2-doped films. Furthermore, solution-processed single-molecule white organic light-emitting diodes are also successfully developed based on BP2 as the solely emitter, demonstrating an external quantum efficiency of 2.61% at CIE coordinates of (0.33, 0.36). [ABSTRACT FROM AUTHOR] more...

Mixed halide perovskites are widely investigated as emitters for efficient light‐emitting diodes owing to their excellent optoelectronic properties. Compared with red and green emissions, encouraging progress in efficiency for blue emission has only been achieved in sky‐blue region. A high Cl/Br ratio is indispensable to achieve deep‐blue emission, which often leads to pronounced halogen migration in perovskite light‐emitting diodes (PeLEDs) and thus diminished efficacy. To avoid the negative effects of excessive chloride necessary to achieve deep‐blue emission, alloyed perovskite quantum dotes (QDs) passivated by dual‐functional guanidine sulfamate are synthesized, where S═O of sulfamate coordinates with Pb, and guanidine can form N‐H‐X (Cl/Br) with halogen ions to complete passivation. As a result, deep‐blue emission is achieved for the alloyed perovskite QDs. Owing to the suppressed defects and the reduced surface electrostatic potential of the perovskite QDs film, the carrier recombination region in the PeLEDs is regulated. Finally, deep‐blue PeLEDs with a spectrally stable electroluminescence peak at 458 nm, peak external quantum efficiency of 3.65% and maximum brightness of 223 cd m−2 are realized. [ABSTRACT FROM AUTHOR] more...

In purely organic room‐temperature phosphorescence (RTP) materials, fluorescence radiative transitions generally compete against inter‐system crossing (ISC) transitions to give fluorescence/phosphorescence dual emission. In order to achieve pure phosphorescence in RTP organic light‐emitting diodes (OLEDs), extended π‐conjugation is introduced into Se‐containing donors to suppress the fluorescence radiative transitions by the symmetry excited state orbitals in the introduced π–π* transitions that cancel the overlap of the orbitals, and two novel nonaromatic amine donor containing orange RTP emitters namely 2‐(benzo[c]phenoxaselenin‐10‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (BPXSeDRZ) and 2‐(dibenzo[a,c]phenoxaselenin‐11‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (DBPXSeDRZ) are developed, both of which exhibit efficient orange pure phosphorescence in doped films thanks to the sufficient ISC transitions. As a result, high external quantum efficiencies of 17.2% and 17.9% are respectively achieved for the orange RTP‐OLEDs based on BPXSeDRZ and DBPXSeDRZ for the first time, and they also exhibit stable pure electro‐phosphorescence spectra in a wide driving voltage. Moreover, by adopting DBPXSeDRZ as a sensitizer to harvest the triplet excitons and tetraphenyldibenzoperiflanthene as a conventional fluorescent emitter, the external quantum efficiency of the sensitized red fluorescent OLED can be elevated to 10.1%, which greatly expands the potential applications of the metal‐free phosphors in OLEDs. [ABSTRACT FROM AUTHOR] more...

In recent years, thermally activated delayed fluorescence (TADF) materials with high horizontal dipole ratios (Θ//) have attracted enormous attention in constructing high‐efficiency organic light–emitting diodes (OLEDs). However, the common strategy to improve Θ// based on extending π‐conjugation tends to induce bathochromic emission shift, and emitters with Θ// exceeding 90% are rarely reported. Herein, a non‐conjugated extension strategy is developed to promote molecular horizontal dipole orientation. By simply modifying the spiro‐acridine with extra 9‐phenylcarbazole groups, two high‐efficiency and versatile TADF emitters 36DPCZSFAC‐TRZ and 36DPCZSFAC‐PYPM are constructed without bathochromic emission shift, and state‐of‐the‐art ultra‐high Θ// of 92% and 96% are achieved, respectively. More fascinatingly, due to the special spiro molecular structures, the TADF emitters hold distinguished merits of aggregation‐induced emission property, near unitary photoluminescence quantum yields, fast reverse intersystem crossing rates, and enhanced charge‐carrier transport property, which enable outstanding external quantum efficiency values of up to 22.1/20.9% and 37.4/34.2% in non‐doped/doped OLEDs for 36DPCZSFAC‐TRZ and 36DPCZSFAC‐PYPM, respectively, demonstrating their great potentials in the fabrication of high‐efficiency OLEDs. [ABSTRACT FROM AUTHOR] more...

Narrowband organic emitters are promising for their potential applications in wide‐color gamut and high‐resolution displays. Multiple resonance (MR) thermally activated delayed fluorescence (TADF) emitters are flourishing because of their attractive narrow emission bandwidth and excellent device performance. In this work, a series of MR‐TADF emitters embedded with sulfur, sulfone, and carbonyl have been developed, and their intrinsic effects on the exciton dynamics like intersystem crossing rate (kISC) and reverse intersystem crossing rate (kRISC) and full width at half maximum are systematically investigated. Benefitting from the heavy atom effect of the sulfur atom, fast kRISC are achieved to give highly efficient and stable organic light‐emitting diodes with reduced efficiency roll‐off. By fusing donor unit containing carbonyl into boron‐nitrogen compounds, carbonyl reinforced short range charge transfer can induce a red‐shifted pure‐green emission with simultaneous fast kRISC and narrow emission bandwidth, and a moderate device lifetime of LT90 (the time to 90% of the initial luminance of 1000 cd m‐2) of 127.3 h is achieved for the device utilizing TCZBAO as emitter. [ABSTRACT FROM AUTHOR] more...