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This study explores the effect of molecular permanent dipole moment (PDM) on aggregation of guest molecules in phosphorescent host–guest organic light-emitting diodes (OLEDs). Through a combination of photoluminescence measurements, high-angle annular dark-field scanning transmission electron microscopy analysis, and an Ising model based physical vapor-deposition simulation, we show that higher PDM of tris[2-phenylpyridinato-C2,N]iridium(III) guest can actually lead to a reduced aggregation relative to tris[bis[2-(2-pyridinyl-N)phenyl-C] (acetylacetonato)iridium(III) when doped into a non-polar host 1,3,5-tris(carbazol-9-yl)benzene. This study further explores the effect of host polarity by using a polar host 3′,5′-di(carbazol-9-yl)-[1,1′-biphenyl]-3,5-dicarbonitrile, and it is shown that the polar host leads to reduced guest aggregation. This study provides a comprehensive understanding of the impact of molecular PDM on OLED material efficiency and stability, providing insights for optimizing phosphorescent OLED materials. [ABSTRACT FROM AUTHOR]

Many photocatalysts were initially developed or used as emitters for organic light emitting diodes (OLEDs). This feature article summarizes the different generations of OLED emitters and connects the photophysical processes with those relevant for photocatalysis. The focus is on the general properties OLED emitters and photocatalysts are designed for and how photocatalysis has benefitted from OLED research. Sometimes optimization of an OLED emitter leads to a better photocatalyst while some properties are optimized into opposite directions. To discover new classes of photocatalysts in the future it is important to consider what good OLED emitters and good photocatalyst have in common and where they diverge. Within recent years, fully organic thermally activated delayed fluorescence (TADF) emitters had the most significant impact in both fields and thus are discussed with specific focus. [ABSTRACT FROM AUTHOR]

Crystalline host matrix (CHM)‐nanoaggregates (NA) structure combines the advantages of a crystalline host matrix and high‐performance luminescent materials. This structure emerges as a highly effective strategy for achieving efficient blue organic light‐emitting diodes (OLEDs). This approach can tackle the current challenge of achieving low voltage and high brightness in amorphous OLEDs. In this work, triplet‐triplet annihilation (TTA) material NA are embedded into CHM and sensitize the fluorescent dopant (D) BD1. As a result, a CHM‐TTANA‐D structure device is created, demonstrating an outstanding external quantum efficiency (EQE) of 8.46%. Notably, the efficiency roll‐off is mitigated. The device maintains an EQE of ≈7.50% at 1000 cd m−2, which is the highest values among blue crystalline OLEDs. The device leverages the benefits of CHM and exhibits swift turn‐on and a rapid increase in brightness and current density. This leads to a significant improvement in blue photon output and a reduced series‐resistance Joule heat loss ratio. The findings underscore the promising nature of the CHM‐TTANA‐D structure as a favorable design paradigm for high‐performance crystalline thin‐film OLEDs (C‐OLEDs). [ABSTRACT FROM AUTHOR]

Developing highly efficient pure‐blue organic light‐emitting diodes (OLEDs) that meet the stringent BT.2020 standard by using multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials has long been a formidable challenge. In this study, a strategy is demonstrated for high‐performance blue MR‐TADF emitters by gradually decorating the MR framework with alkyl groups, and subsequently introducing a diarylamino group at the para‐position of boron atom. The proof‐of‐concept molecule, IPrBN‐mCP, exhibits a narrowband deep‐blue emission peaking at 452 nm, with a very narrow full‐width at half maximum (FWHM) of 19 nm in solution, and a remarkably high photoluminescence quantum yield (PLQY) approaching unity in doped films. As a result, OLEDs based on IPrBN‐mCP achieve not only a high maximum external quantum efficiency (EQEmax) of 33.4% but also ultrapure blue emission with a Commission Internationale de L'Eclairage (CIE) y value of 0.046, fully satisfying the BT.2020 blue standard. This represents the first OLED example fully meeting the rigorous color requirements of the BT.2020 blue standard while simultaneously achieving an EQE exceeding 30%. [ABSTRACT FROM AUTHOR]

Despite the rapid development of thermally activated delayed fluorescent (TADF) materials, developing organic light‐emitting diodes (OLEDs) with small efficiency roll‐off remains a formidable challenge. Herein, we have designed a TADF molecule (mClSFO) based on the spiro fluorene skeleton. The highly twisted structure and multiple charge‐transfer channels effectively suppress aggregation‐caused quenching (ACQ) and endow mClSFO with excellent exciton dynamic properties to reduce efficiency roll‐off. Fast radiative rate (kr) and rapid reverse intersystem crossing (RISC) rate (kRISC) of 1.6×107 s−1 and 1.07×106 s−1, respectively, are obtained in mClSFO. As a result, OLEDs based on mClSFO obtain impressive maximum external quantum efficiency (EQEmax) exceeding 20 % across a wide doping concentration range of 10–60 wt %. 30 wt % doped OLED exhibits an EQEmax of 23.1 % with a small efficiency roll‐off, maintaining an EQE of 18.6 % at 1000 cd m−2. The small efficiency roll‐off and low concentration dependence observed in the TADF emitter underscore its significant potential. [ABSTRACT FROM AUTHOR]

Acenes are attractive as building blocks for low gap organic materials with applications, for example, in organic light emitting diodes, solar cells, bioimaging and diagnostics. Previously, we have shown that modification of dipyridylanthracene via B–N Lewis pair fusion (BDPA) strongly redshifts the emission, while facilitating self‐sensitized reactivity toward O2 to reversibly generate the corresponding endoperoxides. Herein, we report on the further expansion of the π‐system of BDPA to a vinyl‐substituted monomer, vinylene‐bridged dimer, and a polymer with an average of 20 chromophores. The extension of π‐conjugation results in largely reduced band gaps of 1.8 eV for the dimer and 1.7 eV for the polymer, the latter giving rise to NIR emission with a maximum at 731 nm and an appreciable quantum yield of 7 %. Electrochemical and computational studies reveal efficient delocalization of the lowest unoccupied molecular orbital (LUMO) along the pyridyl‐anthracene‐pyridyl axis, which results in effective electronic communication between BDPA units, selectively lowers the LUMO, and ultimately narrows the band gap. Time‐resolved emission and transient absorption (TA) measurements offer insights into the pertinent photophysical processes. Extension of π‐conjugation also slows down the self‐sensitized formation of endoperoxides, while significantly accelerating the thermal release of singlet oxygen to regenerate the parent acenes. [ABSTRACT FROM AUTHOR]

A novel "Ring-expansion" strategy is proposed to optimize traditional host molecular structures, featuring a rigid molecular skeleton and excellent transport of carriers. Consequently, the two novel host materials facilitate the fabrication of efficient phosphorescent OLEDs with suppressed efficiency roll-off compared to OLEDs based on the conventional host material (mCP). [ABSTRACT FROM AUTHOR]

Micro-light-emitting diodes offer vibrant colors and energy-efficient performance, holding promise for next-generation inorganic displays. However, their widespread adoption requires the development of cost-effective chips and low-defect pixelation processes. Addressing these challenges, nanorod-light-emitting diodes utilize inkjet and dielectrophoretic assembly techniques. Nevertheless, the small volume and edge-directed emission of nanorod-light-emitting diodes necessitate brightness and light extraction improvements. As an alternative, we propose dielectrophoretic-friendly fin-light-emitting diodes, designed to enhance brightness and light extraction efficiency through face-selective dielectrophoretic assembly technology. Our results confirm the potential for next-generation inorganic displays, with a wafer utilization ratio exceeding 90%, a vertical assembly ratio of 91.3%, and a pixel production yield of 99.93%. Moreover, blue fin-light-emitting diodes achieve an external quantum efficiency of 9.1% and a brightness of 8640 cd m−2 at 5.0 V, which, even at this early stage, are comparable to existing technologies. Lee et al. report blue fin-LEDs with improved brightness and light extraction efficiency comparing to nanorod-LEDs by using a face-selective dielectrophoretic assembly technology. The wafer utilization ratio exceeds 90%, with a vertical assembly ratio of 91.3% and pixel production yield of 99.93%. [ABSTRACT FROM AUTHOR]

Different classes of Imidazopyridine i.e., Imidazo[1,2-a]pyridine, Imidazo[1,5-a] pyridine, Imidazo[4,5-b]pyridine, have shown versatile applications in various fields. In this review, we have concisely presented the usefulness of the fluorescent property of imidazopyridine in different fields such as imaging tools, optoelectronics, metal ion detection, etc. Fluorescence mechanisms such as excited state intramolecular proton transfer, photoinduced electron transfer, fluorescence resonance energy transfer, intramolecular charge transfer, etc. are incorporated in the designed fluorophore to make it for fluorescent applications. It has been widely employed for metal ion detection, where selective metal ion detection is possible with triazole-attached imidazopyridine, β-carboline imidazopyridine hybrid, quinoline conjugated imidazopyridine, and many more. Also, other popular applications involve organic light emitting diodes and cell imaging. This review shed a light on recent development in this area especially focusing on the optical properties of the molecules with their usage which would be helpful in designing application-based new imidazopyridine derivatives. [ABSTRACT FROM AUTHOR]

Exploring possible strategy to balance the radiative decay and reverse intersystem crossing (RISC) are of great significance in thermally activated delayed fluorescent (TADF) emitters for enabling both high efficiency and low efficiency roll‐off. Herein, by introducing a multi‐resonance (MR) type acceptor, two TADF emitters featuring hybridized short‐range charge transfer (SRCT) and long‐rang charge transfer (LRCT) are designed. LRCT‐dominate photoluminescent nature is maintained with a short delayed lifetime of 1.5–3.4 µs. While the incorporated SRCT accelerates the radiative decay. Consequently, both emitters demonstrate remarkable electroluminescent performance with maximum EQE (EQEmax) of 40.8% for IT‐BO and 39.0% for IA‐BO, respectively, along with ultra‐high luminance of up to 120 000 cd m−2. More encouragingly, both emitters can enable small efficiency roll‐off with a minimum value of only 4%, highlighting the significance of enhanced kr in suppressing the roll‐off. Moreover, when served as sensitizers, both compounds can also endow excellent performances with EQEmax ≈38%. This work presents an innovative approach by hybridizing SRCT and LRCT for developing practical TADF emitters. [ABSTRACT FROM AUTHOR]

Multifunctional molecular switches have attracted much attention because of their unique stimulus response behavior and advanced applications. However, precise regulation of the structure for property enrichment is still a great challenge. Herein, the first case of a single‐molecule switch BN‐S with multiple structurally tunable and full‐color fluorescent properties is reported. Interestingly, BN‐S exhibits a butterfly‐like "metamorphosis" crystal growth process accompanied by full‐color fluorescence emission (including white light, CIE = 0.33, 0.33; 456 nm → 610 nm). It is shown that this is related to the reversible B←N bonding and the tunability of the spatial structure of the BN‐S. Thus, BN‐S exhibits superior multicolor tunability in different states (solid, liquid, and film), and its applications in white‐light optical light emitting diodes (OLEDs) and multicolor fluorescent inks also show great promise. This will provide a new strategy for designing and synthesizing the development of multifunctional molecular switching materials and enriching the variety of organoboron luminescent materials. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) employing multi‐resonance (MR) emitters have attracted much attention due to their high luminescent efficiency and color purity, however, the development of deep‐blue multi‐resonance OLEDs is hindered by the lack of suitable sensitizers. Here a novel design strategy is reported for thermally activated delayed fluorescence sensitizer with high reverse intersystem crossing (kRISC) and radiative transition (kR) rate by regulating atom distribution of a spatially‐aligned carbazole donor/diphenylpyrimidine acceptor structure to manipulate through‐space charge transfer (CT) process. It is found that diphenylpyrimidine acceptor with 1,3‐position nitrogen atoms is un‐conjugated to bridging phenyl moiety by the conjugation node of pyrimidine, while the acceptor with 1,5‐position nitrogen atoms is conjugated to bridging phenyl through conjugation site, opening through‐bond CT pathway via bridging phenyl besides through‐space CT from spatial donor‐acceptor interactions. As a result, the sensitizer with 1,5‐position nitrogen atoms exhibits enhanced oscillator strength by 3.5 folds and accelerated kR of 3.57 × 107 s−1, while keeping high kRISC of 4.03 × 106 s−1 and high singlet (S1) state (2.88 eV). Solution‐processed OLEDs using the sensitizer and deep‐blue multi‐resonance emitter exhibit efficient narrowband electroluminescence with CIE coordinates of (0.14, 0.13) and EQEmax of 15.6%, representing the state‐of‐the‐art device performance for deep‐blue multi‐resonance OLEDs by solution process. [ABSTRACT FROM AUTHOR]

In the IoT era, the demand for wearable displays is rapidly growing, catalyzing the advancement of research into textile-based organic light-emitting diodes (OLEDs). This growing interest stems particularly from the inherent flexibility of textile-based OLEDs1,2, allowing for seamless integration into the dynamic and interactive functionalities of cutting-edge wearable technology, alongside their superior electrical performance. The durability and mechanical robustness of these displays, especially under physical stress and deformation, are critical to their practical application and longevity. Thus, understanding and enhancing the mechanical properties of textile-based OLEDs is paramount for their successful integration into wearable technologies. However, many studies assessing the mechanical properties of OLEDs have predominantly relied on simplistic bending test outcomes determined by the radius, often neglecting or insufficiently analyzing the strain exerted on the OLEDs atop textile substrates in relation to curvature of these devices. Existing analyses typically presume pure bending, though such an assumption leads to considerable errors in strain estimations, making such approaches problematic if the goal is practical application in actual wearable display products. To address these limitations, an analytic model that includes a comprehensive energy equation is introduced, considering the stretching energy, bending energy, and shear energy of each layer composing the textile substrate. This holistic approach provides a novel formula specifically designed to calculate the top surface strain of textile substrates. Robust validation of this formula is conducted by comparing its results with strain measurements obtained from digital image correlation (DIC) and finite element analysis (FEA) outcomes from ANSYS across various bending radii (or equivalently, curvatures). The close alignment of the calculated strain values with those derived from DIC and FEA not only underscores the precision of this formula but also highlights its significant potential for enhancing the designs and functionalities of future wearable display technologies under real-world conditions. [ABSTRACT FROM AUTHOR]

Multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have garnered significant attention in recent years due to their remarkable properties, such as high luminescent quantum yield, robustness, and their compliance with the Broadcast Television 2020 standard for the new generation of ultrahigh‐definition. Despite these advancements, the operational lifetimes of organic light‐emitting diodes (OLEDs) relying on MR‐TADF emitters still fall short for practical application. It is believed that the enhancement of the intrinsic molecular stability of tBu‐DABNA, a fundamental backbone of MR‐TADF emitters, holds great promise to be a universal strategy for all MR‐TADF emitters improving the operational lifetimes of OLEDs. Herein, the design and synthesis of targeted deuteration are reported on donor and/or backbone of MR‐TADF emitters, where the structure‐property relationship between intrinsic molecular stability upon isotopic effect and device operational stability are examined. The isotopic analogs show a gradual increase in the device operational stability and achieve long‐lifetime LT80 (80% of the initial luminance of 1000 cd m−2) of 24.3 h for TADF‐sensitized fluorescence OLED, representing a sevenfold enhancement when compared with the undeuterated counterpart. This strategic deuteration approach underlines the importance of structural modification on materials toward device operational stability. [ABSTRACT FROM AUTHOR]

High‐efficiency non‐doped deep‐blue organic light‐emitting diodes (OLEDs) meeting the standard of BT.2020 color gamut is desired but rarely reported. Herein, an asymmetric structural engineering based on crossed long‐short axis (CLSA) strategy is developed to obtain three new deep‐blue emitters (BICZ, PHDPYCZ, and PHPYCZ) with a hot‐exciton characteristic. Compared to 2BuCz‐CNCz featuring a symmetric single hole‐transport framework, these asymmetric emitters with the introduction of different electron‐transport units show the enhancement of photoluminescence efficiency and improvement of bipolar charge transport capacity. Further combined with high radiative exciton utilization efficiency and light outcoupling efficiency, the non‐doped OLED based on PHPYCZ exhibits the best performance with an excellent current efficiency of 3.49%, a record‐high maximum external quantum efficiency of 9.5%, and a CIE y coordinate of 0.049 approaching the BT.2020 blue point. The breakthrough obtained in this work can inspire the molecular design of deep‐blue emitters for high‐performance non‐doped BT.2020 blue OLEDs. [ABSTRACT FROM AUTHOR]

High‐efficiency organic blue light‐emitting materials with narrow‐band emission are fundamental components for constructing high color purity and high resolution in high‐performance organic light‐emitting diode (OLED) devices. Herein, new pyrene‐based blue emitters (8–10) with narrow‐band emission are synthesized by asymmetrically introducing biphenyl and triphenylamine units at the 1‐ and 3‐positions of pyrene, respectively. Due to the steric effect and through‐space conjugation, the synergistic effects of both groups not only boost these emitters 8–10 (CIEy < 0.11) with aggregation‐induced emission (AIE) characteristics and high fluorescence quantum yield (>0.68), but also endow narrow full width at half maxima (FWHM) emission (≤36 nm) in the crystallized state (FWHM ≤ 55 nm in the film state). The EL spectra of pyrene‐based 8–10 in nondoped OLEDs exhibit blue emission with a maximum emission (λmax em) in the range of 448–453 nm (CIEy ≤ 0.12). The compounds 8–10 in doped‐OLEDs show a blue emission with a λmax em in the range of 443–445 nm and CIEy ≤ 0.08, with FWHM emission of 57–61 nm. The compound 10‐based doped OLED displays an impressive EL performance with a maximum brightness of 9756 cd m−2 and a maximum external quantum efficiency of 2.58%. [ABSTRACT FROM AUTHOR]

Advanced multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with high efficiency and color purity have emerged as a research focus in the development of ultra‐high‐definition displays. Herein, we disclose an approach to modulate the charge‐transfer excited states of MR emitters via intramolecular covalent bond locking. This strategy can promote the evolution of strong intramolecular charge‐transfer (ICT) states into weak ICT states, ultimately narrowing the full‐width at half‐maximum (FWHM) of emitters. To modulate the ICT intensity, two octagonal rings are introduced to yield molecule m‐DCzDAz‐BNCz. Compounds m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit bright light‐green and green fluorescence in toluene, with emission maxima of 504 and 513 nm, and FWHMs of 28 and 34 nm, respectively. Sensitized organic light‐emitting diodes (OLEDs) employing emitters m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit green emission with peaks of 508 and 520 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.12, 0.65) and (0.19, 0.69), and maximum external quantum efficiencies (EQEs) of 30.2 % and 32.6 %, respectively. [ABSTRACT FROM AUTHOR]

In this work, we report the syntheses of three Pt(II) emitters, namely, Pt4N1, Pt4N2, and Pt4N3, to which their tetradentate chelates were assembled by linking two pyrazolate chelates with a single xylenylamino entity. Functionalization of Pt4N1 was achieved upon the addition of electronegative CF3 substituent on pyridinyl groups and switching to more electron‐deficient pyrazinyl groups in giving Pt4N2 and Pt4N3, respectively. The vertically arranged xylenylamino entity has effectively suppressed the inter‐molecular π‐π stacking and Pt⋅⋅⋅Pt interaction, as shown by the single crystal X‐ray structural analyses. Upon fabrication of OLED devices, Pt4N2 and Pt4N3 based devices delivered efficient cyan and green emission, with an EQEmax of 15.2 % and 11.2 %, respectively, affirming the successfulness of the tetradentate chelating strategy. [ABSTRACT FROM AUTHOR]

Molecular emitters that combined thermally activated delayed and circularly polarized fluorescence (CP‐TADF) is of paramount importance for the next generation of displays. While most efforts have thus far focused on covalent donor and acceptor CP‐TADF emitters, a novel strategy based on chiral exciplexes has recently emerged. In this context, we present the synthesis and chiroptical properties of four new CP‐TADF exciplexes, involving two distinct C2‐symmetric bicarbazole systems and two terpyridine‐based derivatives, which serve as the chiral donor and achiral acceptor units, respectively. These exciplexes exhibit CP‐luminescence, with intensity dependent on both the chiral donor and achiral constituents, resulting in emission dissymmetry factors reaching up to 10⁻2 in the thin‐film solid state. Additionally, small singlet‐triplet gaps (∆EST ≤ 0.1 eV) have been measured, leading to TADF characteristics with a photoluminescence quantum yield of 20% for the most efficient emitter, which is also successfully used in non‐optimized organic lightemitting diodes (OLEDs). Interestingly, these chiral exciplexes allow us to explore the impact of the locally‐excited (LE) state of the chiral donor on overall exciplex emission, particularly in relation to the intensity of polarized emission—potentially highlighting a key factor in the design of this type of bimolecular CP‐TADF emitter. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) using a simple solution‐processing approach have natural advantages in cost‐effective commercialization. However, solution‐processed deep‐red OLEDs are rarely reported due to the scarcity of efficient purely organic narrowband red emitters with commendable film‐forming capabilities. Herein, a simple strategy is proposed to develop organic molecules with narrowband red emission by expanding a rigid conjugated frame to block the rotation of α position in the boron‐dipyrromethene (BODIPY) core due to restricted twisting vibration. Furtherly, by introducing a moderate donor to the meso‐position of the BODIPY core, bathochromic‐shifted emission can be achieved without sacrificing narrow full‐width at half‐maximum (FWHM) by increasing the electron density of the whole molecule and repulsive force of distal units to suppress stretching/scissoring vibration. By employing the developed BODIPY‐derived materials as terminal emitters and thermally activated delayed fluorescence material as assistant host to fabricate solution‐processed OLED devices, a maximum external quantum efficiency of 16.43% is achieved with an emission peak at 672 nm and a FWHM of 28 nm. This work, according to the knowledge, represents the best instance of solution‐processed deep‐red narrowband OLEDs based on typical fluorescent emitters. [ABSTRACT FROM AUTHOR]

Achieving the concurrent manifestation of thermally activated delayed fluorescence (TADF) and aggregation‐induced emission (AIE) within a single molecular system is highly sought after for organic light‐emitting diodes (OLEDs), yet remains rare. In this study, we present a novel TADF‐AIE dye, named PQMO‐PXZ, which has been designed, synthesized, and systematically characterized. Our comprehensive investigation, which includes structural analysis, theoretical calculations, and optical studies, evaluates the potential of PQMO‐PXZ for integration into OLEDs. Unlike existing azaryl‐ketone‐based emitters, PQMO‐PXZ exhibits red‐shifted emission and enhanced luminescence efficiency, due to its rigid structure and strong intramolecular charge transfer characteristics. Significantly, PQMO‐PXZ demonstrates pronounced AIE properties and TADF with a short delayed lifetime. When utilized as the emissive core, OLED devices based on PQMO‐PXZ achieve a respectable external quantum efficiency of up to 11.8 % with minimal efficiency roll‐off, underscoring PQMO‐PXZ's promise as a highly efficient candidate for OLED applications. [ABSTRACT FROM AUTHOR]

Stable and efficient deep‐blue organic light‐emitting diodes (OLEDs) are in high demand for display and lighting applications but are rarely reported due to their poor operational lifetimes. Herein, the study designs and synthesizes two novel N‐heterocyclic carbene (NHC)‐based tetradentate Pt(II) complexes PtON5‐dtb and PtON5N‐dtb, and thoroughly investigate their electrochemical and photophysical properties. Functionalization of the NHC moieties can increase the metal‐to‐ligand charge transfer (1/3MLCT) characters in their lowest triplet excited‐states, resulting in significantly shortened photoluminescent lifetimes and remarkably improved device performance. A deep blue OLED employing PtON5N‐dtb as an emitter exhibits a narrow spectral bandwidth with a full‐width at half maximum (FWHM) of 30 nm and a CIEy value of 0.17 and demonstrates a maximum external quantum efficiency (EQE) of 20.4% with a small efficiency roll‐off, which maintains a high EQE of 18.5% at 1000 cd m−2. Moreover, the deep blue OLED also realizes a long‐measured operational lifetime LT90 (time to 90% of the initial luminance) of 71 hours with an initial brightness of 1134 cd m−2, corresponding to an estimated device lifetime LT90 of 85 h at 1000 cd m−2. This represented an eightfold lifetime improvement for PtON5N‐dtb‐based deep blue OLED compared to PtON7‐dtb in the same device setting. [ABSTRACT FROM AUTHOR]

Despite considerable interest, uniform and robust flexible transparent conducting electrodes (FTCEs) that can be seamlessly integrated and used for highly efficient large‐area flexible oganic light‐emitting diodes (OLEDs) remain elusive. In this study, a large‐area fabrication of uniform transparent electrodes for high‐performance flexible OLEDs by exploiting the rapid nanowelding process of silver nanowires (AgNWs) onto polyethylene terephthalate substrate under Xe‐lamp irradiation and mechanical pressing treatment is reported. The performance of AgNWs FTCEs is significantly enhanced by applying the Xe‐lamp beam irradiation for 5 s and subsequent compression at 20 MPa for 15 s, achieving a low sheet resistance of 26.5 Ω sq−1, a high transmittance of 95.2% (at 550 nm), and very smooth surfaces with root‐mean‐square of 5.4 nm. Meanwhile, the nanowelded AgNWs FTCEs maintain excellent electrical conductivity (only a 2.96% increase in ΔR/R0) after 1000 bending cycles. The resulting AgNWs FTCEs‐based green phosphorescent OLED achieves an unprecedented external quantum efficiency (EQE) of 23.7% and a current efficiency as high as 81.5 cd A−1. Benefiting from the uniform properties for resulting AgNWs FTCEs, the fabricated flexible OLED with a large area of 25 × 25 mm2 still retains a high EQE of 22.2% and a current efficiency of 78.0 cd A−1. [ABSTRACT FROM AUTHOR]

High photoluminescence quantum yield (PLQY) especially in solid‐state together with harvesting radiative triplet excitons are essential to achieve efficient organic light‐emitting diodes (OLEDs). Herein, the aggregation induced emission (AIE) active tetraphenyl buta‐1,3‐diene (TPB) moiety has been employed and tactfully modified to obtain orthogonally oriented donor‐acceptor (D‐A‐π‐A‐D) type derivatives (namely, TPB‐CHO‐TPA and TPB‐CN‐TPA) which possess additionally the hybridized local and charge transfer (HLCT) type excited‐state. Moreover, computational studies have revealed the possibility of triplet harvesting through hot exciton mechanism in these designed emitters. These key features along with excellent solubility in most of the organic solvents have encouraged to utilize these as light emitting materials for solution processed non‐doped and doped OLED devices. The optimal OLED device using TPB‐CHO‐TPA exhibits yellow light emission (ELmax = 572 nm and CIEx,y = 0.48, 0.51) having maximum external quantum efficiency (EQEmax) of 7.6% with power and current efficiency of 6.1 lm W−1 and 8.9 cd A−1 where the calculated exciton utilization efficiency (EUE) approaches to 97%, indicating efficient triplet harvesting in electroluminescence process. This work signifies a novel design strategy for AIE‐based HLCT type emitters having efficient hot exciton utilization which can pave the way for future development of TPB based highly efficient OLED devices. [ABSTRACT FROM AUTHOR]

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Organic light‐emitting diodes (OLEDs) are promising lighting solutions for sustainability and energy efficiency. Incorporating thermally activated delayed fluorescence (TADF) molecules enables OLEDs to achieve internal quantum efficiency (IQE), in principle, up to 100 %; therefore, new classes of promising TADF emitters and modifications of existing ones are sought after. This study explores the TADF emission properties of six designed TADF emitters, examining their photophysical responses using experimental and theoretical methods. The design strategy involves creating six distinct types of a donor‐acceptor (D−A) system, where tert‐butylcarbazoles are used as donors, while the acceptor component incorporates three different functional groups: nitrile, tetrazole and oxadiazole, with varying electron‐withdrawing character. Additionally, the donor‐acceptor distance is adjusted using a phenylene spacer, and its influence on TADF functionality is examined. The clear dependency of an additional spacer, inhibiting TADF, could be revealed. Emitters with a direct donor‐acceptor connection are demonstrated to exhibit TADF moderate emissive behavior. The analysis emphasizes the impact of charge transfer, singlet‐triplet energy gaps (ΔEST), and other microscopic parameters on photophysical rates, permitting TADF. Among the emitters, TCz‐CN shows optimal performance as a blue‐green emitter with an 88 % photoluminescence quantum yield (PLQY) and fast rate of reversible intersystem crossing of 2×106 s−1 and 1×107 s−1, obtained from time‐resolved photoluminescence (TRPL) experiment in PMMA matrix and quantum mechanical calculations, respectively. This comprehensive exploration identifies molecular bases of superior TADF emitters and provides insights for future designs, advancing the optimization of TADF properties in OLEDs. [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]

Due to the feature of the strong intermolecular interactions causing aggregation‐caused excitons quenching (ACQ) of solution process, realizing high‐performance solution‐processed organic light‐emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters remains a formidable challenge nowadays. To address this issue, herein, a novel strategy is proposed to construct solution‐processable ternary exciplex emitters by utilizing the dendritic oligomer as the substrate, simultaneously realizing excellent solution‐process adaptability, good dispersibility to restrain harmful ACQ, and improved exciton utilization with multiple reverse intersystem crossing channels. Accordingly, dendritic oligomer‐based exciplex systems are constructed by combining small‐molecule donor and acceptor components with the multi‐carbazole‐substituted tetraphenylsilane‐core analog as substrate. And their film morphologies, photoluminescence quantum yields (ΦPLs), and non‐radiative decay rates of triplet excitons (knrTs) are significantly improved. Among them, DMAC‐DPS:PO‐T2T:SimCP3 exhibits the highest ΦPL of 97.5% and the lowest knrT of 1.0 × 103 s−1, and realizes the best maximum external quantum efficiency of 29.7% in solution‐processed OLED, which is comparable with the highest electroluminescence efficiencies of all solution‐processable emitters. Therefore, this work will provide a prospective pathway to develop efficient solution‐processable exciplex emitters and promote the progress of solution‐processed OLEDs. [ABSTRACT FROM AUTHOR]

Different from conventional luminescent dendrimers with fluorophore tethered outside to dendron, here we first developed endo‐encapsulated luminescent dendrimers with multi‐resonance (MR) fluorophore embedded inside of carbazole dendrons by growing dendrons through 1,8‐positions of central carbazole moiety to create a cavity for accommodating the fluorophore. This endo‐encapsulated structure not only shields the fluorophore to fully resist aggregation‐caused spectral broadening, but also induce through‐space interactions between dendron and fluorophore via intramolecular π‐stacking, giving lowered singlet state energy and reduced singlet‐triplet energy splitting to accelerate reverse intersystem crossing (RISC) from triplet to singlet states. The resultant dendrimer containing 1,8‐linked second‐generation carbazole dendrons and boron, sulfur‐doped polycyclic MR fluorophore exhibits narrowband blue emission at 471 nm with FWHM kept at 34 nm even in neat film, together with ~4 times enhancement of RISC rate constant compared to its exo‐tethered counterpart. Solution‐processed OLEDs based on the endo‐encapsulated dendrimer reveal efficient narrowband blue emissions with maximum external quantum efficiency of 22.6 %, representing the best device efficiency for blue‐emitting multi‐resonance dendrimers so far. [ABSTRACT FROM AUTHOR]

To enhance organic light emitting diode (OLED) performance, host materials with high triplet energies are crucial for confining excitons, despite increasing driving voltages due to the singlet‐triplet energy gap. We synthesized sulfonylbis(4,1‐phenylene)bis(3,6‐disubstituted‐9H‐carbazole) derivatives as donor‐acceptor‐donor host materials, namely compounds 3, 5 and 7, with varying fluorination levels. These compounds show moderate singlet‐triplet energy splitting and molecular dipole moments, allowing for fine‐tuning of hole‐transport mobilities, deeper frontier orbital energies, and a red shift in singlet emission while maintaining high triplet energy levels. These adjustments impact a range of physical, electronic and optical properties. The materials exhibit exceptional thermal stability, with decomposition starting above 400 °C and glass transition temperatures over 130 °C. Used with the green TADF emitter DACT‐II, these hosts enable reverse intersystem crossing rates between 7.43×104 s−1 and 1.77×105 s−1. While OLEDs using mCP as a reference host achieve a maximum quantum efficiency of 18.5 %, those with host 5 show lower efficiency roll‐off, leading to higher external quantum efficiency at brightness levels above 2000 cd/m2 without colour shift. The reduced roll‐off in devices with host 5 compared to mCP is attributed to effective Förster and Dexter energy transfers to DACT‐II at high currents, enhancing light emission pathways. [ABSTRACT FROM AUTHOR]

Deep‐red and near‐infrared emitters with twisted donor–acceptor (D–A) structures often exhibit suboptimal performance in organic light‐emitting diodes (OLEDs) due to constraints imposed by the energy gap law. In this work, a pure hydrogen carbon (PHC) host material named SBF‐DTP is purposefully tailored for deep‐red OLEDs. The excellent capacity of SBF‐DTP to support D–A type DR emitters effectively arises from its distinctive attributes: localized excitation states, 3D configuration, and low polarity. When employing SBF‐DTP as the host for the fluorescence emitter DCPA‐TPA and the thermally activated delayed fluorescence emitter APDC‐DTPA, doped films exhibit substantially enhanced photoluminescence quantum yields. This improvement leads to high‐efficiency OLEDs with external quantum efficiencies of 5.47% for DCPA‐TPA and 20.03% for APDC‐DTPA, respectively, which is about twice as high as the initial reports. This findings underscore the paramount significance of developing efficient host materials in the pursuit of high‐performance deep red and even near‐infrared OLEDs. [ABSTRACT FROM AUTHOR]

Developing highly efficient red/near‐infrared (NIR) thermally activated delayed fluorescence (TADF) materials is important for organic light‐emitting diodes (OLEDs). Here, two TADF emitters, APTT and APTI, which have the same D/A backbone but different attaching groups at acenaphtho‐[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC) core, are reported. The appended regulating groups can not only suppress the D/A rotation due to the space confinement effects but also modulate the locally excited triplet state (3LE). The improved molecular rigidity suppresses the non‐radiative process, accounting for the improved photoluminescence quantum yields (PLQYs), while the modulated 3LE promotes the reverse intersystem crossing (RISC) process due to the high utilization efficiency of triplets. Consequently, both APTT and APTI demonstrate high PLQY and fast RISC process, thereby enhancing TADF efficiency. The doped devices based on APTT and APTI achieve maximum external quantum efficiency (EQEmax) values of 20.5% and 25.4% with emission peaks at 664 and 670 nm, respectively. The non‐doped devices of APTT and APTI achieve the EQEmax of 2.8% and 2.9% with emission peaks at 788 and 794 nm, respectively. Encouragingly, the non‐doped devices of APTI have set new records for near‐infrared TADF OLEDs based on the APDC core. This study provides an efficient approach to modulating the optoelectronic properties of highly efficient NIR TADF OLEDs. [ABSTRACT FROM AUTHOR]

Thin‐film encapsulation is a core technology that determines the reliability of next‐generation displays, including wearable and stretchable displays. However, the encapsulation technologies developed to date are highly vulnerable to mechanical stress and harsh hygrothermal environments. Therefore, the degradation of their original encapsulation performance (as determined by mechanical and environmental reliability tests) is a major limitation. This paper describes a novel inorganic/organic multibarrier encapsulation method based on structural and material design to overcome the reliability problems of freeform displays. The highly reliable mechanical properties of the encapsulation system are verified using the tensile‐testing‐on‐water method, which is the most reliable method for thin films with thicknesses of tens to hundreds of nanometers. The optimal encapsulation system developed herein achieves an unprecedented elongation of 2.8% in its freestanding form, surpassing the elastic limit of traditional inorganic materials, and maintains a notable elongation of 1.43% after being exposed to harsh environments for 30 h (85 °C and 85% relative humidity). The inorganic/organic hybrid encapsulation system designed through systematic analysis in this study is expected to increase the lifetime of devices and facilitate high outdoor usability in applying ultraflexible wearable organic light‐emitting diodes. [ABSTRACT FROM AUTHOR]

Benzophenone skeletons containing a carbonyl unit (O=C) have been widely used as electron acceptors in the thermally activated delayed fluorescence (TADF) materials. Herein, we present a novel molecular design concept for TADF materials by transitioning from a carbonyl to an amide (O=C−N) skeleton as the acceptor. The amide unit, compared to its carbonyl counterpart, offers a more stable electronic configuration. Leveraging this insight, we have developed a series of high‐performance TADF molecules based on benzoyl carbazole and carbazoline acceptors. These molecules exhibit exceptionally small singlet‐triplet energy gaps and pronounced aggregation‐enhanced emission properties, achieving photoluminescence quantum yields in neat films as high as 99 %. Consequently, these materials serve as efficient emitters in non‐doped organic light‐eimtting diodes (OLEDs), reaching a maximum quantum efficiency (EQEmax) of up to 26.0 %, significantly higher than the 17.0 % obtained with benzophenone acceptor‐based TADF molecules. Additionally, they have been used as TADF hosts in narrowband red fluorescent OLEDs, setting a record‐high EQEmax of 22.4 %. [ABSTRACT FROM AUTHOR]

[Objective] The preparation of luminescent display pixels using inkjet printing technology offers significant advantages, including low cost, flexibility, and the potential for large-scale production. This approach effectively reduces the production cost of OLED displays. The process of inkjet printing organic light-emitting layers is particularly crucial and complex. It requires designing and optimizing driving waveforms to achieve stable droplet formation without satellite points. Additionally, the printing line width and thickness must be adjusted to produce a dense and uniform thin film. Before preparing display pixels, it is essential to observe the inkjet droplets and assess their stability. However, changes in driving waveform parameters, ink ratio, or printing temperature can affect various parameters, including ink droplet uniformity, stability, volume, and injection speed--changes that are often undetectable by the naked eye. [Methods] This study investigates an automatic measurement technology for inkjet droplet parameters. A droplet-driving waveform customization module has been integrated into LabVIEW software using the NI Vision visual development module. This optimization of the droplet-driving waveform aims to achieve perfect jet droplets. The droplet image is captured using phase delay technology, which employs two control signals of the same frequency and a constant phase difference. One signal is the droplet drive signal, while the other is a square wave signal that triggers the camera and strobe light source. When the first driving waveform from the nozzle arrives, another signal is output as a pulse square wave after a delay of Δt. At this moment, the strobe light source activates, and the camera captures an image of the ink droplet. When the nozzle continuously sprays ink droplets at a fixed frequency, Δt remains constant, resulting in multiple images captured by the camera that maintain consistency, giving the appearance that the ink droplets are stationary in the air. By varying the delay time Δt between the two signals, the position of the ink droplets changes, allowing for the simulation of the dynamic falling process of the ink droplets. [Results] Droplet images are obtained at different times with a phase delay of Δt = 10 µs, capturing a complete spraying process. The images undergo filter denoising, binary conversion, morphological operations, and edge detection to obtain clear droplet contours. The volume of the ink droplets is calculated using an integral formula, and the diameter of the droplets is further determined using the spherical volume formula. The spray speed of the droplets is calculated based on the differences in ink droplet positions across multiple frames of images. [Conclusions] This research on automatic measurement technology for inkjet droplet parameters has resulted in the development of a hardware device for droplet observation, with a software control system implemented in LabVIEW graphical programming language. Droplet images are captured at different times with a phase delay of Δt=10 µs. Each image undergoes filtering, denoising, binary conversion, morphological operations, and edge detection to obtain clear droplet contours, thereby capturing a complete spraying process. The effective extraction of droplet contours, along with the automatic calculation of droplet spraying speed, diameter, and volume parameters, provides a visualization tool for optimizing ink preparation and inkjet printing, thereby facilitating the production of high-quality films. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) molecules are regarded as promising materials for realizing high‐performance organic light‐emitting diodes (OLEDs). The connecting groups between donor (D) and acceptor (A) units in D–A type TADF molecules could affect the charge transfer and luminescence performance of TADF materials in aggregated states. In this work, we design and synthesize four TADF molecules using planar and twisted linkers to connect the aza‐azulene donor (D) and triazine acceptor (A). Compared with planar linkers, the twisted ones (Az‐NP‐T and Az‐NN‐T) can enhance A–A aggregation interaction between adjacent molecules to balance hole and electron density. As a result, highly efficient and stable deep‐red top‐emission OLEDs with a high electroluminescence efficiency of 57.3% and an impressive long operational lifetime (LT95 ∼ 30,000 h, initial luminance of 1000 cd m−2) are obtained. This study provides a new strategy for designing more efficient and stable electroluminescent devices through linker aggregation engineering in donor–acceptor molecules. [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]

Solution‐processed fluorescent organic light‐emitting diodes (OLEDs) are believed to be favorable for low‐cost, large‐area, and flexible displays but still suffer from the limited external quantum efficiency (EQE) below 5%. Herein, we demonstrate the EQE breakthrough by introducing a donor–acceptor type thermally activated delayed fluorescence (TADF) polymer as the sensitizer for the typical green‐emitting fluorescent dopants. Benefitting from their matched energy alignment, the unwanted trap‐assisted recombination directly on fluorescent dopant is prevented to avoid the additional loss of triplet excitons. Indeed, triplet excitons are mainly formed on the polymeric TADF sensitizer via a Langevin recombination and then spin‐flipped to singlet excitons due to the good upconversion capability. Followed by an efficient Förster energy transfer, both singlet and triplet excitons can be harvested by fluorescent dopants, leading to a promising solution‐processed green hyperfluorescence with a record‐high EQE of 21.2% (72.2 cd/A, 59.7 lm/W) and Commission Internationale de L'Eclairage coordinates of (0.32, 0.59). The results clearly highlight the great potential of solution‐processed fluorescent OLEDs based on TADF polymers as the sensitizer. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) have emerged as one of the dominant technologies in displays due to their high emission efficiency and low power consumption. However, the development of blue color emitters has fallen behind that of red and green emitters, posing challenges in achieving optimal efficiency, stability, and accessibility. In this context, thermally activated delayed fluorescence (TADF) emitters hold promise as a potential solution for cost-effective, exceptionally efficient, and stable blue OLEDs due to their potential high efficiency and stability. TADF is a principle where certain organic materials can efficiently convert both singlet and triplet excitons, theoretically achieving up to 100% internal quantum efficiency. This research focused on diphenyl sulfone derivatives with carbazole groups as TADF compounds. Quantum chemical calculations and photoluminescence properties show the potential TADF properties of the molecules. New materials exhibit glass transition temperatures that would classify them as molecular glasses. Depending on the structure of the molecule, the photoluminescence emission is in the blue or green spectral region. Organic light-emitting diodes were fabricated from neat thin films of emitters by the wet casting method. The best performance in the deep blue emission region was achieved by a device with a turn-on voltage of 4 V and a maximum brightness of 178 cd/m2. In the blue-green emission region, the best performance was observed by an OLED with a turn-on voltage of 3.5 V, reaching a maximum brightness of 660 cd/m2. [ABSTRACT FROM AUTHOR]

Thin films of molecular materials are commonly employed in organic light‐emitting diodes, field‐effect transistors, and solar cells. The morphology of these organic films is shown to depend heavily on the processing used during manufacturing, such as vapor co‐deposition. However, the prediction of processing‐dependent morphologies has until now posed a significant challenge, particularly in cases where self‐assembly and ordering are involved. In this work, a method is developed based on coarse‐graining that is capable of predicting molecular ordering in vapor‐deposited films of organic materials. The method is tested on an extensive database of novel and known organic semiconductors. A good agreement between the anisotropy of the refractive indices of the simulated and experimental vapor‐deposited films suggests that the method is quantitative and can predict the molecular orientations in organic films at an atomistic resolution. The methodology can be readily utilized for screening materials for organic light‐emitting diodes. [ABSTRACT FROM AUTHOR]

In this study, two novel multiple resonance (MR)-type blue emitters, namely SBN-1 and SBN-2, were synthesized and prepared for the development of highly efficient and stable blue fluorescent organic light-emitting diodes (OLEDs). The MR-type blue emitters are characterized by the presence of two benzothiophene groups within their MR-conjugated systems, with small dihedral angles, which distinguishes them from the well-known DABNA-1 derivatives and results in highly planar conjugated structures. Additionally, the MR effect still contributes to narrowband emissions of SBN-1 and SBN-2, showing small full width at half maximums (FWHMs) of 21 and 20 nm in toluene, respectively. Simultaneously, the MR-type materials embedding benzothiophene fragments could restrain the quenching effect between intermolecular interaction by introducing auxiliary aryl/heteroaryl amines containing the tert-butylbenzene or 9,9-dimethylxanthene group, giving long device lifetime. The fluorescent OLEDs based on SBN-1 and SBN-2 demonstrate pure blue emissions at 462 and 458 nm with CIE coordinates of (0.126, 0.194) and (0.133, 0.139), along with high external quantum efficiencies of 4.9% and 5.0%, respectively. Notably, SBN-2 exhibits an operational lifetime of up to approximately 220 hours until reaching a luminance level equivalent to 95% initial luminance (LT95) at an intensity level of 1000 cd m−2. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes have a huge gain in popularity over the past 25 years for display and lighting applications, but the production of low‐cost efficient devices remains a challenge. OLEDs using sub‐nanometer undoped emissive layers are a route to fabricate cost‐effective devices but, as they are inherently thin, it opens to issues with variation in thickness and shunting paths. At the same time, lead chloride perovskites are currently being investigated as charge transport materials in light‐emitting devices owing to their wide bandgap, and remarkable high carrier mobility. In this work, for the first time, OLEDs that combine vacuum‐processed thick cesium lead chloride perovskite hole transport layers with ultrathin Ir complex‐based emissive layers are reported. Defects on the perovskite film are suppressed and the thickness of the emitting layer is optimized. Semitransparent devices are also fabricated with an average visible transmittance of over 50%. The results show extraordinarily thick devices (>1 µm) with low turn‐on voltage (3.3 V), high luminance (>15 000 cd m−2) and efficiencies (up to 54.1 cd A−1), and a negligible efficiency roll‐off in the display applications luminance region. [ABSTRACT FROM AUTHOR]

Herein this work, a novel donor‐π‐acceptor (D‐π‐A) pure‐blue hybrid local and charge‐transfer (HLCT) fluorescent material TDFBO and its functionalization as organic light emitting diode (OLED) emitter and photoinitiator (PI) in photopolymerization is reported. The weak‐hybridization property involved by the fluorene π‐bridge can simultaneously give satisfied photo‐luminescent quantum yield (PLQY) and make efficient "hot‐exciton" channel achievable. Moreover, the D‐π‐A structure can also promote an exceeding electron mobility as high as 3.57×10−4 cm2 V−1 s−1. Finally, it is noted that the TDFBO‐doped OLED can be regarded as the best one among the pure‐blue emissive OLEDs, which exhibits a high maximum external quantum efficiency of 11.1%, while the rolling‐off only stands on a low level, as 6% at 100 cd m−2. Additionally, a relatively high final conversion of C = C double bond in a representative acrylate monomer is also attained by photoinitiation of TDFBO under 405 nm LED, where the photopolymerization has been applied to 3D printing. [ABSTRACT FROM AUTHOR]

The development of highly efficient pure near‐infrared (NIR) emitting organic materials with emission beyond 800 nm is extremely challenging due to the limitation of the energy gap law. Herein, three efficient NIR emitting iridium(III) complexes are developed adopting pyrido[3,4‐b]pyrazine derivatives as the cyclometalated C^N ligands, namely (Epptt)2Iracac (1), (pptt)2Iracac (2), and (ppCz)2Irtmd (3). Due to the enhanced donor–acceptor interaction inside the ligand, the conjugation‐extended and electron‐richer N‐phenylcarbazole unit at the C‐part of the ligands endows complex 3 with a large bathochromic shift of emission peak from 796 to 862 nm in toluene solution, compared with thieno[3,2‐b]thiophene C‐part in complex 2. The solution‐processed OLEDs based on complex 3 achieved a record high maximum external quantum efficiency of 3.75% and low efficiency roll‐off with the emission peak at 830 nm, a champion efficiency in the Ir(III) based OLEDs with emission peak exceeding 800 nm. This work opens a new avenue for the development of high‐efficiency pure NIR organic emitters based on Ir(III) complexes for various applications. [ABSTRACT FROM AUTHOR]

A series of green multi-resonance thermally activated delayed fluorescence polymeric emitters featuring conjugation-interrupted main chains were facilely prepared via metal-free superacid-catalyzed Friedel–Crafts polyhydroxyalkylation. These emitters exhibited photoluminescence quantum yields of up to 76% and small full-widths at half maximum of 35–38 nm in toluene. The corresponding solution-processed OLEDs achieved an excellent maximum external quantum efficiency of 19.4%, with CIE coordinates of (0.20, 0.62). [ABSTRACT FROM AUTHOR]

The growing demand for low‐temperature thin‐film encapsulation (TFE) in advanced flexible and wearable organic light‐emitting diodes (OLEDs) has intensified to mitigate thermal issues, which deteriorate the device performance. Herein, Al2O3/TiO2 nanolaminates (A/T NLs)are introduced and fabricated via thermal atomic layer deposition at an exceptionally low temperature of 40 °C, which exhibited enhanced mechanical and environmental robustness. Compared to the single‐layer Al2O3 and TiO2 thin films (0.06% and 0.31%), the A/T NLs with sublayer thickness under 15 nm exhibit dramatic improvement in elongation (0.46–0.53%), attributed to the effective decoupling of critical defects by the Al2O3/TiO2 interfaces. Furthermore, the A/T NLs with 3 nm‐thick‐sublayer demonstrate highly improved water vapor transmission rates of 9.48 × 10−5 g m−2 day−1, making them promising candidates for TFE in wearable OLEDs. Notably, the optimized A/T NL‐encapsulated wearable phosphorescent OLEDs (phOLEDs) exhibit extended lifetimes (LT70), surpassing 200 h in the accelerated environmental conditions (40 °C/90% RH) which is 40 times longer lifetimes compared to the not encapsulated OLEDs. Additionally, the A/T NL‐encapsulated wearable phOLEDs displayed mechanical endurance, enduring 125 h even under the bending strain of 0.4% compared to the Al2O3‐ and TiO2‐encapsulated OLEDs (4 and 18 h). [ABSTRACT FROM AUTHOR]

Attaining phosphorescent materials with narrowband emission is crucial for advancing wide‐color‐gamut organic light‐emitting diode (OLED). Herein, a rigid modification strategy is introduced for iridium(III) complexes to achieve the narrowband red emission with negligible 0–1 peak. By introducing the rigid indolo[3,2,1‐jk]carbazole (ICz) into the cyclometalated ligand, Ir(III) complexes, ICziq‐Ir and ICzqz‐Ir, exhibit pure red phosphorescence with emission peaks at 608 and 613 nm and full widths at half‐maximum (FWHMs) of 37 and 38 nm (0.12 and 0.13 eV) in toluene, respectively. Furthermore, the specific site modification of ICzqz‐Ir greatly suppresses the high‐frequency vibration of the structure, resulting in the narrowband photoluminescent spectrum close to the Gaussian distribution with superior color purity. The OLEDs utilizing ICziq‐Ir and ICzqz‐Ir demonstrate maximum external quantum efficiencies of 21.4 and 17.8% as well as mild efficiency roll‐off. Remarkably, the electroluminescence spectra exhibit similar narrowband red emission with FWHMs of 37 and 43 nm and CIE coordinates of (0.65, 0.35) and (0.66, 0.34), attesting to the excellent color purity of the phosphorescent OLEDs. [ABSTRACT FROM AUTHOR]

Simultaneously improving radiative decay and reverse intersystem crossing (RISC) of through‐space charge‐transfer (TSCT) thermally‐activated delayed fluorescence (TADF) emitters has remained a challenge. Here, space‐confined TSCT‐TADF emitters are developed with a planar indolo[3,2,1‐kl]phenoxazine donor, a spiro‐carbon‐fixed benzophenone acceptor, and a fluorene (for 1) or xanthene (for 2) bridge. Close, cofacial donor/acceptor alignments and efficient intramolecular TSCT have been observed for both emitters. Intriguingly, emitter 1 exhibits an intermolecular donor/acceptor interaction as strong as the intramolecular one, which opens efficient intermolecular TSCT, improving the radiative decay rate (kr,s) to the same level as emitter 2 featuring a much stronger intramolecular donor/acceptor interaction. The intermolecular TSCT also largely enhances the RISC rate (kRISC). In the 20 wt.% doped films, emitters 1 and 2 show green TADF with high kr,s/kRISC at 1.1 × 107 s−1/1.3 × 106 s−1 and 1.2 × 107 s−1/7.7 × 105 s−1, respectively. Organic light–emitting diodes (OLEDs) using the emitters show high external quantum efficiencies (EQEs) up to 27.5% and low‐efficiency roll‐offs. Hyperfluorescent OLEDs using the emitters as sensitizers afford narrowband blue‐green emission with high EQEs up to 30.6% and largely suppressed efficiency roll‐offs. The work reveals that strengthening intermolecular TSCT is a promising avenue to simultaneously improve kr,s, and kRISC of TSCT‐TADF emitters for high‐performance OLEDs. [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]

Simultaneously achieving high-efficiency, deep-red emission, and solution-processed organic light-emitting diodes (OLEDs) remains a huge challenge. In this work, a thermally activated delayed fluorescent (TADF) material of CzPXZ that exhibits aggregation-induced emission property and a deep-red phosphorescent emitter of Ir(dmppy)(piq)2(od) are developed to build effective energy transfer pathways by dissolving them in a non-polar organic solvent. The electroluminescent emission peaks of CzPXZ:Ir(III)-based OLEDs are located at deep-red 626 nm, demonstrating efficient energy transfer from CzPXZ to the Ir(III) complex. Furthermore, an optimized DPEPO hole-blocking layer is utilized in such Ir(III)-doped OLEDs to enhance the radiative recombination. Therefore, a high external quantum efficiency of 43.76% is achieved for CzPXZ:Ir(III)-based OLEDs. This work sheds light on the great potential of energy transfer from AIE-TADF to red phosphorescent emitters for high-efficiency, solution-processed, deep-red OLEDs. [ABSTRACT FROM AUTHOR]