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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]

Red to near-infrared organic light-emitting diodes (OLEDs) utilizing thermally activated delayed fluorescence (TADF) emitters continue to exhibit significant external quantum efficiency (EQE) roll-off at high luminance levels exceeding 1000 cd m−2, attributed to the relatively modest reverse intersystem crossing rate constant (kRISC) of approximately 103–104 s−1. This study presents a novel TADF molecule, TCPP-DTPA, featuring a structurally rigid π-stacked multiple donor/acceptor design. The enhanced donor/acceptor interactions minimize the energy gap between the singlet and triplet states of the TCPP-DTPA, allowing for an efficient RISC process with a high rate constant of 4.67 × 106 s−1. The OLED utilizing TCPP-DTPA demonstrates a peak EQE of 23.5% at a wavelength of 618 nm. Additionally, notable EQE values of 7.8% and 14.9% are observed at a luminance of 1000 cd m−2 for OLEDs without and with an energy-transfer assistant dopant in the emissive layer, respectively. This research contributes to enhancing the efficiency of high-brightness red TADF OLEDs, while also offering valuable insights for the optimization of molecular design and device engineering to mitigate the electroluminescence efficiency roll-off. [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]

The current availability of multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials with excellent color purity and high device efficiency in the deep‐blue region is appealing. To address this issue in the emerged nitrogen/carbonyl MR‐TADF system, we propose a spiro‐lock strategy. By incorporating spiro functionalization into a concise molecular skeleton, a series of emitters (SFQ, SOQ, SSQ, and SSeQ) can enhance molecular rigidity, blue‐shift the emission peak, narrow the emission band, increase the photoluminescence quantum yield by over 92 %, and suppress intermolecular interactions in the film state. The referent CZQ without spiro structure has a more planar skeleton, and its bluer emission in the solution state redshifts over 40 nm with serious spectrum broadening and a low PLQY in the film state. As a result, SSQ achieves an external quantum efficiency of 25.5 % with a peak at 456 nm and a small full width at half maximum of 31 nm in a simple unsensitized device, significantly outperforming CZQ. This work discloses the importance of spiro‐junction in modulating deep‐blue MR‐TADF emitters. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) with high-definition displays require narrowband emission from each pixel. Recently, boron-based thermally activated delayed fluorescence (TADF) emitters have gained broad attention in the OLED research field. They can effectively utilize both singlet and triplet excitons for electroluminescence, resulting in a small full width of half maximum (FWHM). The fused nitrogen/boron (N/B) system, known as the multi-resonance TADF (MR-TADF) system, has been making rapid progress. In this review, we summarize the current research progress in both traditional and MR-type boron derivatives with TADF characteristics from a molecular construction perspective. We discuss the molecular design strategy involved in maintaining high device efficiency and simultaneously achieving a narrowband emission profile. This review aims to provide insight and guidance for future developments for improving the stability, color purity, and performance of boron-based materials. [ABSTRACT FROM AUTHOR]

Precise fabrication of organic micro/nanostructures with regular morphology has gained a considerable concern in developing high‐performance optoelectronic devices, which is still a huge challenge to realize tunable morphology without the dependence on molecule packing arrangement. Herein, a thermodynamic/kinetic controlled self‐assembly for triphenylene‐7,7,8,8‐tetracyanoquinodimethane (TP‐TCNQ) cocrystal, with well‐defined microwires and microplates based on the same crystal structure, is proposed. With the low solution concentration of C = 5 mm, the comparable growth rates along [011] driven by π–π interaction and along [100] driven by charge‐transfer (CT) interaction facilitate the formation of thermodynamically favored shape of microplates. In contrast, the prominent CT interaction along [100] leads to the construction of microwires at kinetic state under high‐concentration solution of C = 10 mm. Furthermore, the prepared TP‐TCNQ microwires and microplates demonstrate isotropic photonic transmissions with the low optical loss coefficient of 0.033 and 0.042 dB µm−1, respectively. This strategy provides a novel avenue to finely construct the organic microcrystals with desired morphology for potential optoelectronics. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (PeNCs) deliver size‐ and composition‐tunable luminescence of high efficiency and color purity in the visible range. However, attaining efficient electroluminescence (EL) in the near‐infrared (NIR) region from PeNCs is challenging, limiting their potential applications. Here we demonstrate a highly efficient NIR light‐emitting diode (LED) by doping ytterbium ions into a PeNCs host (Yb3+ : PeNCs), extending the EL wavelengths toward 1000 nm, which is achieved through a direct sensitization of Yb3+ ions by the PeNC host. Efficient quantum‐cutting processes enable high photoluminescence quantum yields (PLQYs) of up to 126 % from the Yb3+ : PeNCs. Through halide‐composition engineering and surface passivation to improve both PLQY and charge‐transport balance, we demonstrate an efficient NIR LED with a peak external quantum efficiency of 7.7 % at a central wavelength of 990 nm, representing the most efficient perovskite‐based LEDs with emission wavelengths beyond 850 nm. [ABSTRACT FROM AUTHOR]

Conformational engineering is essential to further reinforce the luminescent properties of thermally activated delayed fluorescence (TADF) materials featuring through‐space charge transfer (TSCT) characteristics. Herein, two TSCT‐TADF emitters (8MeDM‐B and 8FDM‐B) with the methyl and fluorine moieties substituted at the C8 site of the rigid spiro‐fluorene bridge is reported. Derivation of the C8 site is first proposed to control the molecular configuration with the ability to indirectly tune the intramolecular interaction between donor and acceptor groups. As a result, 8MeDM‐B and 8FDM‐B both present small singlet‐triplet energy gaps, fast reverse intersystem crossing rates, and high photoluminescence quantum yields. Interestingly, the smaller fluorine atom not the bigger methyl group exhibits more evident electrostatic repulsive force onto the central donor and thus rectifies the central spiro structure. Consequently, the high external quantum efficiency values of 28.8% and 31.7% for 8MeDM‐B and 8FDM‐B‐based electroluminescence devices are achieved, respectively. This study offers a measure for enhancing TSCT‐TADF emitters without directly modifying the donor or acceptor. [ABSTRACT FROM AUTHOR]

Carbonyl‐containing derivatives show enduring vitality in the field of thermally activated delayed fluorescence (TADF) materials; they can realize high device efficiency by using both singlet and triplet excitons for electroluminescence. Recently, a system based on fused ketone/amine exhibited huge potential for constructing multi‐resonance TADF (MR‐TADF) emitters, which exhibit higher narrow‐band emission than conventional TADF emitters with twisted donor‐acceptor (D‐A) structure. Herein, we summarize current research progress in both traditional and MR‐type ketone derivatives with TADF characteristics for introducing the molecular design strategy of maintaining high device efficiency while keeping narrow‐band emission profile. We hope this review can inspire the emergence of more high‐performance narrow‐band materials. [ABSTRACT FROM AUTHOR]

Excited‐state intramolecular proton transfer (ESIPT)‐active organic semiconductor materials, characterized by a or several resonance‐assisted hydrogen bonds (RAHBs), are supposed to be ideal candidates for achieving high‐performance near‐infrared (NIR) lasers. However, according to the energy gap law, the development of ESIPT‐active gain materials is still limited by the serious nonradiative decays. Herein, it is demonstrated that RAHBs can activate ESIPT lasing by inhibiting nonradiative decays. A new ESIPT‐active material 1,5‐dihydroxy‐2,6‐diphenylanthraquinone (DP‐DHAQ) containing two centrosymmetric RAHBs is developed, which exhibits a ≈100‐fold higher radiative decay rate (kr = 1.1 × 1010 s–1) in doped polystyrene (PS) film than that of 1‐hydroxy‐5‐methoxy‐2,6‐diphenylanthraquinone (DP‐HMAQ) and 1,5‐dimethoxy‐2,6‐diphenylanthraquinone (DP‐DMAQ), in which one and two RAHBs are broken, respectively, by introducing methyl groups. Both DP‐DHAQ and DP‐HMAQ can form four‐level systems based on the ESIPT processes, but only DP‐DHAQ doped PS microspheres exhibit laser emission at 710 nm under the test conditions. It is worth mentioning that single‐crystal microplates of DP‐DHAQ can realize NIR laser emission at 725 nm. The results suggest that RAHBs can effectively activate the gain property of ESIPT‐active materials, which deepens insights into NIR ESIPT lasing and provides a new proposal for the design of organic laser‐active molecules. [ABSTRACT FROM AUTHOR]

Organic materials with multi‐stimulus response (MSR) properties have demonstrated many potential and practical applications. Herein, a π‐stacked thermally activated delayed fluorescence (TADF) material with multi‐stimulus response (MSR) properties, named SDMAC, was designed and synthesized using distorted 9,9‐dimethyl‐10‐phenyl‐9,10‐dihydroacridine as a donor. SDMAC possesses a rigid π‐stacked configuration with intramolecular through‐space interactions and exhibits aggregation‐induced emission enhancement (AIEE), solvatochromic, piezochromic, and circularly polarized luminescence (CPL) under different external stimuli. The rigid molecular structure and efficient TADF properties of SDMAC can be used in displays and lighting. Using SDMAC as an emitter, the maximum external quantum efficiency (EQE) of the fabricated organic light‐emitting diodes (OLEDs) is as high as 28.4 %, which make them the most efficient CP‐TADF OLEDs based on the through‐space charge transfer strategy. The CP organic light‐emitting diodes (CP‐OLEDs) exhibit circularly polarized electroluminescence (CPEL) signals. [ABSTRACT FROM AUTHOR]

The employment of thermally activated delayed fluorescence (TADF) emitters is one of the most promising ways to realize the external quantum efficiency (EQE) of over 25% for organic light-emitting diodes (OLEDs). In addition, the TADF emitter based on oxygen-bridged boron (BO) fragment can maintain blue emission with high color purity. Herein, we constructed two blue TADF emitters, 3TBO and 5TBO, for OLEDs application. Both emitters consist of three donors linked at the oxygen-bridged boron acceptor. OLED devices based on 3TBO and 5TBO exhibited both high excellent device efficiency and high color purity with a maximum EQE; full-width at half-maximum (FWHM); and CIE coordinates of 17.3%, 47 nm, (0.120, 0.294), and 26.2%, 57 nm, (0.125, 0.275), respectively. [ABSTRACT FROM AUTHOR]

Optical interconnects exhibit superior potential in the precise regulation of photon transmission for organic photonic circuits. However, the rational design of well‐defined organic heterostructures toward active optoelectronics remains challenging. Herein, we designed organic branched heterostructures (OBHs) with accurate spatial organization for optical interconnection. Notably, the precise regulation of OBHs has been controllably achieved including the trunk morphologies and the branched microwire number. Significantly, these as‐prepared OBHs inherently exhibit the multichannel coupling outputs and the excitation position‐dependent waveguide characteristics, leading to various outcoupling signals with tunable intensity and emission colors. The optical interconnects are realized due to the occurrence of exciton conversion and photon propagation between branch and trunk at the heterojunction, benefiting the application possibilities of two‐dimensional (2D) optical barcodes. [ABSTRACT FROM AUTHOR]

A hetero-bichromophore thermally activated delayed fluorescence (TADF) emitter named BOQAO was designed and synthesized, which consists of two multi-resonance TADF (MR-TADF) cores, tBuBO and tBuQAO. The short-range intramolecular charge transfer (ICT) characteristics of tBuBO and tBuQAO weaken its electron-donating and electron-withdrawing ability, respectively. Thus, weak long-range ICT from tBuBO to tBuQAO is established in BOQAO for holding blue fluorescence emission with a slight redshift, keeping a small FWHM, and maintaining the TADF properties, simultaneously. The simple doped devices exhibited high color purity with FWHMs of less than 35 nm in a wide doping ratio range from 1 wt% to 40 wt%. At a 5 wt% doping ratio, the device based on BOQAO exhibited the best device performance with an EQE of 21.8% and an FWHM of 32 nm. This work provides a simple and practical strategy for suppressing aggregation-induced spectral broadening for the development of MR-TADF. [ABSTRACT FROM AUTHOR]

This work presents the first circularly polarized thermally activated delayed fluorescence hetero-[4]helicene with a carbonyl-/sulfone-bridged triarylamine structure (QPO-PhCz), demonstrating circularly polarized light emission through effective intramolecular steric hindrance and intramolecular space charge transfer. The new molecular architecture displays a good quantum yield (0.51) and clearly circularly polarized luminescence with an absolute luminescence dissymmetry factor of 1.2 × 10−3 in dichloromethane solution. Moreover, for their racemates, characterization of the electroluminescence device shows a sky-blue emission (488 nm) and a maximum external quantum efficiency of 10.6%. Finally, the circularly polarized organic light-emitting diodes exhibit circularly polarized electroluminescence signals with an electroluminescence dissymmetry factor of +1.6 × 10−3 and −1.1 × 10−3 for (M)-QPO-PhCz and (P)-QPO-PhCz , respectively. [ABSTRACT FROM AUTHOR]

Multi‐layer π‐stacked emitters based on spatially confined donor/acceptor/donor (D/A/D) patterns have been developed to achieve high‐efficiency thermally activated delayed fluorescence (TADF). In this case, dual donor moieties and a single acceptor moiety are introduced to form two three‐dimensional (3D) emitters, DM‐BD1 and DM‐BD2, which rely on spatial charge transfer (CT). Owing to the enforced face‐to‐face D/A/D pattern, effective CT interactions are realized, which lead to high photoluminescence quantum yields (PLQYs) of 94.2 % and 92.8 % for the two molecules, respectively. The resulting emitters exhibit small singlet–triplet energy splitting (ΔEST) and fast reverse intersystem crossing (RISC) processes. Maximum external quantum efficiencies (EQEs) of 28.0 % and 26.6 % were realized for devices based on DM‐BD1 and DM‐BD2, respectively, which are higher than those of their D/A‐type analogues. [ABSTRACT FROM AUTHOR]

Organic materials with violet electroluminescence are highly interesting for organic light‐emitting diode (OLED) application. However, the design and synthesis of new molecules combining with desirable violet emission and high luminous efficiency are a challenging task. Here, three novel organic molecules consisting of a pyrene unit and a highly rigid skeleton, namely TFPy2, TFPy3, and TFPy4, are developed for violet‐emitting OLEDs (VOLEDs). These emitters exhibit excellent thermal stability and violet emission with a narrow full width at half‐maximum (FWHM) and high photoluminescence quantum yields (PLQYs). Photophysical results show that the emission peaks can be tuned by the introduction of pyrene units at different positions, and the emission will have a blue shift with increasing steric hindrance. Moreover, OLEDs fabricated with TFPy2, TFPy3, and TFPy4 as the emitters exhibit maximum external quantum efficiencies (EQEs), emission peaks, and CIEs (x,y) of 3.8%, 414 nm, and (0.15, 0.03); 4.8%, 406 nm, and (0.16, 0.02); and 5.1%, 404 nm, and (0.16, 0.02), respectively. The two molecules TFPy3 and TFPy4 exhibit violet emissions with EL peaks at ≈405 nm with a record low CIEy of 0.02. Therefore, these materials and their construction strategy are promising for future VOLEDs with wide‐color‐gamut display and potential biological applications. [ABSTRACT FROM AUTHOR]

Derivatives based on anthryleno[1,2‐b]pyrazine‐2,3‐dicarbonitrile (DCPA) are used as luminescent materials, to realize near‐infrared (NIR) electroluminescence. By functionalizing DCPA with aromatic amine donors, two emitters named DCPA‐TPA and DCPA‐BBPA are designed and synthesized. Both molecules have large dipole moments owing to the strong intramolecular charge transfer interactions between the amine donors and the DCPA acceptor. Thus, compared with doped films, the emission of neat films of DCPA‐TPA and DCPA‐BBPA can fully fall into the NIR region (>700 nm) with increasing surrounding polarity by increasing doping ratio. Moreover, the non‐doped devices based on DCPA‐TPA and DCPA‐BBPA provide NIR emission with peaks at 838 and 916 nm, respectively. A maximum radiance of 20707 mW Sr−1 m−2 was realized for the further optimized device based on DCPA‐TPA. This work provides a simple and efficient strategy of molecular design for developing NIR emitting materials. [ABSTRACT FROM AUTHOR]

A universal host material for red, green and blue phosphors raises challenges for the fabrication of efficient phosphorescent organic light-emitting diodes (PHOLEDs). Herein, two spiro host materials, namely 3-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′,9′-dimethyl-9′H-spiro[fluorene-9,5′-quinolino[3,2,1-de]acridine] (QAF-TRZ) and 3′-(4,6-diphenyl-1,3,5-triazin-2-yl)-10-phenyl-10H-spiro[acridine-9,9′-fluorene] (STF-TRZ), are designed and synthesized. The designed strategy is more appropriate and rarely found among the reported spiro-based skeletons for organic light-emitting diodes (OLEDs). Both materials exhibited excellent electroluminescence performance. In particular, the RGB three-color PHOLEDs based on QAF-TRZ and STF-TRZ as hosts and FIrpic, Ir(ppy)2acac, and Ir(MDQ)2acac as emitters are fabricated. The blue PHOLEDs based on QAF-TRZ realize a maximum external quantum efficiency (EQE) of 19.4%, and remain 17.2% at 1000 cd m−2. On the other hand, green PHOLEDs show maximum EQEs of 21% and 19% for QAF-TRZ and STF-TRZ, respectively, and both devices exhibit low efficiency roll-off. The red devices obtain EQEs of 22.6% and 19.4% based on QAF-TRZ and STF-TRZ, respectively, in which the former has among the most efficient value. Consequently, these results confirm that host materials incorporating the spiro-motif with sufficiently high triplet energy are promising for obtaining high performance RGB-based PHOLEDs. The better device performance based on QAF-TRZ stems from its better hole transport capability, resulting in a superior charge recombination efficiency. [ABSTRACT FROM AUTHOR]

Near‐infrared exciplex can weaken molecular design difficulties, and has the advantage of easy bathochromic‐shift spectra via selecting the suitable electron donors and acceptors. In this contribution, exciplex is applied to fabricate near‐infrared (NIR) organic light‐emitting diodes (OLEDs) incorporating a synthesized fluorescent material 3‐([1,1″:3′,1″‐terphenyl]‐5′‐yl)acenaphtho[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC‐tPh) and a commercially available material 4,4′,4″‐tris(carbazol‐9‐yl)triphenylamine (TCTA). The device having a mixed TCTA:APDC‐tPh as an emitting layer shows a 730 nm NIR emission with a maximum external quantum efficiency (EQE) of about 0.1%, while the device having 2‐[4‐(diphenylamino)phenyl]‐10,10‐dioxide‐9H‐thioxanthen‐9‐one (TXO‐TPA):APDC‐tPh as the emitting layer exhibits an emission peak of 704 nm with a maximum EQE of 1.27%. These results prove the feasibility of fabricating the efficient exciplex‐based NIR OLEDs. [ABSTRACT FROM AUTHOR]

In this study, two isomers, namely 2P-BT-N-2TPA and 2TPA-BT-N-2P, have been designed and synthesized with hybridized local and charge transfer (HLCT) properties. 2TPA-BT-N-2P has been found to have not only stronger intra/intermolecular interactions with regular molecular packing, which stabilized the excited-state configuration, but also aggregation-induced emission enhancement (AIEE) properties. The AIEE properties can effectively inhibit the aggregation-caused quenching (ACQ) effects in the aggregation state and its photoluminescence quantum yield (PLQY) is up to 91%, which is extremely high in a solid-state film. When 2TPA-BT-N-2P is applied as a dopant to form a doped OLED, the device exhibited an excellent external quantum efficiency (EQE) of 6.6%, with an emission peak of 588 nm. Moreover, when 2TPA-BT-N-2P is applied as a pure emitting layer to form a non-doped OLED, the device still achieved an EQE of 5.8% and 5.1% at 100 cd m−2 and 1000 cd m−2, respectively, with the lowest efficiency roll-off currently reported from the HLCT molecule in the orange emission. [ABSTRACT FROM AUTHOR]

Herein, two orange-red emitters, 3,6-bis(9,9-dimethylacridin-10(9H)-yl)-9H-fluoren-9-one (DMAC-FO) and 3,6-di(10H-SP[acridine-9,9′-fluoren]-10-yl)-9H-fluoren-9-one (SPAC-FO), based on fluorenone have been designed and synthesized. As compared to the widely reported benzophenone acceptor, fluorenone has deeper lowest unoccupied molecular orbital (LUMO) because of its more conjugated skeleton and thus it can red-shift the emission maximum. The molecular simulation exhibits both emitters has separated highest occupied molecular orbitals (HOMOs) (@donors) and LUMOs (@acceptor), indicating they could act as thermally activated delayed fluorescence (TADF) materials which are further confirmed by the transient spectra. Consequently, external quantum efficiencies (EQEs) of 10.0% for DMAC-FO and 14.2% for SPAC-FO are achieved in the organic light-emitting diodes (OLEDs). Image 1 • Two orange-red emitters, DMAC-FO and SPAC-FO, based on fluorenone have been designed and synthesized. • TADF properties were realized in DMAC-FO and SPAC-FO due to the highly twisted structure. • High EQEs of 10.0% for DMAC-FO and 14.2% for SPAC-FO were achieved in OLEDs. [ABSTRACT FROM AUTHOR]

The exploitation of universal spiro-type hosts suitable for full-color phosphors is still a bottleneck for fabricating highly efficient phosphorescent organic light-emitting diodes (PHOLEDs) with a similar device structure. In this work, a novel spiro-configured host 3,6-di(9H-carbazol-9-yl)spiro[indolo[3,2,1-de]acridine-8,9′-thioxanthene]10′,10′-dioxide (TCZSO2) incorporating 9′H-9,3′:6′,9′′-tercarbazole and 9H-thioxanthene 10,10-dioxide moieties is designed and synthesized. Utilizing 9′H-9,3′:6′,9′′-tercarbazole as the building-block in designing new spiro-type host materials in organic light-emitting diodes (OLEDs) is seldom reported. In particular, the three color-based devices based on TCZSO2/bis(4,6-(difluorophenyl)pyridinato-N,C2′)picolinate (FIrpic), TCZSO2/iridium(iii) bis(2-phenylpyridinato-N,C2′)acetylacetonate (Ir(ppy)2(acac)) and TCZSO2/iridium(iii) bis(2-methyldibenzo[f,h]quinoxaline)acetylacetonate (Ir(MDQ)2(acac)) exhibit respectable external quantum efficiencies (EQEs) of 22.8%, 24.0% and 21.0%, respectively. More encouragingly, blue and green PHOLED devices have quite low efficiency roll-off (EQE: 22.7%/24.0%, FIrpic/Ir(ppy)2(acac)) at a high brightness of 1000 cd m−2. At a higher brightness of 5000 cd m−2, there is only 5.3% and 4.6% decrease in EQEs from their maximum values, indicating a very low efficiency roll-off. These excellent results confirm a novel spiro-type host design strategy for incorporating reported electron donors with high triplet energy (ET) to achieve high-performance RGB PHOLEDs. [ABSTRACT FROM AUTHOR]

Full width at half maxima (FWHM), ketone derivatives, multi-resonance thermally activated delayed fluorescence (MR-TADF), narrow-band, organic light-emitting diodes (OLEDs) Keywords: full width at half maxima (FWHM); ketone derivatives; multi-resonance thermally activated delayed fluorescence (MR-TADF); narrow-band; organic light-emitting diodes (OLEDs) EN full width at half maxima (FWHM) ketone derivatives multi-resonance thermally activated delayed fluorescence (MR-TADF) narrow-band organic light-emitting diodes (OLEDs) 1 1 1 01/27/23 20230124 NES 230124 B The molecular modification strategies b for maintaining both high efficiency and narrow-band profiles are highlighted by a review of the progress in iterations of carbonyl-containing thermally activated delayed fluorescence (TADF) molecules from conventional TADF emitters with twisted donor-acceptor structures to multi-resonance TADF molecules with fused skeletons. Frontispiece: Carbonyl-Containing Thermally Activated Delayed Fluorescence Emitters for Narrow-Band Electroluminescence. [Extracted from the article]

Multiple resonances induced thermally activated delayed fluorescence (MR‐TADF) has great advantages in high color purity display. Up to now, current MR‐TADF emitters are only based on the boron‐nitrogen‐containing fragment. Reported herein is a novel class of MR‐TADF emitter, quinolino[3,2,1‐de]acridine‐5,9‐dione (QAO), realized by the opposite resonance effect of the carbonyl and the nitrogen atoms, which is also the smallest TADF emitter reported so far. The QAO‐based pure blue organic light‐emitting diode achieves a maximum external quantum efficiency (EQEmax) of 19.4% with a small full width at half maximum of 39 nm. Moreover, tert‐butyl modified QAO can be employed as an efficient electron acceptor to construct an efficient yellow‐green evaporation and solution process feasible TADF emitter, 7‐(tert‐butyl)‐3,11‐bis(9,9‐dimethylacridin‐10(9H)‐yl)quinolino[3,2,1‐de]acridine‐5,9‐dione (QAO‐DAd), with significantly improved performance as compared to the previous flexible diketone‐based emitters. A novel class of multiple resonance induced thermally activated delayed fluorescence (MR‐TADF) emitter (QAO) is developed, by using the opposite resonance effect of the carbonyl group and the nitrogen atom. Moreover, QAO can be employed as an efficient electron acceptor to construct traditional donor–acceptor–donor type TADF emitter, QAO‐DAd, and then achieve high performances in evaporation and solution‐processed devices. [ABSTRACT FROM AUTHOR]

Abstract A new sky-blue thermally activated delayed fluorescent (TADF) emitter TRZ-DCF, has been developed based on 2-(9H-carbazol-9-yl)-7,7-dimethyl-5,7-dihydroindeno[2,1- b ]carbazole (DCF) as donor and 2,4-diphenyl-1,3,5-triazine as acceptor. Due to the fusion of fluorene and carbazole moieties into the single carbazole donor, the multimodified emitter exhibits obvious TADF characteristics with a smaller singlet-triplet splitting (Δ E ST) value of 0.22 eV and relatively high photoluminance quantum yield (PLQY) of 84%. As a result, a maximum external quantum efficiency (EQE) of 18.7%, a current efficiency (CE) of 39.0 cd A−1 and a power efficiency (PE) of 30.5 lm W−1 with a Commission Internationale de L' Eclairage (CIE) coordinates of (0.18, 0.34), significantly surpassing the performance of the reference emitter 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-carbazole (TRTZ), are achieved in optimal device construction. It is found that the EQE roll-off (20.8%) of TRZ-DCF is acceptable, that the efficiency drops to 14.8% at 1000 cd m−2 in optimal device construction. These results demonstrate the multiple modifications of weak electron-donating carbazole donor is an effective way of constructing high-efficiency blue TADF emitters with small roll-off. Graphical abstract Image 1 Highlights • We present a new sky-blue thermally activated delayed fluorescence emitter combining a novel multimodified carbazole donor moiety with triazine-based unit for efficient organic light-emitting diodes. • The external quantum efficiency (18.7%), singlet-triplet splitting (0.22 eV) and photoluminance quantum yield (84%) as well as the roll-off behavior (20.8%) of the emitter TRZ-DCF have been finely tuned through multiple modification of the reference emitter TRTZ. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (PeNCs) deliver size- and composition-tunable luminescence of high efficiency and color purity in the visible range. However, attaining efficient electroluminescence (EL) in the near-infrared (NIR) region from PeNCs is challenging, limiting their potential applications. Here we demonstrate a highly efficient NIR light-emitting diode (LED) by doping ytterbium ions into a PeNCs host (Yb 3+  : PeNCs), extending the EL wavelengths toward 1000 nm, which is achieved through a direct sensitization of Yb 3+ ions by the PeNC host. Efficient quantum-cutting processes enable high photoluminescence quantum yields (PLQYs) of up to 126 % from the Yb 3+  : PeNCs. Through halide-composition engineering and surface passivation to improve both PLQY and charge-transport balance, we demonstrate an efficient NIR LED with a peak external quantum efficiency of 7.7 % at a central wavelength of 990 nm, representing the most efficient perovskite-based LEDs with emission wavelengths beyond 850 nm., (© 2023 Wiley-VCH GmbH.)

Organic materials with multi-stimulus response (MSR) properties have demonstrated many potential and practical applications. Herein, a π-stacked thermally activated delayed fluorescence (TADF) material with multi-stimulus response (MSR) properties, named SDMAC, was designed and synthesized using distorted 9,9-dimethyl-10-phenyl-9,10-dihydroacridine as a donor. SDMAC possesses a rigid π-stacked configuration with intramolecular through-space interactions and exhibits aggregation-induced emission enhancement (AIEE), solvatochromic, piezochromic, and circularly polarized luminescence (CPL) under different external stimuli. The rigid molecular structure and efficient TADF properties of SDMAC can be used in displays and lighting. Using SDMAC as an emitter, the maximum external quantum efficiency (EQE) of the fabricated organic light-emitting diodes (OLEDs) is as high as 28.4 %, which make them the most efficient CP-TADF OLEDs based on the through-space charge transfer strategy. The CP organic light-emitting diodes (CP-OLEDs) exhibit circularly polarized electroluminescence (CPEL) signals., (© 2022 Wiley-VCH GmbH.)

Optical interconnects exhibit superior potential in the precise regulation of photon transmission for organic photonic circuits. However, the rational design of well-defined organic heterostructures toward active optoelectronics remains challenging. Herein, we designed organic branched heterostructures (OBHs) with accurate spatial organization for optical interconnection. Notably, the precise regulation of OBHs has been controllably achieved including the trunk morphologies and the branched microwire number. Significantly, these as-prepared OBHs inherently exhibit the multichannel coupling outputs and the excitation position-dependent waveguide characteristics, leading to various outcoupling signals with tunable intensity and emission colors. The optical interconnects are realized due to the occurrence of exciton conversion and photon propagation between branch and trunk at the heterojunction, benefiting the application possibilities of two-dimensional (2D) optical barcodes., (© 2022 Wiley-VCH GmbH.)

Triplet excitons can be utilized upon introduction of phosphors into exciplexes, and such a scenario has been studied in the development of high-performance near-infrared (NIR) organic light-emitting diodes (OLEDs). To generate exciplexes in an emitting layer (EML) in the device, commercially available phosphors bis(2-phenylpyridinato-N,C 2 ')iridium(acetylacetonate) [Ir(ppy) 2 acac] and iridium(III) bis(4-phenylthieno[3,2- c ]pyridinato-N,C 2 ')acetylacetonate (PO-01) were selected as donor components; in addition, a new designed fluorescent molecule, 3-([1,1':3',1″-terphenyl]-5'-yl)acenaphtho[1,2- b ]quinoxaline-9,10-dicarbonitrile (AQDC-tPh), and recently reported 3-([1,1':3',1″-terphenyl]-5'-yl)acenaphtho[1,2- b ]pyrazine-8,9-dicarbonitrile (APDC-tPh) were selected as acceptor components. An OLED with PO-01:AQDC-tPh blends as the EML has realized NIR emission at 750 nm and a maximum external quantum efficiency (EQE) of >0.23%. Furthermore, an OLED containing a PO-01:APDC-tPh blend realizes a maximum EQE of 0.16% at 824 nm. The high performance of these devices underlying phosphor-based exciplexes proves the potential and feasibility of our strategy for the construction of efficient NIR OLEDs.

Multi-layer π-stacked emitters based on spatially confined donor/acceptor/donor (D/A/D) patterns have been developed to achieve high-efficiency thermally activated delayed fluorescence (TADF). In this case, dual donor moieties and a single acceptor moiety are introduced to form two three-dimensional (3D) emitters, DM-BD1 and DM-BD2, which rely on spatial charge transfer (CT). Owing to the enforced face-to-face D/A/D pattern, effective CT interactions are realized, which lead to high photoluminescence quantum yields (PLQYs) of 94.2 % and 92.8 % for the two molecules, respectively. The resulting emitters exhibit small singlet-triplet energy splitting (ΔE ST ) and fast reverse intersystem crossing (RISC) processes. Maximum external quantum efficiencies (EQEs) of 28.0 % and 26.6 % were realized for devices based on DM-BD1 and DM-BD2, respectively, which are higher than those of their D/A-type analogues., (© 2020 Wiley-VCH GmbH.)

Epidemiological studies suggest that nerve growth factor (NGF) is associated with a reduced risk of acute or chronic neuropathies. We studied the synergistic protective effect of picroside II and NGF against the oxidative stress in PC12 cells induced by hydrogen peroxide (H2O2). The fluorescent probe CDCFH was used to assess the intracellular reactive oxygen species (ROS) level, and MTT assay, morphological observation as well as LDH leakage test were conducted to measure cellular injury. The H2O2-induced cytotoxicity was significantly attenuated in the presence of picroside II (25 microg/ml ) and NGF (2 ng/ml). Cultures with this combined treatment possessed decreased level of ROS while increased cell survival, as compared to that of picroside II or NGF alone-treated cells. Accordingly, it was concluded that their synergistic protective activities against oxidative stress in vitro were demonstrated in various aspects, including reversing morphological changes, enhancing the ability of cell proliferation and ROS scavenging. Such action supports the therapeutic potential of picroside II and NGF in treating nervous disorders based on their synergistic effect.