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Organic and quantum-dot hybrid white LEDs using a narrow bandwidth blue TADF emitter
摘要： White electroluminescence is of particular importance for high resolution full-color flexible displays which employ the down-conversion scheme to generate the individual red, green and blue emissions from the color filters. Quantum dots (QD) light emitting diodes possess ultrahigh brightness and considerably narrow full-width-half-maximum (FWHM) spectra. Nevertheless, inefficient blue QDs limit the overall device performances. Herein, we introduced a boron-based blue thermally activated delayed fluorescence compound and utilized the host-guest system to construct the solution-process white devices. Red and green QDs combined with the blue emitter make it feasible to design the flexible white devices with the sharp peaks and thus intrinsically wide color gamuts. The proof-of-concept hybrid white devices with a single emissive layer exhibited the external quantum efficiencies of 6.9% (on rigid substrate) and 2.3% (on flexible substrate). The color mixing effect and energy transfer among the lumophores were exemplified with three sharp peaks at around 464, 538 and 622 nm, respectively accompanied with the corresponding FWHM of 30, 34 and 31 nm of each component.
关键词： Thermally activated delayed fluorescence,Color gamuts,White electroluminescence,Flexible displays,Quantum dots
更新于2025-09-23 15:19:57
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Diboron-Based Delayed Fluorescent Emitters with Orange-to-Red Emission and Superior Organic Light-Emitting Diode Efficiency
摘要： For the application of OLEDs in lighting and panels, the basic requirement is to include a full spectrum color range. Compared with the development of blue and green luminophores in thermally activated delayed fluorescence (TADF) technology, the progress of orange-to-red materials is slow and needs further investigation. In this study, three diboron compound-based materials, dPhADBA, dmAcDBA, and SpAcDBA, were designed and synthesized by nucleophilic arylation of three amine donors on 9,10-diboraanthracene (DBA) in a two-step reaction. With increasing electron-donating ability, they show orange-to-red emission with TADF characteristics. The electroluminescence (EL) of these diboron compounds exhibits emissions λmax at 613, 583, and 567 nm, for dPhADBA, dmAcDBA, and SpAcDBA, respectively. It is noteworthy that the rod-like D-A-D structures can achieve high horizontal ratios (84~86%) and outstanding device performance for orange-to-red TADF OLEDs: the highest external quantum efficiencies (ηEQE) for dPhADBA, dmAcDBA, and SpAcDBA are 11.1 ± 0.5%, 24.9 ± 0.5%, and 30.0 ± 0.8%, respectively. Therefore, these diboron-based molecules offer a promising avenue for the design of orange-to-red TADF emitters and the development of highly efficient orange-to-red OLEDs.
关键词： thermally activated delayed fluorescence,9,10-diboraanthracene,horizontal dipole ratio,diboron compound,orange-red color,organic light-emitting diode
更新于2025-09-23 15:19:57
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Dual nature of exciplexes: exciplex-forming properties of carbazole and fluorene hybrid trimers
摘要： Two exciplexes were detected for the first time for the known exciplex-forming system consisting of electron donating 1,3-bis-(N-carbazolyl)benzene and electron accepting 2,4,6-tris[3-(diphenyl-phosphinyl)phenyl]-1,3,5-triazine. Exploiting thermal treatment, sky-blue (high-energy) and orange (low-energy) exciplexes were observed for a solid-state mixture of the compounds under electrical excitation. Similarly, stable high-energy and low-energy exciplexes were observed for new exciplex-forming systems consisting of 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine and one of four selected carbazole and fluorene hybrid trimers as donors. The high-energy exciplexes were observed when there was a small energy barrier between the locally excited state and the high-energy exciplex state. A large energy barrier between the locally excited state and the low-energy exciplex state was the reason that the dual nature of exciplexes was not discovered yet. Emission of both exciplexes was observed in electroluminescence spectra of exciplex-interface based devices using developed exiplex-forming systems as emitters. Observed under optical and electrical excitations, the low-energy exciplexes were separated using thermal treatment of the studied exciplex-forming systems. The exciplex-forming system consisting of 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine and 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole, which exhibits thermally activated delayed fluorescence, showed the best performance in organic light-emitting diodes (OLEDs) based on interface and volume exciplex emitters. The best device showed maximum external quantum and maximum current efficiencies of 18% and 54 cd A?1 respectively. Additionally, white OLEDs were fabricated exploiting sky-blue and orange emissions from a single exciplex-forming system. Our findings provide evidence of the dual nature of exciplexes and pave the way towards design of new exciplex-forming systems with high photoluminescence quantum yields and efficient exciplex-based devices.
关键词： OLEDs,fluorene,exciplexes,hybrid trimers,thermally activated delayed fluorescence,carbazole
更新于2025-09-19 17:15:36
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Phosphane tuning in heteroleptic [Cu(N^N)(P^P)] <sup>+</sup> complexes for light-emitting electrochemical cells
摘要： The synthesis and characterization of five [Cu(P^P)(N^N)][PF6] complexes in which P^P = 2,7-bis(tert-butyl)-4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (tBu2xantphos) or the chiral 4,5-bis(mesitylphenylphosphino)-9,9-dimethylxanthene (xantphosMes2) and N^N = 2,2’-bipyridine (bpy), 6-methyl-2,2’-bipyridine (6-Mebpy) or 6,6’-dimethyl-2,2’-bipyridine (6,6’-Me2bpy) are reported. Single crystal structures of four of the compounds confirm that the copper(I) centre is in a distorted tetrahedral environment. In [Cu(xantphosMes2)(6-Mebpy)][PF6], the 6-Mebpy unit is disordered over two equally populated orientations and this disorder parallels a combination of two dynamic processes which we propose for [Cu(xantphosMes2)(N^N)]+ cations in solution. Density functional theory (DFT) calculations reveal that the energy difference between the two conformers observed in the solid-state structure of [Cu(xantphosMes2)(6-Mebpy)][PF6] differ in energy by only 0.28 kcal mol?1. Upon excitation into the MLCT region (λexc = 365 nm), the [Cu(P^P)(N^N)][PF6] compounds are yellow to orange emitters. Increasing the number of Me groups in the bpy unit shifts the emission to higher energies, and moves the Cu+/Cu2+ oxidation to higher potentials. Photoluminescence quantum yields (PLQYs) of the compounds are low in solution, but in the solid state PLQYs of up to 59% (for [Cu(tBu2xantphos)(6,6’-Me2bpy)]+) are observed. Increased excited-state lifetimes at low temperature are consistent with the complexes exhibiting thermally activated delayed fluorescence (TADF). This is supported by the small energy difference calculated between the lowest-energy singlet and triplet excited states (0.17–0.25 eV). The compounds were tested in simple bilayer light-emitting electrochemical cells (LECs). The optoelectronic performances of complexes containing xantphosMes2 were generally lower with respect to those with tBu2xantphos, which led to bright and efficient devices. The best performing LECs were obtained for the complex [Cu(tBu2xantphos)(6,6’-Me2bpy)][PF6] due to the increased steric hindrance at the N^N ligand, resulting in higher PLQY.
关键词： photoluminescence quantum yields,heteroleptic copper complexes,light-emitting electrochemical cells,thermally activated delayed fluorescence,Phosphane tuning
更新于2025-09-19 17:15:36
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Achieving Dual-Emissive and Time-Dependent Evolutive Organic Afterglow by Bridging Molecules with Weak Intermolecular Hydrogen Bonding
摘要： It is discovered that “bridging” traditional persistent room-temperature phosphorescence (pRTP) dibenzofuran moieties by intermolecular hydrogen bonding can induce interesting photophysical properties. The light-emitting material 4-(4-((4-methoxyphenyl)sulfonyl)phenyl)dibenzo[b,d]furan (SOBF-OMe) is synthesized and excitingly shows novel dual-emissive afterglow material properties in which orange pRTP (at ≈580 nm, 627 ms) from the dibenzofuran moiety and another blue ultralong intermolecular charge transfer emission (≈476 nm, 204 ms, with TADF characteristics) can be detected. Due to the different decay lifetimes, the ratio of the two afterglow emission bands continuously changes. Accordingly, the emission colors are unusually tuned gradually from cold-white to orange during the afterglow decay process. The blue afterglow emission, which relates to intermolecular interactions, is sensitive to mechanical stimuli and the afterglow emission properties of SOBF-OMe (single-emissive or dual-emissive) can easily be manipulated by grinding/fuming. This single-component material is a rare example of a light-emitting compound showing dual-emissive and real-time changing afterglow properties in which a rational bridging strategy via weak intermolecular hydrogen bonding is utilized.
关键词： afterglow emission,dual-emissive,thermally activated delayed fluorescence,intermolecular charge transfer,hydrogen bonds
更新于2025-09-19 17:15:36
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An iminodibenzyl–quinoxaline–iminodibenzyl scaffold as a mechanochromic and dual emitter: donor and bridge effects on optical properties
摘要： The influence of phenyl linkage and donor strength on the photophysical properties of new derivatives of quinoxaline-containing iminodibenzyl and iminostilbene moieties is studied. The donor–acceptor derivatives showed dual thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) despite a large energy gap between the excited singlet and triplet states (ca. 0.5 eV). This extremely rare observation is explained by the twisted and rigidified structure of the iminodibenzyl moiety.
关键词： dual emitter,quinoxaline,room temperature phosphorescence,iminodibenzyl,optical properties,mechanochromic,bridge effects,thermally activated delayed fluorescence,donor
更新于2025-09-19 17:15:36
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Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff
摘要： Aromatic organic deep-blue emitters that exhibit thermally activated delayed fluorescence (TADF) can harvest all excitons in electrically generated singlets and triplets as light emission. However, blue TADF emitters generally have long exciton lifetimes, leading to severe efficiency decrease, i.e., rolloff, at high current density and luminance by exciton annihilations in organic light-emitting diodes (OLEDs). Here, we report a deep-blue TADF emitter employing simple molecular design, in which an activation energy as well as spin–orbit coupling between excited states with different spin multiplicities, were simultaneously controlled. An extremely fast exciton lifetime of 750 ns was realized in a donor–acceptor-type molecular structure without heavy metal elements. An OLED utilizing this TADF emitter displayed deep-blue electroluminescence (EL) with CIE chromaticity coordinates of (0.14, 0.18) and a high maximum EL quantum efficiency of 20.7%. Further, the high maximum efficiency were retained to be 20.2% and 17.4% even at high luminance.
关键词： deep-blue OLEDs,organic light-emitting diodes (OLEDs),small efficiency rolloff,Nanosecond-time-scale delayed fluorescence,thermally activated delayed fluorescence (TADF)
更新于2025-09-19 17:13:59
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Rational design, synthesis, and characterization of a photocrosslinkable hole-transporting polymer for high performance solution-processed thermally activated delayed fluorescence OLEDs
摘要： A new photocrosslinkable hole-transporting homopolymer (PX2Cz) was successfully synthesized using 9-((3-methyloxetan-3-yl)methyl)-90-(4-vinylbenzyl)-9H,90H-3,30-bicarbazole monomer via radical polymerization. Biscarbazole, as a hole-transporting material, has two reactive sites that can introduce a radical polymerizable styrene moiety and a photocrosslinkable oxetane moiety. The photocuring temperature and time for the PX2Cz film was optimized to be 120 1C and 10 s. The photocured films showed good solvent resistance, which is favorable for the deposition of an emitting-layer solution on them. In particular, the highest occupied molecular orbital (HOMO) energy of the as-cast PX2Cz film was determined to be (cid:2)5.37 eV which remained unchanged even after photocuring, thus facilitating hole transportation from the hole-injection layer. Subsequently, solution-processed, green, thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs) were manufactured using PX2Cz as the hole-transport material. The devices displayed a notable performance with an exceptionally low turn-on voltage (Von) of only 2.8 V and a high external quantum e?ciency (EQE) of 22.5%; these values are substantially better than those of commonly used poly(9-vinylcarbazole) (PVK)-based OLEDs (Von = 3.6 V, EQE of 15.5%). The remarkably low turn-on voltage and high EQE were ascribed to the shallower HOMO energy level and more pronounced hole-transport ability of the photocured PX2Cz film.
关键词： OLEDs,photocrosslinkable,hole-transporting polymer,solution-processed,thermally activated delayed fluorescence
更新于2025-09-19 17:13:59
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Phenothiazine dioxide-containing derivatives as efficient hosts for blue, green and yellow thermally activated delayed fluorescence OLEDs
摘要： By conjugating 10-phenyl-10H-phenothiazine-5,5-dioxide (2PTO) with aromatic amine substituents (PhCz and DMACMN), three novel host materials namely 10-(9-phenyl-9H-carbazol-3-yl)-10H-phenothiazine 5,5-dioxide (3CzNPTO), (10-(4-(9H-carbazol-9-yl)phenyl)-10H-phenothiazine 5,5-dioxide (9CzNPTO) and 10-(4-(9,9-dimethylacridin-10(9H)-yl)-2,5-dimethylphenyl)-10H-phenothiazine 5,5-dioxide (DMACMNPTO) were designed and synthesized. DMACMNPTO with thermally activated delayed fluorescence (TADF) feature exhibited the bipolar characteristic resulting from the completely separated HOMO/LUMO distribution. Using DMACMNPTO as a host for TADF emitters, the devices showed a maximum external quantum efficiencies (EQEmax), current e?ciency (CEmax) and power e?ciency (PEmax) of 18.3%, 33.3 cd/A and 37.4 lm/W in the blue-emitting diode, 18.6%, 49.1 cd/A and 47.2 lm/W in the green-emitting diode, and 19.1%, 59.2 cd/A and 66.0 lm/W in the yellow-emitting diode, respectively. These results corroborated the potential of phenothiazine dioxide-containing derivatives as host materials in a sequence of colors TADF-OLEDs.
关键词： phenothiazine dioxide,Organic light-emitting devices,thermally activated delayed fluorescence,host
更新于2025-09-19 17:13:59
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Calix[4]resorcinarene-based Hyper-Structured Molecular Thermally Activated Delayed Fluorescence Yellow-Green Emitters for Non-doped OLEDs
摘要： A novel hyper-structured molecular (HSM) thermally activated delayed fluorescent (TADF) emitters, in which the TADF units and host units are bound together into one inactive core through the flexible linkage, was designed. Phenoxazine-triphenyltriazine (PXZ-Trz), 1,3-bis(9H-carbazol-9-yl)benzene (mCP) and calix[4]resorcinarene (CRA) were chosed as TADF unit, host unit and core, respectively, a series of CRA-based HSM emitter, CRA-PXZ-Trz(X)-mCP(100-X). (x=0, 12.5, 25, 50, 75, 87.5 or 100) were succesfully synthesized by a two-step click reaction. Using non-doped CRA-PXZ-Trz(87.5)-mCP(12.5) as the light-emitting layer, the solotion-precessable OLEDs emitted yellow-green light, and dispiayed a external quantum efficiency of 16.7% at 100 cd/m2.
关键词： Thermally activated delayed fluorescence,Solution-processable,Non-doped OLEDs,Calix[4]resorcinarene,Hyper-structured molecular
更新于2025-09-19 17:13:59