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Oxadiazole derivatives as bipolar host materials for high-performance blue and green phosphorescent organic light-emitting diodes
摘要： By combining two n-type groups, pyridine and oxadiazole, with one p-type carbazole group, two novel bipolar hosts, namely 2-(3-(9H-carbazol-9-yl)-[1,10-biphenyl]-3-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (PyOxd-mCz) and 2-(40-(9H-carbazol-9-yl)-[1,10-biphenyl]-3-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (PyOxd-pCz) have been developed as hosts for blue and green phosphorescent organic light-emitting diodes (PhOLEDs). The two compounds exhibit similar HOMO levels of ?5.64 eV for PyOxd-mCz and ?5.63 eV for PyOxd-pCz and the same LUMO level of ?2.60 eV. With a more twisted configuration due to meta connections, PyOxd-mCz possesses a higher triplet energy level (ET = 2.77 eV) and more balanced carrier transport than PyOxd-pCz (ET = 2.60 eV). PyOxd-mCz hosted devices achieve a peak current efficiency of 39.7 cd A?1 and a maximum EQE of 20.8% with a low turn-on voltage of 3.5 V for FIrpic and 55.2 cd A?1 and 16.4% for Ir(ppy)3. Apart from the appropriate frontier molecular orbital levels and sufficiently high triplet energy of PyOxd-mCz, the more balanced carrier transport plays a key role for excellent device performance.
关键词： phosphorescent organic light-emitting diodes,bipolar host materials,blue and green PhOLEDs,PyOxd-mCz,PyOxd-pCz
更新于2025-09-16 10:30:52
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Fluorescent Supramolecular Polymersomes Based on Pillararene/Paraquat Molecular Recognition for pH-controlled Drug Release
摘要： Researchers have put significant efforts on developing versatile fluorescent polymeric systems due to their promising biological/biomedical labelling, tracking, monitoring, imaging, and diagnostic applications. However, complicated organic/polymeric synthesis or post-modification of these functionalized platforms is still a big obstacle for their further application and thereby provides clear motivation for exploring alternative strategies for the design and fabrication of easily available fluorescent systems. The marriage of supramolecular polymers and fluorescent imaging can provide a facile and dynamic manner instead of tedious and time-consuming synthesis due to the dynamic and reversible nature of noncovalent interactions. Herein, based on water-soluble pillararene/paraquat molecular recognition, we successfully prepare two amphiphilic polypseudorotaxanes which can self-assemble into supramolecular polymersomes in water. These polymersomes can be reversibly destroyed and reformed by tuning the solution pH. Attributed to the aggregation-induced emission of tetraphenylethylene groups, intense fluorescence can be introduced into the obtained supramolecular polymersomes. Furthermore, pH-triggered release of an encapsulated water-insoluble drug (doxorubicin) from the self-assembled fluorescent supramolecular polymersomes is also investigated.
关键词： Responsiveness,Aggregation-induced emission,Host-guest interactions,Fluorescent polymers
更新于2025-09-16 10:30:52
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High-performance hybrid white organic light-emitting diodes with bipolar host material and thermally activated delayed fluorescent emitter
摘要： Bipolar host material and thermally activated delayed fluorescent (TADF) emitter were used in hybrid white organic light-emitting diodes (OLEDs) with the aim to achieve high performance. First of all, the single color OLEDs was optimized by changing the thickness of hole transporting layer, electron transporting layer and the doping concentration of emission material. Then, white organic light-emitting diodes (WOLEDs) were fabricated on the basis of the former single color OLEDs by modifying the doping concentration of TADF emitter. Finally, an optimized white device shows the best results of 43.67 cd/A, 45.73 lm/W and 18.52% for current efficiency, power efficiency and external quantum efficiency, respectively. This research may supply a theoretical basis for the development of WOLEDs.
关键词： Thermally activated delayed fluorescent (TADF),Energy transfer,Hybrid white organic light-emitting diodes (WOLEDs),Bipolar host material,High performance
更新于2025-09-16 10:30:52
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Ablative fractional laser resurfacing for treatment of sclerosis and contractures in chronic graft-versus-host disease: A pilot study
摘要： To the Editor: Cutaneous sclerosis is a disabling complication of chronic graft-versus-host disease (cGVHD) that leads to joint contractures and reduced range of motion (ROM). Current therapies are limited by adverse effects and poor efficacy, and no systemic treatment successfully reverses cGVHD-induced sclerotic skin changes.1 There is an urgent need for therapies to address the debilitating effects of cutaneous sclerosis in cGVHD. The ablative fractional CO2 laser remodels collagen and reduces fibrosis. It has been used for treatment of scars and contractures secondary to linear morphea, burns, and traumatic injury, conditions resembling the sclerosis of cGVHD.2,3 We evaluated the safety, tolerability, and efficacy of the ablative fractional CO2 laser for cGVHD-related sclerosis and joint contractures. Six patients with cGVHD-related sclerosis were enrolled prospectively and completed the study. Eligible patients had clinically severe, refractory sclerosis from longstanding cGVHD, with demonstrable ROM limitation and contractures across a joint amenable to laser therapy. After administration of topical anesthesia, patients had 3 monthly treatments of an approximately 10 3 6-cm area of skin at the target joint using the 10 600-nm fractional Ultrapulse CO2 laser (Ultrapulse Encore; Lumenis, Inc, Santa Clara, CA) in Deep FX mode (energy settings, 20-25 mJ; density, 5%-15%). Photographs, ROM measurements, and high-resolution ultrasonography were recorded at baseline, 1 week after each laser session, and 3 months after the final session. Punch biopsy and patient and provider assessments, including validated health and disability questionnaires, were performed at baseline and 3 months after the final session. The study was approved by the University of Pennsylvania institutional review board, and all patients provided written informed consent. Before enrollment, patients had received a mean of 5.5 systemic therapies for cGVHD-related sclerosis. Laser treatments were well tolerated, without infectious or other serious complications. ROM measurements, particularly the twisting motions of supination and pronation, improved in all patients (Table I). Immunohistochemical analysis of skin biopsy specimens showed decreased thickened collagen bundles, decreased intensity of collagen staining, and greater abundance of type III collagen in treated areas (Fig 1).3 Dermal echogenicity measured via high-resolution ultrasonography increased after the laser treatment, suggestive of collagen remodeling. Less haphazard organization of collagen is postulated to produce increased echogenicity.4 Patient photographs and disability assessments similarly showed evidence of improvement. The results of this pilot study highlight the safety, tolerability, and potential efficacy of the fractional ablative CO2 laser for treatment of cGVHD-related sclerosis and joint contracture, resulting in small but measurable histologic, radiologic, and functional improvements. Small sample size, small treatment area, and imperfect objective response measures are limitations. Longer follow-up, larger treatment areas, use of other laser settings, and laser-assisted delivery of topical medications should be evaluated in future studies.5 In summary, the fractional ablative CO2 laser was safe and well tolerated in a small group of medically complex patients with treatment-refractory cGVHD. Treatment of a target area of sclerotic skin appeared to induce collagen remodeling, with resulting modest improvement in ROM and joint function. These findings suggest that the fractional ablative CO2 laser may be an effective novel therapy for disabling sclerotic joint contractures in some patients with cGVHD.
关键词： sclerosis,ablative fractional laser resurfacing,contractures,chronic graft-versus-host disease,collagen remodeling
更新于2025-09-16 10:30:52
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Novel Carbazole/Fluorene-Based Host Material for Stable and Efficient Phosphorescent OLEDs
摘要： A novel host material of "M"-type carbazole/fluorene-based mDCzPF with a high triplet energy by utilizing meta-substituted phenyl groups as linkers was developed. It was demonstrated that the position of the substituents significantly affected the molecular configuration and dipole moment, which played a critical role in the device performances. Red phosphorescent OLED utilizing the "M"-type mDCzPF as the host represented a 10-fold operational lifetime improvement over the OLED using a "V"-type pDCzPF linked by para-substituted phenyl groups as the host because of the good charge transport ability of the mDCzPF. Additionally, the "M"-type mDCzPF host was also compatible with a blue emitting phosphorescent emitter PtNON. The PtNON-doped OLED using mDCzPF as the host exhibited a peak EQE of 18.3% with a small roll off, yet maintained an EQE of 13.3% at a high brightness of 5000 cd/m2. Thus, the novel "M"-type mDCzPF could be employed as stable host material for efficient OLED emitting across the whole visible spectrum. This study should provide a viable method for designing new host materials for the development of stable and efficient phosphorescent OLEDs.
关键词： operational lifetime,host material,blue device,OLED,high triplet energy
更新于2025-09-16 10:30:52
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A Silanea??based Bipolar Host with High Triplet Energy for High Efficiency Deepa??Blue Phosphorescent OLEDs with Improved Device Lifetime
摘要： A high triplet energy host is developed using silane moiety. 9-(4-(triphenylsilyl)dibenzo[b,d]furan-2-yl)-9H-carbazole (SiDBFCz) is designed through extensive density functional theory (DFT) calculations to obtain appropriate hole and electron injection barriers. The chemical hardness and the charge transport characteristics are comprehensively investigated to realize a bipolar host with high triplet energy over 2.9 eV for deep blue phosphorescent organic light-emitting diodes (PHOLEDs). The synthesized SiDBFCz clearly exhibits the bipolar characteristics especially with emitter molecules doped. An external quantum efficiency over 19% without any microcavity optimization is achieved thanks to the good charge balance in the SiDBFCz PHOLED. The device lifetime of the SiDBFCz PHOLED is improved more than 1000%, compared to the unipolar control devices at an initial luminance of 500 cd/m2. The dramatic enhancement of the operational stability of the deep blue PHOLED is also thoroughly investigated in terms of electrochemical stability of host molecules in charged or excited states. The results clearly indicate that the device lifetime is strongly correlated with the bond dissociation energy and the activation energy for the bond dissociation reaction in triplet excited state.
关键词： deep blue phosphorescent OLEDs,bond dissociation energy in triplet excited state,high triplet bipolar host,lifetime
更新于2025-09-16 10:30:52
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Cyclohexane-cored dendritic host materials with high triplet energy for efficient solution-processed blue thermally activated delayed fluorescence OLEDs
摘要： Two dendritic host materials (CH-2D1 and CH-2D2) are developed by using non-conjugated cyclohexane core and two first/second generation carbazole dendrons, which show excellent solubility in organic solvents, high thermal stability and high triplet energy (ET) of 2.78–2.84 eV, making them suitable for fabrication of solution-processed blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). Compared to CH-2D1 with the first-generation carbazole dendron which shows low-lying highest occupied molecular orbital (HOMO) energy level of (cid:0) 5.48 eV, CH-2D2 with the second-generation carbazole dendrons exhibits higher HOMO level of (cid:0) 5.37 eV, which is more favourable for hole injection from the anode to the emissive layers. Consequently, solution-processed blue TADF OLEDs utilizing CH-2D2 as host show promising device performance with a low turn-on voltage of 3.4 V, maximum external quantum efficiency of 17.8%, (cid:0) 1, which can compare with the most efficient solution-processed blue TADF OLEDs based on small-molecule and polymer hosts. These results indicate that dendritic host materials with well-defined chemical structure and good solubility are an attractive approach–beyond the soluble small-molecule hosts and polymer hosts–for the development of efficient solution-processed TADF OLEDs.
关键词： Thermally activated delayed fluorescence,Dendritic host materials,Organic light-emitting diodes,High triplet energy
更新于2025-09-12 10:27:22
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Exciplex hosts for blue phosphorescent organic light-emitting diodes
摘要： The host material of organic light-emitting diodes (OLEDs) has been advanced from a single host to a mixed host for high efficiency and long lifetime. Several types of mixed host have been reported in the literature, but the exciplex host has been popular as the mixed host of OLEDs. The exciplex host has been developed mostly for red and green phosphorescent OLEDs, and has upgraded device performances, but it is difficult to develop the exciplex host for blue phosphorescent OLEDs. Recently, several works demonstrated the potential of the exciplex host for blue phosphorescent OLEDs. In this paper, the exciplex host for blue OLEDs is reviewed, and its prospects are presented.
关键词： OLEDs,Exciplex host,quantum efficiency,blue phosphorescent device
更新于2025-09-12 10:27:22
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Phthalonitrile-based bipolar host for efficient green to red phosphorescent and TADF OLEDs
摘要： A bipolar host material named 4-(9H-carbazol-9-yl)phthalonitrile (CzPN) was developed by combining carbazole and phthalonitrile as donor and acceptor units, respectively. The introduction of the phthalonitrile unit realized a relatively small energy gap of 3.00 eV as well as a deep lowest unoccupied molecular orbital level of ?2.72 eV. The characterization of carrier-only devices demonstrated the bipolar charge transporting property of CzPN. With a triplet energy of 2.70 eV, CzPN was investigated as host in green, yellow, and red phosphorescent organic light-emitting diodes (PhOLEDs) and green thermally activated delayed fluorescence (TADF) devices. A low turn-on voltage of 2.8 V was achieved by all the four diodes. Both PhOLEDs and TADF devices exhibited high external quantum efficiency values over 20% with relatively small efficiency roll-offs. These findings demonstrate that CzPN is an excellent host material for both phosphorescent and TADF emitters, and phthalonitrile is a promising unit to develop universal host materials.
关键词： Phthalonitrile,Bipolar host,Phosphorescent organic light-emitting diode,Thermally activated delayed fluorescence
更新于2025-09-12 10:27:22
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Harnessing A New Co-Host System and Low Concentration of New TADF Emitters Equipped with Trifluoromethyl and Cyano Substituted Benzene as Core for High Efficiency Blue OLEDs
摘要： A strategic approach combining a new co-host system and low concentration of new TADF emitters to make efficient blue TADF OLED was developed. The benchmark TADF molecule, 4CzIPN, was adopted as a probe to examine the feasibility of a co-host composing of a hole-transporter SimCP and an electron-transporter oCF3-T2T. As a result, a sky blue device with 1wt% 4CzIPN doped in SimCP:oCF3-T2T co-host exhibited 100% energy transfer and achieved high EQE up to 26.1%. Importantly, this device showed limited efficiency roll-off with EQE of 24% at 1000 cd m-2. To further shift the emission toward blue, three new TADF molecules, 4CzIPN-CF3, 3CzIPN-H-CF3 and 3CzIPN-CF3, modified either by lowering the electron-withdrawing ability of acceptor group or reducing the number of carbazole donors of 4CzIPN, have been synthesized and characterized. Among them, 4CzIPN-CF3 and 3CzIPN-H-CF3 display hypsochromic shift emissions as compared to that of 4CzIPN. These new compounds were then explored for their potential applications as TADF emitters. Blue TADF OLEDs with 1wt% of 4CzIPN-CF3 and 3CzIPN-H-CF3 dispersed in SimCP:oCF3-T2T co-host achieved EQE of 23.1% and 16.5%, and retained high EQE of 20.9% and 14.7% at 1000 cd m-2, respectively.
关键词： 4CzIPN,TADF emitter,co-host,horizontal dipole ratio,OLED
更新于2025-09-12 10:27:22