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A bipolar deep blue-emitting fluorescent material based on imidazole and triphenylamine for efficient non-doped OLEDs
摘要： A bipolar deep blue-emitting fluorescent material, 1-(4-tert-butyl phenyl)-2-[4-(N,N- diphenyl)phenyl]-4,5-diphenyl-1H-imidazole (TPA-PIM) has been designed and synthesized for efficient blue organic light-emitting diodes (OLEDs). The photophysical, thermal and electrochemical properties of TPA-PIM are investigated. TPA-PIM possesses high thermal stabilities with decomposition temperature of 396 °C and shows a strong deep-blue emission at 407 nm in N, N-dimethylformamide (DMF) solution. Single-carrier devices are fabricated to show that TPA-PIM has good bipolar characteristics. The non-doped fluorescent OLEDs using TPA-PIM as emitter exhibited stable and efficient deep-blue emissions with the CIE coordinates of (0.16, 0.09), the maximum luminance of 1392 cd m?2 and the maximum current efficiency of 2.60 cd A?1.
关键词： Triphenylamine,Blue light-emitting materials,Bipolar materials,Imidazole,Non-doped OLEDs
更新于2025-11-19 16:56:42
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Realizing efficient bipolar deep-blue light-emitting poly(2,7-carbazole) derivatives by suppressing intramolecular charge transfer
摘要： Two series of twisted bipolar poly(2,7-carbazole) derivatives, namely PCz-37RSOs and PCz-28SOs, were synthesized by introducing electron-deficient 2,8-dioctyl-dibenzothiophene-S,S-dioxide-3,7-diyl (37RSO) and dibenzothiophene-S,S-dioxide-2,8-diyl (28SO) unit into poly(9-heptadecanyl-2,7-carbazole) (PCz) backbone, respectively. The incorporation of electron-withdrawing 37RSO and 28SO into PCz backbone decreased effective conjugation length, and further restrained charge transfer effect existed in dipolar system, simultaneously, the balanced charge carrier injection/transportation were realized due to the electrophilicity of SO unit. Consequently, the resulting polymers showed hypsochromic shift and narrowed emission spectra regarding to PCz-37SOs that contains linear SO unit in main chain, and exhibited balanced hole/electron fluxes with respect to PCz in the range of 0–10 V. The single-layer devices based on resulting bipolar polymers exhibited excellent electroluminescent spectra stability in the current densities from 100 to 400 mA cm?2, and displayed deep blue electroluminescence spectra with the Commission Internationale de L’ Eclairage (CIE) of (0.16, 0.07) for PCz-37RSO5 and (0.16, 0.09) for PCz-28SO5. The superior device performance was achieved with the maximum luminous efficiency (LEmax) of 2.69 cd A?1 for PCz-28SO20, which obviously outperformed that of 0.24 cd A?1 for PCz. These results indicated that twisted molecular structure design is a promising strategy for efficient deep blue light-emitting polymers.
关键词： Poly(2,7-carbazole),Bipolar,Twisted structure,Blue light-emitting polymers,Charge transfer effect
更新于2025-09-23 15:22:29
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Blue LED phototherapy in preterm infants: effects on an oxidative marker of DNA damage
摘要： background Phototherapy is used on the majority of preterm infants with unconjugated hyperbilirubinaemia. The use of fluorescent tube phototherapy is known to induce oxidative DNA damage in infants and has largely been replaced by blue light- emitting diode phototherapy (BLP). To date, it is unknown whether BLP also induces oxidative DNA damage in preterm infants. Objective To determine whether BLP in preterm infants induces oxidative DNA damage as indicated by 8- hydroxy-2′deoxyguanosine (8- OHdG). Design Observational cohort study. Methods Urine samples (n=481) were collected in a cohort of 40 preterm infants (24–32 weeks’ gestational age) during the first week after birth. Urine was analysed for the oxidative marker of DNA damage 8- OHdG and for creatinine, and the 8- OHdG/creatinine ratio was calculated. Durations of phototherapy and levels of irradiance were monitored as well as total serum bilirubin concentrations. results BLP did not alter urinary 8- OHdG/creatinine ratios (B=0.2, 95% CI ?6.2 to 6.6) at either low (10–30 μW/cm2/nm) or high (>30 μW/cm2/nm) irradiance: (B=2.3, 95% CI ?5.7 to 10.2 and B=?3.0, 95% CI ?11.7 to 5.6, respectively). Also, the 8- OHdG/creatinine ratios were independent on phototherapy duration (B=?0.1, 95% CI ?0.3 to 0.1). Conclusions BLP at irradiances up to 35 μW/cm2/nm given to preterm infants ≤32 weeks’ gestation does not affect 8- OHdG, an oxidative marker of DNA damage.
关键词： preterm infants,phototherapy,8-hydroxy-2′deoxyguanosine,blue light-emitting diode phototherapy,oxidative DNA damage
更新于2025-09-23 15:21:01
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High brightness blue light-emitting diodes based on CsPb(Cl/Br)3 perovskite QDs with phenethylammonium chloridesynonym passivation.
摘要： All inorganic perovskite quantum dots (QDs) (CsPbX3, X=Cl, Br, I) have been applied on the light-emitting devices (LEDs) in recent years due to their excellent optical and optoelectronic properties. However, the blue-light emitting perovskite QD LEDs (PQD-LEDs) exhibit the poor performances comparing with their green- and red-light emitting counterparts. Herein, we fabricated the high performing blue-light emitting PQD-LEDs based on the phenethylammonium chloridesynonym (PEACl) modified CsPb(Cl/Br)3 QDs. Firstly, the PEA-CsPbCl3 QDs were synthesized by introducing the certain amounts of PEACl in the conventional hot-injection synthesis process. The merit of our synthesis lies in the fact that not only the Cl vacancies of CsPbCl3 QDs are efficiently modified by introducing the PEACl precursor, but also the partial long-chain organic ligands (OLA) capping on the surface of CsPbCl3 QDs are simultaneously replaced by the shorter PEACl chains. Consequently, the PEA-CsPbCl3 QDs emitted at 410 nm with the PLQY of 62.3% was achieved. Furthermore, to meet the requirement of display application, we exchanged Cl- with Br- ions at room temperature to precisely control the blue emission in 460-470 nm spectral regions and with the maximum PLQY of 80.2% at 470 nm. Finally, the PQD-LEDs based on PEA-CsPb(Cl/Br)3 perovskite QDs emitted at 462, 465, 468 and 470 nm were fabricated. The PQD-LEDs exhibit the maximal EQE of 2.15% and luminance of 620 cd/m2, which provides a highest value of luminance for the PQD-LEDs in the blue spectral range that satisfying the practical display application.
关键词： perovskite quantum dots,LEDs,CsPb(Cl/Br)3,blue-light emitting,phenethylammonium chloride
更新于2025-09-23 15:21:01
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Low-temperature growth of n<sup>++</sup>-GaN by metalorganic chemical vapor deposition to achieve low-resistivity tunnel junctions on blue light emitting diodes
摘要： We report on low-resistivity GaN tunnel junctions (TJ) on blue light-emitting diodes (LEDs). Si-doped n++-GaN layers are grown by metalorganic chemical vapor deposition directly on LED epiwafers. Low growth temperature (< 800 °C) was used to hinder Mg-passivation by hydrogen in the p++-GaN top surface. This allows achieving low-resistivity TJs without the need for post-growth Mg activation. TJs are further improved by inserting a 5 nm thick In0.15Ga0.85N interlayer (IL) within the GaN TJ thanks to piezoelectric polarization induced band bending. Eventually, the impact of InGaN IL on the internal quantum efficiency of blue LEDs is discussed.
关键词： metalorganic chemical vapor deposition,GaN tunnel junctions,blue light-emitting diodes
更新于2025-09-23 15:21:01
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Photocontrolled Iodine-Mediated Green Reversible-Deactivation Radical Polymerization of Methacrylates: Effect of Water in the Polymerization System
摘要： Photocontrolled iodine-mediated reversible-deactivation radical polymerization (RDRP) is a facile and highly efficient access to precision polymers. Herein, a facile photocontrolled iodine-mediated green RDRP strategy was successfully established in water by using 2-iodo-2-methylpropionitrile (CP-I) as the initiator and water-soluble functional monomers including poly(ethylene glycol) methyl ether methacrylate (PEGMA), 2-hydroxyethyl methacrylate (HEMA), and 2-hydroxypropyl methacrylate (HPMA) as the model monomers under blue-light-emitting diode (LED) irradiation at room temperature. Well-defined polymers (PPEGMA, PHEMA, PHPMA) with narrow polydispersities (1.09?1.21) were obtained, and amphiphilic block copolymers which can form nanospheres in situ in water (PPEGMA-b-poly(benzyl methacrylate) (PPEGMA-b-PBnMA) and PPEGMA-b-PHPMA) were prepared. To explore the role of water in our polymerization, control experiments were successfully carried out by using oil-soluble monomer methyl methacrylate (MMA) with the help of trace amounts of water. Notably, the green solvent—water—has an additionally positive effect in accelerating the polymerization and makes our polymerization system an environmentally friendly polymerization system. Therefore, this simple strategy conducted in the presence of water enables the green preparation of well-defined water-soluble or water-insoluble polymers and clean synthesis of amphiphilic copolymer nanoparticles in situ.
关键词： blue-light-emitting diode,water-soluble functional monomers,amphiphilic block copolymers,green solvent,RDRP,Photocontrolled iodine-mediated reversible-deactivation radical polymerization
更新于2025-09-19 17:13:59
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New Class of Supramolecular Bowl-Shaped Columnar Mesogens Derived from Thiacalix[4]arene Exhibiting Gelation and Organic Light-Emitting Diodes Applications
摘要： A new class of blue light-emitting bowl-shaped mesogens with the thiacalix[4]arene core appended with 1,3,4-thiadiazole derivatives having peripheral alkoxy side chains have been synthesized and well characterized. The liquid crystalline behavior of present synthesized derivatives was examined by optical polarizing microscopy, di?erential scanning calorimetry, and X-ray di?raction studies. It was observed that these thiacalix[4]arene derivatives were capable of stabilizing the observed Colh phase with a higher temperature range. The cone-shaped thiacalix[4]-arene-based liquid crystals with peripheral alkoxy side chains able to pack into the interactions and thermal behavior. All derivatives showed blue luminescence in solution, solid thin-?lm, and gelation state. The hexagonal columnar phase and emissive nature of thiadiazole-based thiacalixarene compounds having xerogel behavior make them favorable in the application of emissive electronic display devices. The electrochemical properties of these thiacalixarene-based compounds demonstrate the e?ect of alkyl side chain on the highest occupied molecular orbital?lowest unoccupied molecular orbital energy levels and also exhibited lower electron band gaps. The electroluminescence behavior of the compound 10c was examined as emissive layers in the fabrication of organic light-emitting diodes.
关键词： thiacalix[4]arene,bowl-shaped mesogens,blue light-emitting,organic light-emitting diodes,1,3,4-thiadiazole derivatives,liquid crystalline behavior
更新于2025-09-12 10:27:22