Spin-Flip-Restricted Multiple-Resonance Emitters for Extended Device Lifetime in Indolocarbazole-Based Blue Organic Light-Emitting Diodes.

In this study, a multiple-resonance (MR) core structure is developed with a spin-flip-restricted emission mechanism based on a fused indolo[3,2,1-jk]carbazole (ICz) framework as emitters to improve the lifetime of blue organic light-emitting diodes. The molecular skeleton modulation approach applied to the conjugated π-system effectively stabilizes the triplet energy of the fused ICz emitters and narrows the full-width-at-half maximum (<20 nm). In addition, the emitters exhibit higher exciton stability than conventional boron-based MR emitters.

Direct identification of interfacial degradation in blue OLEDs using nanoscale chemical depth profiling.

Understanding the degradation mechanism of organic light-emitting diodes (OLED) is essential to improve device performance and stability. OLED failure, if not process-related, arises mostly from chemical instability. However, the challenges of sampling from nanoscale organic layers and interfaces with enough analytical information has hampered identification of degradation products and mechanisms.

Critical role of electrons in the short lifetime of blue OLEDs.

Designing robust blue organic light-emitting diodes is a long-standing challenge in the display industry. The highly energetic states of blue emitters cause various degradation paths, leading to collective luminance drops in a competitive manner. However, a key mechanism of the operational degradation of organic light-emitting diodes has yet to be elucidated.

Post-Traumatic Growth of Nurses in COVID-19 Designated Hospitals in Korea.

Background: This descriptive survey aimed to identify the factors affecting the post-traumatic growth (PTG) of nurses in COVID-19 designated hospitals on the basis of a PTG model.

Methods: A survey of 250 nurses working at three COVID-19 hospitals in Seoul, South Korea, was conducted from May to July 2021. The collected data were analyzed using the IBM SPSS 25 (IBM Inc.

Spiritual needs among Koreans and Americans with advanced chronic illnesses: A cultural comparison.

Aims And Objectives: This study aimed to measure the frequency of spiritual needs, identify the factors associated with these needs among Korean and American persons living with an advance chronic illness and compare them from a cross-cultural perspective.

Background: Persons with serious or life-limiting illnesses often have spiritual needs. Unmet spiritual needs are associated with poor well-being and threaten psychological health.

Improved Efficiency and Lifetime of Deep-Blue Hyperfluorescent Organic Light-Emitting Diode using Pt(II) Complex as Phosphorescent Sensitizer.

Although the organic light-emitting diode (OLED) has been successfully commercialized, the development of deep-blue OLEDs with high efficiency and long lifetime remains a challenge. Here, a novel hyperfluorescent OLED that incorporates the Pt(II) complex (PtON7-dtb) as a phosphorescent sensitizer and a hydrocarbon-based and multiple resonance-based fluorophore as an emitter (TBPDP and ν-DABNA) in the device emissive layer (EML), is proposed. Such an EML system can promote efficient energy transfer from the triplet excited states of the sensitizer to the singlet excited states of the fluorophore, thus significantly improving the efficiency and lifetime of the device.

2-Phenylpyridine- and 2-(benzo[b]thiophen-2-yl)pyridine-based o-carboranyl compounds: impact of the structural formation of aromatic rings on photophysical properties.

2-Phenylpyridine- and 2-(benzo[b]thiophen-2-yl)pyridine-based (ppy- and btp-based) o-carboranyl (Car1 and Car2) and their B(CH3)2-C∧N-chelated (Car1B and Car2B) compounds were prepared and fully characterised by multinuclear NMR spectroscopy and elemental analysis. The solid-state structure of Car2B was determined by single-crystal X-ray diffraction, which revealed a four-coordinated dimethylboryl centre. All compounds displayed major absorption bands that were assigned to π-π* transitions involving the ppy and btp moieties, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their aryl groups.

Effect of Planarity of Aromatic Rings Appended to o-Carborane on Photophysical Properties: A Series of o-Carboranyl Compounds Based on 2-Phenylpyridine- and 2-(Benzo[b]thiophen-2-yl)pyridine.

Herein, we investigated the effect of ring planarity by fully characterizing four pyridine-based -carboranyl compounds. -Carborane was introduced to the C4 position of the pyridine rings of 2-phenylpyridine and 2-(benzo[]thiophen-2-yl)pyridine ( and , respectively), and the compounds were subsequently borylated to obtain the corresponding -chelated compounds and . Single-crystal X-ray diffraction analysis of the molecular structures of and confirmed that -carborane is appended to the aryl moiety.

Degradation of blue-phosphorescent organic light-emitting devices involves exciton-induced generation of polaron pair within emitting layers.

Degradation of organic materials is responsible for the short operation lifetimes of organic light-emitting devices, but the mechanism by which such degradation is initiated has yet to be fully established. Here we report a new mechanism for degradation of emitting layers in blue-phosphorescent devices. We investigate binary mixtures of a wide bandgap host and a series of novel Ir(III) complex dopants having N-heterocyclocarbenic ligands.

Colorless and transparent copolyimide nanocomposites.

Copolyimides (Co-PIs) were synthesized from 2,2'-bis(trifluoromethyl) benzidine (TFB) and different ratios of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and pyromellitic dianhydride (PMDA). The Co-PI films were obtained from poly(amic acid) (PAA) by solution-casting through typical chemical and thermal imidizations. The thermal properties and optical transparency of the Co-PI films with various PMDA monomer contents were investigated.

Deep red phosphorescence of cyclometalated iridium complexes by o-carborane substitution.

Heteroleptic (C(∧)N)2Ir(acac) (C(∧)N = 5-MeCBbtp (5a); 4-BuCBbtp (5b); 5-BuCBbtp (5c); 5-(R)CBbtp = 2-(2'-benzothienyl)-5-(2-R-ortho-carboran-1-yl)-pyridinato-C(2),N, R = Me and n-Bu; 4-BuCBbtp = 2-(2'-benzothienyl)-4-(2-n-Bu-ortho-carboran-1-yl)-pyridinato-C(2),N, acac = acetylacetonate) complexes supported by o-carborane substituted C(∧)N-chelating ligand were prepared, and the crystal structures of 5a and 5b were determined by X-ray diffraction. While 5a and 5c exhibit a deep red phosphorescence band centered at 644 nm, which is substantially red-shifted compared to that of unsubstituted (btp)2Ir(acac) (6) (λem = 612 nm), 5b is nonemissive in THF solution at room temperature. In contrast, all complexes are emissive at 77 K and in the solid state.

Through-space charge transfer and emission color tuning of di-o-carborane substituted benzene.

1,4-Di-(1-Ar-o-carboran-2-yl)benzene (Ar = 3,5-bis(trifluoromethyl)phenyl (1), phenyl (2), 4-n-butylphenyl (3), 4-N,N-dimethylaniline (4)) compounds that are electronically modulated at the C1-position of o-carborane with the electron-withdrawing or -donating aryl groups were prepared and characterized. The X-ray crystal structures of 1, 3, and 4 reveal that the two aryl groups on the C1-carborane carbon atoms are oppositely positioned, featuring overall C2-symmetry, and the C1-C2 bond length of carborane increases with the increasing order of electron-donating effect of an aryl group. UV-vis absorption spectra exhibit small low-energy absorption bands at around 275-300 nm for 1-3 while 4 shows a broad absorption tail at 350-400 nm.

Heteroleptic tris-cyclometalated iridium(III) complexes supported by an o-carboranyl-pyridine ligand.

Heteroleptic tris-cyclometalated Ir(III) complexes supported by the o-carboranyl-pyridine (CBpy) as a novel C^N chelating ligand were synthesized and characterized. While the CBpy ligand contributes to the electronic stabilization of complexes, their photophysical properties are dominated by 2-arylpyridine ligands.

Synthesis and electron transporting properties of methanofullerene-o-carborane dyads in organic field-effect transistors.

A series of methanofullerene-o-carborane dyads (PCB-Ph-CB, PCB-Cn-CB, n = 1, 3, 6, 11) were synthesized via esterification of [6,6]-phenyl-C61-butyric acid (PCBA) with 2-alcohol functionalized o-carborane derivatives, 1-(4-n-BuC6H4)-2-R-1,2-closo-C2B10H10 (R = p-C6H4OH, (CH2)nOH, n = 1, 3, 6, 11). All the dyads are highly soluble in chlorinated and aromatic solvents under ambient conditions. UV-vis absorption and electrochemical reduction of the dyads exhibited features almost identical to each other, as well as to their parent PCBM, suggesting that the electronic properties of the dyads would be dominated by the methanofullerene moiety.

Genotoxic evaluation of the biocomponents of the cricket, Gryllus bimaculatus, using three mutagenicity tests.

The mutagenic potential of the extracted components of Gryllus bimaculatus, a species of cricket, was evaluated using short-term genotoxicity tests including the Ames, chromosome aberration, and micronuclei tests. In a Salmonella typhimurium assay, G. bimaculatus extract did not produce any mutagenic response in the absence or presence of S9 mix with TA98, TA100, TA1535, and TA1537.

Ras transgene expression in TG-AC mice treated with benzo[a]pyrene.

Transgene expression and skin tumorigenicity were investigated in transgenic TG-AC mice carrying the v-Ha-ras after treatment with benzo[a]pyrene (BP). Animals treated with 40 microg BP (x2/week/mouse) showed 100% tumor response after 25 weeks, as did 40% of the mice treated with 20 microg BP but 10 microg BP did not produce a tumor response. In the case of animals treated with 40 microg BP for 25 weeks, most of the tumors were proven to be carcinomas (80%, 4 out of 5 mice), and all tumors were shown to be positive in terms of transgene expression detected by in situ hybridization.