Blue Host Research Articles

Three acceptors based bipolar materials with tunable excited state natures and applications as non-doped blue emitters and hosts in OLEDs

Four bipolar materials including of CN-TAZ-1Cz, CN-TAZ-2Cz, CN-TAZ-3Cz and CN-TAZ-4Cz were successfully designed and synthesized by incorporating electron-accepting cyano, 1, 2, 4-triazole and pyridine and electron-donating carbazole. The synthesized materials displayed deep-blue and blue emissions in the range of 404–475 nm in CH2Cl2 solution and thin film. The charge-transfer (CT) excited state in CN-TAZ-1Cz and CN-TAZ-3Cz resulted in a large redshift of 163 and 144 nm with the increasing polarities of solvents. The dominated local-electron (LE) and weak CT excited state were observed in emission of CN-TAZ-2Cz, while CN-TAZ-4Cz exhibited mainly CT excited state with redshift of 23 nm. Their performances in organic light-emitting devices (OLEDs) were characterized by using titled bipolar materials as emitting materials and hosts. The non-doped blue device based CN-TAZ-3Cz exhibits the maximum EQE of 3.9% and the. The device hosted CN-TAZ-3Cz and doped Ir(ppy)3 achieved the maximum current efficiency of 64.5 l m/W, external quantum efficiency (EQE) of 18.4% and radiative exciton yield of 66%.

Dual transcriptomics reveals co-evolutionary mechanisms of intestinal parasite infections in blue mussels Mytilus edulis.

On theoretical grounds, antagonistic co-evolution between hosts and their parasites should be a widespread phenomenon but only received little empirical support so far. Consequently, the underlying molecular mechanisms and evolutionary steps remain elusive, especially in nonmodel systems. Here, we utilized the natural history of invasive parasites to document the molecular underpinnings of co-evolutionary trajectories. We applied a dual-species transcriptomics approach to experimental cross-infections of blue mussel Mytilus edulis hosts and their invasive parasitic copepods Mytilicola intestinalis from two invasion fronts in the Wadden Sea. We identified differentially regulated genes from an experimental infection contrast for hosts (infected vs. control) and a sympatry contrast (sympatric vs. allopatric combinations) for both hosts and parasites. The damage incurred by Mytilicola infection and the following immune response of the host were mainly reflected in cell division processes, wound healing, apoptosis and the production of reactive oxygen species (ROS). Furthermore, the functional coupling of host and parasite sympatry contrasts revealed the concerted regulation of chitin digestion by a Chitotriosidase 1 homolog in hosts with several cuticle proteins in the parasite. Together with the coupled regulation of ROS producers and antagonists, these genes represent candidates that mediate the different evolutionary trajectories within the parasite's invasion. The host-parasite combination-specific coupling of these effector mechanisms suggests that underlying recognition mechanisms create specificity and local adaptation. In this way, our study demonstrates the use of invasive species' natural history to elucidate molecular mechanisms of host-parasite co-evolution in the wild.

Novel Blue Bipolar Thermally Activated Delayed Fluorescence Material as Host Emitter for High‐Efficiency Hybrid Warm‐White OLEDs with Stable High Color‐Rendering Index

AbstractA novel thermally activated delayed fluorescence (TADF) molecule, PHCz2BP, is synthesized and used to construct high performance organic light‐emitting diodes (OLEDs) in this work. PHCz2BP is not only the neat emitting layer for efficient sky‐blue OLED, with very high peak external quantum efficiency/power efficiency (EQE/PE) values of 4.0%/6.9 lm W−1, but also acts as a host to sensitize high‐luminance and high‐efficiency green, orange, and red electrophosphorescence with the universal high EQEs of >20%. More importantly, two hybrid white OLEDs based on the double‐layer emitting system of PHCz2BP:green phosphor/PHCz2BP:red phosphor are achieved. To the best of the knowledge, this is the first report for three‐color (blue–green–red) white devices that adopt a TADF blue host emitter and two phosphorescent dopants without any other additional host. Such simple emitting systems thus realized the best electroluminescent performance to date for the WOLEDs utilizing the hybrid TADF/phosphor strategy: forward‐viewing EQEs of 25.1/23.6% and PEs of 24.1/22.5 lm W−1 at the luminance of 1000 cd m−2 with the color rendering indexes of 85/87 and warm‐white Commission Internationale de L'Eclairage coordinates of (0.41, 0.46)/(0.42, 0.45), indicating its potential to be used as practical eye‐friendly solid‐state lighting in future.

A novel luminophor and host polymer from fluorene-carbazole derivatives for preparing solution-processed non-doped blue and closed-white light devices

A novel blue light emitting polymer was designed and synthesized via alternative conjugated 9,9-dioctylfluorene and 9-(6-(9H-carbazol-9-yl)hexyl)-9H-carbazole, named PF2Cz. It exhibited high thermal stability, good film morphology and strong deep-blue emission peaks at 408 and 429 nm in film. The triplet energy level of PF2Cz (ET = 2.30 eV) was also improved. Non-doped and doped devices were both prepared by solution process to characterize the electroluminescent (EL) properties of PF2Cz. In non-doped devices, PF2Cz acted as blue emitter which exhibited a Commission Internation de L'Eclairage (CIE) coordinate of (0.164, 0.102) and a external quantum efficiency (EQE) values of 1.28%. Moreover, the doped phosphorescent devices utilized PF2Cz as host material obtained a closed-white light emission with a content of 1 wt% dopant. All these results indicated that the fluorene-carbazole derivatives could be a promising molecular design strategy for the synthesis of blue light and host organic semiconductors.

Novel tetraarylsilane-based hosts for blue phosphorescent organic light-emitting diodes

Abstract Two highly twisted tetraarylsilane derivatives containing carbazole and benzimidazole were designed and synthesized with high triplet energy level (ET) as hosts for blue phosphorescent organic light-emitting diodes (PHOLEDs). The thermal, photophysical, electrochemical properties and geometry optimization of materials were studied. The central silicon atom effectively disconnected the electronic interactions among the three functional units in a molecule, resulting in high ET and relatively wide band gap (Eg) (≥3.5 eV). Finally, the blue PHOLED devices using 3,3′-((phenyl(4-(9-phenyl-9H-carbazol-2-yl)phenyl)silanediyl)bis(4,1-phenylene)) bis(9-phenyl-9H-carbazole) (TCzSi) as host material achieved a maximum current efficiency of 25.5 cd A−1, a maximum power efficiency of 18.15 lm W−1, a maximum luminance of 6285 cd m−2 and a maximum external quantum efficiency (EQE) of 13.32%. This study showed a molecular design strategy to develop novel tetraarylsilane-based compounds for blue hosts.

Low efficiency roll-off and high color stability pure fluorescent white organic light-emitting diode based exciplex host.

Pure fluorescent WOLEDs with low efficiency roll-off and high color stability were realized by employing an exciplex host. Due to incomplete energy transfer from the blue exciplex host of mCP : PO-T2T to the orange fluorescent dopant of rubrene, the WOLEDs showed a maximum current efficiency, power efficiency and EQE of 14.2 cd A−1, 12.8 lm W−1 and 4.90%, respectively. To our surprise, a rather small roll-off ratio of 8.2% from the maximum EQE to the EQE at 1000 cd m−2 and stable white light-emitting spectra with CIE coordinates of (0.384 ± 0.001, 0.439 ± 0.002) from 4 V to 8 V were obtained simultaneously. The bipolarity and triplet exciton up-conversion of the exciplex host played key roles in delivering excellent performance. More detailed discussions are also provided.

High efficiency (∼100 lm W−1) hybrid WOLEDs by simply introducing ultrathin non-doped phosphorescent emitters in a blue exciplex host

A simple but efficacious structure comprising exciplex combined with non-doped ultrathin layer has been applied for ultrahigh-performance hybrid WOLEDs.

Non-doped white organic light-emitting diodes with superior efficiency/color stability by employing ultra-thin phosphorescent emitters

By modulating the location and quantity of ultra-thin red emitters in blue host of mSOAD, high EQE of 17.3% and high color stability WOLEDs with non-doped structure are achieved.

Predicting the Operational Stability of Phosphorescent OLED Host Molecules from First Principles: A Case Study

Low operational stability is the main limiting factor for commercialization of the blue phosphorescent organic light emitting diodes (PhOLEDs). The high energy and long lifetime of triplet excitons in blue PhOLEDs makes them more prone to degradation. Degradation of the host molecules in the emitting layer of PhOLEDs is one of the possible mechanisms leading to the luminosity loss in the course of device operation. Although possible degradation mechanisms are proposed in the literature, predicting the degradation kinetics is not straightforward because the evolution of excited states should be accurately described. We propose a computational scheme to assess the operational stability of PhOLED host materials. Our protocol relies on the usage of the multireference CASSCF/XMCQDPT2 method. In the present work we consider the degradation of four prototypical blue PhOLED host molecules in the charged and excited states as well as the degradation induced by exciton–polaron and exciton–exciton annihilation proce...

Plasmodium falciparum Heat Shock Protein 70 Lacks Immune Modulatory Activity.

Heat shock protein 70 (Hsp70) family are conserved molecules that constitute a major part of the cell's protein folding machinery. The role of Hsp70s of parasitic origin in host cell immune modulation has remained contentious. This is largely due to the fact that several studies implicating Hsp70 in immune modulation rely on the use of recombinant protein derived from bacteria which is often fraught with lipopolysaccharide (LPS) contamination. For this reason, there is need to clarify the role of parasite Hsp70 in modulating host immune cells. The current study sought to investigate the role of Plasmodium falciparum Hsp70 (PfHsp70) in immune modulation. We expressed recombinant PfHsp70 using three bacterial expression hosts: E. coli XL1 Blue, E. coli ClearColi BL21 and Brevibacillus choshinensis, respectively. We further investigated the immunostimulatory capability of PfHsp70 by monitoring cytokine production by murine immune cells cultured in the presence of the protein. Recombinant PfHsp70 produced using E. coli XL1 Blue expression host induced IL6 and IL8 cytokines. On the other hand, PfHsp70 produced in E. coli ClearColi and B. choshinensis expression systems was associated with no detectable traces of LPS and exhibited no immunomodulatory activity. Our findings demonstrate that PfHsp70 does not possess immunomodulatory function. Furthermore, our study further confirm E. coli ClearColi and B. choshinensis as appropriate expression systems for the production of LPS-free recombinant protein.

Adesis to expand Delaware operations

The contract research firm Adesis has purchased its building in New Castle, Del., doubling its available space to about 4,400 m2. Adesis was acquired last year by Universal Display, a provider of emitters and other materials for organic light-emitting diodes. Universal CEO Steven V. Abramson says the purchase and a planned expansion will boost Adesis’s contract research business as well as help Universal develop red, green, yellow, and blue emitters and emitter hosts.

Synthesis and properties of polymeric host materials constructed by silane-carbazole backbone and electron-affinitive cyanohexyl substituent for blue phosphorescence dopant

A series of blue phosphor hosts, using 3,6-linked carbazole with δ-π tetraphenylsilane segment as the main chain and modified by peripheral cyanohexyl group with different ratios, was designed and synthesized. These polymers show good solubility in common organic solvents. They all possess wide bandgap of 3.40 eV, high thermal stabilities and good film forming abilities. The peripheral cyanohexyl substituents have no effect on the polymer backbones but enhance the electron transporting properties of the polymers in devices. Among them, doped devices using poly[(tetraphenylsilicon/9-hexyl-9H-3,6-carbazole)50-co-(tetraphenylsilicon/9-hexanenitrile-9H-3,6-carbazole)50 (PCNCzSi50) as the host and bis[(4,6-difluorophenyl)pyridinato-N,C2]-(picolinato)iridium(III)(FIrpic) as the guest show the best performance with the maximum current efficiency and power efficiency of 2.00 cd/A and 1.40 lm/W, respectively.

Correction: Thermally activated delayed fluorescence blue dopants and hosts: from the design strategy to organic light-emitting diode applications

Correction for ‘Thermally activated delayed fluorescence blue dopants and hosts: from the design strategy to organic light-emitting diode applications’ by Mallesham Godumala et al., J. Mater. Chem. C, 2016, DOI: 10.1039/c6tc04377a.

One-Step Synthesized Novel Spiro[fluorene-9, 9'-xanthene]-Based Materials as Highly Efficient Blue Phosphorescent Hosts in Organic Light-Emitting Devices

One-Step Synthesized Novel Spiro[fluorene-9, 9'-xanthene]-Based Materials as Highly Efficient Blue Phosphorescent Hosts in Organic Light-Emitting Devices

Low color-temperature, high color rendering index hybrid white organic light-emitting diodes by the effective control of exciton recombination zone

Excitons dominate the optoelectronic properties of organic devices.

Solution-processed small-molecular white organic light-emitting diodes based on a thermally activated delayed fluorescence dendrimer

Solution-processed white OLEDs based on a blue TADF dendrimer host and an orange iridium complex dopant achieved a maximum EQE of 10.1% with low efficiency roll-off at high current density.

An ambipolar 3,3′-dimethyl-9,9′-bianthracene derivative as a blue host material for high-performance OLEDs

A new ambipolar 3,3′-dimethyl-9,9′-bianthracene derivative (MBAn-(4)-tBu) was designed as a deep blue fluorophore and blue host material for high-performance OLEDs.

Synthesis and device properties of mCP analogues based on fused-ring carbazole moiety

Novel mCP analogues consisting of blue phosphorescent host materials with fused-ring, 1,3-bis(5H-benzofuro[3,2-c]carbazol-5-yl)benzene (BFCz) and 1,3-bis(5H-benzo[4,5]thieno[3,2-c]carbazol-5-yl)benzene (BTCz) were designed and synthesized using benzofurocarbazole and benzothienocarbazole donor moieties. BFCz and BTCz exhibit high glass transition temperatures of 147 and 157 °C, respectively, and high triplet bandgaps of 2.94 and 2.93 eV, respectively. To explore the electroluminescence properties of these materials, multilayer blue phosphorescent organic light-emitting diodes (PHOLEDs) were fabricated in the following device structure: indium–tin-oxide (ITO)/PEDOT:PSS/4,4’-cyclohexylidene bis[N,N-bis(4-methylphenyl)aniline] (TAPC)/1,3-bis(N-carbazolyl) benzene (mCP)/host:FIrpic/diphenylphosphine oxide-4-(triphenylsilyl)phenyl (TSPO1)/LiF)/Al. The PHOLEDs with BTCz exhibited efficient blue emission with luminous and quantum efficiencies of 30.9 cd/A and 15.5% at 1000 cd/m2, respectively.

Photometric properties of intermediate-redshift Type Ia supernovae observed by the Sloan Digital Sky Survey-II Supernova Survey

We have analyzed multi-band light curves of 328 intermediate redshift (0.05 <= z < 0.24) type Ia supernovae (SNe Ia) observed by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). The multi-band light curves were parameterized by using the Multi-band Stretch Method, which can simply parameterize light curve shapes and peak brightness without dust extinction models. We found that most of the SNe Ia which appeared in red host galaxies (u - r > 2.5) don't have a broad light curve width and the SNe Ia which appeared in blue host galaxies (u - r < 2.0) have a variety of light curve widths. The Kolmogorov-Smirnov test shows that the colour distribution of SNe Ia appeared in red / blue host galaxies is different (significance level of 99.9%). We also investigate the extinction law of host galaxy dust. As a result, we find the value of Rv derived from SNe Ia with medium light curve width is consistent with the standard Galactic value. On the other hand, the value of Rv derived from SNe Ia that appeared in red host galaxies becomes significantly smaller. These results indicate that there may be two types of SNe Ia with different intrinsic colours, and they are obscured by host galaxy dust with two different properties.

A Theoretical Guideline for Designing Effective Host Materials Based on 4,4′-Bis(9-carbazolyl)-1,1′-biphenyl Derivatives for Blue Phosphorescent Devices

Abstract Development of host materials is crucial for organic electroluminescent devices. In order to generalize the way to molecular design the host materials, we here present a guideline to design effective host materials for blue phosphorescent devices based on 4,4′-bis(9-carbazolyl)-1,1′-biphenyl (CBP) derivatives, comparing some theoretical parameters of seven CBP derivatives with experimental ones in terms of thermal stability, T1 energy level, and band gap. Although our computation at the density functional theory level could not reproduce the absolute values and phenomena that were experimentally obtained, theoretical relative correlations between different molecules agreed with experimental ones. Indeed, both experimental and theoretical approaches predicted that the same molecule (1,1-bis(4-(9-carbazolyl)-phenyl)cyclohexane) was viable as blue host material among the target molecules in terms of thermal stability, the T1 state with the LE character within carbazole moieties and T1 energy 3.00 eV higher than that of blue emitters. The qualitative guideline we proposed would be potentially helpful to save experimental work to design other hole- or electron-transporting materials.