Search

The development of the triazine derivatives as the n-type (electron transport type) host for long device lifetime in deep blue phosphorescent organic light-emitting diodes (PhOLEDs) was studied by synthesizing two hosts with dibenzofuran and triphenylsily blocking groups. The triazine core was located at the center of the molecule and the triphenylsilyl group behaved as the blocking group of the planar core. The dibenzofuran was also attached to the triazine core for electron transport and high triplet energy. Two hosts with different number of dibenzofuran and tripheynylsilyl units were synthesized and the number of triphenylsilyl group was critical to the device lifetime results. The two hosts showed high external quantum efficiency over 20%, but the device lifetime was doubled by introducing two triphenylsilyl units instead of one triphenylsilyl group. A device lifetime of 2200 h at 100 cd/m2 was achieved using the new host. It was revealed that enlarging the intermolecular distance by inserting two bulky groups in the hosts had positive effects on increasing the device lifetime.

In this work, a design approach of three thermally activated delayed fluorescence (TADF) emitters to extend the device lifetime of the TADF sensitized fluorescent devices was studied. Three TADF materials, 5-{4,6-bis[4-(tert-butyl)phenyl]-1,3,5-triazin-2-yl}-2-(10,15-diphenyl-10,15-dihydro-5H-diindolo[3,2-a:3',2'-c]carbazol-5-yl)benzonitrile (tTCNTruX), 4-[3-cyano-4-(10,15-diphenyl-10,15-dihydro-5H-diindolo[3,2-a:3',2'-c]carbazol-5-yl)phenyl]-2,6-diphenylpyrimidine-5-carbonitrile (PCNTruX) and 4-(4-{10,15-bis[4-(tert-butyl)phenyl]-10,15-dihydro-5H-diindolo[3,2-a:3',2'-c]carbazol-5-yl}-3-cyanophenyl)-2,6-diphenylpyrimidine-5-carbonitrile (PCNtTruX), were synthesized as sensitizers for TADF-sensitized fluorescent organic light-emitting diodes. The two tTCNTruX and PCNtTruX TADF emitters were designed to have Dexter energy transfer with blocking groups either in the donor or acceptor unit of the donor-acceptor-type TADF sensitizer. The TADF materials showed small singlet-triplet energy splitting and a high reverse intersystem crossing (RISC) rate for effective sensitization of the fluorescent emission of the fluorescent emitter. tTCNTruX- and PCNtTruX-sensitized fluorescent devices showed maximum external quantum efficiencies (EQEs) of 17.7 % and 11.5 % in the yellow and red devices, respectively, which were higher than those of TADF-sensitized devices with the corresponding TADF sensitizer without a blocking group. Moreover, the device lifetime was also extended by employing the tTCNTruX and PCNtTruX sensitizers. This work demonstrated that the tTCNTruX and PCNtTruX sensitizers are effective to improve the maximum EQE and device lifetime of TADF-sensitized fluorescent devices.

Highly efficient and stable thermally activated delayed fluorescence (TADF) emitters are in urgent demand for their commercial application. However, the simultaneous achievement of high external quantum efficiency (EQE) and long lifetime in single organic molecular design is a herculean task. In particular, it is even more difficult in the long wavelength TADF emitter designs due to the compulsory molecular designing rules. Herein, we designed and synthesized two orange-red TADF emitters, namely 2-(4-(10,15-diphenyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazol-5-yl)phenyl)-3-phenylquinoxaline-6,7-dicarbonitrile (6,7-DCNQx-DICz) and 2-(4-(10,15-diphenyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazol-5-yl)phenyl)-3-phenylquinoxaline-5,8-dicarbonitrile (5,8-DCNQx-DICz) by utilizing diindolocarbazole (DICz) and 6,7/5,8 dicyano substituted quinoxaline (DCQx) as a stable donor–acceptor combination. In particular, organic light emitting diodes (OLEDs) fabricated with 6,7-DCNQx-DICz as the TADF emitter achieved a high EQE up to 23.9% and a long lifetime of 931 h with up to 90% of its initial luminescence at 1000 cd m−2. At the same time, a comparatively low EQE of 12.5%, but a longer lifetime of 1184 h was achieved by utilizing 5,8-DCNQx-DICz as the TADF emitter. Hence, the amalgamation of the rigidified DICz unit and DCQx unit can be considered as a chemical platform in the future design of highly efficient and long lifetime orange-red TADF OLEDs.

A novel electroplex host with two triplet exciton up-converting channels for suppressed triplet exciton triggered degradation mechanisms was developed using an electron transport type host (n-type host) with thermally activated delayed fluorescence (TADF) characteristics to improve the device lifetime of deep blue phosphorescent organic light-emitting diodes (PhOLEDs). The TADF-natured n-type host with high triplet energy was derived from triazine with benzonitrile and carbazole units to induce the TADF characteristics. The TADF natured n-type host generated an electroplex with a hole transport type host and the electroplex-based PhOLEDs revealed an extended device lifetime by more than twice compared to the non-TADF natured n-type host based electroplex host. Transient photoluminescence and electroluminescence analyses revealed that two reverse intersystem crossing (RISC) mechanisms through the n-type TADF host and electroplex host could suppress triplet exciton related degradation and improved the device lifetime. Kinetic modeling of the electroplex supported the RISC mechanisms of the electroplex.

In the organic light-emitting diodes (OLEDs), the achievement of high efficiency and long device lifetime has been a goal due to the short device lifetime of the high efficiency blue OLED devices. The strategy for the device structure in this study suggests a solution for high efficiency and long lifetime of blue thermally activated delayed fluorescent (TADF) OLEDs by selectively managing the long-living triplet excitons of TADF emitters mainly responsible for the short lifetime of TADF OLEDs. The introduction of a triplet exciton quenching layer (QL) positioned at a short distance from the recombination zone could quench the long-living triplet excitons of TADF emitters and dramatically enhance the device lifetime of TADF OLEDs without efficiency loss. Ultimately, the device lifetime was doubled while achieving a high external quantum efficiency of 22.0% compared to the conventional TADF OLED by selective quenching long-living triplet exciton. This study verifies the potential of QL in TADF OLEDs as a future strategy to achieve high efficiency and long lifetime in the blue OLEDs.

A molecular design with a negative polaron stabilizing unit was developed to extend the device lifetime of blue phosphorescent organic light-emitting diodes (PhOLEDs). A novel p-type host material, 5,10-diphenyl-5,10-dihydrofuro[3,2-c:4,5-c′]dicarbazole (DBFBCzPh), with two carbazoles fused by a furan negative polaron stabilizing unit, was developed and synthesized in this work. A 9,9′-diphenyl-9H,9′H-3,3′-bicarbazole (BCzPh) p-type host material was used to compare the effect of the negative polaron stabilizing unit on the device characteristics. Compared with BCzPh, the DBFBCzPh showed improved stability against negative polarons, and thus the device lifetime was extended by more than two times. In the case of efficiency, the maximum external quantum efficiencies of the BCzPh and DBFBCzPh devices were 15.5% and 22.3%, respectively, in which the DBFBCzPh host containing a furan moiety showed 6.8% higher efficiency than the BCzPh host. Accordingly, the molecular design with the furan-based fused structure is advantageous in terms of both efficiency and device lifetime, and can be a platform for solving the lifetime issue of blue PhOLEDs.

Molecular design strategies are crucial to develop highly efficient and long-wavelength thermally activated delayed fluorescent (TADF) emitters because the inherent limitation of the energy gap law degrades the efficiency of the red or orange TADF emitters. To resolve the low efficiency issue, we designed and synthesized two TADF emitters, 4,4'-(6-(9,9-dimethylacridin-10(9H)-yl)-7-fluoroquinoxaline-2,3-diyl)dibenzonitrile (FDQCNAc) and 11-(9,9-dimethylacridin-10(9H)-yl)-12-fluorodibenzo[a,c]phenazine-3,6-dicarbonitrile (FBPCNAc), by utilizing fluorine and peripheral cyano-substituted quinoxaline and phenazine acceptors of 4,4'-(6-fluoroquinoxaline-2,3-diyl)dibenzonitrile (FDQCN) and 11-fluorodibenzo[a,c]phenazine-3,6-dicarbonitrile (FBPCN), respectively. A fluorine atom at the ortho position of the acridine donor acts as an auxiliary acceptor to minimize the singlet-triplet energy gap (ΔEST) below 0.1 eV and promotes the reverse intersystem crossing (RISC) process. Organic light-emitting diodes (OLEDs) fabricated with FDQCNAc and FBPCNAc emitters demonstrated high external quantum efficiencies (EQEs) of 27.6 and 23.8% in the yellow-red TADF OLEDs, respectively. In particular, the combination of the F auxiliary acceptor unit and the rigidified FBPCN acceptor unit enabled red-shifted emission by about 58 nm without much sacrifice of the EQE in the red region.

Herein we unveiled the synthetic approach to C1-, C2-, and C3-modified carbazoles for the first time and designed high-triplet-energy bipolar host materials for green phosphorescent organic light-emitting devices. The compounds revealed excellent performance with a maximum external quantum efficiency as high as 23.6% and extremely low-efficiency roll-off of 2.1% at high brightness of 1000 cd/m

Imidazole- and N-methylimidazole carboxylate have been introduced to serve as ancillary ligands in heteroleptic Ir(III) complexes containing 2-phenylpyridine-based main ligands, with consideration of the frontier orbital energy levels. Complexes Ir1–Ir4 were synthesized and found to have LUMO levels higher than that of the corresponding Ir(III) complex containing pyridyl carboxylate. All the synthesized Ir(III) complexes exhibited blue phosphorescence emission maxima in the region of 465–467 nm at room temperature. Phosphorescent quantum efficiencies were increased by a factor of 1.8–6.7 by blocking the intermolecular hydrogen bonding between the imidazole carboxylate ligands of neighboring Ir(III) complexes, which was achieved by N-methylation of the imidazole carboxylate ancillary ligand. The organic light-emitting diodes fabricated using Ir3 and Ir4 as dopant materials in the emissive layers were found to emit blue emission with peaks at 469 and 471 nm and maximum external quantum efficiencies of 20.0 and 22.4%, respectively. Moreover, all the fabricated devices with Ir3 and Ir4 exhibited low efficiency roll-off, indicating excellent stability of the materials.

A novel mixed host employing a negative polaron stabilizing p-type host was developed to extend the device lifetime of blue phosphorescent organic light-emitting diodes (PhOLEDs). Instead of a conventional p-type host with only a hole transport unit, a p-type host with a negative polaron resistant unit in addition to the hole transport unit was used in the mixed host consisting of a p-type host and an n-type host. The p-type host had benzonitrile as a negative polaron resistant unit which stabilized the molecule under negative polarons. The use of the p-type host with the benzonitrile unit almost doubled the device lifetime of the blue PhOLEDs due to the improved negative polaron stability of the hosts. Therefore, the p-type host with the weak electron accepting benzonitrile unit can play the role of a lifetime extending p-type host to replace a conventional p-type host.

A molecular design approach for synthesizing color-tunable and high-efficiency TADF emitters in the long-wavelength region was developed. The synthesis involves the direct attachment of three different electron-donating groups, namely 3,6-di-tert-butylcarbazole (tCz), 9,9-dimethyl-9,10-dihydroacridine (Ac), and N3,N3,N6,N6-tetraphenyl-9H-carbazole-3,6-diamine (DACz), to the highly rigid dibenzo[a,c]phenazine-2,7-dicarbonitrile (BPCN) acceptor unit. Among them, the highly distorted donor–acceptor-based Ac-BPCN emitter exhibited a high EQE of above 20% with color coordinates of (0.54, 0.45) and a peak wavelength of 597 nm. Highly red-shifted emission of up to 631 nm with color coordinates of (0.60, 0.39) was enabled by the DACz-BPCN emitter due to the strong donor character of DACz. The emission wavelengths of the three TADF emitters cover a wide range of the long-wavelength region of the visible spectrum, from yellow (548 nm) to deep-red (631 nm). The peripheral cyano-substituted rigid BPCN unit proved its potential as an efficient electron acceptor for the design of highly efficient and long-wavelength TADF emitters.

Two novel acridine-benzofuran/benzothiophene hybrid donors of 34BxAc (x = F, 34BFAc: 13,13-dimethyl-8,13-dihydrobenzofuro[3,2-a]acridine; x = T, 34BTAc: 13,13-dimethyl-8,13-dihydrobenzo[4,5]thieno[3,2-a]acridine) were developed as aromatic fused donors by combining dimethyl acridine (Ac) with benzofuran and benzothiophene, respectively. As a comparison, the hybrid donors of 12BxAc (x = F, 12BFAc: 5,5-dimethyl-5,13-dihydrobenzofuro[3,2-c]acridine; x = T, 12BTAc: 5,5-dimethyl-5,13-dihydrobenzofuro[3,2-c]acridine) were also prepared. By attaching the TPPM (2,4,6-triphenylpyrimidine) acceptor to these fused hybrid donors (12BFAc, 12BTAc, 34BFAc and 34BTAc), 12BxAc-PM (12FAc-PM and 12BTAc-PM) and 34BxAc-PM (34BFAc-PM and 34BTAc-PM) were further designed and synthesized. It was revealed that 34BxAc-PM was better than 12BxAc-PM at shrinking the singlet–triplet energy gap and decay lifetime, and increasing the photoluminescence quantum yield. The sky-blue thermally activated delayed fluorescent organic light-emitting diodes (OLEDs) with 12BFAc-PM as a dopant just showed a maximum external quantum efficiency (EQE) of 12.9% and a CIEx,y of (0.16, 0.29). The 12BTAc-PM-based device achieved a maximum EQE of 25.6%, however, the efficiency roll-off was relatively serious. In contrast, high-performance and low efficiency roll-off OLEDs can be developed using 34BxAc-PM. For instance, the 34BFAc-PM-based device realized a maximum EQE of 27.7%, and still a high EQE of 24.6% at 1000 cd m−2 and 19.6 cd m−2 at 5000 cd m−2, respectively, indicative of the superiorities of the novel donors (34BFAc and 34BTAc).

A series of green-emitting fluorophores based on a tetra-azaacene core is synthesized by introducing nitrile substituents at different positions. Their molecular structure-optical property relationship [i.e., vibronic transitions in photoluminescence (PL) and electroluminescence (EL) spectra] is investigated to obtain a sharp emission where the vibronic peak ν0-0 should be intensified by suppressing ν0-n (n = 1, 2, 3...) transitions. The intensity ratios (I0-1/I0-0) of the ν0-1 and ν0-0 vibronic transitions in the PL spectra of DBBNP, DBBNP2CN1, and DBBNP2CN2 in hexane are 1.13, 0.80, and 0.67, respectively. Theoretical calculations explain that the CN substitution at positions 8 and 13 in DBBNP2CN2 induces a uniform charge distribution and reduces the Huang-Rhys factors (HRFs) of the vibrational normal modes coupled to the electronic transition. The organic light-emitting diode (OLED) fabricated with DBBNP2CN2 shows a narrower green EL emission at 518 nm with a smaller bandwidth (50 nm) than those of devices adopting DBBNP or DBBNP2CN1. The careful modification of the molecular structures and positions of substituents enables us to reduce the HRFs of vibrations to achieve a narrow emission bandwidth with decreased I0-1/I0-0, which suggests a design strategy to develop narrowband organic fluorophores to improve the color purity for wide-gamut OLED displays.

Dimethyl acridine (Ac) and carbazole (Cz) donors are fused to produce acridine–carbazole hybrid donors 12AcCz (8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine) and 23AcCz (13,13-dimethyl-7-phenyl-7,13-dihydro-5H-indolo[3,2-b]acridine). By combining the TPPM (2,4,6-triphenylpyrimidine) acceptor with the Ac–Cz-fused donors of 12AcCz and 23AcCz, two emitters, 12AcCz-PM (13-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine) and 23AcCz-PM (5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-13,13-dimethyl-7-phenyl-7,13-dihydro-5H-indolo[3,2-b]acridine), are designed and synthesized. The impact of the different fused topologies of the hybrid donors on the molecular configuration and photophysical and optoelectrical properties is systematically investigated. For 12AcCz-PM, the large steric hindrance between the donor and acceptor compels Ac of 12AcCz to be crooked, which endows it with a relatively planar quasi-axial conformation. No blatant TADF character is observed, but the 12AcCz-PM doped device still presents ultradeep blue emission with CIEx,y of (0.15, 0.05) and a maximum external quantum efficiency (EQEmax) of 6.4%. Whereas, 23AcCz-PM shows a quasi-equatorial conformation and possesses notable TADF behavior. The 23AcCz-PM doped device reachs an EQEmax of 28.4% at low dopant concentration and 26.1% at high dopant concentration. Additionally, low efficiency roll-off (EQEs of 24.8% at 1000 cd m−2 and 20.7% at 5000 cd m−2) further confirms its superiority as a TADF emitter.

High performance deep blue phosphorescent organic light-emitting diodes (PhOLEDs) were developed using a thermally activated delayed fluorescence type exciplex host. Three isomeric electron transport type host materials based on a triazine core, tetraphenylsilane and benzonitrile groups were synthesized for high triplet energy and good electron transport property in solid state. They formed thermally activated delayed fluorescence type exciplexes with a carbazole based hole transport type host. Among the three hosts, 3-(4,6-bis(3-(triphenylsilyl)phenyl)-1,3,5-triazin-2-yl)benzonitrile host achieved high external quantum efficiency of 21.0% and deep blue color coordinate of (0.14, 0.18). Moreover, the lifetime of the deep blue PhOLEDs was improved by more than 1.6 times using the new exciplex host compared with the state of the art mixed host.

Violet organic light-emitting diodes (OLEDs) with a very narrow emission spectrum with a full width at half maximum of 14 nm and y color coordinate of 0.02 are developed using a indolo[3,2,1-jk]carbazole-derived pure violet emitter. The violet emitter, 2,5,13,16-tetra-tert-butylindolo[3,2,1-jk]-indolo[1',2',3':1,7]indolo[2,3-b]carbazole (tDIDCz), is designed to have a very rigid molecular structure driven by the multiresonance-type core structure through the alternating carbon and nitrogen atoms. The violet emitter is decorated with t-butyl groups to prevent intermolecular aggregation and packing, which allow pure violet emission without excimer emission. The violet OLEDs derived from the tDIDCz emitter show a violet color coordinate of (0.164, 0.018) with a narrow emission spectrum and a full width at half maximum of 14 nm (105 meV). The external quantum efficiency of the pure violet OLEDs is 3.3%. This is the first work reporting pure violet emission without any ultraviolet emission below 380 nm and blue emission above 450 nm by showing a very narrow emission spectrum.

An exciton stabilizing electron transport type (n-type) host material was developed for application in long lifetime blue phosphorescent organic light-emitting diodes (PhOLEDs). A conjugation breaking diphenylsilyl backbone structure combined with a diphenyltriazine unit was a basic molecular platform to obtain high triplet energy and electron transport property. Two hosts with and without carbazole were synthesized as the bipolar and unipolar n-type hosts derived from diphenylsilyl backbone and diphenyltriazine unit. The blue PhOLEDs using the two hosts showed high external quantum efficiency above 20% and blue color coordinate of (0.14, 0.17). Particularly, the bipolar n-type host with the carbazole unit extended the device lifetime by more than 1.4 times compared with the unipolar host and by more than three times relative to a conventional diphenyltriazine based host without the diphenylsilyl core because of the exciton stabilizing function of the host. This work proved the potential of the diphenyltriazine and carbazole merged diphenylsilyl skeleton as a chemical platform of the n-type hosts.

Two thermally activated delayed fluorescent (TADF) emitters built on the design approach isolating two TADF chromophores were developed by coupling them through a meta- functionalized phenyl linker. The rate constant of reverse intersystem crossing (RISC) was improved by the chromophore isolation method via a reduced singlet–triplet energy gap and the photoluminescence quantum yield was enhanced by the two independent TADF emitting units. The external quantum efficiency of the TADF emitters was over 20%, which was much higher than that of the previously reported TADF emitter (13.5%) by electronically separating the two TADF chromophores. This work demonstrated that the newly proposed design can increase the EQE and facilitate RISC process by electronic separation of the two TADF units via the meta functionalized phenyl linker.

The design strategy of thermally activated delayed fluorescence (TADF) emitters for high quantum efficiency in the TADF devices was developed by addition of a secondary donor in an ortho- linkage based donor–acceptor type TADF emitter. The secondary donors were substituted at para- position of the acceptor in the ortho- linkage based TADF compound to improve the absorption and emission properties. The external quantum efficiency of the TADF emitters was increased from 15.8% to 22.7% by the introduction of the secondary donor without changing the emission color of the devices. Based on these results, the molecular design strategy presented in this work can be effective to develop highly efficient blue TADF devices.

Herein, we report two simple and efficient high triplet energy bipolar host materials named 2'-(9H-carbazol-9-yl)-[1,1′-biphenyl]-2-carbonitrile (CzBPCN) and 9-(2′-cyano-[1,1′-biphenyl]-2-yl)-9H-carbazole-3-carbonitrile (CNCzBPCN) by connecting carbazole type donor and cyano acceptor on 2 and 2′ positions of a biphenyl linker, respectively. The effect of cyano substitution on carbazole building block on photophysical and electroluminescence properties was unveiled. Both the compounds revealed high triplet energy (ET) of above 3.0 eV attributed to the interrupted interchromophoric electronic interactions between the donor and acceptor units. The computational studies and carrier transport analysis proved that the compounds secured good bipolar charge transporting feature. The applicability of these materials as hosts for blue phosphorescent organic light emitting diodes (PhOLEDs) was tested. Interestingly, the CNCzBPCN hosted device exhibited superior performance with three fold improved external quantum efficiency (EQEmax) of 20.2% over the CzBPCN hosted device which showed EQEmax of 7.1%. Importantly, the CNCzBPCN hosted device demonstrated 11 fold extended operational lifetime of 121 h up to 50% of its intimal luminance (L0 = 200 cd/m2) compared to CzBPCN. We believe that this work demonstrates the cost-effective and efficient high triplet energy bipolar host materials for simultaneous achievement of high EQE over 20% and long operational lifetime of blue PhOLEDs.

A strongly electron deficient and high triplet energy host for blue emitters was developed by decorating a dibenzofuran modified biphenyl backbone structure with multiple CN units. Two hosts, 6,6′-bis(6-cyanodibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-3,3′-dicarbonitrile(CNDBF1) and 2,2′-bis(6-cyanodibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-4,4′-dicarbonitrile(CNDBF2), were derived from the CN decoration strategy for application in blue organic light-emitting diodes requiring high triplet energy host. They showed high triplet energy above 2.79 eV and acted as the electron transport type host based on the strong electron deficiency. The mixture of the CNDBF1 and CNDBF2 hosts with a hole transport type 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl host performed as the exciplex host of a blue phosphor and accomplished high external quantum efficiency of 22.7% in the blue phosphorescent organic light-emitting diodes.

Many researchers have reported dibenzo[b,d]furan segment as a building block of organic light-emitting diode (OLED) materials because it has high thermal stability and triplet energy. However, most of the research has focused on symmetrically substituting the same functional groups at 2-position due to easy functionalization or substituting the same functional groups at different positions of dibenzo[b,d]furan. Herein, we design and synthesize three new hole blocking materials based on asymmetrically difunctionalized dibenzo[b,d]furan, diphenyl (2-(pyridin-3-yl)dibenzo[b,d]furan-6-yl)phosphine oxide (DBFPO-Py), diphenyl(2-(pyrimidin-5-yl)dibenzo[b,d]furan-6-yl)phosphine oxide (DBFPO-Pyr), and diphenyl(2-(4-(triphenylsilyl)phenyl)dibenzo[b,d]furan-6-yl)phosphine oxide (DBFPO-Si) for high-performance phosphorescent OLEDs. Phosphine oxide, tetraphenylsilane, pyridine, and pyrimidine segments are successfully introduced into the asymmetric position of a dibenzo[b,d]furan. It is found that DBFPO-Py, DBFPO-Pyr, and DBFPO-Si possess high thermal stability; high triplet energies of 2.96, 2.98, and 2.80 eV; and deep highest occupied molecular orbital (HOMO) energy levels of −7.13, −7.23 and −7.07 eV; respectively. Blue phosphorescent OLEDs with DBFPO-Py, DBFPO-Pyr, and DBFPO-Si show low turn-on voltages, high current and power efficiencies, and superior external quantum efficiencies. Blue phosphorescent OLEDs with DBFPO-Py and DBFPO-Pyr showed improved performance in terms of current and power efficiencies, etc, compared with the device with 1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPB), which is commonly used as a hole blocking layer. More importantly, the blue phosphorescent OLEDs with DBFPO-Pyr showed the best performance with maximum external quantum efficiency of 23.6%, current efficiency of 29.8 cd A−1, power efficiency of 26.0 lm W−1, and low efficiency roll-off of 6.38%. Novel hole blocking materials based on asymmetrically difunctionalized dibenzo[b,d]furan are expected to make a significant contribution to the development of blue phosphorescent OLEDs.

Recurrence after thoracoscopic surgery for primary spontaneous pneumothorax is a lingering problem, and many intraoperative methods to induce pleural symphysis have been introduced. We analyzed the effects of chemical pleurodesis during thoracoscopic procedures. Between August 2003 and July 2005, 141 patients among indicated surgical treatment for primary spontaneous pneumothorax in two hospitals of our institution allowed this prospective study. The patients were randomly assigned to 3 groups: thoracoscopic procedure only (group A, n=50), thoracoscopic procedure and pleurodesis with dextrose solution (group B, n=49), and thoracoscopic procedure and pleurodesis with talc-dextrose mixed solution (group C, n=42). There was no significant difference in demographic data among the three groups. The two groups that underwent intraoperative pleurodesis had significantly longer postoperative hospital stays (A/B/C: 2.50+/-1.85/4.49+/-2.10/6.00+/-2.58 days; p=0.001) and a higher incidence of postoperative fever (A/B/C: 10.0/22.45/52.38%; chi(2)= 21.598, p=0.00). No significant differences were found for recurrence rates or the number of postoperative days until chest tube removal. Therefore, the results of our study indicate that intraoperative chemical pleurodesis gives no additional advantage to surgery alone in deterring recurrence for patients with primary spontaneous pneumothorax. Thus, the use of such scarifying agents in the operating room must be reconsidered.

We address via numerical simulation the two-dimensional bimolecular annihilation reaction $A + A \to \emptyset$ in the presence of quenched, random impurities. Renormalization group calculations have suggested that this reaction displays anomalous kinetics at long times, $c_{A}(t) \sim at^{\delta -1}$, for certain types of topological or charged reactants and impurities. Both the exponent and the prefactor depend on the strength of disorder. The decay exponents determined from our simulations agree well with the values predicted by theory. The observed renormalization of the prefactor also agrees well with the values predicted by theory.

Pleural effusion due to hepatic cirrhosis and ascites is well known. But rarely a pleural effusion may develop in a cirrhotic patient in the absence of detectable ascites. The differential diagnosis of a right-sided transudative pleural effusion in a patient with chronic liver disease with or without ascites includes congestive heart failure and nephrotic syndrome. These diseases are usually ruled out with standard clinical tests. Patients with hepatic hydrothorax should be treated with fluid restriction, diuretics and the correction of hypoalbuminemia. Patients with severe symptoms due to refractory hepatic hydrothorax might benefit from pleural sclerosis and surgical closure of diaphragmatic defect. We experienced a case of right-sided pleural effusion in liver cirrhosis without ascites.

The progress in anti-platelet therapy and percutaneous coronary intervention led to reconfigure indications of hybrid re-vascularisation. However, there are still some controversies over indication, timing and patient management during the procedure. The case discussed here is a patient who was diagnosed with myocardial infarction and treated with hybrid re-vascularisation. The patient underwent stent insertion followed by bypass surgery. After the hybrid procedure, the patient was stable but eventually died on the 12th day after the surgery owing to unexpected stent thrombosis. We discuss the current controversy over hybrid re-vascularisation, variables that can affect the outcome and the requirement for establishing accurate logistics based on our case.

Background We evaluated the feasibility and accuracy of a needlescopic procedure for lung biopsies in patients with interstitial lung disease or indeterminate pulmonary nodules. Methods Sixty-five patients (36 women; mean age, 51.3 ± 15.6; range, 13 to 76 years) underwent a needlescopic procedure to obtain lung biopsy specimens. Forty had indeterminate pulmonary nodules, and 25 had interstitial lung disease. A 2-mm needlescope and a 2-mm MiniSite Endo Grasp (Covidien, Norwalk, CT) were inserted at the sixth intercostal space along the middle and the posterior axillary line, respectively. Biopsy specimens were obtained using endostaplers. Results The average number of biopsy specimens was 1.7 ± 0.6 (range, 1 to 4). For 9 patients, a frozen specimen was sent twice to pathology. Complete resection was continued after intraoperative pathology confirmation in 13 patients (lobectomy, 7; segmentectomy, 3; mass removal, 1; metastasectomy, 2). The volume of lung tissue was 8.7 ± 11.8 cm 3 (range, 0.15 to 55.44 cm 3 ). The operation time was 58.7 ± 37.5 minutes (range, 15 to 160 minutes). The final pathologic results were confirmed in all patients. No thoracoscopic procedure was converted to an open thoracotomy. Three patients (4.3%) had prolonged air leakage (> 5 days), and the chest tube remained in the pleural space for 2.3 ± 2.4 days (range, 1 to 8 days). Conclusions Needlescopic operation for lung biopsies in patients with interstitial lung disease and indeterminate pulmonary nodules is a minimally invasive procedure that is safe and effective for obtaining a diagnosis in selected patients.

Purpose Bar displacement is a major complication in repair of pectus excavatum with the Nuss technique. Mechanisms of bar displacement have been elucidated by case-by-case analysis, and specific bar fixation techniques have been developed to deal with each mechanism. The efficacy of our bar fixation techniques is appraised. Methods Data from 725 consecutive patients between 1999 and 2006 who were repaired with our modifications to the Nuss procedure were retrospectively analyzed. Results The mechanism of bar displacement consisted of one or a combination of the following types: type 1, "bar flipping"—rotation of the bar along the axis of hinge; type 2, "lateral sliding"—horizontal slipping of the bar to one side in asymmetric pectus excavatum; and type 3, "hinge-point disruption"—a dorsal shift of the bar owing to tearing of the supporting intercostal musculature. Specific bar fixation techniques have been tailored to compensate for potential mechanisms of bar displacement according to pectus morphology: multipoint pericostal bar fixation (MPF) (n = 496) for type 1 displacement; incorporation of a stabilizer on the depressed side (n = 169) for type 2 displacement; and hinge point reinforcement and the crane technique (n = 122) for type 3 displacement. The bar displacement rate was decreased with our mechanism-based approach (4.6% before MPF vs 1.8% after MPF, P = .045). In addition, the major complication rates (6.8% before MPF vs 2.0% after MPF, P = .001) and reoperation rates (5.5% before MPF vs 1.6% after MPF, P = .019) decreased. Conclusions Mechanism-based bar fixation techniques, especially multipoint pericostal wire fixation, seems to be effective in preventing bar displacement following pectus excavatum repair.

The growth and development of Gymnophalloides seoi were studied in C3H/HeN mice and effects of immunosuppression of the host on the worm development were observed. Two hundred metacercariae of G. seoi were orally administered to each mouse, and worms were recovered on days 1, 3, 5, 7, 14 and 21 post-infection (PI). The worm recovery rate was significantly higher in immunosuppressed (ImSP) mice than in immunocompetent (ImCT) mice except on days 1 and 3 PI. The worms attained sexual maturity by day 3 PI with eggs in the uterus, and worm dimensions and the number of uterine eggs continuously increased until day 14 PI in ImSP mice. Worms recovered from ImSP mice were significantly larger in size than those from ImCT mice on days 1 and 3 PI, and the number of uterine eggs was significantly larger in ImSP mice on days 5 and 7 PI. Genital organs such as the ovary, testes, and vitellaria, that were already developed in the metacercarial stage, grew a little in size until day 14 PI. The results show that the C3H/HeN mouse is, though not excellent, a suitable laboratory host for G. seoi.