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In general, electron transport layer (ETL) in organic light-emtting diodes (OLEDs) consists of single component of electron transporting material (ETM) or a mixture with n-dopant such as 8-hydroxyquinolinolato-lithium (Liq). However, there exists a limit to controlling a wide range of carrier density in OLEDs according to the required characteristics of the devices due to electrically insulating property of Liq. Here, we suggest a universal strategy to construct an efficient ETL. We synthesized two ETMs, diphenyl-[4-(10-phenyl-anthracene-9-yl)-phenyl]-amine (An-Ph) and phneyl-[4-(10-phenyl-anthracene-9-yl)-phenyl]-pyridin-3-yl-amine (An-Py) that have the same core structures with different polarities in functional groups. The electrical characteristics of electron-only-devices (EODs) were investigated by space charge limited current (SCLC) modeling and impedance spectroscopy analysis. Interestingly, the homostructure type ETL composed of An-Ph and An-Py showed not only superior electron transporting capability, but also the possibility of controlling electron injection and transporting in a wide range compared to the heterostructure type ETL of An-Ph and Liq. Compared to the An-Ph-only EOD, the electron mobility in 75% An-Py-mixed homostructure EOD increased by almost 4 orders of magnitude. Such dramatic variation of electron mobility was achieved thanks to the molecular design strategy to separate charge injection and charge transport regions within a molecule, which consequently induced the giant surface potential (GSP) effect between the ETL/cathode interface. As a result, the external quantum efficiency (EQE) of blue fluorescent and phosphorescent OLEDs with the homostructure ETLs was enhanced by 28.6% and 34%, respectively, compared to that of each control device without manipulating outcoupling effects.

We explored interfacial electronic structures in indium tin oxide (ITO)/DNTPD/N,N'-diphenyl-N,N'-bis(1naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB) layer stack in an OLED to clarify the real role of an aromatic amine-based hole injection layer, DNTPD. A hole injection barrier at the ITO/DNTPD interface is lowered by 0.20 eV but a new hole barrier of 0.36 eV at the DNTPD/NPB is created. The new barrier at the DNTPD/NPB interface and its higher bulk resistance serve as hole retardation, and thus those cause the operation voltage for the ITO/DNTPD/NPB to increase. However, it improves current efficiency through balancing holes and electrons in the emitting layer.

This experiment was conducted to evaluate the effects of dietary CP levels in gestation under equal lysine content on reproductive performance, blood metabolites and milk composition of gilts. A total of 25 gilts (F-1, YorkshirexLandrace) were allotted to 4 dietary treatments at breeding in a completely randomized design, and fed 1 of 4 experimental diets containing different CP levels (11%, 13%, 15%, or 17%) at 2.0 kg/d throughout the gestation. Body weight of gilts at 24 h postpartum tended to increase linearly (p = 0.09) as dietary CP level increased. In lactation, backfat thickness, ADFI, lifter size and weaning to estrus interval (WET) did not differ among dietary treatments. There were linear increases in litter and piglet weight at 21 d of lactation (p

Two solution-processible new triplet bipolar host molecules, 4,4′-bis[N-(1-naphthyl)-N(3-pyridinylamino]biphenyl (NPyB) and 4,4′-bis [N-(3-quinolinyl)-N-phenylamino]biphenyl (QuPB) were synthesized and characterized for phosphorescent organic light-emitting diodes (PHOLEDs). They exhibit good triplet energies as 2.3–2.4 eV for red PHOLEDs and show good amorphous film characteristics with high solubility, allowing a solution processing. The NPyB and QuPB hosts were evaluated for soluble red PHOLEDs with ITO/PEDOT:PSS/Ir complex:host/TPBI/LiF/Al structure. A maximum light output of 14,440 cd/m2, driving voltage of 5.9 V, external quantum efficiency of 14.2%, and maximum current/power efficiencies of 21.0 cd/A and 11.3 lm/W have been achieved by NPyB host and bis(2-phenylquinoline(acetylacetonate)iridium (Ir(phq)2acac) red dopant.

9,10-Bis-(9′,9′-diethyl-7′-diphenylamino-fluoren-2-yl)-anthracene was synthesized from 9.10-anthracene diboronic acid and (7-bromo-9,9-diethyl-fluoren-2-yl)-diphenyl-amine in a Suzuki coupling reaction. A theoretical calculation of the three-dimensional structure suggests that it has a non-coplanar structure and inhibited intermolecular interactions. Upon excitation, the photoluminescence maximum of 9,10-bis-(9′,9′-diethyl-7′-diphenylamino-fluoren-2-yl)-anthracene in solution and film were at 454 nm (solution) and 462 nm (film). The full width at half maximum of 9,10-bis-(9′,9′-diethyl-7′-diphenylamino-fluoren-2-yl)-anthracene is 54 nm regardless of whether it is in a solution or a solid state. A multi-layered device using 9,10-bis-(9′,9′-diethyl-7′-diphenylamino-fluoren-2-yl)-anthracene as emitting material exhibits maximum quantum efficiency of 3.3% (power efficiency of 2.1 lm/W, current efficiency of 4.17 cd/A) and a blue Commission Internationale de l'Eclairage chromaticity coordinates ( x = 0.14, y = 0.17).

9,10-Di-(1′-naphthyl)anthracene is often used as electroluminescence materials in organic light-emitting diodes. Because of the hindered rotation about the σ-bond between naphthyl and anthracene chromophore, two possible stereoisomers can be isolated. HPLC, 1H NMR, and 13C NMR spectra gave two different sets of peaks and the X-ray single crystal analysis confirmed the structures of the two isomers, anti and syn. syn was more soluble than anti in THF as well as toluene and the thermal properties of the two were quite different. Differential scanning calorimetry study and HPLC analysis showed that the isomerization between anti and syn in the solid state took place at >370 °C.

The homoleptic Ir(III) complex, fac-tris{2-(3′-trimethylsilylphenyl)-5-trimethylsilylpyridinato}iridium, has been synthesized and characterized to investigate the effect of the substitution of bulky silyl groups on the photophysical properties and electroluminescence (EL) characteristics of Ir(ppy)3 (ppy = 2-phenylpyridine). The absorption, emission, cyclic voltammetry and electroluminescent performance of the complex have also been evaluated. A power efficiency of 17.3 lm/W at 10 mA/cm2 compared to 11.7 lm/W for Ir(ppy)3 is achieved with the new complex as a dopant in phosphorescent organic light-emitting diodes (OLEDs). In addition, the complex shows a narrow emission band of a small full width at half-maximum (fwhm, ca. 50 nm) value.

We synthesized new kinds of pyrene-based electron transport materials: 1,6-di(pyridin-3-yl)-3,8-di(naphthalen-1-yl)pyrene (N1PP) and 1,6-di(pyridin-3-yl)-3,8-di(naphthalen-2-yl)pyrene (N2PP). The external quantum efficiencies of the device with these electron transport materials increase by more than 50% at 1 mA cm−2 compared with those of the device with representative Alq3 as an electron transport material. The enhanced quantum efficiency is due to a balanced charge recombination in an emissive layer. Electron mobilities in N1PP and N2PP films are three times higher than that in Alq3. Highly enhanced power efficiency is achieved due to a low electron injection barrier and a high electron mobility. We find that the luminance degradation in the blue OLEDs is correlated with the HOMO energy levels of electron transport materials.

Two new amorphous molecular materials, 2,5-bis(2′,5′-dimethyl-4-triphenylsilyl-phenyl)-[1,3,4]oxadiazole (BDTSO) and 2,5-bis(2′,5′-dimethyl-4-triphenylsilyl-phenyl)-[1,3,4]thiadiazole (BDTST) were synthesized and investigated as hole blocking materials (HBM) for organic light-emitting diodes. The efficiency of electroluminescent device was improved by using BDTSO instead of BAlq. The current and power efficiency of the device using BDTSO as HBM is 39.6 cd/A and 13.1 lm/W at 10 mA/cm2, respectively, which is higher compared to the same values for devices using BDTST and BAq which are typically used as HBM.

The new amorphous molecular material, 2,5-bis(4-triphenylsilanyl-phenyl)-[1,3,4]oxadiazole, that functions as good hole blocker as well as electron transporting layer in the phosphorescent devices. The obtained material forms homogeneous and stable amorphous film. The new synthesized showed the reversible cathodic reduction for hole blocking material and the low reduction potential for electron transporting material in organic electroluminescent (EL) devices. The fabricated devices exhibited high performance with high current efficiency and power efficiency of 45 cd/A and 17.7 lm/W in 10 mA/cm2, which is superior to the result of the device using BAlq (current efficiency: 31.5 cd/A and power efficiency: 13.5 lm/W in 10 mA/cm2) as well-known hole blocker. The ITO/DNTPD/α-NPD/6% Ir(ppy)3 doped CBP/2,5-bis(4-triphenylsilanyl-phenyl)-[1,3,4]oxadiazole as both hole blocking and electron transporting layer/Al device showed efficiency of 45 cd/A and maximum brightness of 3000 cd/m2 in 10 mA/cm2.

The new green Ir(III) complex, fac-tris[4-methyl-2-(4′-trimethylsilylph-enyl)pyridine] [Ir(msippy)3], is synthesized and phosphorescent light emitting devices fabricated by using them as triplet emissive dopants. Ir(dsippy)3 in UV-Vis. spectra showed absorption band at 395 nm originating from 1MLCT. The EL devices with configuration of ITO/CuPc (10 nm)/α -NPD (40 nm)/CBP-Ir(msippy)3 (20 nm)/BCP (10 nm)/Alq3 (40 nm)/LiF (1 nm)/Al (100 nm).showed the emission maximum at 516 nm, due to the radiative decay from 3MLCT state to ground state. The 6% doped devices showed the maximum efficiency of 49.9 cd/A and power efficiency 25.3 lm/W. The observed PL quantum efficiency (0.43) of the [Ir(msippy)3] in CH2Cl2 shows slightly higher than that of reported Ir(ppy)3 (Φ = 0.40).

A new 1,3,5-triazine derivative containing the phenothiazine moiety (PTZ-TRZ) has been synthesized for use as a host material of phosphorescent dye. The photoluminescence and electroluminescence pr...

We report the enhancement of hole current density in the hole transport part of an inverted top-emission organic light emitted diode by applying an organic insertion layer of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN). Poor hole transporting performance of Al/4,4′-bis(N-phenyl-1-naphthylamino)biphenyl (NPB)/indium tin oxide is greatly improved by the HAT-CN insertion between Al and NPB layer. The highest occupied molecular orbital level onset of the NPB bends toward Fermi level at the HAT-CN/NPB interface. This extra charge generation layer made of pure organic molecules substantially enhances hole injection from Al anode as revealed by the results of ultraviolet photoelectron spectroscopy and J-V measurement data.

The novel blue light emitting materials, 9,10-Bis(9′,9′-diethyl-7′-diphenylamino-fluoren-2-yl)-anthracene, which is composed of an anthracene as main unit and a rigid, bulky, easy hole transportable and energy transferable phenylamine substituted fluorene containing as side unit, was designed and synthesized. The theoretical calculation of 3 dimensional structure and the energy densities of HOMO and LUMO states, as well as optical properties of new obtained material, support that it has a non coplanar structure and that intramolecular energy transfer occurs from the side units to the main unit, resulting in high luminescent efficiency and high color purity. With the newly designed blue emitting material in the multilayer device structure, it was possible to achieve the luminous efficiency of 4.2 cd/A (3.3 % of quantum efficiency at 7.5V). The EL spectrum of the multilayer device showed a narrow emission band with full width at half maximum (fwhm) 53 nm and a λmax = 461 nm.