Search

The symmetry adapted cluster (SAC) and SAC-configuration interaction (SAC-CI) theories are applied to the calculations of the ground and excited states of MnO-4. With the use of three different active spaces, we examine the convergence of the results. Electron correlations work to relax charge polarizations of the Mn–O bonds in the ground state. The experimental spectrum of MnO-4 is well reproduced by the present calculations. All of the observed peaks are assigned to the electronic allowed transitions to the 1T2 excited states. They are characterized as the excitations from the nonbonding orbitals of oxygen to the antibonding orbitals between the metal and oxygens. For reasonable descriptions of the ground and excited states of MnO-4, electron correlations should be considered with the use of large enough active space for expressing the relaxations of valence electrons. In this sense, all of the previous theoretical assignments of the spectra are unreliable, since they are not the results of calculations including sufficient amount of electron correlations. [ABSTRACT FROM AUTHOR]

Examines the ratio dependence of molecular-beam epitaxy grown gallium-aluminum-antimony material system. Description of X-ray diffraction; Discussion on growth mechanisms; Details of the Raman scattering measurement.

Organic electroluminescent diode (OELD) has been investigated for use as a light source of polymeric optical integrated devices. The OLED was fabricated by organic molecular beam deposition (OMBD) technique. The OLEDs were fabricated on both glass and polymeric substrates. The device fabricated on a polymeric substrate shows similar device characteristics to those on a glass substrate. Optical signals of faster than 100 MHz has been created by applying pulsed voltages directly. Optical photo detectors (OPDs) utilizing phthalocyanine superlattice structure provide increased pulse response with optical signals and have response for optical pulse of faster than 1 MHz. [ABSTRACT FROM AUTHOR]

Reports on the electroluminescent (EL) characteristics of the EL diode with evaporated metal-free phthalocyanine (H2Pc) film. Optical measurement of the organic thin film of H2Pc to form EL diode; Findings and discussion of the experiments; Conclusions.

Examines the spectral narrowing and emission energy shift in organic electroluminescent (EL) diode utilizing 8-hydroxyquinoline aluminum or aromatic diamine multilayer structure. Components of the organic EL diode; Mechanism of spectral narrowing and the emission energy; Results of the confined carriers in the multilayer system.

Examines the fabrication and characteristics of 8-hydroxyquinoline aluminum and aromatic diamine multiple quantum well (MQW). Growth of MQW by organic molecular beam deposition; Indication of a quantum size effect by the photoluminescence; Production of an electroluminescent diode.

Investigates the use of beta-borylallylsilanes as a novel tool for convenient synthesis of alkenylboranes. Nucleophilic allylation in organic synthesis; Selective carbon-carbon bond-forming reactions with functional groups; Synthetic application of silylboranes; Palladium-catalyzed silaboration of allenes.

The effects of molecular packing on the field-effect mobility and external quantum efficiency of polymer light-emitting transistors based on films composed of a donor–acceptor polymer, poly(9,9-dioctylfluorene- al t-benzothiadiazole) (F8BT), are investigated. The molecular packing structures of F8BT films are modified by annealing at different temperatures, such that large grains in a mesophase are formed. In the case of F8BT films in the mesophase, highly crystalline three-dimensional configurations with adjacent chains result in effective electron transport. The electron mobility, μ e , in a device in which the F8BT film is in the mesophase is approximately ten times greater than that for F8BT films annealed at other temperatures, and is estimated to be approximately 3.4 × 10 −3 cm 2 V −1 s −1 . This same device exhibits the highest hole and electron mobilities along with the highest maximum external quantum efficiency (approximately 1.4%) due to improved electron transport and carrier balance. [ABSTRACT FROM AUTHOR]

Highlights: [•] ITO modified by phosphonic acid-based self-assembled monolayer (SAM). [•] 1H,1H,2H,2H-Perfluorooctanephosphonic acid (FOPA) is used as SAM. [•] Lowering of the injection barrier at the ITO/organic layer interface. [•] Lowering of the contact resistance between ITO and the organic layer. [•] Polymer photodetector with FOPA exhibits high efficiency and high on/off ratio. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cs2CO3:conjugated polyelectrolyte blended interfacial layer is used. [•] Improved electron injection from Ag electrode is achieved. [•] Solution-processed Ag cathode is fabricated using Ag nano-ink. [•] Interfacial layer prevents Ag nano-ink from penetrating into emissive layer. [•] Solution-processed device using Ag nano-ink exhibits luminance (10,000cd/m2). [Copyright &y& Elsevier]

The emission characteristics and transient electroluminescence (EL) of organic light-emitting diodes (OLEDs) using tris(8-hydroxyquinolinato)aluminum (Alq3) as an emissive layer with LiF/Al cathode and LiF doped Al composite cathode (LiF:Al alloy cathode) were investigated. A device with LiF:Al (1:10) alloy cathode showed the maximum current efficiency of 4 cd/A. The emission characteristics of this device were almost the same as that with LiF/Al cathode. Rise time of the device with LiF:Al alloy cathode was shorter than that of a device with LiF/Al cathode, because the waveform rounding of current density occurred for the device with LiF/Al cathode. [ABSTRACT FROM PUBLISHER]

This study focused on the performance of solution-processed multilayer polymer light-emitting diodes (PLEDs) with both the hole and electron transport layers using poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as an active layer. By insertion of both the hole and electron transport layers, improved emission and transient characteristics were achieved for the electro-optical conversion devices. For the multilayer device, the maximum current efficiency of 2.2 cd/A and the short response times of electroluminescence (ca. 30 ns) were achieved. [ABSTRACT FROM PUBLISHER]

Abstract: The effects of film morphology on ambipolar transport in solution-processed top-gate-type organic field-effect transistors (OFETs) utilizing poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) films were investigated. All the F8T2 OFETs without toluene-vapor treatment showed ambipolar characteristics. In contrast, for toluene-vapor-treated F8T2 films at below 250°C, which were observed to have a small fibrillar structure and a large number of grain boundaries, electron conduction decreased remarkably. Structure ordering in F8T2 films has a strong influence on ambipolar charge transport in OFETs. With an increase in the annealing temperature, the electron transport characteristics were improved. Improving the interface geometry of the F8T2 film, which is related with the decrease of grain boundaries, led to an increase in mobility, and the appearance of ambipolar characteristics. These results suggest that the appearance of electron conduction results not only from the increase in grain size but also from improvements in the connections between grain boundaries in F8T2. Ambipolar F8T2 OFETs exhibited yellow EL emissions, hole and electron field-effect mobilities of approximately 10−3 cm2 V−1 s−1, and maximum external quantum efficiency of approximately 0.2%. [Copyright &y& Elsevier]

Abstract: The characteristics of visible to near-infrared OLEDs with co-doping three phosphorescent dyes, iridium (III) bis(2-(4,6-difluorephenyl)pyridinato-N,C2′) (FIrpic), tris(1-phenylisoquinoline)iridium(III) (Ir(piq)3), Pt-tetraphenyltetrabenzoporphyrin (Pt(tpbp)) in poly(N-vinylcarbazole) host as blue, red and near-infrared emitters are investigated. Visible to near-infrared OLEDs covering the wavelength range from 450 to 850 nm were achieved. The device with 11.7 wt.% FIrpic, 0.3 wt.% Ir(piq)3 and 0.1 wt.% Pt(tpbp) showed white light emission of CIE (0.34, 0.39). The co-doping results in efficient cascade energy transfer from host through Ir complexes. For 0.1 wt.% Pt(tpbp), the optimal device exhibited the maximum output power of 3 mW/cm2, maximum luminance of 2900 cd/m2 and the maximum efficiency of 7 cd/A. [Copyright &y& Elsevier]

Abstract: The optical and electroluminescent properties of 3,4,6-triphenyl-α-pyrone (α-pyrone), a new blue fluoresce dye, are investigated using films prepared by wet and dry process and organic light-emitting diodes (OLEDs) fabricated with an α-pyrone-emitting layer. The optical properties of α-pyrone are found to be affected by its crystallinity. In the fabrication of OLEDs, wet processing (spin coating) is shown to be more suitable for preparation of the α-pyrone layer than dry processing (thermal evaporation). The best device performance is obtained for a device prepared using poly (n-vinylcarbazole) as the dye host, and a bathocuproine/tris-(8-hydroxyquinoline)aluminum bilayer as a hole-blocking and carrier-injection layer. The maximum luminance of this device is 3000cd/m2 at a current density of 0.2A/cm2, with a current efficiency of 1.8cd/A at 0.02A/cm2. [Copyright &y& Elsevier]

Abstract: The characteristics and patterning of organic light-emitting diodes (OLEDs) utilizing a sputter deposited amorphous carbon nitride (a-C:N) as a buffer layer have been discussed. Increased device performance has been achieved in a device of the a-C:N buffer layer that was less than 10 nm in thickness. The device with a 5-nm-thick a-C:N exhibited the maximum luminance of 32,000 cd/m2 and the current efficiency of 4.6 cd/A at the current density of 1.2 A/cm2 and 0.06 A/cm2, respectively. The OLEDs with a-C:N buffer layer are useful for preventing the photodegradation suffered during photolithography process. The patterned emission of the device was obtained by using the a-C:N buffer layer as the protective layer to perform photolithography after deposited organic layer. [Copyright &y& Elsevier]

Abstract: We studied the transient characteristics of poly(9,9-dioctylfluorene) (PFO)-based polymer light-emitting diodes (PLEDs) doped with red emissive phosphor tris(1-phenylisoquinoline) iridium (III) [Ir(piq)3] by applying the voltage pulse on the devices. The emission from the host was observed when the narrow pulse of 100 ns was applied. In order to change the electroluminescent (EL) spectrum, PFO-based white PLEDs have been demonstrated to utilize the pulse width and frequency. The maximum luminance reached 4800 cd/m2 and the Commission Internationale de L''Eclairage (CIE) coordinates obtained the ideal white emission of (0.33, 0.35) at the pulse width and frequency of 100 ns and 1 kHz, respectively. [Copyright &y& Elsevier]

Abstract: We investigated the transient electroluminescence (EL) and modulation characteristics of red organic light-emitting diodes (OLEDs) consisting of 4-(dicyanomethylene)-2-i-propyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTI) and 5,6,11,12-tetraphenylnaphthacene (rubrene) doped into tris(8-hydroxyquinoline)aluminum (Alq3). The transient EL waveforms showed two components, an initial overshooting peak followed by a constant component, indicating that the excess amount of accumulated charges simultaneously recombine at the moment of onset. This overshoot effect reduced the rise time of transient EL and enhanced the optical output of the OLEDs, and hence the cutoff frequency was increased when the pulse voltage was applied to the device. We demonstrated that the red OLEDs are suitable for use in high-speed switching applications driven at more than 100 MHz, and in electro-optical conversion devices for transmitting video signals. [Copyright &y& Elsevier]

We demonstrate high efficiency electrophosphorescence in organic light-emitting devices employing a phosphorescent dye doped into a low-molecule material. Methoxy-substituted 1,3,5-tris[4-(diphenylamino)phenyl]benzene (TDAPB) was selected as the host material for the phosphorescent dopant fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)3], and organic films were fabricated by spin-coating. A peak external quantum efficiency of 8.2% (29 cd/A), luminous power efficiency of 17.3 lm/W, and luminance of 33,000 cd/m2 were achieved at 9.4 V with a 90 nm-thick emitting layer. Emission from the host TDAPB material was not observed in the electroluminescence (EL) and photoluminescence (PL) spectra. The decrease in efficiencies at a high current is analyzed using the triplet–triplet annihilation model. The high performance for the simple device structure in this study is attributed to excellent film forming properties of the material and efficient energy transfer from the host to dopants. [Copyright &y& Elsevier]

An organic electroluminescence diode (OLED) fabricated on polyimide substrate has been investigated to realize a flexible electro-optic device for optical links. The device fabricated on polyimide substrate shows similar device characteristic to that on glass substrate. The modulation performance of the OLED was significantly improved by applying a positive, low-level DC bias, which results in a slower falling time. An undershoot voltage applied to the falling edge of the input voltage pulse results in faster falling time and a decrease in intensity of the optical output. We demonstrate that the OLEDs can be applied to short-range optical communication fields, such as electro-optical conversion devices for optical links. [Copyright &y& Elsevier]

We studied improvement of the electrode/organic interface in organic electroluminescent diodes which consist of 8-hydroxyquinoline aluminum (Alq3) and diamine derivative (TPD). An aluminum oxide (Al2O3) monolayer was inserted between TPD and the indium tin oxide (ITO) anode. An improvement of emission is observed in a diode with an Al2O3 layer between 0.5 and 1 nm thick inserted in the surface of the anode/organic layer. The mechanism of increase in emission efficiency is discussed. © 2000 Scripta Technica Electr Eng Jpn 132(3): 14–18, 2000 [ABSTRACT FROM AUTHOR]

We have realized a three-layered multicolor organic electroluminescent device utilizing poly (9,9-dihexylfluorene) and perylene derivatives as emission layers, with diamine derivatives as an electron blocking layer. Emission colors could be selected either blue or red by changing the polarity of the applied voltage. By driving with an ac biased electric field, both emission colors were observed and the intensity ratio of each emission color was modulated by the frequency of the applied ac field. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reveals that the characteristics of Schottky gated field effect transistors fabricated utilizing poly(3-alkylthiophene) containing diphenyliodonium hexafluoroarsenate can be controlled by irradiating light on it. Results and discussion.

Studies the dependencies of photoluminescence in five membered heterocyclic conducting polymers on heteroatoms and temperature. Photoluminescence spectra of poly(3-hexylthiophene) at various temperatures; Temperature dependence of luminescence intensity of poly(3-alkylthiophene) with various alkyl chain lengths; Absorption spectra of poly(3-hexylthiopene) at various temperatures.

SUMMARY Organic photodetectors based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends with indium tin oxide (ITO) modified by phosphonic acid-based self-assembled monolayer (SAM) treatment in a short time are investigated. The mixed SAMs serve to tune the surface free energy and the work function of ITO by varying the blend ratio. The phosphonic acid-based SAM treatment results not only in lowering of the injection barrier at the ITO/organic layer interface but also in the lowering of the contact resistance between ITO and the organic layer, as shown by impedance spectroscopy in P3HT hole-only device with SAMs. P3HT:PCBM device with ITO modified by short treatment time of 1H,1H,2H,2H-perfluorooctane-phosphonic acid exhibits an incident-photon-to-current conversion efficiency of above 50% at -2 V, a high on/off ratio, and improved durability. [ABSTRACT FROM AUTHOR]

We report polarized in-plane emission at full-channel area in ambipolar heterostructure organic light-emitting transistors (OLETs) utilizing bilayer oriented fluorene-type polymers. The present work demonstrates that carrier balance between bilayers is a key factor in achieving in-plane emission at almost full-channel area when hole transport is dominant in the upper layer, which acts as an electron blocking layer, and electrons are injected into the lower layer. Hole accumulation in the upper layer affects electron injection from the electrode to the lower layer and the probability of recombination of holes in the upper layer with electrons in the lower layer near the bilayer interface. For OLETs having an oriented bilayer with the channel direction parallel to orientation of the polymer chains, a uniform in-plane emission pattern, an increased electroluminescence intensity, and a high external quantum efficiency can be achieved by improving the hole mobility in the upper layer and optimizing the carrier balance. These results are expected to be very useful for the development of surface micro-light sources. [ABSTRACT FROM AUTHOR]

The concept of using an ambipolar bilayer semiconducting heterostructure in organic light-emitting transistors (OLETs) is introduced to provide a new approach to achieve surface emission. The properties of top-gate-type bilayer OLETs with ambipolar materials based on two types of fluorene-type polymers used as an emissive layer and an electron blocking layer are investigated. Line-shaped yellow–green emission occurs near a hole-injection electrode. When hole transport is dominant in the upper layer which acts as an electron blocking layer, and electrons are injected into the lower layer, an in-plane light-emitting pattern is observed. The measured in-plane emission zone confirms that both hole and electron transport are determined to occur mainly along the different organic layers between the source and drain electrodes, and an in-plane recombination zone of electrons and holes exists near the bilayer organic interface. This work is anticipated to be useful for the development of in-plane light-emitting transistors. [ABSTRACT FROM AUTHOR]

Abstract: The properties of polymer light-emitting transistors with Ag-nanowire (AgNW) source/drain electrodes fabricated on a polymer substrate are investigated. Organic field-effect transistors (OFETs) based on poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) with AgNW source/drain electrodes exhibit ambipolar characteristics. For an ambipolar F8BT OFET, yellow-green light emission is observed. The maximum external quantum efficiency is 0.6%. We demonstrate the possibility of producing flexible polymer light-emitting transistors using AgNW electrodes. [Copyright &y& Elsevier]

Highlights: [•] Indium tin oxide (ITO) and Ag are used as source/drain (S/D) electrodes. [•] Influence of S/D electrodes on external quantum efficiency (EQE). [•] Exciton quenching by Ag electrodes results in a low EQE. [•] A relatively high EQE of 1% regardless of the emission site for the device with ITO. [•] Lower exciton quenching at the interface of S/D electrodes for the device with ITO. [ABSTRACT FROM AUTHOR]

This study focuses on the carrier balance factor and transient characteristics of organic light-emitting diodes (OLEDs) utilizing tris[4-(5-phenylthiophen-2-yl)phenyl] amine (TPTPA) as a blue emissive material or a host material of a red phosphorescent dye, which exhibits the highest level of hole drift mobility (µ = 1.0×10-2 cm2V-1s-1) among those reported for organic disordered systems. We investigated the doping effect of a red phos-phorescent material in the TPTPA. The peak wavelengths and the shape of the electroluminescent (EL) spectra agree with those of the photoluminescent spectra, which indicate that the EL originates from the excited state of the TPTPA and dopant. The maximum luminance of approximately 11,000 and 2,000 cd/m2 were achieved for devices without and with dopant. While TPTPA device achieved good carrier balance, the hole current was decreased by doping a red phosphorescent material. Compared with the short response times of TPTPA device, relatively long response times of doped device was observed owing to phosphorescent recombination lifetime of a dopant. The TPTPA device exhibited the relatively high light outcoupling efficiency of approximately 34% (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The influence of ultraviolet (UV) irradiation on carrier conduction and emission characteristic of the top-gate-type ambipolar organic field-effect transistors (OFETs) utilizing crystallized poly(9,9-dioctylfluorene) (F8) films were investigated. For a device with irradiated UV light, only p-type conduction was exhibited and the hole field-effect mobility was almost the same as that without UV irradiation. As a result, the EL emission was not observed owing to the decrease of n-type conduction after UV irradiation. It is suggested that the quenching center which is generated in F8 film by UV irradiation is greatly related to the electron trap site of OFETs. [ABSTRACT FROM PUBLISHER]

Abstract: In order to obtain phosphorescent emission from organic field-effect transistors, thermal diffusion of a phosphorescent dye at the interface between the active layer and gate insulator was controlled by utilizing the fact that liquid-crystalline semiconducting polymers self-organize due to reorientation of the molecules and increase in the size of the crystalline regions during thermal annealing. For top-gate type devices using poly(alkylfluorene) doped with a red emissive phosphorescent material, ambipolar characteristics and red emission from the phosphorescent material were clearly observed. We demonstrate the possibility of producing phosphorescent organic light-emitting transistors using a liquid-crystalline semiconducting polymer doped with phosphorescent emissive dopants by the thermal diffusion method. [Copyright &y& Elsevier]

Abstract: Properties of solution-processed organic photodetectors with iridium (Ir) complexes doped in fluorene-type conjugated polymer, poly(dioctylfluorene-co-benzothiadiazole) [F8BT] as a host were investigated. F8BT devices had blue sensitivity. Ir complexes as triplet materials can enhance the incident-photon-to-current conversion efficiency (IPCE) of the devices when their triplet levels are lower than the lowest excited singlet states (S1) of the host and higher than the lowest excited triplet states (T1) of the host. A bilayer F8BT device utilizing solution-processable starburst molecular and tris(2-phenylpyridine)iridium(III) [Ir(ppy)3] as a hole transporting layer and a dopant, respectively, showed larger photocurrent than an non-doped bilayer device under high applied voltage. For the bilayer device with Ir(ppy)3, a cut-off frequency of more than 10MHz was observed under forward bias of 5V and clear response pulses at 10MHz were received using a sinusoidal modulated laser light illumination. [Copyright &y& Elsevier]

This study focuses on the performance of organic light-emitting diodes (OLEDs) using an emissive material with high hole drift mobility, tris[4-(5-phenylthiophen- 2-yl)]amine (TPTPA), which exhibits the highest level of hole drift mobility (1.0 × 10-2 cm2 V-1 s-1) among those reported for organic disordered systems. Clear blue emission was observed from TPTPA which was used as the hole transporting and emissive layer in the OLEDs. The maximum luminance of 1.2 × 104 cd/m2, and the maximum current efficiency of 3.9 cd/A were achieved. The short response times of electroluminescence (ca. 10 ns) were achieved under the application of rectangular-shaped voltages. [ABSTRACT FROM AUTHOR]

Abstract: The effects of adding solution-processed polyfluorene derivatives as buffer layers between the polymer insulator and active layer of n-channel organic field-effect transistors (OFETs) containing a carbonyl-bridged bithiazole derivative were investigated. The surface free energy was modified by the polyfluorene derivatives. A poly(9,9-dioctylfluorene) (F8) buffer layer, which has a hydrophobic nature, a low surface free energy, and consists almost entirely of a dispersion component, improved the growth morphology of the OFET active layer. An OFET with an F8 buffer layer exhibited n-channel characteristics, and an electron field-effect mobility of 0.025cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Abstract: The characteristics of solution processed top-gate-type organic field-effect transistors (OFETs) with indium–tin oxide (ITO) drain/source electrodes using polyfluorene derivatives were investigated. An OFET with poly(9,9-dioctylfluorene) (F8) as an active layer, which contains only a fluorene backbone, exhibited ambipolar characteristics with hole and electron field-effect mobilities of approximately 10−3 cm2 V−1 s−1. All OFETs with fluorene derivatives exhibited ambipolar characteristics because the value of the work function of the ITO electrode is approximately in the middle between the highest occupied molecular orbital and lowest unoccupied molecular orbital levels of fluorene derivatives. Fluorene derivatives can conduct both holes and electrons. Ambipolar OFETs with F8 and a fluorene derivative doped in F8 can be applied to various color tunable light-emitting devices. [Copyright &y& Elsevier]

Abstract: Poly (9,9-dioctylfluorene)(F8) gel with β phase has been investigated in terms of optical absorption, photoluminescence measurements and Fourier transform infrared spectroscopy. The optical properties of the F8 gel markedly changed in the temperature range from 70 to 80°C owing to the vibration of polymer chain related to the glass transition temperature of F8. F8 films by thermal printing method had the characteristic particulate morphology. Current efficiencies of polymer light emitting diodes (PLEDs) with the β phase of F8 fabricated by the thermal printing method were better than that with the amorphous phase of F8 by the spin-coating method. We demonstrate the β phase effects of PLEDs characteristics by the thermal printing method. [Copyright &y& Elsevier]

Abstract: The effect of dry process and wet process on the characteristics of phosphorescence organic light-emitting devices (OLEDs) employing a phosphorescent dye fac-tris(2-phenylpyridine) iridium(III) (Ir(ppy)3) doped into a methoxy-substituted starburst low-molecule material methoxy-substituted 1,3,5-tris[4-(diphenylamino) phenyl]benzene (TDAPB) are investigated. The FT-IR and absorption spectra of TDAPB films fabricated by a dry process, and a wet process are almost same, and the PL spectra of those films are different. The carrier transport capability of TDAPB by a dry process is lower than that by a wet process. The photoluminescence intensity of Ir(ppy)3 doped in TDAPB fabricated by a wet process is higher than that by a dry process. A maximum external current efficiency of more than 20 cd/A and luminance of more than 10,000 cd/m2 were obtained. Maximum luminance of devices monotonously decreases with increasing the thickness of a dry-processed emitting layer. The main emission zone of the OLED was located in almost at the center of the emitting layer. The improvement of device performance in the OLED fabricated by a wet process was achieved due to the high efficient energy transfer from TDAPB to Ir(ppy)3, high carrier transporting capability and the formation of homogeneous film, compared with that fabricated by a dry process. [Copyright &y& Elsevier]

Abstract: The optical and electroluminescent (EL) properties of newly synthesized tris(hexafluoroacethylacetonato)(phenanthroline)samarium(III)mono-methanol [Sm(hfa)3(phen)2MeOH]-based organic light-emitting diodes (OLEDs) were investigated. The as-prepared photoluminescence (PL) spectrum of Sm(hfa)3(phen)2MeOH-doped PMMA film exhibits the peaks at the wavelength around 564, 598, 645 and 710 nm which correspond to the 4G5/2 → 7H5/2, 4G7/2 → 7H7/2, 4G5/2 → 7H9/2 and 4G5/2 → 7H11/2 transitions of the Sm3+ ion, respectively. The best organic light-emitting device performance is obtained for a device using 8 wt.% Sm(hfa)3(phen)2MeOH and 40 wt.% 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4,-oxadiazole doped in poly(N-vinylcarbazole) as a emitting layer. The optimal device exhibits maximum luminance of 135 candela (cd)/m2 at the current density of 0.16 A/cm2, with current efficiency of 0.1 cd/A at the current density of 0.08 A/cm2. The EL spectrum from optimal device has the Commission Internationale De L''Eclairage (CIE) coordinate of (0.60, 0.36). [Copyright &y& Elsevier]

The effect of electron injection in polymer light-emitting diodes based on the phosphorescent material of fac-tris(2-phenylpyridine) iridium (Ir(ppy)3) devices with CsF/MgAg/Ag cathodes were investigated. The device with MgAg (1 nm)/CsF (3 nm)/Ag cathode showed almost similar current density-voltage-luminance characteristics to that with CsF (3 nm)/MgAg (1 nm)/Ag cathode. The existence of interface between the organic layer and Cs or CsF results in low turn on voltage. To achieve the efficient electron injection and the low turn on voltage, it is necessary to exist MgAg and CsF interface at the position of about 1 nm from organic layer. To achieve the efficient electron injection, it is necessary to exist Cs layer just on the organic layer. The electron injection effects between devices with CsF and Cs are different. It is suggested that the dipole of CsF affect the efficient electron injection. [ABSTRACT FROM AUTHOR]

Abstract: The integrated device of the organic field transistor (OFET) based on α,ω-dihexylsexithiophene and the organic light emitting diode (OLED) was fabricated on the same indium tin oxide (ITO)-coated glass substrate by using the photoresist gate insulator with an average surface roughness of 0.2 nm. OFET has a top contact structure with the Au source and drain electrodes. The current and luminance of an OLED were controlled by varying the gate voltage. The field effect mobility of the OFET with non-treated photoresist gate insulator increases with increasing the substrate temperature and is obtained up to about 0.1 cm2/V s at a substrate temperature of 90 °C, while the devices with octadecyltrichlorosilane (OTS)-treated gate insulator are almost independent of the substrate temperature and have up to about 0.1 cm2/V s at the substrate temperature region from 20 °C to 90 °C. The OTS-treated OFET at 60 °C has a highest carrier mobility of 0.137 cm2/V s and a current on/off ratio of 105. The OTS treated gate insulator obviously plays an important role in improving the performance of the OFETs. Current in the order of more than 0.1 μA flows from the semitransparent top contact type OFET utilizing the sputter deposited amorphous carbon nitride /ITO bilayer instead of Au electrode as the source and drain electrodes. [Copyright &y& Elsevier]

Abstract: The characteristics of organic photodetectors (OPDs) by solution process using one of the polyfluorene derivatives poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) and two fullerene derivatives [6-6]phenyl-C61-butyric acid methyl ester (PCBM) or N-Ts aziridinofullerene (TsAF) are investigated. F8T2:PCBM devices showed good rectifying characteristics in a dark state and photosensitive characteristics, and fast frequency responses. Weight ratio of 1:1 device showed larger photocurrent than 1:4 device and obtained over 50MHz of cutoff frequency under reverse bias voltage of 10V. This result suggests that F8T2:PCBM device can be applied to a photodetector for detecting several tens of megahertz optical signals under blue light irradiation. The polarity of J–V characteristics of F8T2:fullerene derivative device is strongly affected by charge injection and extraction between fullerene derivative and electrodes. [Copyright &y& Elsevier]

pn-Heterojunction organic photovoltaic devices (OPVs) using amorphous molecular materials with high hole drift mobilities of 10-2 cm2 V-1 s-1, tris[4-(2-thienyl)phenyl]amine and tris[4-(5-phenylthiophen-2-yl)phenyl]amine, as electron donors and fullerene as an electron acceptor were fabricated. In spite of the use of amorphous materials instead of crystalline materials, the devices exhibited high performance with fill factors of 0.62–0.71 and power conversion efficiencies of 1.5%–1.7% under air-mass 1.5 G illumination at an intensity of 100 mW cm-2. [ABSTRACT FROM AUTHOR]

Poly(methyl methacrylate) (PMMA) gate dielectric formed using fluorine‐based solvent, CF3CH2OCF2CHF2 (AGC, AE‐3000), is useful to prevent mixing of the dielectric layer with the emissive layer for top‐gated organic light‐emitting transistor (OLET) device fabrication. The device performance of OLETs based on a poly(p‐phenylene vinylene) derivative, Super Yellow, is improved because of the fabrication without intermixing. For an OLET with Pt‐tetraphenyltetrabenzoporphyrin [Pt(tpbp)] doped in poly(alkylfluorene), a near‐infrared emission from Pt(tpbp) and a relatively high external quantum efficiency of approximately 1% are achieved. This device fabrication method opens perspectives in the development of the damage‐free fabrication processes in printed top‐gated OLETs. [ABSTRACT FROM AUTHOR]

For the purpose of exploring near-infrared emission, the photoluminescence (PL) and electro- luminescence (EL) of N,N′-bis(neopentyl)-3,4:9,10-perylenebis(dicarboximide) (BNPTCD): tris(8-quinolinolato)aluminum (Alq3) mixed films were investigated. It was found that BNPTCD:Alq3 mixed films exhibit PL in the near-infrared wavelength region and that organic light-emitting diodes using Alq3 highly doped with BNPTCD as an emitting layer exhibit near-infrared EL with a peak at 805 nm originating from BNPTCD aggregates. [ABSTRACT FROM AUTHOR]