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The formation of excitons in organic molecules by charge injection is an essential process in organic light-emitting diodes (OLEDs).sup.1-7. According to a simple model based on spin statistics, the injected charges form spin-singlet (S.sub.1) excitons and spin-triplet (T.sub.1) excitons in a 1:3 ratio.sup.2-4. After the first report of a highly efficient OLED.sup.2 based on phosphorescence, which is produced by the decay of T.sub.1 excitons, more effective use of these excitons has been the primary strategy for increasing the energy efficiency of OLEDs. Another route to improving OLED energy efficiency is reduction of the operating voltage.sup.2-6. Because T.sub.1 excitons have lower energy than S.sub.1 excitons (owing to the exchange interaction), use of the energy difference could--in principle--enable exclusive production of T.sub.1 excitons at low OLED operating voltages. However, a way to achieve such selective and direct formation of these excitons has not yet been established. Here we report a single-molecule investigation of electroluminescence using a scanning tunnelling microscope.sup.8-20 and demonstrate a simple method of selective formation of T.sub.1 excitons that utilizes a charged molecule. A 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) molecule.sup.21-25 adsorbed on a three-monolayer NaCl film atop Ag(111) shows both phosphorescence and fluorescence signals at high applied voltage. In contrast, only phosphorescence occurs at low applied voltage, indicating selective formation of T.sub.1 excitons without creating their S.sub.1 counterparts. The bias voltage dependence of the phosphorescence, combined with differential conductance measurements, reveals that spin-selective electron removal from a negatively charged PTCDA molecule is the dominant formation mechanism of T.sub.1 excitons in this system, which can be explained by considering the exchange interaction in the charged molecule. Our findings show that the electron transport process accompanying exciton formation can be controlled by manipulating an electron spin inside a molecule. We anticipate that designing a device taking into account the exchange interaction could realize an OLED with a lower operating voltage. Recombination of excitons to produce molecular light emission is made more efficient by controlling electron spin within the molecule to produce spin-triplet excitons only, without the usual accompanying spin-singlet excitons., Author(s): Kensuke Kimura [sup.1] [sup.2] , Kuniyuki Miwa [sup.1] [sup.3] [sup.5] , Hiroshi Imada [sup.1] , Miyabi Imai-Imada [sup.1] [sup.2] , Shota Kawahara [sup.1] , Jun Takeya [sup.2] , Maki [...]

4H-SiC Junction Barrier Schottky (JBS) diodes are processed by using the same technology with two different layouts. Electroluminescence measurements have displayed the expansion of stacking faults in 3.5 kV diodes unlike in 1.2-kV diodes.

The results of an investigation of the thermoluminescence and electroluminescence of arylated methylenecyclopropanes 1 are described. The mechanistic features of this reaction system have the potential of overcoming significant problems associated with organic light emitting diodes.

The properties of nominally undoped ZnO films, which are deposited by reactive sputtering on the lightly boron-doped([p.sup.-]) and heavily boron-doped([p.sup.+]) silicon substrates, are studied. The analysis reveals that the ZnO/[p.sup.+]-Si hetereojunctions are electroluminescent to a certain extent in the visible region, whereas the ZnO/[p.sup.-]-Si heterojunctions does not exhibit this property.

The synthesis and structural, photophysical, electrochemical and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are described in which the hole-transporting triarylamine, electron-transporting oxadiazole and electroluminescent metal components are integrated into a single molecule. The management of the relative electroluminescent (EL) intensities of the singlet and triplet excitons is shown to be a good tool for making efficient single-dopant white organic light-emitting devices (WOLEDs).

A sensitive electrochemiluminescent detection scheme by solid-phase extraction at Ru[(bpy).sub.3.sup.2+]-modified ceramic carbon electrodes (CCEs) was developed. The as-prepared Ru[(bpy).sub.3.sup.2+]-modified CCEs show much better long-term stability than other Nation-based Ru[(bpy).sub.3.sup.2+]-modified electrodes and enjoy the inherent advantages of CCEs. The log-log calibration plot for dioxopromethazine is linear from 1.0 x [10.sup.-9] to 1.0 x [10.sup.-4] mol [L.sup.-1] using the new detection scheme. The detection limit is 6.6 x [10.sup.-10] mol [L.sup.-1] at a signal-to-noise ratio of 3. The new scheme improves the sensitivity by ~3 orders of magnitude, which is the most sensitive Ru[(bpy).sub.3.sup.2+] ECL method. The scheme allows the detection of dioxopromethazine in a urine sample within 3 min. Since Ru[(bpy).sub.3.sup.2+] ECL is a powerful technique for determination of numerous amine-containing substances, the new detection scheme holds great promise in measurement of free concentrations, investigation of protein-drug interactions and DNA-drug interactions, pharmaceutical analysis, and so on.

A study uses microfluidics applicator in the fabrication of a polyfluorene based polymer light emitting diode (PLED). Room temperature analysis of the poly(di-n-octylfluorene) indicates that the combination of high-speed deposition and rapid drying process traps the polymer into a metastable conformational state.

A simple thermal process for the preparation of small Pt nanoparticles is presented, carried out by heating a [H.sub.2]Pt[Cl.sub.6]/3-thiophenemalonic acid aqueous solution. The following treatment of such colloidal Pt solution with Ru[(bpy).sub.3.sup.2+] causes the assembly of Pt nanoparticles into aggregates. Most importantly, directly placing such aggregates on bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.

The electroluminescence (EL) properties of the [Gd.sup.3+] ultraviolet (UV) luminescent centers in Si[O.sub.2] metal-oxide-semiconductor light emitting devices (MOSLEDs) are investigated. The strong EL quenching related to a negative charge trapping around the optically active [Gd.sup.3+] luminescent centers is observed during excitation by hot electron injection, suggesting different methods for improving the EL stability of rare-earth doped MOSLEDs.

A significant improvement in the external electroluminescence efficiency of red-emitting polymer light emitting diodes (LEDs) by modifying the optical structure of the device is demonstrated. Improvements in the external efficiency of polymer LEDs by a factor of 1.6 times compared to a device using a cathode composed of calcium backed with lower reflectivity aluminum is measured.

Electroluminescence (EL) produced by a commercially available additive free low density polyethylene film has been investigated under a 50Hz ac electrical stress. The spatial distribution, spectral characteristics and the phase angle relationship of EL with respect to the 50Hz applied ac voltage were studied using a sensitive Peltier cooled charge-couple device (CCD) camera. The experimental results from several test samples show that the EL can be divided into two different groups according to the EL spatial distribution: (1) homogeneous EL and (2) inhomogeneous EL. At the same applied voltage, the spectra of the homogenous and inhomogeneous EL were found to be significantly different. Homogeneous EL had maximum emission intensity in the red and near infra-red (> 700nm), whereas the inhomogeneous emission had maximum intensity at shorter wavelengths (550-600 nm). Phase resolved measurements showed that homogeneous EL always produced equal emission intensity in the positive and negative half-cycles (symmetric distribution), whereas, inhomogeneous EL produced an asymmetric intensity distribution. To explain these results, it is suggested that homogeneous emission is associated with charge injection and bipolar recombination in the surface states on both sides of the sample, whereas inhomogeneous emission is associated with field enhancement at defects on one of the two sides of the film which allow charge to be injected into states more representative of the bulk material. Index Terms--Electroluminescence, thin Films, polyethylene, ac electrical stress.

Electroluminescent ZnS:Mn thin films were deposited by the atomic layer deposition (ALD) technique. The results show that a relatively small change in the Zn precursor can have a clear impact on the electro-optical properties of the devices, and that a mixed halide/metalorganic ALD process can produce an electroluminescent device that ages relatively slowly.

The quantum efficiency of negative and positive luminescence in binary type-II InAs-GaSb superlattice photobodies in the midinfrared spectral range around the 5-mum wavelength is investigated. A negative luminescence efficiency of 45% is found for infrared diodes with a 2-mum absorbing layer, processed without anti-reflection coating.

A series of cationic bis-cyclometalated iridium(III) complexes are synthesized and their electrochemical, photophysical, electroluminescent properties are studied. The complexes are found to be luminescent both in a fluid solution and as neat solids at 298 K, while single-layer electroluminescent devices that give blue, green, and red electroluminescence are also fabricated.

Bright electroluminescence (EL) from an organic field-effect transistor (OFET) structure is demonstrated with a 1 wt%-rubrene:tetraphenypyrene (TPPy) codeposited film as an active layer. Results reveal a maximum eta(sub ext) of ~0.8% in a short channel device with MgAl/Au double-layer source and drain (S-D) electrodes.

Electroluminescence (EL) at submicron-sized breakdown sites is identified and studied using metal-insulator-silicon (MIS) tunnel diodes with ITO transparent electrodes. The number of sites grows linearly with the current, consistent with the dielectric breakdown of the insulator.

An easy but effective technique is described here for quick fabrication of low-cost electrochemiluminescence detection cells for capillary electrophoresis. The technique is based on molding of poly(dimethylsiloxane) (PDMS) with a capillary column inserted into a pipet tip. Two access holes are left in the PDMS slab; they provide neat accommodations for the separation capillary and the working electrode made with the same type of tip. Since the access holes are well-aligned, the electrode and the capillary are automatically aligned; thus, end-column detection is easily obtained. Fabrication of the detection cell is straightforward; no micromechanical operation is included. Also the principle for the procedure makes it possible to efficiently batch production detection cells with good reproducibility. Because of the end-column scheme, the cell can be adopted for electrophoresis with electrochemical detection as well.

A new series of Os(II) diimine complexes with the general formula [Os(N^N)(CO)2I2] N^N=2,2'-bipyidine (bpy), 4,4'-di-tert-butyl-2,2'- bipyidine, 4,7-diphenyl-1,10-phenanthroline, 2-(2'-pyridyl)-benzoxazole and 5-tert-butyl-2-(2'-pyridyl)benzoxazole were synthesized and characterized. The potential to serve as a phosphor for organic light emitting diodes were evaluted by examing their electroluminescent performances.

The electroluminescent properties of polyamidoamine dendrimers containing pendant [Ru(bpy)(sub 3)](super +2) are investigated. Indium tin oxide (ITO) and gold electrodes were used to make devices and they were compared to devices made from [Ru(bpy)(sub 3)](super +2) films.

A new driving scheme for the improvement and flexibility of a color temperature without sacrificing a peak white luminance using an independent control of the red, green, and blue luminance in an alternate current plasma display panel (ac-PDP) is presented. PDPs must overcome several serious problems for the complete replacements of the conventional cathode ray tube (CRT).

The generation and evolution of defects in 4H-SiC p-n junctions due to carrier injection under forward bias are investigated by synchrotron white beam x-ray topography, electroluminescence imaging, and KOH etching. Low angle grain boundaries are observed to act as one of a number of possible nucleation sites of stacking faults.

The thick-dielectric electroluminescent (TDEL) approach has been studied and it has been observed that it possesses some clear advantages over the thin-dielectric electroluminescence (TFEL) and I-TDEL structures. In fact, it could replace some of the TFEL applications and could strongly be considered for applications such as flat TVs.

The temperature dependence of visible and infrared (IR) rare-earth-activated electroluminescence of Er-doped GaN has been reported. It is shown that a simple model consisting of two back-to-back Schottky diodes accurately describes the I-V relationship.

The overshoot effect in transient electro luminescence (EL) is attributed to an accumulation and trapping of holes at the polymer/metal interface and this effect is enhanced at large reverse bias. The roughness of the Al(sub 2)O(sub 3) has an important bearing on the electron-hole recombination near the interface and its useful manifestation is the appearance of a large EL-spike upon reversing the driving voltage.

An n-sheet, state-space model is employed for the assessment of insulator issues of relevance to the operation of alternating-current thin-film electroluminescent (ACTFEL) devices. Simulation demonstrates that ACTFEL devices which have large insulator capacitances and no space charge present in the phosphor are optimal in terms of providing maximum luminance and efficiency.

The electroluminescence mechanisms of the lanthanide complex Eu(TTA)phen doped into CBP are investigated. The results suggest that lanthanide complexes face the same limitations as other metallorganic phosphors via triplet-metal ion transitions.

Synthesis of a terpyridine ruthenium (II) complex containing a substituted and an unsubstituted terpyridine ligand is done and its luminescence properties are studied in a solid-state single-layer light-emitting electrochemical cell. The obtained devices emitted light of a very deep red colour at low external applied bias.

Room temperature 1.54 mum electro luminescence (EL) was observed from Au/SiO(sub 2):Er/n(super +)-Si and Au/SiO(sub x):Si:Er/n(super +)-Si diodes. A SiO(sub x):Si:Er film deposited on a n(super +)-Si substrate by the magnetron sputtering technique was revealed to be a promising material for efficient Er(super 3+) EL.

The dependence of the voltage-controlled negative resistance and other characteristics of the Al-[Al.sub.2][O.sub.3]-Au diodes on the temperature is analyzed. The temperature dependent metal-nonmetal transition exhibited by the electroluminescence of the diodes is also discussed.

Equations describing effect of electronic nonuniformities on electroluminescence (EL) and the electron beam induced current (EBOC) images are analyzed on Cu(In,Ga)[Se.sub.2] solar cells. The samples have shown the largest variation in carrier collection function on a length scale of over 100 [micro]m while the band gap has varied almost linearly across the cell and the impact of shunt, series and stack resistances on EL images is discussed.

A blue light emitting diode (LED) is grown on top of a (Ga, In)N/GaN multiple quantum well (QW) acting as a light converter from blue to green-yellow wavelength. A very low blueshift is observed as a function of the injection current, which is explained by the fact that the carrier density per QW in the light converter has stayed relatively low when compared to the case of classical current-injected green LEDs.

Several experimental analyses are conducted to explain the mechanisms involved in the suppression of the roll-off characteristics of electroluminescence efficiency exhibited by the organic light emitting diodes at high current densities. At the current densities above 100 A/[cm.sup.2], the diodes are shown to exhibit the suppression with a balanced bipolar injection and transport.

A method for surface reconstruction of electron injection layers based on conjugated oligoelectrolytes atop an electroluminescent layer in the presence of air is described. The proposed mechanism involves hydration and concomitant increase of the interfacial energy with the underlying hydrophobic surface followed by dewetting via a nucleation process.

The article explains the synthesis and properties of the various ZnO-organic hybrid white light emitting diodes that are grown on flexible plastic via the low temperature aqueous chemical method. The various properties exhibited by these diodes are also studied.

A model is developed for predicting the performances of microscale Cu(In,Ga)[Se.sub.2] (CIGS) solar cells under concentrated sunlight, which is based on the analysis of the impact of the window spread sheet resistance. The model is used for extracting the value of the sheet resistance from simple current-voltage or electroluminescence measurements.

The electroluminescence (EL) characteristics of a set of InAs/GaInNAs quantum dot (QD) light-emitting diodes with varying In and N contents are studied. The studies have shown that the EL thermal quenching has an activation energy that is attributed to carrier escape from the QD to the capping layer.

The analysis of the electroluminescence (EL) intensity distribution has helped in obtaining the current density distribution under a certain current bias and the sheet resistance. Two-dimensional numerical simulation of the current density distribution is used to a GaInP cell and a reciprocity theorem is found for current spreading, which is used for interpreting the EL images.

The effect of rare-earth clustering in dielectric media on the electroluminescence (EL) intensity, the charge trapping and the EL quenching is examined by using Tb and Eu-implanted Si[O.sub.2] layers. It is shown that in the case of Eu-implanted Si[O.sub.2], the quenching of the main EL line of [Eu.sup.3+] is correlated with positive charge trapping in the bulk of the dielectric.

The article presents a new approach, which can be used for the modulated photocarrier radiometric imaging of the various multicrystalline Si solar cells. The methodology is shown to be extremely advantageous, as it exhibits the highest contrast, as well as sensitivity to the defects, hence giving extremely accurate results.

The article presents a complete analysis of the circularly polarized electroluminescence that is exhibited by the various InAs-based spin-light emitting diode structures. The results demonstrate the absence of any relationship between the optical and the spin polarization of such semiconductors.

Several studies are conducted to explain the reverse voltage current characteristics and the electroluminescence of the various 4H-SiC avalanche photodiodes. The excess leakage currents occurring in the diodes with edge or screw dislocations are also analyzed.