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Ultraviolet (UV) organic optoelectronic devices have attracted extensive research owing to their great potential in variety of applications such as biological and chemical sensing, excitation light sources, high-density information storage, and optoelectronic circuits. This review focusses on UV organic light-emitting diodes and organic solid-state lasers, and covers their recent development from organic chromophores and device configuration to practical applications. Firstly, materials with efficient short-wavelength emission are summarized with an emphasis on the characteristics of their structures. Subsequently, we outline the device architectures used for increasing the efficiency and performance of the devices. Finally, we discuss the progress and challenges of using UV OLEDs and organic solid-state lasers as excitation sources in emerging applications and hope this can help stimulate the exploitation of UV light sources in more applications in future.

Warm white organic light-emitting diodes (WOLEDs) based on efficient phosphor-only emitting systems exhibit very high peak electroluminescence (EL) efficiencies of 25.0/22.5% and 71.3/59.3 lm W−1 and desirable color rendering index (CRI) of 81/90.

A simple single-emitting layer only containing two phosphors of FMPYPCA (sky blue)/BZQBA (orange red) realizes a high-quality warm-white electroluminescence with CIEx,y of (0.42, 0.45) and very high peak efficiencies of 22.4%/65.4 lm W−1.

Several examples of a new class of materials which exhibit thermally-activated delayed fluorescence (TADF) were designed and synthesised. Structure-activity relationships were explored in order to colour-tune the fluorescence (from yellow to blue) and to improve the luminescence quantum yield. Device architectures were optimised for four materials in this class. Notably, the yellow device (CIE1931xy coordinates 0.407, 0.557) displays a maximum external quantum efficiency (EQE) of 14.3%.

Comparing rigid inorganic layer, polymeric semiconducting gate layer exhibits superior flexibility as well as efficient carrier manipulation in high frequency AC cycles. Mechanism of the carrier manipulation at the gate in forward and reversed bias of AC cycle is studied. The flexible PET-based AC-OEL device with poly[(9,9-bis(3'-((N,N-dimethyl)-Nethylammonium)- propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN-Br) gate shows a stable electroluminescent performance in frequency sweep with a color rendering index (CRI) over 81 at 2800K color temperature.

The first application of electroluminescence detected electron spin resonance technique on electroluminescent thermally activated delayed fluorescence (TADF) devices is shown. It indubitably proves the involvement of spins in the emergence of TADF electroluminescence and reveals the temperature dependency of such spin-dependent processes on bilayer devices that consist of two different material systems.

The blue organic electroluminescent device using TPBi as hole blocking layer is reported. The structure of device is ITO/ NPB(30 nm)/ DPVBi (15 nm)/ TPBi (x nm,x=0, 6)/ Alq (30 nm)/ LiF(1 nm)/ Al (200 nm) . With the addition of the TPBi not only make the highly of the blue organic electroluminescent device stable attachment x=0.168,y=0.170, but also the color coordinates change is very small and the chromaticity is relatively stable, which is coming from TPBi blocked hole in the organic emitting layer so as to improve the balance of the carrier, the composite probability of the exciton in organic functional layer and the efficiency of the organic electroluminescence device. The experiment shows the efficiency of the device is 3.32 cd/A, the maximum brightness of the device can reach 2222 cd/m2when the voltage is 20V, respectively.

Purpose. To determine whether organic electroluminescence (OLED) screens can be used as visual stimulators to elicit pattern-reversal visual evoked potentials (p-VEPs).Method. Checkerboard patterns were generated on a conventional cathode-ray tube (S710, Compaq Computer Co., USA) screen and on an OLED (17 inches, 320 × 230 mm, PVM-1741, Sony, Tokyo, Japan) screen. The time course of the luminance changes of each monitor was measured with a photodiode. The p-VEPs elicited by these two screens were recorded from 15 eyes of 9 healthy volunteers (22.0 ± 0.8 years).Results. The OLED screen had a constant time delay from the onset of the trigger signal to the start of the luminescence change. The delay during the reversal phase from black to white for the pattern was 1.0 msec on the cathode-ray tube (CRT) screen and 0.5 msec on the OLED screen. No significant differences in the amplitudes of P100 and the implicit times of N75 and P100 were observed in the p-VEPs elicited by the CRT and the OLED screens.Conclusion. The OLED screen can be used as a visual stimulator to elicit p-VEPs; however the time delay and the specific properties in the luminance change must be taken into account.

We report on an alternating current (AC) field induced organic electroluminescence (EL) device with internal charge carrier generation and recombination luminance of over 5000 cd m −2 under AC drive without charge carrier injection from external electrodes. The ultra-bright AC-EL is attributed to an optical optimization performed on the devices via numerical optical simulations based on an optical thin film model as well as an increase in the number of charge carriers achieved via the concept of molecular doping within the device. The luminance levels achieved are highest reported so far in literature for AC organic light emitting devices.

To improve the performance of blue fluorescent and green phosphorescent organic light-emitting diode devices, Merck developed novel green phosphorescent host and electron-transporting materials. The newly developed electron-transporting material improves the external quantum efficiency of blue fluorescent devices up to 8.7%, with an excellent lifetime. In combination with the newly developed host materials, the efficiency of green phosphorescent devices can be improved by a factor of 1.7, and the lifetime by a factor of 7.

Novel pyridine-containing compounds were synthesized and their properties were studied. Organic electroluminescent devices using these compounds as electron-transporting layer were fabricated. It was demonstrated that these compounds were useful for organic light-emitting diodes (OLED) and solid state lighting technology in favor of energy-saving and environmental protection fields.

We report highly efficient, variable-color light-emitting diodes (LEDs) realized via mixing of molecular exciton and excimer phosphorescent emissions from a new organic phosphor platinum N boolean AND C(2)boolean AND N-[1,3-di(4-methoxy-pyrid-2-yl)-4,6-difluorobenzene] chloride (PtL(26)Cl), a member of the Pt(N boolean AND C boolean AND N) complex series, where N boolean AND C boolean AND N represents a cyclometallating tridentate ligand based on 1,3-dipyridylbenzene, L. PtL(26)Cl-doped TCTA blends [TCTA = 4,4',4 ''-tris(N-carbazolyl-triphenylamine)] have been used as either the low-concentration bluish-green (molecular) phosphorescence emitter or high-concentration red (excimer) phosphorescence emitter. By adjusting the relative amount of blue and red emissive species, the color of the light emission was tuned from bluish-green through green and white up to red. The concentration-optimized devices can easily reach high brightness up to B = 10,000 cd/m(2), achieving extremely high external quantum efficiency (EQE) up to 20% at low-current densities (

A review of recent studies of pyrazoloquinoline and quinoxaline derivative chromophore used as organic light emitting diodes and photovoltaic elements is done. We present both the principal ways of modifications of these materials as well as a possible chemical modifications to achieve more suitable technological parameters.

A Low-Temperature Thermal CVD process (LT-TCVD) is presented to fabricate a mechanically robust and thermally stable FAR2.2™ polymer thin film for either a monolithic thin-film barrier layer or as part of a multi-layer barrier layer stack for encapsulation of OLED devices. FAR2.2™ polymer thin film is not only free of pinholes but also has a good step coverage. In particular, the LT-TCVD film deposition process is compatible with and benign to the underlying organic electroluminescence materials.

A novel Re complex functionalized by a hole-transport and an electron-transport groups was utilized to fabricate organic light-emitting devices (OLEDs). A current efficiency up to 8.2 cd A−1 corresponding to a power efficiency of 4.6 ml W−1 and a peak brightness as high as 5500 cd m−2 were obtained. These results represent the best values reported for OLEDs based on rhenium complexes. Short lifetime, enhanced carrier injection capability of Re complex, and efficient charge-trapping followed by exciton confinement in the emissive layer should be responsible for the outstanding electrophosphorescent performances.

The Japanese chemical industry has built general chemicals factories overseas. Nevertheless, it has been reluctant to build factories that produce high-technology functional chemicals overseas, first because these factories are inseparable from RD liquid crystal electronic display (LCD); plasma electronic display panel (PDP); organic electroluminescence (organic EL); surface-conduction electron-emitter electronic display (SED); or electronic paper.

This review paper describes the present status of passivation films with organic/Inorganic multilayer structure on flexible organic film substrate designed for electronic devices such as organic light emitting diode (OLED). Passivation film of SiNx/CN:H multilayer showed an excellent barrier properties for water and oxygen and strongly suppressed an appearance of dark spots on OLED surface during operation. The luminous efficiency of flexible OLED thus formed with passivation films revealed to be equivalent to that on glass substrate encapsulated by can. substrate.

We report the synthesis of a red light‐emitting and photopolymerizable smectic liquid crystal (reactive mesogen). We investigate the suitability of polymer networks formed from smectic reactive mesogens for use in organic light‐emitting diodes (OLEDs). The use of mixtures of smectic reactive mesogens is shown to lower the processing temperature for the fabrication of OLEDs to room temperature. We also report efficient energy transfer from a nematic polymer network host to a smectic light‐emitting dopant and polarized emission from a polymer network formed from an aligned smectic reactive mesogen.

The UV–vis absorption and fluorescence spectra, solubility, and application as emitters in single-layer organic electroluminescence (EL) devices of novel quinacridone- and squarylium-dye-centred de...

Spectral and electric properties of five new materials for electroluminescent devices are described including materials for emitting layers and a high-Tg hole-transporting material.

Highly oriented p -sexiphenyl (6P) film was successfully prepared by epitaxial-growth on rubbed 6P film on hole-transporting poly(9,9 ′ -dioctylfluorene) (POF). Using the epitaxial-growth film of 6P, we prepared tri-layered device, ITO/POF/epitaxial-growth film of 6P/electron-transporting ozadiazole derivative (OXD7)/LiF/A1. The device with the epitaxial-growth film of 6P as emissive layer exhibited highly polarized and efficient blue electroluminescence (EL). EL peaking around 430 nm corresponded well to photoluminescence of 6P film. The maximum value of polarization ratio I p / I s of the blue EL was 37, where I p and I s are EL intensity parallel and perpendicular to the orientation direction, respectively. The values of maximum luminance L max and maximum current efficiency η max of the tri-layered device were enhanced comparing to those of a double-layered device ITO/6P/OXD7/LiF/Al; L max =146 cd m −2 and η max =0.41 cd A −1 for the tri-layered device whereas L max =32 cd m −2 and η max =0.07 cd A −1 for the double-layered device.

Effects of metallophthalocyanines (MPcs) are systematically investigated on electroluminescence (EL) characteristics of ITO/MPc/TPD/Alq3/Mg–Ag devices. A linear relationship is found between driving voltages of the devices and energies of the highest occupied molecular orbital (HOMO) level of MPcs, showing that the driving voltage of the device is substantially determined by the energy barrier for hole injection at the ITO/MPc interface. When an MPc having a higher HOMO level, such as CuPc or ZnPc, is selected as a hole transport material, the driving voltage of the device at a luminance of 100 cd m−2 significantly reaches as low as 5.5 V compared with 7.8 V for the device without an MPc layer. The insertion of MPc layer leads to increasing of the EL output, but does not affect the EL efficiency of the devices.

This paper aims to highlight some recent innovations in liquid crystal displays (LCDs) specifically where significant technological steps are being made in what is often considered as a mature display technology. Whilst this paper is set in the context of a series of organic electroluminescence (OEL) papers, the main intention is describing relevant technological detail pertinent to OEL display development rather than making LC–OEL display performance comparisons. Both mobile and large-area displays are considered.

N , N ′-biphenyl- N , N ′-bis-(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD) and N , N ′-biphenyl- N , N ′-bis-(1-naphenyl)-[1,1′-biphenyl]-4,4′-diamine (NPB) are typical hole transporting materials, which are widely used in current organic eletroluminescence (EL) research. NPB is regarded as a better hole transporting material than TPD, since it has a higher glass transition temperature ( T g ). In this paper, the photostability and morphological stability of TPD and NPB have been studied in film states. It is concluded that NPB thin film is a better hole transporting material for organic EL than TPD, not only because it has a higher T g , but also because it is more photostable and has a better morphological stability in thin film state.

This review intends to give a qualitative account of the basic physical processes involved in organic electroluminescence, their interplay and their influence on the yields.

In recent years, there is a worldwide interest in the area of organic electroluminescence (EL) stimulated by the promising application of light-emitting diodes for the fabrication of large, flexible, flat and inexpensive displays. This article provides a review based on a part of our research works including design and characterization of highly electron affinitive polymers, multi-functional EL material and organic-soluble rare earth metal complex. Their device performance using these materials as emissive layers is also involved.

This article provides a review about electroluminescence from organic materials and deals in detail with organic light-emitting diodes (OLEDs), light-emitting electro-chemical cells (LECs) and electrogenerated chemilumi-nescence (ECL) reflecting different electrooptical appli-cations of conjugated materials. It is written from an organic chemist's point of view and pays particular attention to the development of organic materials involved in corresponding devices. In recent years a substantial amount of both academic and industrial research has been directed to organic electroluminescence in an effort to improve the processability and tunability of organic materials and the longevity of OLEDs and LECs. On the eve of the commercialization of organic electrolumi-nescence this review provides an overview of lifetimes and efficiencies attained and reflects materials and device concepts developed over the last decade. In this context electrogenerated chemiluminescence is discussed with respect to its importance as a versatile tool to simulate the fundamental electrochemical processes in OLEDs.

Organic phosphors have demanded the attention of the organic electroluminescence community because they enable efficiencies quadruple that of fluorescent materials. In this work, we review the categories of organic phosphors: lanthanide complexes, organic phosphors and metal-organic complexes. The characteristics necessary for efficient phosphor- escence are considered and conclusions are drawn as to the most promising materials.

Organic electroluminescent devices with Eu x Tb 1− x (aca) 3 phen dinuclear complex as the emitting layer were fabricated. When the devices are operated under proper voltage the white light can be obtained. It consists of three parts: red from Eu 3+ , green from Tb 3+ and blue from TPD (or NPB).

Electroluminescence has been a subject of interest for several decades because of its many applications in areas such as telecommunications or information displays. Light-emitting diodes using p-n junctions of inorganic semiconductors have dominated the field in the last twenty years; however, efficient blue emission has only recently been achieved and inorganic semiconductors are difficult to form over large areas, making the process uneconomic. During the last decade, an explosive growth of activity in the area of organic electroluminescence has occurred in both academia and industry, stimulated by the promise of light-emitting plastics for the fabrication of large, flexible, inexpensive and efficient screens to be used in different applications. Thus, a substantial amount of research is presently directed towards color control and improvement of manufacturability and reliability of devices in order to make their commercialization viable. A great deal of work has been carried out by physicists and materials scientists concerned with the preparation of different device structures and with the use of different techniques for device manufacture. However, all this work would not be possible without the continuous efforts of synthetic chemists to prepare materials with enhanced luminescent properties and processabilities. This article provides a review of the main types of organic materials that have been used in the fabrica-tion of light-emitting diodes either as emitting materials or as charge-transport layers. Special attention will be paid to the different synthetic strategies that have been followed in order to tune the color of the emission, to increase stability of materials and to enhance their processabilities.

Recent developments in the design and use of vapor-deposited thin-film metal chelates as organic electroluminescent materials for display applications are presented. The material issues pertaining to color, emission efficiencies, and operational

Recently, organic light emitting diodes have received a lot of attention in different research laboratories world-wide. Red, green and blue emitting devices are readily available. Devices with luminous efficiencies greater than 15 lm/W and lifetimes longer than 10,000 hours have been demonstrated. In this article, we will discuss the basic devices used in physics, materials used in organic light emitting diodes, device degradation mechanisms, and the opportunities of using this technology for commercial display applications.

The medical liquid crystal display (LCD) monitor is a conventionally used imaging device for diagnosis and during endoscopic surgery. Recently, a medical organic electroluminescence panel, the organic light-emitting diode (OLED) monitor, was made available commercially. The advantages of the OLED monitor include good color reproducibility, high contrast, and high video responsiveness. In this nonclinical study, we compared the clinical usefulness and image quality of the OLED monitor and those of the LCD monitor using videos of gynecologic endoscopic surgeries. Monitors were set for blind evaluation. Five evaluators with varying experience in endoscopic surgery evaluated 21 surgery videos played simultaneously on an OLED monitor and two LCD monitors for 2 to 3 minutes twice. Evaluators judged 13 clinical usefulness indices and 11 image quality indices using a 5-point scale (1, very good; 5, very poor) for each video. The mean scores of clinical usefulness indices of the OLED monitor and the LCD monitors 1 and 2 were 2.2 to 2.7, 2.1 to 3.3, and 3.0 to 3.2, respectively. Of seven indices measured, five including motion response, the ability to differentiate organs, recognize lesions, and reproduce actual images, and the general impression of picture quality were statistically superior with use of the OLED monitor compared with the LCD monitor 1, and two including ability to distinguish blood vessels and the ureters were statistically superior with use of the LCD monitor 1 compared with the OLED monitor. The mean scores of image quality indices of the OLED monitor and the LCD monitors 1 and 2 were 1.8 to 3.2, 2.6 to 3.6, and 2.8 to 4.0, respectively. Each index of the OLED monitor was superior to or comparable with those of the LCD monitors. We conclude that the OLED monitor is superior to the LCD monitors insofar as several video presentation characteristics required in gynecologic endoscopic surgery. These findings suggest that the OLED monitor is expected to contribute detailed assessment of organs and the operative field.

Some physical factors affecting the relative advantages of organic and inorganic electroluminescence are discussed. Especial attention is given to carrier transport, the strength of radiative transitions and carrier-carrier interactions. Speculations are made concerning devices in which organic electroluminescence could compete effectively with existing technologies.

A class of anthracene derivative which is suitable used as emitting materials for producing efficient and stable blue emission for full color organic electroluminescence (EL) devices has been developed. Multilayer organic EL devices using these fluorescent materials as an emitting layer produced blue emissions with good chromaticity and luminous efficiency as high as 3.5 cd/A. The half life of 4000 h of blue emission EL device with initial light output 700 cd/m2 has been achieved.

Korea Basic Science Institute, Pusan Branch, Pusan National University, Pusan 609-735, KoreaReceived October 16, 2001Keywords : Electroluminescence, Pendant, Polyurethane, Organic electroluminescence device.There have been extensive research efforts on organicelectroluminescent devices (OELDs) with the aim of appli-cation for the flat panel display (FPD). OELDs have alsoattracted much interest because of their particular lowdriving voltage, convenient design of the device structures,possible control of emission band, and low fabrication costcompared with any other devices.

Eelectroluminescence is a solid light. Based on the different structure and working principle, Electroluminescence (EL) can be divided into inorganic electroluminescence and organic electroluminescence. In this paper some rresearches on electroluminescence are reviewed. The principle, structure and application of inorganic electroluminescence and organic electroluminescence are illustrated. Some recent focuses are discussed. EL has wide future. They are better than other display technologies for the flat panel display applications.

We fabricate a buckling structure by thermally depositing aluminum on a polymer surface and cooling it to room temperature, and utilize the structure as a microlens aggregate for organic light emitting diodes. The aspect ratio of the lens is increased by a multiple deposition process. We demonstrate that the characteristics of the outcoupled emission of this device are improved from various perspectives such as efficiency, emission angle, and reduced spectral change. These improved characteristics originate from randomized double-curvatured lens structure with full surface coverage.

Porous alumina based organic electroluminescence structure doped with naphthalimide deriative is developed. The usage of porous alumina cathode results in more inhomogeneous electric field and, as a consequence, more intensive autoelectron emission. Organic electroluminescent devices of this type are easily produced and can be more efficient and stable as compared with usual structures.

Some styryl type dyes, such as 2-(4-Dimethylaminostyryl)benzoxazole (1), were found to be useful as novel emitting materials for the electroluminescent (EL) device. The EL devices with hole transporting layer have more efficiency than that with only emitting layer, but the electron trans porting layer do not work effectively. The EL intensity of the H-type device with 1 was 3.8 cd/m2 at the dc bias voltage of 60 volt.

We investigate quenching mechanisms of excited states in emitter layers for organic light emitting diodes (LEDs). An extensive study of a strong electric field-induced modulation (over 50%) of the time-resolved luminescence in a diamine derivative (TPD): polycarbonate blend films doped with an organic complex of europium are presented as a typical example of an important class of emitters for organic monochromatic LEDs. Using this method allowed us to identify the quenched species as the excited ligand precursors of the emissive europium ion states. Manipulating the electrode materials and their electrical bias, the electric field-enhanced dissociation, and interaction with injected charge could be separated and found as principal quenching mechanisms. We show the first one to follow the three-dimensional Onsager theory of geminate recombination, and the second one raised by their interaction with the TPD-transported holes. The interaction rate constant is found to be underlain by the three-dimensional diffusion of excited ligand singlets, combining the exciton diffusion coefficient and long-range (Forster type) energy transfer parameters. The dynamic parameters of the hole-precursor excitons interactions, extracted from the experimental data, allow us to establish the criteria for identifying useful ligands and matrices in the optimized design of electrophosphorescent, linelike emitting molecules, and device structure for organic LEDs. (C) 2008 American Institute of Physics.

The purpose of this paper is to provide general information about basic physical processes involved in organic electroluminescence and to present the main parameters and advantages of organic light emitting devices (OLEDs).

We report that fluorescent organic light-emitting diodes (FOLEDs) with the emitting layer including a dianthranide derivative material produced highly efficient and bright emission in the deep blue region. It is found that this material works as an excellent host for creating high-performance FOLEDs with Commission International de L'Eclairage (CIE) coordinates (x = 0.147, y = 0.125), high current efficiency (CE) of 6.4 cd A−1 and external quantum efficiency (EQE) of 7.40% at 20 mA cm−2.

A comprehensive review about functional spiro compounds, their synthesis, physical properties and applications in optoelectronic devices is given.

We report that organic electroluminescence devices with a distyrylarylene (DSA) emitting layer including a new dopant realized highly efficient and bright emission in blue region. This dopant was amino‐substituted DSA. The luminous efficiency was obtained to be 1.5 lm/W. The external quantum efficiency was estimated to be 2.4%, which is one of the highest efficiencies ever reported in blue emitting organic EL devices.