Showing papers on "OLED published in 2000"
TL;DR: This work demonstrates that by increasing the doping level of Doped π-conjugated polymer layers, the barrier to hole injection can be continuously reduced in OLED devices with hole-limited electroluminescence, finding that it is possible to significantly reduce the operating voltage while improving the light output and efficiency.
Abstract: Organic light-emitting diodes (OLEDs) represent a promising technology for large, flexible, lightweight, flat-panel displays. Such devices consist of one or several semiconducting organic layer(s) sandwiched between two electrodes. When an electric field is applied, electrons are injected by the cathode into the lowest unoccupied molecular orbital of the adjacent molecules (simultaneously, holes are injected by the anode into the highest occupied molecular orbital). The two types of carriers migrate towards each other and a fraction of them recombine to form excitons, some of which decay radiatively to the ground state by spontaneous emission. Doped pi-conjugated polymer layers improve the injection of holes in OLED devices; this is thought to result from the more favourable work function of these injection layers compared with the more commonly used layer material (indium tin oxide). Here we demonstrate that by increasing the doping level of such polymers, the barrier to hole injection can be continuously reduced. The use of combinatorial devices allows us to quickly screen for the optimum doping level. We apply this concept in OLED devices with hole-limited electroluminescence (such as polyfluorene-based systems), finding that it is possible to significantly reduce the operating voltage while improving the light output and efficiency.
538 citations
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29 Nov 2000TL;DR: In this paper, an emitter layer comprising organometallic complexes of transition metals of formula L2MX is obtained with an improved electroluminescent efficiency in organic light emitting diodes.
Abstract: Improved electroluminescent efficiency in organic light emitting diodes is obtained with an emitter layer comprising organometallic complexes of transition metals of formula L2MX, wherein L and X are distinct bidentate ligands. Compounds of this formula can be synthesized more facilely than in previous approaches and synthetic options allow insertion of fluorescent molecules into a phosphorescent complex, ligands to fine tune the color of emission, and ligands to trap carriers.
476 citations
TL;DR: In this article, the authors applied spherically shaped patterns to the back of an organic light-emitting diode to capture light previously lost to waveguiding in the substrate and, with proper choice of substrate, to recover the lost light in the organic/anode layers.
Abstract: The emission intensity of an organic light-emitting diode at normal viewing angle and the total external emission efficiency have been increased by factors of 9.6 and 3.0, respectively, by applying spherically shaped patterns to the back of the device substrate. The technique captures light previously lost to waveguiding in the substrate and, with proper choice of substrate, light previously lost to waveguiding in the organic/anode layers. A method of applying the technique using laminated films and an optical model for evaluating coupling efficiency are also presented.
372 citations
TL;DR: Using organic light-emitting devices (OLEDs), organic full-color displays may eventually replace liquid-crystal displays (LCDs) for use with laptop and even desktop computers.
Abstract: Organic semiconductors are poised to transform the world of circuit and display technology. Major electronics firms such as Philips and Pioneer, and smaller companies such as Cambridge Display Technology, Universal Display, and Uniax, are betting that the future holds tremendous opportunity for the low cost and sometimes surprisingly high performance offered by organic electronic and optoelectronic devices. Using organic light-emitting devices (OLEDs), organic full-color displays may eventually replace liquid-crystal displays (LCDs) for use with laptop and even desktop computers. Such displays can be deposited on flexible plastic foils, eliminating the fragile and heavy glass substrates used in LCDs, and can emit bright light without the pronounced directionality inherent in LCD viewing, all with efficiencies higher than can be obtained with incandescent light bulbs.
268 citations
TL;DR: A dependency between the molecular weight distribution of polyfluorene and its aggregation tendency on operation in organic light-emitting devices (OLED) is described in this paper, which leads to PFO-based OLEDs which do not show aggregation on operation anymore but exhibit highly efficient and stable blue electroluminescence.
Abstract: A dependency between the molecular weight distribution of polyfluorene (PFO) and its aggregation tendency on operation in organic light-emitting devices (OLED) is described. As a result of these findings, low molecular parts of the polymer could be made responsible for the aggregation in liquid crystalline PFO. Consequently, a procedure was developed which leads to PFO-based OLEDs which do not show aggregation on operation anymore but exhibit highly efficient and stable blue electroluminescence.
255 citations
Patent•
22 Dec 2000
TL;DR: In this paper, an organic light emitting diode containing a first electrode, a second electrode, at least one organic light-emitting layer, and an output coupler which reduces a Fresnel loss is provided.
Abstract: An organic light emitting diode containing a first electrode, a second electrode, at least one organic light emitting layer, and an output coupler which reduces a Fresnel loss is provided. The index of refraction of the output coupler is matched to that of the adjacent layer of the device. The output coupler may be a dimpled transparent material or a composite layer containing light scattering particles to also reduce a critical angle loss.
245 citations
TL;DR: In this paper, a light-emitting diodes have been prepared by depositing three organic layers successively by spin-coated and evaporation techniques, and the combination of polymeric and monomeric organic layers leads to highly efficient devices, opening new ways to modify device architectures.
209 citations
TL;DR: In this paper, a high performance polymer electroluminescent device based on a bi-layer structure consisting of a hole transporting layer (poly(vinylcarbazole)) and an electron transporting layer poly(9,9-bis(octyl)-fluorene-2,7-diyl) (BOc-PF) doped with platinum(II)-2,8,12,17,tetraethyl-3,7,13,18-tetramethylporphyrin (PtOX).
172 citations
TL;DR: A variety of 5,11-diaryl-5, 11-dihydroindolo[3,2-b] carbazole derivatives have been synthesized for use as hole-transport layers in organic light-emitting devices (OLED).
139 citations
Patent•
15 Nov 2000TL;DR: Improved electroluminescent efficiency in organic light emitting diodes was obtained with an emitter layer comprising organic complexes of transition metals with benzoxazole derivatives in this article, where a dimethylated benzoxaxole derivative with zinc showed blue fluorescence and phosphorescence.
Abstract: Improved electroluminescent efficiency in organic light emitting diodes is obtained with an emitter layer comprising organic complexes of transition metals with benzoxazole derivatives. A dimethylated benzoxazole derivative with zinc shows blue fluorescence and phosphorescence.
138 citations
TL;DR: In this paper, the authors investigated the continuous operating lifetime of organic light emitting devices (OLEDs) using the phosphorescent dopant, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (II) as the light emitting molecule.
Abstract: We investigate the continuous operating lifetime of organic light emitting devices (OLEDs) using the phosphorescent dopant, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (II) as the light emitting molecule. We characterize devices based on two different electron transporting hosts: tris-(8-hydroxyquinoline) aluminum and 4,4′-N,N′-dicarbazolyl-biphenyl (CBP). The OLEDs lose ∼25% of their luminance in the first 50 h of operation, followed by extremely slow degradation with negligible growth of dark spots. The device lifetime of CBP-based phosphorescent OLEDs projected to 50% initial brightness is >107 h at a mean current density of 10 mA/cm2 under 50% duty cycle pulsed operation. These extremely long lifetimes are speculated to be an intrinsic property of electrophosphorescent OLEDs, where radiative phosphors significantly shorten the lifetime of potentially reactive triplet states in the conductive host material.
Patent•
22 Mar 2000TL;DR: In this article, the emissive layer comprises a host material containing an emissives molecule, which molecule is apdated to luminescence when a voltage is applied across the heterostructure, and selected from the group of phosphorescent organometallic complexes, including cyclometallated platinum complexes.
Abstract: Organic light emitting devices are described wherein the emissive layer comprises a host material containing an emissive molecule, which molecule is apdated to luminescence when a voltage is applied across the heterostructure, and the emissive molecule is selected from the group of phosphorescent organometallic complexes, including cyclometallated platinum complexes.
TL;DR: In this article, a two-layer organic light-emitting diodes with 8-hydroxyquinolinolato-Al(III) (Alq3) as emitter material was optimized by combinatorial methods.
Abstract: We synthesized lithium−quinolate complexes, 8-hydroxyquinolinolatolithium (Liq) and 2-methyl-8-hydroxyquinolinolatolithium (LiMeq), as emitter and electron injection/transport materials to be used in conventional two-layer organic light-emitting diodes in combination with N,N‘-bis(p-methoxyphenyl)-N,N‘-diphenylbenzidine (DMeOTPD) as hole transport material (HTL). The lithium complexes were also examined as interface materials in combination with 8-hydroxyquinolinolato-Al(III) (Alq3) as emitter material. The device efficiency with these complexes was optimized by combinatorial methods. We also compared the electron injection, transport, and emission properties of Li complexes with the well-known emitter Alq3 in the same experiment by taking advantage of the combinatorial approach. The Li quinolates are found to be efficient emitter molecules. But the efficiencies of lithium quinolate devices are lower than that of Alq3 devices. Contrary to the Alq3 emission, the Li quinolates exhibit a bathochromic shift o...
TL;DR: In this article, the authors present device model calculations of single layer and bilayer organic LED characteristics that demonstrate the improvements in device performance that can occur in bilayer devices, where the role of the bilayer structure in this case is to move the recombination away from the electrode that injects the low mobility carrier.
Abstract: Organic materials that have desirable luminescence properties, such as a favorable emission spectrum and high luminescence efficiency, are not necessarily suitable for single layer organic light-emitting diodes (LEDs) because the material may have unequal carrier mobilities or contact limited injection properties. As a result, single layer LEDs made from such organic materials are inefficient. In this article, we present device model calculations of single layer and bilayer organic LED characteristics that demonstrate the improvements in device performance that can occur in bilayer devices. We first consider an organic material where the mobilities of the electrons and holes are significantly different. The role of the bilayer structure in this case is to move the recombination away from the electrode that injects the low mobility carrier. We then consider an organic material with equal electron and hole mobilities but where it is not possible to make a good contact for one carrier type, say electrons. Th...
Patent•
17 Aug 2000TL;DR: In this paper, a flexible organic light emitting diode (OLED) fiber light source is provided, which contains a fiber core, a cathode, at least one organic radiation emitting layer and a transparent anode.
Abstract: A flexible organic light emitting diode (OLED) fiber light source is provided. The OLED contains a fiber core, a cathode, at least one organic radiation emitting layer and a transparent anode. The fiber light source may be used as a flexible novelty lighting article or coiled inside a large area lighting source.
TL;DR: In this article, the quenching effect in tris(8-hydroxyquinoline)aluminum is analyzed, and ways to improve the device efficiency by suppressing the interaction with the electrode are discussed.
Abstract: The quantum efficiency of organic light emitting devices depends on the exciton emission efficiency. Exciton quenching at the metal cathode can be responsible for lowering the device performance. We consider exciton quenching by the metal cathode, taking into account both exciton diffusion and radiationless energy transfer to the metal. The quenching effect in tris(8-hydroxyquinoline)aluminum is analyzed, and ways to improve the device efficiency by suppressing the interaction with the electrode are discussed.
TL;DR: In this paper, an ultrathin SiO2 layer between the organic and ITO was inserted to improve the hole-injection barrier in organic light-emitting devices (OLEDs).
Abstract: Ultraviolet photoelectron spectroscopy has been applied to the investigation of modified hole injection barriers in organic light-emitting devices (OLEDs). Different from those reported previously, the indium tin oxide (ITO) surface treated in situ by oxygen plasma possesses a work function of 5.2 eV, and the organic ITO interface thereafter formed shows a 0.5 eV smaller hole injection barrier compared to that on untreated ITO. Insertion of an ultrathin SiO2 layer between the organic and ITO results in a similar reduction of the barrier. This indicates that improved hole injection favors efficient operation of OLEDs, as manifested by enhanced efficiency by the SiO2 insertion.
Patent•
18 Dec 2000
TL;DR: In this paper, a simplified OLED structure comprising an anode layer, a hole injecting layer (HIL), an emissive organic electron transporting layer (ETL), and a cathode layer was presented.
Abstract: The present invention is directed to simplified OLED structures comprising an anode layer, a hole injecting layer (HIL) in direct contact with the anode layer, an emissive organic electron transporting layer (ETL) in direct contact with the hole injecting layer, and a cathode layer in direct contact with the emissive organic electron transporting layer. The hole injecting material used in the hole injecting layer is characterized, in particular, as being an organic material having an ionization potential that is not more than about 0.7 eV greater than the ionization potential of the material used for the anode layer. The emissive organic electron transporting layer comprises an organic electron transporting material and an organic hole-trapping emissive material, for example, an organic phosphorescent material that produces emission from a triplet excited state of an organic molecule.
TL;DR: In this paper, the photoluminescence and electroluminescent properties of neodymium tris-(8-hydroxyquinoline) tris were studied.
Abstract: We have studied the photoluminescence and electroluminescence of neodymium tris-(8-hydroxyquinoline) and have found evidence, from the Stark splitting of the neodymium emission, for two isomers of the molecule. Following sublimation it appears that one of these isomers predominates. Photoluminescence can be excited through absorption into the organic ligands and there appears to be efficient coupling between the singlet and triplet exciton levels in the ligand and the internal levels of the neodymium. We can obtain bright infrared electroluminescence from the intraatomic levels within the neodymium at wavelengths of 900, 1064, and 1337 nm.
Patent•
24 Nov 2000TL;DR: In this article, a pixel structure of an active matrix full-color OLED display device and its manufacturing method are provided, which simplifies the process, reduces the leakage of light and increases the contrast of the display device.
Abstract: A pixel structure of an active matrix full-color OLED display device and its manufacturing method are provided. The pixel structure of the display device comprises two thin film transistors, a storage capacitor, a color filter, and an OLED device structure constructed on a top surface of a substrate, a black matrix region outside the color filter region and under the thin film transistors. In this pixel, structure of the OLED display device, the OLED device structure and the color filter are integrated in a thin-film-transistor array. This simplifies the process, reduces the leakage of light and increases the contrast of the display device. A white OEL device is used to emit light. A light then passes a color filter to get red, green or blue color of light. Therefore, a full-color OLED is formed. A poly-silicon thin film transistor is used to provide current to the OLED device structure and served as an active drive device. The advantages of the display device include simple fabrication process, high-resolution, high lighting efficiency and wide viewing angle.
TL;DR: In this paper, two new materials for the light-emitting layer in organic light emitting devices, N′N′Bis (2,6-xylyl)perylene-3,4:9,10-bis(dicarboximide) (DPP-PTCDI) and N,N′-Dimethylperylene -3, 4:9-10-bi (DMe-PTFDI) are compared by an spectroscopic and opto-electronic study.
TL;DR: Using a derivative of the blue-emitting polyfluorene, efficient devices exhibiting a power efficiency close to 2.7 cd A(-1) at 100 cd m(-2) light output were realized.
Abstract: Using a derivative of the blue-emitting polyfluorene (see the graph for the output spectrum and the inset picture for the color), efficient devices exhibiting a power efficiency close to 2.7 cd A(-1) at 100 cd m(-2) light output were realized.
01 Jan 2000
TL;DR: This paper will summarize the status of active matrix full color OLED display development, the key technical challenges, and the path ahead.
Abstract: In October 1999, Eastman Kodak and Sanyo Electric jointly announced the development of a high quality, 2.4 inch diagonal Full Color active matrix Organic Light Emitting Diode (OLED) display. This technology demonstration resulted from the successful integration of Kodak's organic electroluminescence display technology and Sanyo's low temperature polysilicon TFT technology. Commercial samples are expected to reach the market in 2001. The active matrix OLED displays feature a wider viewing angle and a faster response speed than conventional LCDs. With its low power consumption, high brightness and thin design, these OLED displays when incorporated in digital cameras, personal digital assistants (PDA), videophones and other portable imaging devices, will offer a superior value proposition to consumer electronics products. Several OLED display designs are under development now to serve various market segments. This paper will summarize the status of active matrix full color OLED display development, the key technical challenges, and the path ahead.
01 May 2000
TL;DR: In this article, the authors summarized the status of active matrix full color OLED display development, the key technical challenges, and the path ahead, and summarized the current state of the art.
Abstract: In October 1999, Eastman Kodak and Sanyo Electric jointly announced the development of a high quality, 2.4 inch diagonal Full Color active matrix Organic Light Emitting Diode (OLED) display. This technology demonstration resulted from the successful integration of Kodak's organic electroluminescence display technology and Sanyo's low temperature polysilicon TFT technology. Commercial samples are expected to reach the market in 2001. The active matrix OLED displays feature a wider viewing angle and a faster response speed than conventional LCDs. With its low power consumption, high brightness and thin design, these OLED displays when incorporated in digital cameras, personal digital assistants (PDA), videophones and other portable imaging devices, will offer a superior value proposition to consumer electronics products. Several OLED display designs are under development now to serve various market segments. This paper will summarize the status of active matrix full color OLED display development, the key technical challenges, and the path ahead.
01 May 2000
TL;DR: A novel type of digital driving manner of TFT‐OLED display by time‐ratio gray‐scale (TRG) expression that is remarkable especially in large, color, or high‐resolution TFT-OLED displays is proposed.
Abstract: We propose a novel type of digital driving manner of TFT-OLED display by time-ratio gray-scale (TRG) expression. The advantage of this is remarkable especially in large, color, or high-resolution TFT-OLED displays. A 4.0-in. TFT-OLED monochrome display employing this sophisticated digital driving method is demonstrated.
TL;DR: In this article, a uniform thin silicon nitride film, used as an anode modification layer, has been deposited on ITO coated glass by plasma enhanced chemical vapor deposition, which improved the interface between the organic layer and the metallic layer of an organic light-emitting diode.
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31 Jul 2000TL;DR: In this paper, a transparent cathode is defined as an electron injector, a metal layer over the injector and a transparent layer deposited over the metal layer and having a refractive index equal to or greater than 1.2.
Abstract: An transparent cathode includes an electron injector, a
metal layer over the injector, and transparent layer deposited over the metal layer
and having a refractive index equal to or greater than 1.2.
TL;DR: In this article, an erbium-containing organic light-emitting diode (OLED) structure which utilizes p++ silicon as the hole injection contact has been fabricated on silicon substrates.
Abstract: 1.5-μm light-emitting diodes which operate at room temperature have been fabricated on silicon substrates. The devices use an erbium-containing organic light-emitting diode (OLED) structure which utilizes p++ silicon as the hole injection contact. The OLEDs use N, N′-diphenyl-N,N′-bis(3-methyl)-1,1′-biphenyl-4,4′-diamine as the hole transporting layer and erbium tris(8-hydroxyquinoline) as the electron conducting and emitting layer.
TL;DR: In this paper, the SF6 plasma treatment of indium tin oxide highly improves the power efficiency and the stability of the organic light-emitting diode based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4phenylenevinylene].
Abstract: SF6 plasma treatment of indium tin oxide highly improves the power efficiency and the stability of the organic light-emitting diode based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4phenylenevinylene]. The treatment leads to a slight reduction in the surface roughness and a decrease in the surface content of Sn. The major effect, however, has to do with the surface incorporation of fluorine. This fluorinated surface improves the hole injection and thus the device performance.