An Organic Light Emitting Diode

7/30/2019 An Organic Light Emitting Diode

1/24

INTRODUCTION

An organic light emitting diode (OLED) is a light-emitting diode (LED) in which the

emissive electroluminescent layer is a film oforganic compoundswhich emit light in response toan electric current. This layer of organic semiconductor material is situated between twoelectrodes. Generally, at least one of these electrodes is transparent.

OLEDs are used intelevisionscreens,computer monitors, small, portable system screenssuch asmobile phonesandPDAs, watches, advertising, information and indication. OLEDs arealso used in light sources for general space illumination and in large-area light-emittingelements. Due to their comparatively early stage of development, they typically emit less lightper unit area than inorganic solid-state based LED point-light sources.

An OLED display functions without a backlight. Thus, it can display deepblack levels

and can also be thinner and lighter than established liquid crystal displays. Similarly, in lowambient light conditions such as dark rooms, an OLED screen can achieve a higher contrast ratiothan an LCDusing eithercold cathode fluorescent lampsor the more recently developedLEDbacklight.

There are two main families of OLEDs: those based upon small molecules and thoseemployingpolymers. Adding mobile ions to an OLED creates aLight-emitting ElectrochemicalCellor LEC, which has a slightly different mode of operation.

OLED displays can use either passive-matrix (PMOLED) or active-matrix addressingschemes. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch

each individual pixel on or off, and can make higher resolution and larger size displays possible.

Demonstration of a flexible OLED device
http://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_semiconductorhttp://en.wikipedia.org/wiki/Organic_semiconductorhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Mobile_phoneshttp://en.wikipedia.org/wiki/Mobile_phoneshttp://en.wikipedia.org/wiki/Mobile_phoneshttp://en.wikipedia.org/wiki/PDAshttp://en.wikipedia.org/wiki/PDAshttp://en.wikipedia.org/wiki/PDAshttp://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/Black_levelhttp://en.wikipedia.org/wiki/Black_levelhttp://en.wikipedia.org/wiki/Black_levelhttp://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Contrast_ratiohttp://en.wikipedia.org/wiki/Contrast_ratiohttp://en.wikipedia.org/wiki/Contrast_ratiohttp://en.wikipedia.org/wiki/LCDhttp://en.wikipedia.org/wiki/LCDhttp://en.wikipedia.org/wiki/Cold_cathodehttp://en.wikipedia.org/wiki/Cold_cathodehttp://en.wikipedia.org/wiki/Cold_cathodehttp://en.wikipedia.org/wiki/LED-backlit_LCD_televisionhttp://en.wikipedia.org/wiki/LED-backlit_LCD_televisionhttp://en.wikipedia.org/wiki/LED-backlit_LCD_televisionhttp://en.wikipedia.org/wiki/LED-backlit_LCD_televisionhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Small_moleculeshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Small_moleculeshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Polymer_light-emitting_diodeshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Polymer_light-emitting_diodeshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Polymer_light-emitting_diodeshttp://en.wikipedia.org/wiki/Light-emitting_Electrochemical_Cellhttp://en.wikipedia.org/wiki/Light-emitting_Electrochemical_Cellhttp://en.wikipedia.org/wiki/Light-emitting_Electrochemical_Cellhttp://en.wikipedia.org/wiki/Light-emitting_Electrochemical_Cellhttp://en.wikipedia.org/wiki/Passive_matrix_addressinghttp://en.wikipedia.org/wiki/Passive_matrix_addressinghttp://en.wikipedia.org/wiki/Active_matrix_addressinghttp://en.wikipedia.org/wiki/Active_matrix_addressinghttp://en.wikipedia.org/wiki/Active-Matrix_OLEDhttp://en.wikipedia.org/wiki/Active-Matrix_OLEDhttp://en.wikipedia.org/wiki/Active-Matrix_OLEDhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/File:OLED_EarlyProduct.JPGhttp://en.wikipedia.org/wiki/File:OLED_EarlyProduct.JPGhttp://en.wikipedia.org/wiki/File:OLED_EarlyProduct.JPGhttp://en.wikipedia.org/wiki/File:OLED_EarlyProduct.JPGhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Active-Matrix_OLEDhttp://en.wikipedia.org/wiki/Active_matrix_addressinghttp://en.wikipedia.org/wiki/Passive_matrix_addressinghttp://en.wikipedia.org/wiki/Light-emitting_Electrochemical_Cellhttp://en.wikipedia.org/wiki/Light-emitting_Electrochemical_Cellhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Polymer_light-emitting_diodeshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#Small_moleculeshttp://en.wikipedia.org/wiki/LED-backlit_LCD_televisionhttp://en.wikipedia.org/wiki/LED-backlit_LCD_televisionhttp://en.wikipedia.org/wiki/Cold_cathodehttp://en.wikipedia.org/wiki/LCDhttp://en.wikipedia.org/wiki/Contrast_ratiohttp://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Black_levelhttp://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/PDAshttp://en.wikipedia.org/wiki/Mobile_phoneshttp://en.wikipedia.org/wiki/Computer_monitorhttp://en.wikipedia.org/wiki/Televisionhttp://en.wikipedia.org/wiki/Organic_semiconductorhttp://en.wikipedia.org/wiki/Organic_compound


2/24

History

The first observations ofelectroluminescencein organic materials were in the early 1950sby A. Bernanose and co-workers at the Nancy-Universit, France. They applied high-voltagealternating current(AC) fields in air to materials such asacridine orange, either deposited on or

dissolved in cellulose or cellophane thin films. The proposed mechanism was either directexcitation of the dye molecules or excitation of electrons.

In 1960, Martin Pope and co-workers at New York University developed ohmic dark-injecting electrode contacts to organic crystals.[6][7][8] They further described the necessaryenergetic requirements (work functions) for hole and electron injecting electrode contacts. Thesecontacts are the basis of charge injection in all modern OLED devices. Pope's group also firstobserved direct current (DC) electroluminescence under vacuum on a pure single crystal ofanthracene and on anthracene crystals doped with tetracene in 1963 using a small area silverelectrode at 400V. The proposed mechanism was field-accelerated electron excitation ofmolecular fluorescence.

Pope's group reported in 1965 that in the absence of an external electric field, theelectroluminescence in anthracene crystals is caused by the recombination of a thermalizedelectron and hole, and that the conducting level of anthracene is higher in energy than the excitonenergy level. Also in 1965, W. Helfrich and W. G. Schneider of theNational Research Councilin Canada produced double injection recombination electroluminescence for the first time in ananthracene single crystal using hole and electron injecting electrodes, the forerunner of moderndouble injection devices. In the same year, Dow Chemical researchers patented a method ofpreparing electroluminescent cells using high voltage (5001500 V) AC-driven (1003000 Hz)electrically-insulated one millimetre thin layers of a melted phosphor consisting of groundanthracene powder, tetracene, and graphite powder. Their proposed mechanism involved

electronic excitation at the contacts between the graphite particles and the anthracene molecules.

Device performance was limited by the poor electrical conductivity of contemporaryorganic materials. However this was overcome by the discovery and development of highlyconductive polymers. For more on the history of such materials, seeconductive polymers.

Electroluminescence from polymer films was first observed by Roger Partridge at theNational Physical Laboratoryin the United Kingdom. The device consisted of a film of poly(n-vinylcarbazole) up to 2.2 micrometres thick located between two charge injecting electrodes. Theresults of the project were patented in 1975 and published in 1983.

The first diode device was reported at Eastman Kodak byChing W. TangandSteven VanSlykein 1987. This device used a novel two-layer structure with separate hole transporting andelectron transporting layers such that recombination and light emission occurred in the middle ofthe organic layer. This resulted in a reduction in operating voltage and improvements inefficiency and led to the current era of OLED research and device production.
http://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Nancy-Universit%C3%A9http://en.wikipedia.org/wiki/Nancy-Universit%C3%A9http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Acridine_orangehttp://en.wikipedia.org/wiki/Acridine_orangehttp://en.wikipedia.org/wiki/Acridine_orangehttp://en.wikipedia.org/wiki/Martin_Popehttp://en.wikipedia.org/wiki/Martin_Popehttp://en.wikipedia.org/wiki/New_York_Universityhttp://en.wikipedia.org/wiki/New_York_Universityhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-5http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-5http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-7http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-7http://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Anthracenehttp://en.wikipedia.org/wiki/Anthracenehttp://en.wikipedia.org/wiki/National_Research_Council_%28Canada%29http://en.wikipedia.org/wiki/National_Research_Council_%28Canada%29http://en.wikipedia.org/wiki/National_Research_Council_%28Canada%29http://en.wikipedia.org/wiki/Dow_Chemicalhttp://en.wikipedia.org/wiki/Dow_Chemicalhttp://en.wikipedia.org/wiki/Conductive_polymershttp://en.wikipedia.org/wiki/Conductive_polymershttp://en.wikipedia.org/wiki/Conductive_polymershttp://en.wikipedia.org/wiki/National_Physical_Laboratory_%28United_Kingdom%29http://en.wikipedia.org/wiki/National_Physical_Laboratory_%28United_Kingdom%29http://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/Steven_Van_Slykehttp://en.wikipedia.org/wiki/Steven_Van_Slykehttp://en.wikipedia.org/wiki/Steven_Van_Slykehttp://en.wikipedia.org/wiki/Steven_Van_Slykehttp://en.wikipedia.org/wiki/Steven_Van_Slykehttp://en.wikipedia.org/wiki/Steven_Van_Slykehttp://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/National_Physical_Laboratory_%28United_Kingdom%29http://en.wikipedia.org/wiki/Conductive_polymershttp://en.wikipedia.org/wiki/Dow_Chemicalhttp://en.wikipedia.org/wiki/National_Research_Council_%28Canada%29http://en.wikipedia.org/wiki/Anthracenehttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-7http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-5http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-5http://en.wikipedia.org/wiki/New_York_Universityhttp://en.wikipedia.org/wiki/Martin_Popehttp://en.wikipedia.org/wiki/Acridine_orangehttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Nancy-Universit%C3%A9http://en.wikipedia.org/wiki/Electroluminescence


3/24

Research into polymer electroluminescence culminated in 1990 with J. H. Burroughes et al. attheCavendish Laboratoryin Cambridge reporting a high efficiency green light-emitting polymerbased device using 100 nm thick films ofpoly(p-phenylene vinylene).

What is OLED?

OLED stands for Organic Light Emitting Diode. The "organic" in OLED refers to organicmaterial. Carbon is the basis of all organic matter. Examples of carbon-based substances includesugar, wood and the majority of plastics. The "LED" stands for "Light Emitting Diode" anddescribes the process of converting electric energy into light. There are two types of OLEDssmall molecule OLED and polymer OLED. Sony uses the small molecule type because it has alonger lifespan.

Working principle

Schematic of a bilayer OLED: 1. Cathode (), 2. Emissive Layer, 3. Emission of radiation, 4.Conductive Layer, 5. Anode (+)

A typical OLED is composed of a layer of organic materials situated between two electrodes, theanode and cathode, all deposited on a substrate. The organic molecules are electricallyconductive as a result ofdelocalizationofpi electronscaused byconjugationover all or part ofthe molecule. These materials have conductivity levels ranging from insulators to conductors,and therefore are considered organic semiconductors. The highest occupied and lowestunoccupied molecular orbitals (HOMO and LUMO) of organic semiconductors are analogous tothevalenceandconductionbands of inorganic semiconductors.

Originally, the most basic polymer OLEDs consisted of a single organic layer. One example wasthe first light-emitting device synthesised by J. H. Burroughes et al., which involved a singlelayer ofpoly(p-phenylene vinylene). However multilayer OLEDs can be fabricated with two ormore layers in order to improve device efficiency. As well as conductive properties, differentmaterials may be chosen to aid charge injection at electrodes by providing a more gradualelectronic profile, or block a charge from reaching the opposite electrode and being wasted.Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layerand an emissive layer.
http://en.wikipedia.org/wiki/Cavendish_Laboratoryhttp://en.wikipedia.org/wiki/Cavendish_Laboratoryhttp://en.wikipedia.org/wiki/Cavendish_Laboratoryhttp://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://www.oled-display.net/http://www.oled-display.net/http://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Substrate_%28materials_science%29http://en.wikipedia.org/wiki/Substrate_%28materials_science%29http://en.wikipedia.org/wiki/Delocalized_electronhttp://en.wikipedia.org/wiki/Delocalized_electronhttp://en.wikipedia.org/wiki/Delocalized_electronhttp://en.wikipedia.org/wiki/Pi_electronshttp://en.wikipedia.org/wiki/Pi_electronshttp://en.wikipedia.org/wiki/Pi_electronshttp://en.wikipedia.org/wiki/Conjugated_systemhttp://en.wikipedia.org/wiki/Conjugated_systemhttp://en.wikipedia.org/wiki/Conjugated_systemhttp://en.wikipedia.org/wiki/Organic_semiconductorhttp://en.wikipedia.org/wiki/Organic_semiconductorhttp://en.wikipedia.org/wiki/HOMO/LUMOhttp://en.wikipedia.org/wiki/HOMO/LUMOhttp://en.wikipedia.org/wiki/HOMO/LUMOhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/File:OLED_schematic.svghttp://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/HOMO/LUMOhttp://en.wikipedia.org/wiki/Organic_semiconductorhttp://en.wikipedia.org/wiki/Conjugated_systemhttp://en.wikipedia.org/wiki/Pi_electronshttp://en.wikipedia.org/wiki/Delocalized_electronhttp://en.wikipedia.org/wiki/Substrate_%28materials_science%29http://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Anodehttp://www.oled-display.net/http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Cavendish_Laboratory


4/24

During operation, a voltage is applied across the OLED such that the anode is positive withrespect to the cathode. A current ofelectronsflows through the device from cathode to anode, aselectrons are injected into the LUMO of the organic layer at the cathode and withdrawn from theHOMO at the anode. This latter process may also be described as the injection ofelectron holesinto the HOMO. Electrostatic forces bring the electrons and the holes towards each other and

they recombine forming anexciton, a bound state of the electron and hole. This happens closer tothe emissive layer, because in organic semiconductors holes are generally more mobile thanelectrons. The decay of this excited state results in a relaxation of the energy levels of theelectron, accompanied by emission of radiation whose frequency is in the visible region. Thefrequency of this radiation depends on theband gapof the material, in this case the difference inenergy between the HOMO and LUMO.

As electrons and holes arefermionswith half integerspin, an exciton may either be in asingletstateor atriplet statedepending on how the spins of the electron and hole have been combined.Statistically three triplet excitons will be formed for each singlet exciton. Decay from tripletstates (phosphorescence) is spin forbidden, increasing the timescale of the transition and limiting

the internal efficiency of fluorescent devices.Phosphorescent organic light-emitting diodesmakeuse ofspinorbit interactionsto facilitateintersystem crossingbetween singlet and triplet states,thus obtaining emission from both singlet and triplet states and improving the internal efficiency.

Indium tin oxide(ITO) is commonly used as the anode material. It is transparent to visible lightand has a high work function which promotes injection of holes into the HOMO level of theorganic layer. A typical conductive layer may consist ofPEDOT:PSSas the HOMO level of thismaterial generally lies between the workfunction of ITO and the HOMO of other commonlyused polymers, reducing the energy barriers for hole injection. Metals such as barium andcalciumare often used for the cathode as they have lowwork functionswhich promote injectionof electrons into the LUMO of the organic layer. Such metals are reactive, so require a cappinglayer ofaluminiumto avoid degradation.

Single carrier devices are typically used to study thekineticsand charge transport mechanisms ofan organic material and can be useful when trying to study energy transfer processes. As currentthrough the device is composed of only one type of charge carrier, either electrons or holes,recombination does not occur and no light is emitted. For example, electron only devices can beobtained by replacing ITO with a lower work function metal which increases the energy barrierof hole injection. Similarly, hole only devices can be made by using a cathode comprised solelyof aluminium, resulting in an energy barrier too large for efficient electron injection.

Generally, An OLED is made by placing a series of organic thin films between two conductors.When electrical current is applied, a bright light is emitted. Here'sKodak's description of OLEDs-

"OLED displays stack up several thin layers of materials. They operate on the attraction betweenpositively and negatively charged particles. When voltage is applied, one layer becomesnegatively charged relative to another transparent layer. As energy passes from the negativelycharged (cathode) layer to the other (anode) layer, it stimulates organic material between the two,which emits light visible through an outermost layer of glass."
http://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Excitonhttp://en.wikipedia.org/wiki/Excitonhttp://en.wikipedia.org/wiki/Excitonhttp://en.wikipedia.org/wiki/Semiconductor_carrier_mobilityhttp://en.wikipedia.org/wiki/Semiconductor_carrier_mobilityhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Fermionhttp://en.wikipedia.org/wiki/Fermionhttp://en.wikipedia.org/wiki/Fermionhttp://en.wikipedia.org/wiki/Spin_%28physics%29http://en.wikipedia.org/wiki/Spin_%28physics%29http://en.wikipedia.org/wiki/Spin_%28physics%29http://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Phosphorescencehttp://en.wikipedia.org/wiki/Phosphorescencehttp://en.wikipedia.org/wiki/Phosphorescencehttp://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Spin%E2%80%93orbit_interactionhttp://en.wikipedia.org/wiki/Spin%E2%80%93orbit_interactionhttp://en.wikipedia.org/wiki/Spin%E2%80%93orbit_interactionhttp://en.wikipedia.org/wiki/Spin%E2%80%93orbit_interactionhttp://en.wikipedia.org/wiki/Spin%E2%80%93orbit_interactionhttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Indium_tin_oxidehttp://en.wikipedia.org/wiki/Indium_tin_oxidehttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/PEDOT:PSShttp://en.wikipedia.org/wiki/PEDOT:PSShttp://en.wikipedia.org/wiki/PEDOT:PSShttp://en.wikipedia.org/wiki/Bariumhttp://en.wikipedia.org/wiki/Bariumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Chemical_kineticshttp://en.wikipedia.org/wiki/Chemical_kineticshttp://en.wikipedia.org/wiki/Chemical_kineticshttp://www.kodak.com/http://www.kodak.com/http://www.kodak.com/http://www.kodak.com/http://en.wikipedia.org/wiki/Chemical_kineticshttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Bariumhttp://en.wikipedia.org/wiki/PEDOT:PSShttp://en.wikipedia.org/wiki/Work_functionhttp://en.wikipedia.org/wiki/Indium_tin_oxidehttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Spin%E2%80%93orbit_interactionhttp://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Phosphorescencehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Spin_%28physics%29http://en.wikipedia.org/wiki/Fermionhttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Visible_spectrumhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Semiconductor_carrier_mobilityhttp://en.wikipedia.org/wiki/Excitonhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Electron


5/24

How is color created?

OLED has more control over color expression because it only expresses pure colors when anelectric Current stimulates the relevant Pixels. The OLED primary color matrix is arranged inred, green, and blue Pixels, which are mounted directly to a printed circuit board. Each

individual OLED element is housed in a special "micro-cavity" structure designed to greatlyreduce ambient light interference that also works to improve overall color Contrast.The thicknessof the organic Layer is adjusted to produce the strongest light for each of the colors " red, greenand blue - used to render the color picture. The three colors are further refined by a color filter,which purifies each color without the need for a polarizer, rendering outstanding color purity.

Material technologies

Small molecules

Alq3, commonly used in small molecule OLEDs.

Efficient OLEDs using small molecules were first developed by Dr. Ching W. Tanget al.[19]atEastman Kodak. The term OLED traditionally refers specifically to this type of device, though

the term SM-OLED is also in use.

Molecules commonly used in OLEDs include organometallicchelates(for exampleAlq3, used inthe organic light-emitting device reported by Tang et al.), fluorescent and phosphorescent dyesand conjugateddendrimers. A number of materials are used for their charge transport properties,for example triphenylamineand derivatives are commonly used as materials for hole transportlayers. Fluorescent dyes can be chosen to obtain light emission at different wavelengths, andcompounds such asperylene,rubreneandquinacridonederivatives are often used. Alq3 has beenused as a green emitter, electron transport material and as a host for yellow and red emittingdyes.

The production of small molecule devices and displays usually involvesthermal evaporationin avacuum. This makes the production process more expensive and of limited use for large-areadevices than other processing techniques. However, contrary to polymer-based devices, thevacuum deposition process enables the formation of well controlled, homogeneous films, and theconstruction of very complex multi-layer structures. This high flexibility in layer design,enabling distinct charge transport and charge blocking layers to be formed, is the main reason forthe high efficiencies of the small molecule OLEDs.
http://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-ApplPhy87-18http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-ApplPhy87-18http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-ApplPhy87-18http://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/Chelationhttp://en.wikipedia.org/wiki/Chelationhttp://en.wikipedia.org/wiki/Chelationhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Dendrimerhttp://en.wikipedia.org/wiki/Dendrimerhttp://en.wikipedia.org/wiki/Dendrimerhttp://en.wikipedia.org/wiki/Triphenylaminehttp://en.wikipedia.org/wiki/Triphenylaminehttp://en.wikipedia.org/wiki/Triphenylaminehttp://en.wikipedia.org/wiki/Perylenehttp://en.wikipedia.org/wiki/Perylenehttp://en.wikipedia.org/wiki/Perylenehttp://en.wikipedia.org/wiki/Rubrenehttp://en.wikipedia.org/wiki/Rubrenehttp://en.wikipedia.org/wiki/Rubrenehttp://en.wikipedia.org/wiki/Quinacridonehttp://en.wikipedia.org/wiki/Quinacridonehttp://en.wikipedia.org/wiki/Quinacridonehttp://en.wikipedia.org/wiki/Evaporation_%28deposition%29http://en.wikipedia.org/wiki/Evaporation_%28deposition%29http://en.wikipedia.org/wiki/Evaporation_%28deposition%29http://en.wikipedia.org/wiki/File:AlumQ3.pnghttp://en.wikipedia.org/wiki/File:AlumQ3.pnghttp://en.wikipedia.org/wiki/File:AlumQ3.pnghttp://en.wikipedia.org/wiki/File:AlumQ3.pnghttp://en.wikipedia.org/wiki/Evaporation_%28deposition%29http://en.wikipedia.org/wiki/Quinacridonehttp://en.wikipedia.org/wiki/Rubrenehttp://en.wikipedia.org/wiki/Perylenehttp://en.wikipedia.org/wiki/Triphenylaminehttp://en.wikipedia.org/wiki/Dendrimerhttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminiumhttp://en.wikipedia.org/wiki/Chelationhttp://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-ApplPhy87-18http://en.wikipedia.org/wiki/Ching_W._Tanghttp://en.wikipedia.org/wiki/Tris%288-hydroxyquinolinato%29aluminium


6/24

Coherent emission from a laser dye-doped tandem SM-OLED device, excited in the pulsedregime, has been demonstrated. The emission is nearly diffraction limited with a spectral widthsimilar to that of broadband dye lasers.

Polymer light-emitting diodes

poly(p-phenylene vinylene), used in the first PLED.[20]

Polymer light-emitting diodes (PLED), also light-emitting polymers (LEP), involve an

electroluminescentconductive polymer that emits lightwhen connected to an external voltage.They are used as athin filmforfull-spectrumcolour displays. Polymer OLEDs are quite efficientand require a relatively small amount of power for the amount of light produced.

Vacuum deposition is not a suitable method for forming thin films of polymers. However,polymers can be processed in solution, andspin coatingis a common method of depositing thinpolymer films. This method is more suited to forming large-area films than thermal evaporation.No vacuum is required, and the emissive materials can also be applied on the substrate by atechnique derived from commercial inkjet printing.[32][33] However, as the application ofsubsequent layers tends to dissolve those already present, formation of multilayer structures isdifficult with these methods. The metal cathode may still need to be deposited by thermal

evaporation in vacuum.

Typical polymers used in PLED displays include derivatives of poly(p-phenylene vinylene)andpolyfluorene.Substitutionof side chains onto the polymer backbone may determine the colour ofemitted light[34] or the stability and solubility of the polymer for performance and ease ofprocessing.[35]

While unsubstituted poly(p-phenylene vinylene) (PPV) is typically insoluble, a number of PPVsand related poly(naphthalene vinylene)s (PNVs) that are soluble in organic solvents or waterhave been prepared viaring opening metathesis polymerization.
http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-b-19http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-b-19http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-b-19http://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Conductive_polymerhttp://en.wikipedia.org/wiki/Conductive_polymerhttp://en.wikipedia.org/wiki/Conductive_polymerhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Thin_filmhttp://en.wikipedia.org/wiki/Thin_filmhttp://en.wikipedia.org/wiki/Thin_filmhttp://en.wikipedia.org/wiki/Full-spectrumhttp://en.wikipedia.org/wiki/Full-spectrumhttp://en.wikipedia.org/wiki/Full-spectrumhttp://en.wikipedia.org/wiki/Spin_coatinghttp://en.wikipedia.org/wiki/Spin_coatinghttp://en.wikipedia.org/wiki/Spin_coatinghttp://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Inkjet_printerhttp://en.wikipedia.org/wiki/Inkjet_printerhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-31http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-31http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-31http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Polyfluorenehttp://en.wikipedia.org/wiki/Polyfluorenehttp://en.wikipedia.org/wiki/Substitution_reactionhttp://en.wikipedia.org/wiki/Substitution_reactionhttp://en.wikipedia.org/wiki/Substitution_reactionhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-33http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-33http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-33http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-33http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-34http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-34http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-34http://en.wikipedia.org/wiki/Ring_opening_metathesis_polymerizationhttp://en.wikipedia.org/wiki/Ring_opening_metathesis_polymerizationhttp://en.wikipedia.org/wiki/Ring_opening_metathesis_polymerizationhttp://en.wikipedia.org/wiki/File:Polyphenylene_vinylene.pnghttp://en.wikipedia.org/wiki/File:Polyphenylene_vinylene.pnghttp://en.wikipedia.org/wiki/File:Polyphenylene_vinylene.pnghttp://en.wikipedia.org/wiki/File:Polyphenylene_vinylene.pnghttp://en.wikipedia.org/wiki/Ring_opening_metathesis_polymerizationhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-34http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-33http://en.wikipedia.org/wiki/Substitution_reactionhttp://en.wikipedia.org/wiki/Polyfluorenehttp://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-31http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-31http://en.wikipedia.org/wiki/Inkjet_printerhttp://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Spin_coatinghttp://en.wikipedia.org/wiki/Full-spectrumhttp://en.wikipedia.org/wiki/Thin_filmhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Conductive_polymerhttp://en.wikipedia.org/wiki/Electroluminescencehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-b-19http://en.wikipedia.org/wiki/Poly%28p-phenylene_vinylene%29


7/24

Phosphorescent materials

Ir(mppy)3, a phosphorescent dopant which emits green light.[39]

Main article:Phosphorescent organic light-emitting diode

Phosphorescent organic light emitting diodes use the principle of electrophosphorescence toconvert electrical energy in an OLED into light in a highly efficient manner,[40][41] with theinternal quantum efficiencies of such devices approaching 100%.[42]

Typically, a polymer such as poly(n-vinylcarbazole) is used as a host material to which anorganometallic complex is added as a dopant. Iridium complexes[41] such as Ir(mppy)3

[39] arecurrently the focus of research, although complexes based on other heavy metals such asplatinum[40]have also been used.

The heavy metal atom at the centre of these complexes exhibits strong spin-orbit coupling,facilitatingintersystem crossingbetweensingletandtripletstates. By using these phosphorescentmaterials, both singlet and triplet excitons will be able to decay radiatively, hence improving theinternal quantum efficiency of the device compared to a standard PLED where only the singletstates will contribute to emission of light.

Applications of OLEDs in solid state lighting require the achievement of high brightness withgoodCIE coordinates(for white emission). The use of macromolecular species like polyhedraloligomeric silsesquioxanes (POSS) in conjunction with the use of phosphorescent species suchas Ir for printed OLEDs have exhibited brightnesses as high as 10,000 cd/m 2.[43]

AMOLED vs PMOLED

These terms relate to the driving method of the OLED display. With Passive-Matrix (PMOLED),one controls the display by switching a certain row and column - in effect lighting the pixel at theintersection. The pixels are turned on and off quickly, and the sequence creates the image. WithActive-Matrix (AMOLEDs)one controls each pixel directly. Passive-Matrix OLEDs are easy andcheap to make, but has a high power consumption and only allow for small sized displays (up to3", typically). Making larger and more efficient displays require the use of AMOLEDs butthese are more expansive to make.

So if you're looking for a TV, it'll probably be an AMOLED TV.PMOLEDsare used in mp3players, secondary displays on cell phones, etc.
http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-41http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-41http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-41http://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/Coordination_complexhttp://en.wikipedia.org/wiki/Coordination_complexhttp://en.wikipedia.org/wiki/Organoiridium_compoundhttp://en.wikipedia.org/wiki/Organoiridium_compoundhttp://en.wikipedia.org/wiki/Organoiridium_compoundhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/CIE_1931_color_spacehttp://en.wikipedia.org/wiki/CIE_1931_color_spacehttp://en.wikipedia.org/wiki/CIE_1931_color_spacehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-42http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-42http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-42http://www.oled-info.com/pmoledhttp://www.oled-info.com/pmoledhttp://www.oled-info.com/pmoledhttp://www.oled-info.com/amoledhttp://www.oled-info.com/amoledhttp://www.oled-info.com/amoledhttp://www.oled-info.com/oled-tvhttp://www.oled-info.com/oled-tvhttp://www.oled-info.com/pmoledhttp://www.oled-info.com/pmoledhttp://www.oled-info.com/pmoledhttp://en.wikipedia.org/wiki/File:Ir(mppy)3.pnghttp://www.oled-info.com/pmoledhttp://www.oled-info.com/oled-tvhttp://www.oled-info.com/amoledhttp://www.oled-info.com/pmoledhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-42http://en.wikipedia.org/wiki/CIE_1931_color_spacehttp://en.wikipedia.org/wiki/Triplet_statehttp://en.wikipedia.org/wiki/Singlet_statehttp://en.wikipedia.org/wiki/Intersystem_crossinghttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38http://en.wikipedia.org/wiki/Organoiridium_compoundhttp://en.wikipedia.org/wiki/Organoiridium_compoundhttp://en.wikipedia.org/wiki/Coordination_complexhttp://en.wikipedia.org/wiki/N-Vinylcarbazolehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-41http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-baldo-39http://en.wikipedia.org/wiki/Phosphorescent_organic_light-emitting_diodehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-yang-38


8/24

Small molecules vs Polymer-based OLEDs

OLED materials can be divided into small- and large- molecules. 'Small Molecules' OLEDs aremore common today, with most displays using those kind of materials. Large Molecules (alsocalledPolymer-based OLEDs, or P-OLEDs) are lagging behind in lifetime and efficiency specs.

P-OLEDsmight be easier to make, though, because they are more easily adapted for printing.Indeed, one can 'ink-jet-print' an OLED, which is a great way to make them.

Fluorescent vs Phosphorescent OLEDs

OLEDs can also be classified based on another property of the material whether it isfluorescent or phosphorescent (PHOLEDs). Originally fluorescent OLEDs were used, butPHOLEDs promise to deliver much more efficient displays.

The major company behind PHOLEDs is Universal-Display. They have recently stated that"virtually all" AMOLEDs use their technology - although only their red material is currently

used (the other colors are fluorescent).

Device Architectures

Structure

Bottom or top emission: Bottom emission devices use a transparent or semi-transparentbottom electrode to get the light through a transparent substrate. Top emission devicesuse a transparent or semi-transparent top electrode emitting light directly. Top-emittingOLEDs are better suited for active-matrix applications as they can be more easily

integrated with a non-transparent transistor backplane.

Transparent OLEDs use transparent or semi-transparent contacts on both sides of thedevice to create displays that can be made to be both top and bottom emitting(transparent). TOLEDs can greatly improve contrast, making it much easier to viewdisplays in bright sunlight.[46]This technology can be used in Head-up displays, smartwindows or augmented reality applications. Novaled's[47] OLED panel presented inFinetech Japan 2010, boasts a transparency of 60-70%.

Stacked OLEDs use a pixel architecture that stacks the red, green, and blue subpixels ontop of one another instead of next to one another, leading to substantial increase in gamut

and color depth, and greatly reducing pixel gap. Currently, other display technologieshave the RGB (and RGBW) pixels mapped next to each other decreasing potentialresolution.

Inverted OLED: In contrast to a conventional OLED, in which the anode is placed onthe substrate, an Inverted OLED uses a bottom cathode that can be connected to the drainend of an n-channel TFT especially for the low cost amorphous siliconTFT backplaneuseful in the manufacturing ofAMOLEDdisplays.[48]
http://www.oled-info.com/p-oledhttp://www.oled-info.com/p-oledhttp://www.oled-info.com/p-oledhttp://www.oled-info.com/p-oledhttp://www.oled-info.com/p-oledhttp://www.oled-info.com/universal_display_udchttp://www.oled-info.com/universal_display_udchttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-45http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-45http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-45http://en.wikipedia.org/wiki/Head-up_displayhttp://en.wikipedia.org/wiki/Head-up_displayhttp://en.wikipedia.org/wiki/Augmented_realityhttp://en.wikipedia.org/wiki/Augmented_realityhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-46http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-46http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-46http://en.wikipedia.org/wiki/Amorphous_siliconhttp://en.wikipedia.org/wiki/Amorphous_siliconhttp://en.wikipedia.org/wiki/Amorphous_siliconhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-47http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-47http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-47http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-47http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Amorphous_siliconhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-46http://en.wikipedia.org/wiki/Augmented_realityhttp://en.wikipedia.org/wiki/Head-up_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-45http://www.oled-info.com/universal_display_udchttp://www.oled-info.com/p-oledhttp://www.oled-info.com/p-oled


9/24

Organic light emitting diodes consist of stacks of organic layers (thickness about 100

nm), which are inserted between a cathode and an anode. Usually, the substrate is glasscoated with a transparent conductive oxide being the anode, followed by the organicstack, consisting of hole transport and electron transport materials, followed

by the inorganic cathode. Key advantages of the organic luminescence are the chemicalvariability of the organic light-emitting diodes, allowing virtually any color includingwhite, and the thin film system, allowing large-area and low-cost deposition, and thepossibility to use thin and even flexible substrates to realize a novel class of lighting anddisplay solutions not possible for other technologies.In the OLED technology, two different material groups have to be distinguished: OLEDmaterials with low molecular weight called small-molecule (SM) OLED. SM-OLEDwere first introduced by the research group led by Dr. Ching Tang at the KodakLaboratories in 1987. The deposition of SM-OLEDs is based on vacuum thermalevaporation. Polymer based OLED (PLEDs) are based on long polymer organic chainsand are deposited by spin-cast or ink-jet principles.

OLED-Manufacturing Process:

LCD-TFT Manufacturing Process:


10/24

So we can see that the manufacturing process of OLED is very simple against to TFT-LCDGraphics from CMELLook at this amazing Video from CNET! Interview with vice president of Universaldisplay about the future of OLED-Displays. You see how Universal Display is workingon OLED technology:

Many electronic appliances are at the threshold of a revolution that began with thediscovery of polymeric conductors in the 1970s. Polymeric materials, which havehistorically been classified exclusively as electrical insulators, are now finding variedapplications as both conductors and semiconductors. Expensive ceramic semiconductors

that are brittle and difficult to pattern have historically been the driving force of thedigital age for the last fifty years. But now a combination of properties exist today inpolymers that are making many previously impossible appliances a reality.

Within a very short time organic conductors have been developed with the conductivityof metals such as copper, while organic electronics has evolved photoelectric cells,diodes, light emitting diodes, lasers and transistors. The result is that a class of plasticmaterials referred to as conjugated polymers are fast displacing traditional materials suchas natural polymers (e.g. wood), metals, ceramics and glass in many applications owingto the combination of their physical/mechanical properties (light weight combined withphysical strength) and ease of processibility (the ability to mould the shape of plasticmaterials or extrude into sheet and rod through a die).

What this means is that OLEDs can be deployed in a wide range of electronic devices andcan be used extensively throughout any given device. Active components of displays canbe polymers, substrates can be polymers, logical electronics can be polymers, and so on.In the years ahead OLEDs will see applications in personal computers, cell phones,televisions, general wide area lighting, signs, billboards, communications and any of anumber of information appliances.

The basic OLED cell structure consists of a stack of thin organic layers sandwichedbetween a transparent anode and a metallic cathode. The organic layers comprise a hole-
http://www.cmel.com.tw/CMELWEB_EN/004.asphttp://www.cmel.com.tw/CMELWEB_EN/004.asp


11/24

injection layer, a hole-transport layer, an emissive layer and an electron-transport layer.When an appropriate voltage (typically a few volts) is applied to the cell, the injectedpositive and negative charges recombine in the emissive layer to produce light(electroluminescence). The structure of the organic layers and the choice of anode andcathode are designed to maximise the recombination process in the emissive layer, thus

maximising the light output from the OLED device. Both the electroluminescentefficiency and control of colour output can be significantly enhanced by "doping" theemissive layer with a small amount of highly fluorescent molecules.AM OLED = Active Matrix OLED deviceFOLED = Flexible Organic Light Emitting Diode (UDC)OLED = Organic Light Emitting Diode/Device/DisplayPhOLED = Phosphorescent Oragnic Light Emitting Diode (UDC)PLED = Polymer Light Emitting Diode (CDT)PMOLED = Passive Matrix OLED devicePOLED = Polymer Oragnic Light Emitting Diode (CDT)RCOLED = Resonant Coloe Oragnic Light Emitting Diode

SmOLED = Small Molecule Ogranic Light Emitting Diode (Kodak)SOLED = Stacked Oragnic Light Emitting Diode (UDC)TOLED = Transparent Oragnic Light Emitting Diode (UDC)

Patterning technologies

Patternable organic light-emitting devices use a light or heat activated electroactive layer. Alatent material (PEDOT-TMA) is included in this layer that, upon activation, becomes highlyefficient as a hole injection layer. Using this process, light-emitting devices with arbitrary

patterns can be prepared.

Colour patterning can be accomplished by means of laser, such as radiation-induced sublimationtransfer (RIST).

Organic vapour jet printing (OVJP) uses an inert carrier gas, such as argon or nitrogen, totransport evaporated organic molecules (as in Organic Vapor Phase Deposition). The gas isexpelled through a micron sized nozzle or nozzle array close to the substrate as it is beingtranslated. This allows printing arbitrary multilayer patterns without the use of solvents.

Conventional OLED displays are formed by vapor thermal evaporation (VTE) and are patterned

by shadow-mask. A mechanical mask has openings allowing the vapor to pass only on thedesired location.

Backplane technologies

For a high resolution display like a TV, a TFT backplane is necessary to drive the pixelscorrectly. Currently, Low TemperaturePolycrystalline siliconLTPS-TFTis used for commercialAMOLED displays. LTPS-TFT has variation of the performance in a display, so various
http://en.wikipedia.org/wiki/PEDOT-TMAhttp://en.wikipedia.org/wiki/PEDOT-TMAhttp://en.wikipedia.org/wiki/PEDOT-TMAhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Polycrystalline_siliconhttp://en.wikipedia.org/wiki/Polycrystalline_siliconhttp://en.wikipedia.org/wiki/Polycrystalline_siliconhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Polycrystalline_siliconhttp://en.wikipedia.org/wiki/Thin-film_transistorhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/PEDOT-TMA


12/24

compensation circuits have been reported. Due to the size limitation of theexcimer laserused forLTPS, the AMOLED size was limited. To cope with the hurdle related to the panel size,amorphous-silicon/microcrystalline-silicon backplanes have been reported with large displayprototype demonstrations.

Advantages

Demonstration of a 4.1" prototypeflexibledisplay from Sony

The different manufacturing process of OLEDs lends itself to several advantages over flat-paneldisplays made with LCD technology.

Lower cost in the future: OLEDs can be printed onto any suitablesubstrateby an inkjetprinter or even by screen printing, theoretically making them cheaper to produce thanLCD orplasma displays. However, fabrication of the OLED substrate is more costly thanthat of a TFT LCD, until mass production methods lower cost through scaleability.

Light weight & flexible plastic substrates: OLED displays can be fabricated on flexibleplastic substrates leading to the possibility ofOrganic light-emitting diode roll-up display

being fabricated or other new applications such asroll-up displaysembedded in fabrics orclothing. As the substrate used can be flexible such as PET., the displays may beproduced inexpensively.

Wider viewing angles & improved brightness: OLEDs can enable a greater artificialcontrast ratio (both dynamic range and static, measured in purely dark conditions) andviewing angle compared to LCDs because OLED pixels directly emit light. OLED pixelcolours appear correct and unshifted, even as the viewing angle approaches 90 degreesfromnormal.

Better power efficiency: LCDs filter the light emitted from abacklight, allowing a smallfraction of light through so they cannot show true black, while an inactive OLED elementdoes not produce light or consume power.[54]

Response time: OLEDs can also have a faster response time than standard LCD screens.Whereas LCD displays are capable of a 1 ms response time or less[55]offering a framerate of 1,000 Hz or higher, an OLED can theoretically have less than 0.01 ms responsetime enabling 100,000 Hzrefresh rates.
http://en.wikipedia.org/wiki/Excimer_laserhttp://en.wikipedia.org/wiki/Excimer_laserhttp://en.wikipedia.org/wiki/Excimer_laserhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Rollable_displayhttp://en.wikipedia.org/wiki/Rollable_displayhttp://en.wikipedia.org/wiki/Rollable_displayhttp://en.wikipedia.org/wiki/Flexible_substratehttp://en.wikipedia.org/wiki/Flexible_substratehttp://en.wikipedia.org/wiki/Polyethylene_terephthalatehttp://en.wikipedia.org/wiki/Polyethylene_terephthalatehttp://en.wikipedia.org/wiki/Surface_normalhttp://en.wikipedia.org/wiki/Surface_normalhttp://en.wikipedia.org/wiki/Surface_normalhttp://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-53http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-53http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-53http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-54http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-54http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-54http://en.wikipedia.org/wiki/Refresh_ratehttp://en.wikipedia.org/wiki/Refresh_ratehttp://en.wikipedia.org/wiki/Refresh_ratehttp://en.wikipedia.org/wiki/File:Ecran_oled_flexible.jpghttp://en.wikipedia.org/wiki/Refresh_ratehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-54http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-53http://en.wikipedia.org/wiki/Backlighthttp://en.wikipedia.org/wiki/Surface_normalhttp://en.wikipedia.org/wiki/Polyethylene_terephthalatehttp://en.wikipedia.org/wiki/Flexible_substratehttp://en.wikipedia.org/wiki/Rollable_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Substrate_%28printing%29http://en.wikipedia.org/wiki/Organic_light-emitting_diode_roll-up_displayhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Excimer_laser


13/24

Disadvantages

LEP display showing partial failure

An old OLEDdisplay showing wear

Lifespan: The biggest technical problem for OLEDs was the limited lifetime of theorganic materials.[56]In particular, blue OLEDs historically have had a lifetime of around14,000 hours to half original brightness (five years at 8 hours a day) when used for flat-panel displays. This is lower than the typical lifetime of LCD, LED orPDPtechnologyeach currently rated for about 25,000 - 40,000 hours to half brightness, depending onmanufacturer and model. However, some manufacturers' displays aim to increase thelifespan of OLED displays, pushing their expected life past that of LCD displays byimproving light outcoupling, thus achieving the same brightness at a lower drive current.In 2007, experimental OLEDs were created which can sustain 400 cd/m2 of luminancefor over 198,000 hours for green OLEDs and 62,000 hours for blue OLEDs.

Color balance issues: Additionally, as the OLED material used to produce blue lightdegrades significantly more rapidly than the materials that produce other colors, bluelight output will decrease relative to the other colors of light. This differential coloroutput change will change the color balance of the display and is much more noticeablethan a decrease in overall luminance.[62]This can be partially avoided by adjusting colourbalance but this may require advanced control circuits and interaction with the user,which is unacceptable for some users. In order to delay the problem, manufacturers biasthe colour balance towards blue so that the display initially has an artificially blue tint,
http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-55http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-55http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-55http://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Luminancehttp://en.wikipedia.org/wiki/Luminancehttp://en.wikipedia.org/wiki/Luminancehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-61http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-61http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-61http://en.wikipedia.org/wiki/File:Oled_display_alterung.jpghttp://en.wikipedia.org/wiki/File:Light_Emitting_Polymer_display_partially_failed.jpghttp://en.wikipedia.org/wiki/File:Oled_display_alterung.jpghttp://en.wikipedia.org/wiki/File:Light_Emitting_Polymer_display_partially_failed.jpghttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-61http://en.wikipedia.org/wiki/Luminancehttp://en.wikipedia.org/wiki/Plasma_displayhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-55


14/24

leading to complaints of artificial-looking, over-saturated colors. More commonly,though, manufacturers optimize the size of the R, G and B subpixels to reduce the currentdensity through the subpixel in order to equalize lifetime at full luminance. For example,a blue subpixel may be 100% larger than the green subpixel. The red subpixel may be10% smaller than the green.

Efficiency of blue OLEDs: Improvements to the efficiency and lifetime of blue OLEDsis vital to the success of OLEDs as replacements for LCD technology. Considerableresearch has been invested in developing blue OLEDs with high external quantumefficiency as well as a deeper blue color.[63][64] External quantum efficiency values of20% and 19% have been reported for red (625 nm) and green (530 nm) diodes,respectively.[65][66] However, blue diodes (430 nm) have only been able to achievemaximum external quantum efficiencies in the range between 4% to 6%.[67]

Water damage: Water can damage the organic materials of the displays. Therefore,improved sealing processes are important for practical manufacturing. Water damage

may especially limit the longevity of more flexible displays.

[68]

Outdoor performance: As an emissive display technology, OLEDs rely completely

upon converting electricity to light, unlike most LCDs which are to some extentreflective; e-ink leads the way in efficiency with ~ 33% ambient light reflectivity,enabling the display to be used without any internal light source. The metallic cathode inan OLED acts as a mirror, with reflectance approaching 80%, leading to poor readabilityin bright ambient light such as outdoors. However, with the proper application of acircular polarizer and anti-reflective coatings, the diffuse reflectance can be reduced toless than 0.1%. With 10,000fcincident illumination (typical test condition for simulatingoutdoor illumination), that yields an approximate photopic contrast of 5:1.

Power consumption: While an OLED will consume around 40% of the power of anLCD displaying an image which is primarily black, for the majority of images it willconsume 6080% of the power of an LCD - however it can use over three times as muchpower to display an image with a white background[69] such as a document or website.This can lead to disappointing real-world battery life in mobile devices.

Screen burn-in: Unlike displays with a common light source, the brightness of eachOLED pixel fades depending on the content displayed. The varied lifespan of the organicdyes can cause a discrepancy between red, green, and blue intensity. This leads to imagepersistence, also known asburn-in.[70]

UV sensitivity: OLED displays can be damaged by prolonged exposure to UV light. Themost pronounced example of this can be seen with a near UV laser (such as a Bluraypointer) and can damage the display almost instantly with more than 20mW leading todim or dead spots where the beam is focussed. This is usually avoided by installing a UVblocking filter over the panel and this can easily be seen as a clear plastic layer on theglass. Removal of this filter can lead to severe damage and an unusable display after onlya few months of room light exposure.
http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-62http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-62http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-62http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-64http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-64http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-64http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-66http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-66http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-66http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-67http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-67http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-67http://en.wikipedia.org/wiki/E-inkhttp://en.wikipedia.org/wiki/E-inkhttp://en.wikipedia.org/wiki/Foot-candlehttp://en.wikipedia.org/wiki/Foot-candlehttp://en.wikipedia.org/wiki/Foot-candlehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-68http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-68http://en.wikipedia.org/wiki/Screen_burn-inhttp://en.wikipedia.org/wiki/Screen_burn-inhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-69http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-69http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-69http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-69http://en.wikipedia.org/wiki/Screen_burn-inhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-68http://en.wikipedia.org/wiki/Foot-candlehttp://en.wikipedia.org/wiki/E-inkhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-67http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-66http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-64http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-64http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-62http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-62


15/24

Manufacturers and Commercial Uses

Magnified image of theAMOLEDscreen on the GoogleNexus Onesmartphone using theRGBG system of thePenTile Matrix Family.

A 3.8 cm (1.5 in) OLED display from a CreativeZEN Vmedia playerOLED technology is used in commercial applications such as displays for mobile phones andportable digital media players, car radios and digital cameras among others. Such portableapplications favor the high light output of OLEDs for readability in sunlight and their low powerdrain. Portable displays are also used intermittently, so the lower lifespan of organic displays isless of an issue. Prototypes have been made of flexible and rollable displays which use OLEDs'unique characteristics. Applications in flexible signs and lighting are also being developed.[71]PhilipsLighting have made OLED lighting samples under the brand name 'Lumiblade' availableonline.[72]

OLEDs have been used in most Motorola and Samsung colour cell phones, as well as someHTC, LG and Sony Ericsson models.[73] Nokia has also recently introduced some OLEDproducts including the N85 and the N86 8MP, both of which feature an AMOLED display.OLED technology can also be found in digital media players such as the Creative ZEN V, theiriver clix, theZune HDand the SonyWalkman X Series.

TheGoogleand HTCNexus Onesmartphone includes anAMOLEDscreen, as does HTC's ownDesireandLegendphones. However due to supply shortages of the Samsung-produced displays,
http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/PenTile_Matrix_Familyhttp://en.wikipedia.org/wiki/PenTile_Matrix_Familyhttp://en.wikipedia.org/wiki/PenTile_Matrix_Familyhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/Digital_media_playerhttp://en.wikipedia.org/wiki/Digital_media_playerhttp://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-70http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-70http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-70http://en.wikipedia.org/wiki/Philipshttp://en.wikipedia.org/wiki/Philipshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-71http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-71http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-71http://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/HTC_Corporationhttp://en.wikipedia.org/wiki/HTC_Corporationhttp://en.wikipedia.org/wiki/LGhttp://en.wikipedia.org/wiki/LGhttp://en.wikipedia.org/wiki/Sony_Ericssonhttp://en.wikipedia.org/wiki/Sony_Ericssonhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-cellphone-72http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-cellphone-72http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-cellphone-72http://en.wikipedia.org/wiki/Nokiahttp://en.wikipedia.org/wiki/Nokiahttp://en.wikipedia.org/wiki/Nokia_N85http://en.wikipedia.org/wiki/Nokia_N85http://en.wikipedia.org/wiki/Nokia_N86_8MPhttp://en.wikipedia.org/wiki/Nokia_N86_8MPhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/Iriver_clixhttp://en.wikipedia.org/wiki/Iriver_clixhttp://en.wikipedia.org/wiki/Zune_HDhttp://en.wikipedia.org/wiki/Zune_HDhttp://en.wikipedia.org/wiki/Zune_HDhttp://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Googlehttp://en.wikipedia.org/wiki/Googlehttp://en.wikipedia.org/wiki/Googlehttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/HTC_Desirehttp://en.wikipedia.org/wiki/HTC_Desirehttp://en.wikipedia.org/wiki/HTC_Legendhttp://en.wikipedia.org/wiki/HTC_Legendhttp://en.wikipedia.org/wiki/HTC_Legendhttp://en.wikipedia.org/wiki/File:OLEDScreen.jpghttp://en.wikipedia.org/wiki/File:Nexus_one_screen_microscope.jpghttp://en.wikipedia.org/wiki/File:OLEDScreen.jpghttp://en.wikipedia.org/wiki/File:Nexus_one_screen_microscope.jpghttp://en.wikipedia.org/wiki/HTC_Legendhttp://en.wikipedia.org/wiki/HTC_Desirehttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/Googlehttp://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Zune_HDhttp://en.wikipedia.org/wiki/Iriver_clixhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Nokia_N86_8MPhttp://en.wikipedia.org/wiki/Nokia_N85http://en.wikipedia.org/wiki/Nokiahttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-cellphone-72http://en.wikipedia.org/wiki/Sony_Ericssonhttp://en.wikipedia.org/wiki/LGhttp://en.wikipedia.org/wiki/HTC_Corporationhttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/Motorolahttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-71http://en.wikipedia.org/wiki/Philipshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-70http://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Digital_media_playerhttp://en.wikipedia.org/wiki/ZEN_Vhttp://en.wikipedia.org/wiki/PenTile_Matrix_Familyhttp://en.wikipedia.org/wiki/Nexus_Onehttp://en.wikipedia.org/wiki/AMOLED


16/24

certain HTC models will use Sony's SLCD displays in the future,[74] while the Google andSamsungNexus Ssmartphone will use "Super Clear LCD" instead in some countries.[75]

Other manufacturers of OLED panels include Anwell Technologies Limited, Chi MeiCorporation,[77]LG,[78]and others.[79]

DuPontstated in a press release in May 2010 that they can produce a 50-inch OLED TV in twominutes with a new printing technology. If this can be scaled up in terms of manufacturing, thenthe total cost of OLED TVs would be greatly reduced. Dupont also states that OLED TVs madewith this less expensive technology can last up to 15 years if left on for a normal eight hourday.[80][81]

Handheld computer manufacturer OQO introduced the smallest Windows netbook computer,including an OLED display, in 2009.[82]

The use of OLEDs may be subject topatentsheld byEastman Kodak,DuPont,General Electric,

Royal Philips Electronics, numerous universities and others.

[83]

There are by now literallythousands of patents associated with OLEDs, both from larger corporations and smallertechnology companies[1].

Samsung applications

By 2004 Samsung, South Korea's largest conglomerate, was the world's largest OLEDmanufacturer, producing 40% of the OLED displays made in the world,[84]and as of 2010 has a98% share of the globalAMOLEDmarket.[85]The company is leading the world OLED industry,generating $100.2 million out of the total $475 million revenues in the global OLED market in2006.[86]As of 2006, it held more than 600 American patents and more than 2800 international

patents, making it the largest owner ofAMOLEDtechnology patents.

[86]

Samsung SDI announced in 2005 the world's largest OLED TV at the time, at 21 inches (53cm).[87]This OLED featured the highest resolution at the time, of 6.22 million pixels. In addition,the company adopted active matrix based technology for its low power consumption and high-resolution qualities. This was exceeded in January 2008, when Samsung showcased the world'slargest and thinnest OLED TV at the time, at 31 inches and 4.3 mm.[88]

In May 2008, Samsung unveiled an ultra-thin 12.1 inch laptop OLED display concept, with a1,280768 resolution with infinite contrast ratio.[89]According to Woo Jong Lee, Vice Presidentof the Mobile Display Marketing Team at Samsung SDI, the company expected OLED displays

to be used in notebook PCs as soon as 2010.

[90]

In October 2008, Samsung showcased the world's thinnest OLED display, also the first to be'flappable' and bendable.[91] It measures just 0.05 mm (thinner than paper), yet a Samsung staffmember said that it is "technically possible to make the panel thinner" .[91] To achieve thisthickness, Samsung etched an OLED panel that uses a normal glass substrate. The drive circuitwas formed by low-temperature polysilicon TFTs. Also, low-molecular organic EL materials
http://en.wikipedia.org/wiki/S-LCDhttp://en.wikipedia.org/wiki/S-LCDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-73http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-73http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-73http://en.wikipedia.org/wiki/Nexus_Shttp://en.wikipedia.org/wiki/Nexus_Shttp://en.wikipedia.org/wiki/Nexus_Shttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-74http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-74http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-74http://en.wikipedia.org/wiki/Anwell_Technologies_Limitedhttp://en.wikipedia.org/wiki/Anwell_Technologies_Limitedhttp://en.wikipedia.org/wiki/Chi_Mei_Corporationhttp://en.wikipedia.org/wiki/Chi_Mei_Corporationhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-76http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-76http://en.wikipedia.org/wiki/LGhttp://en.wikipedia.org/wiki/LGhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-77http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-77http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-77http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-78http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-78http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-78http://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-79http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-79http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-79http://en.wikipedia.org/wiki/OQOhttp://en.wikipedia.org/wiki/OQOhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-81http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-81http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-81http://en.wikipedia.org/wiki/Patenthttp://en.wikipedia.org/wiki/Patenthttp://en.wikipedia.org/wiki/Patenthttp://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/Philipshttp://en.wikipedia.org/wiki/Philipshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-82http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-82http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-82http://www.boliven.com/patents/search?q=organic+ledhttp://www.boliven.com/patents/search?q=organic+ledhttp://www.boliven.com/patents/search?q=organic+ledhttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/South_Koreahttp://en.wikipedia.org/wiki/South_Koreahttp://en.wikipedia.org/wiki/Conglomerate_%28company%29http://en.wikipedia.org/wiki/Conglomerate_%28company%29http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-83http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-83http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-83http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-84http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-84http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-84http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-86http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-86http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-86http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-87http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-87http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-87http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-88http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-88http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-88http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-89http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-89http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-89http://en.wiktionary.org/wiki/flappablehttp://en.wiktionary.org/wiki/flappablehttp://en.wiktionary.org/wiki/flappablehttp://en.wiktionary.org/wiki/bendablehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-flapping-90http://en.wiktionary.org/wiki/bendablehttp://en.wiktionary.org/wiki/flappablehttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-89http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-88http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-87http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-86http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-findarticles.com-85http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-84http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-83http://en.wikipedia.org/wiki/Conglomerate_%28company%29http://en.wikipedia.org/wiki/South_Koreahttp://en.wikipedia.org/wiki/Samsunghttp://www.boliven.com/patents/search?q=organic+ledhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-82http://en.wikipedia.org/wiki/Philipshttp://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/Eastman_Kodakhttp://en.wikipedia.org/wiki/Patenthttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-81http://en.wikipedia.org/wiki/OQOhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-79http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-79http://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-78http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-77http://en.wikipedia.org/wiki/LGhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-76http://en.wikipedia.org/wiki/Chi_Mei_Corporationhttp://en.wikipedia.org/wiki/Chi_Mei_Corporationhttp://en.wikipedia.org/wiki/Anwell_Technologies_Limitedhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-74http://en.wikipedia.org/wiki/Nexus_Shttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-73http://en.wikipedia.org/wiki/S-LCD


17/24

were employed. The pixel count of the display is 480 272. The contrast ratio is 100,000:1, andthe luminance is 200 cd/m. The colour reproduction range is 100% of the NTSC standard.

In the same month, Samsung unveiled what was then the world's largest OLED Television at 40-inch with aFull HDresolution of 19201080 pixel.[92]In the FPD International, Samsung stated

that its 40-inch OLED Panel is the largest size currently possible. The panel has a contrast ratioof 1,000,000:1, a colour gamut of 107% NTSC, and a luminance of 200 cd/m (peak luminanceof 600 cd/m).

At the Consumer Electronics Show (CES) in January 2010, Samsung demonstrated a laptopcomputer with a large, transparent OLED display featuring up to 40% transparency[93] and ananimated OLED display in a photo ID card.[94]

Samsung's latest AMOLED smartphones use their Super AMOLED trademark, with theSamsung Wave S8500andSamsung i9000 Galaxy Sbeing launched in June 2010.

Sony applications

Sony XEL-1, the world's first OLED TV.[1](front)

Sony XEL-1 (side)

The Sony CLI PEG-VZ90 was released in 2004, being the first PDA to feature an OLEDscreen.[95]Other Sony products to feature OLED screens include the MZ-RH1 portable minidiscrecorder, released in 2006[96]and theWalkman X Series.[97]
http://en.wikipedia.org/wiki/Full_HDhttp://en.wikipedia.org/wiki/Full_HDhttp://en.wikipedia.org/wiki/Full_HDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-91http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-91http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-91http://en.wikipedia.org/wiki/Consumer_Electronics_Showhttp://en.wikipedia.org/wiki/Consumer_Electronics_Showhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-laptoptransparent-92http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-laptoptransparent-92http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-photoid-93http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-photoid-93http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-photoid-93http://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Super_AMOLEDhttp://en.wikipedia.org/wiki/Super_AMOLEDhttp://en.wikipedia.org/wiki/Samsung_Wave_S8500http://en.wikipedia.org/wiki/Samsung_Wave_S8500http://en.wikipedia.org/wiki/Samsung_i9000_Galaxy_Shttp://en.wikipedia.org/wiki/Samsung_i9000_Galaxy_Shttp://en.wikipedia.org/wiki/Samsung_i9000_Galaxy_Shttp://en.wikipedia.org/wiki/Sony_XEL-1http://en.wikipedia.org/wiki/Sony_XEL-1http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-xel1-0http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-xel1-0http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-xel1-0http://en.wikipedia.org/wiki/Sony_CLI%C3%89_PEG-VZ90http://en.wikipedia.org/wiki/Sony_CLI%C3%89_PEG-VZ90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-94http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-94http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-94http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-95http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-95http://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-96http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-96http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-96http://en.wikipedia.org/wiki/File:Sony_XEL-1.jpghttp://en.wikipedia.org/wiki/File:Sony_oled.jpghttp://en.wikipedia.org/wiki/File:Sony_XEL-1.jpghttp://en.wikipedia.org/wiki/File:Sony_oled.jpghttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-96http://en.wikipedia.org/wiki/Walkman_X_Serieshttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-95http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-94http://en.wikipedia.org/wiki/Sony_CLI%C3%89_PEG-VZ90http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-xel1-0http://en.wikipedia.org/wiki/Sony_XEL-1http://en.wikipedia.org/wiki/Samsung_i9000_Galaxy_Shttp://en.wikipedia.org/wiki/Samsung_Wave_S8500http://en.wikipedia.org/wiki/Super_AMOLEDhttp://en.wikipedia.org/wiki/AMOLEDhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-photoid-93http://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-laptoptransparent-92http://en.wikipedia.org/wiki/Consumer_Electronics_Showhttp://en.wikipedia.org/wiki/Organic_light-emitting_diode#cite_note-91http://en.wikipedia.org/wiki/Full_HD


18/24

At theLas VegasCES 2007, Sony showcased 11-inch (28 cm, resolution 960540) and 27-inch(68.5 cm, full HD resolution at 19201080) OLED TV models.[98] Both claimed 1,000,000:1contrast ratiosand total thicknesses (including bezels) of 5 mm. In April 2007, Sony announcedit would manufacture 1000 11-inch OLED TVs per month for market testing purposes.[99] OnOctober 1, 2007, Sony announced that the 11-inch model, now called the XEL-1, would be

released commercially;

[1]

the XEL-1 was first released in Japan in December 2007.

[100]

In May 2007, Sony publicly unveiled a video of a 2.5-inch flexible OLED screen which is only0.3 millimeters thick.[101] At the Display 2008 exhibition, Sony demonstrated a 0.2 mm thick3.5 inch display with a resolution of 320200 pixels and a 0.3 mm thick 11 inch display with960540 pixels resolution, one-tenth the thickness of the XEL-1.

In July 2008, a Japanese government body said it would fund a joint project of leading firms,which is to develop a key technology to produce large, energy-saving organic displays. Theproject involves one laboratory and 10 companies including Sony Corp.NEDOsaid the project

Documents

An Organic Light Emitting Diode