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103-568: The manufacturer has indicated the time to acquire auto focus as 0.07 seconds. The electronic OLED viewfinder has a resolution of 2.36 million dots and, as in the predecessor, is tiltable. The 3-inch (76 mm) OLED touchscreen rear display is fully articulated and can display 1.04 million dots. The camera is splash proof. A smaller version of the GX8, the Panasonic GX80 (retailed as the GX85 in

206-401: A rechargeable battery when it is being charged, the roles of the electrodes as anode and cathode are reversed. Conventional current depends not only on the direction the charge carriers move, but also the carriers' electric charge . The currents outside the device are usually carried by electrons in a metal conductor. Since electrons have a negative charge, the direction of electron flow

309-476: A thin film for full-spectrum colour displays. Polymer OLEDs are quite efficient and 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. If the polymeric OLED films are made by vacuum vapor deposition, the chain elements will be cut off and the original photophysical properties will be compromised. However, polymers can be processed in solution, and spin coating

412-406: A controlled and complete operating environment, helping to obtain uniform and stable films, thus ensuring the final fabrication of high-performance OLED devices.However, small molecule organic dyes are prone to fluorescence quenching in the solid state, resulting in lower luminescence efficiency. The doped OLED devices are also prone to crystallization, which reduces the luminescence and efficiency of

515-790: A damage issue due to the sputtering process. Thus, a thin metal film such as pure Ag and the Mg:Ag alloy are used for the semi-transparent cathode due to their high transmittance and high conductivity . In contrast to the bottom emission, light is extracted from the opposite side in top emission without the need of passing through multiple drive circuit layers. Thus, the light generated can be extracted more efficiently. Using deuterium instead of hydrogen, in other words deuterated compounds, in red light , green light , blue light and white light OLED light emitting material layers and other layers nearby in OLED displays can improve their brightness by up to 30%. This

618-497: A direction "from East to West, or, which will strengthen this help to the memory, that in which the sun appears to move", the anode is where the current enters the electrolyte, on the East side: " ano upwards, odos a way; the way which the sun rises". The use of 'East' to mean the 'in' direction (actually 'in' → 'East' → 'sunrise' → 'up') may appear contrived. Previously, as related in the first reference cited above, Faraday had used

721-471: A dopant. Iridium complexes such as Ir(mppy) 3 as of 2004 were a focus of research, although complexes based on other heavy metals such as platinum have also been used. The heavy metal atom at the centre of these complexes exhibits strong spin-orbit coupling, facilitating intersystem crossing between singlet and triplet states. By using these phosphorescent materials, both singlet and triplet excitons will be able to decay radiatively, hence improving

824-417: A driver IC, often mounted using the chip-on-glass (COG) technology with an anisotropic conductive film . The most commonly used patterning method for organic light-emitting displays is shadow masking during film deposition, also called the "RGB side-by-side" method or "RGB pixelation" method. Metal sheets with multiple apertures made of low thermal expansion material, such as nickel alloy, are placed between

927-431: A green light emitter, electron transport material and as a host for yellow light and red light emitting dyes. Because of the structural flexibility of small-molecule electroluminescent materials, thin films can be prepared by vacuum vapor deposition, which is more expensive and of limited use for large-area devices. The vacuum coating system, however, can make the entire process from film growth to OLED device preparation in

1030-636: A melted phosphor consisting of ground anthracene powder, tetracene, and graphite powder. Their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules. The first Polymer LED (PLED) to be created was by Roger Partridge at the National Physical Laboratory in the United Kingdom. It used a film of polyvinylcarbazole up to 2.2 micrometers thick located between two charge-injecting electrodes. The light generated

1133-402: A microcavity in top-emission OLEDs with color filters also contributes to an increase in the contrast ratio by reducing the reflection of incident ambient light. In a conventional panel, a circular polarizer was installed on the panel surface. While this was provided to prevent the reflection of ambient light, it also reduced the light output. By replacing this polarizing layer with color filters,

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1236-419: A more electrically reactive (less noble) metal attached to the vessel hull and electrically connected to form a cathodic protection circuit. A less obvious example of this type of protection is the process of galvanising iron. This process coats iron structures (such as fencing) with a coating of zinc metal. As long as the zinc remains intact, the iron is protected from the effects of corrosion. Inevitably,

1339-470: A more gradual electronic 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 layer and an emissive layer. Developments in OLED architecture in 2011 improved quantum efficiency (up to 19%) by using a graded heterojunction. In the graded heterojunction architecture, the composition of hole and electron-transport materials varies continuously within

1442-472: A mother substrate that is later thinned and cut into several displays. Substrates for OLED displays come in the same sizes as those used for manufacturing LCDs. For OLED manufacture, after the formation of TFTs (for active matrix displays), addressable grids (for passive matrix displays), or indium tin oxide (ITO) segments (for segment displays), the display is coated with hole injection, transport and blocking layers, as well with electroluminescent material after

1545-618: A partnership to jointly research, develop, and produce OLED displays. They announced the world's first 2.4-inch active-matrix, full-color OLED display in September the same year. In September 2002, they presented a prototype of 15-inch HDTV format display based on white OLEDs with color filters at the CEATEC Japan. Manufacturing of small molecule OLEDs was started in 1997 by Pioneer Corporation , followed by TDK in 2001 and Samsung - NEC Mobile Display (SNMD), which later became one of

1648-413: A result of the oxidation reaction. In an electrolytic cell , the anode is the wire or plate upon which excess positive charge is imposed. As a result of this, anions will tend to move towards the anode where they will undergo oxidation. Historically, the anode of a galvanic cell was also known as the zincode because it was usually composed of zinc. The terms anode and cathode are not defined by

1751-475: A similar sensor which do include a low pass filter. No Video | Weather Sealed | All the Rest This camera-related article is a stub . You can help Misplaced Pages by expanding it . OLED An organic light-emitting diode ( OLED ), also known as organic electroluminescent ( organic EL ) diode , is a type of light-emitting diode (LED) in which the emissive electroluminescent layer

1854-597: A single polymer molecule, representing the smallest possible organic light-emitting diode (OLED) device. Scientists will be able to optimize substances to produce more powerful light emissions. Finally, this work is a first step towards making molecule-sized components that combine electronic and optical properties. Similar components could form the basis of a molecular computer. Polymer light-emitting diodes (PLED, P-OLED), also light-emitting polymers (LEP), involve an electroluminescent conductive polymer that emits light when connected to an external voltage. They are used as

1957-404: A small area silver electrode at 400 volts . The proposed mechanism was field-accelerated electron excitation of molecular fluorescence. Pope's group reported in 1965 that in the absence of an external electric field, the electroluminescence in anthracene crystals is caused by the recombination of a thermalized electron and hole, and that the conducting level of anthracene is higher in energy than

2060-407: Is a common method of depositing thin polymer 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 a technique derived from commercial inkjet printing. However, as the application of subsequent layers tends to dissolve those already present, formation of multilayer structures

2163-458: Is achieved by improving the current handling capacity, and lifespan of these materials. Making indentations shaped like lenses on a transparent layer through which light passes from an OLED light emitting material, reduces the amount of scattered light and directs it forward, improving brightness. When light waves meet while traveling along the same medium, wave interference occurs. This interference can be constructive or destructive. It

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2266-460: Is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode , an electrode of the device through which conventional current leaves the device. A common mnemonic is ACID, for "anode current into device". The direction of conventional current (the flow of positive charges) in a circuit is opposite to the direction of electron flow, so (negatively charged) electrons flow from

2369-403: Is an organic compound film that emits light in response to an electric current. This organic layer is situated between two electrodes ; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors , and portable systems such as smartphones and handheld game consoles . A major area of research

2472-463: Is commonly used as the anode material. It is transparent to visible light and has a high work function which promotes injection of holes into the HOMO level of the organic layer. A second conductive (injection) layer is typically added, which may consist of PEDOT:PSS , as the HOMO level of this material generally lies between the work function of ITO and the HOMO of other commonly used polymers, reducing

2575-468: Is difficult with these methods. The metal cathode may still need to be deposited by thermal evaporation in vacuum. An alternative method to vacuum deposition is to deposit a Langmuir-Blodgett film . Typical polymers used in PLED displays include derivatives of poly( p -phenylene vinylene) and polyfluorene . Substitution of side chains onto the polymer backbone may determine the colour of emitted light or

2678-413: Is electrically linked to the protected system. As a result, the metal anode partially corrodes or dissolves instead of the metal system. As an example, an iron or steel ship's hull may be protected by a zinc sacrificial anode , which will dissolve into the seawater and prevent the hull from being corroded. Sacrificial anodes are particularly needed for systems where a static charge is generated by

2781-456: Is opposite to the direction of conventional current. Consequently, electrons leave the device through the anode and enter the device through the cathode. The definition of anode and cathode is different for electrical devices such as diodes and vacuum tubes where the electrode naming is fixed and does not depend on the actual charge flow (current). These devices usually allow substantial current flow in one direction but negligible current in

2884-596: Is optimizing the thickness of the charge transporting layers but is hard to control. Another way is using the exciplex. Exciplex formed between hole-transporting (p-type) and electron-transporting (n-type) side chains to localize electron-hole pairs. Energy is then transferred to luminophore and provide high efficiency. An example of using exciplex is grafting Oxadiazole and carbazole side units in red diketopyrrolopyrrole-doped Copolymer main chain shows improved external quantum efficiency and color purity in no optimized OLED. Organic small-molecule electroluminescent materials have

2987-597: Is similar to that of the Fabry-Perot resonator or laser resonator , which contains two parallel mirrors comparable to the two reflective electrodes), this effect is especially strong in TEOLED. This two-beam interference and the Fabry-Perot interferences are the main factors in determining the output spectral intensity of OLED. This optical effect is called the "micro-cavity effect." In the case of OLED, that means

3090-470: Is sometimes desirable for several waves of the same frequency to sum up into a wave with higher amplitudes. Since both electrodes are reflective in TEOLED, light reflections can happen within the diode, and they cause more complex interferences than those in BEOLEDs. In addition to the two-beam interference, there exists a multi-resonance interference between two electrodes. Because the structure of TEOLEDs

3193-476: Is the architecture that was used in the early-stage AMOLED displays. It had a transparent anode fabricated on a glass substrate, and a shiny reflective cathode. Light is emitted from the transparent anode direction. To reflect all the light towards the anode direction, a relatively thick metal cathode such as aluminum is used. For the anode, high-transparency indium tin oxide (ITO) was a typical choice to emit as much light as possible. Organic thin-films, including

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3296-442: Is the development of white OLED devices for use in solid-state lighting applications. There are two main families of OLED: those based on small molecules and those employing polymers . Adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC) which has a slightly different mode of operation. An OLED display can be driven with a passive-matrix (PMOLED) or active-matrix ( AMOLED ) control scheme. In

3399-460: Is the positively charged electron collector. In a tube, the anode is a charged positive plate that collects the electrons emitted by the cathode through electric attraction. It also accelerates the flow of these electrons. [REDACTED] In a semiconductor diode , the anode is the P-doped layer which initially supplies holes to the junction. In the junction region, the holes supplied by

3502-468: Is to switch the mode of emission. A reflective anode, and a transparent (or more often semi-transparent) cathode are used so that the light emits from the cathode side, and this configuration is called top-emission OLED (TE-OLED). Unlike BEOLEDs where the anode is made of transparent conductive ITO, this time the cathode needs to be transparent, and the ITO material is not an ideal choice for the cathode because of

3605-411: Is used to coat steel, when a breach of the coating occurs it actually accelerates oxidation of the iron. Another cathodic protection is used on the impressed current anode. It is made from titanium and covered with mixed metal oxide . Unlike the sacrificial anode rod, the impressed current anode does not sacrifice its structure. This technology uses an external current provided by a DC source to create

3708-453: Is used to create p- and n-regions by changing the conductivity of the host semiconductor . OLEDs do not employ a crystalline p-n structure. Doping of OLEDs is used to increase radiative efficiency by direct modification of the quantum-mechanical optical recombination rate. Doping is additionally used to determine the wavelength of photon emission. OLED displays are made in a similar way to LCDs, including manufacturing of several displays on

3811-652: The Nancy-Université in France made the first observations of electroluminescence in organic materials in the early 1950s. They applied high alternating voltages in air to materials such as acridine orange dye, either deposited on or dissolved in cellulose or cellophane thin films . The proposed mechanism was either direct excitation of the dye molecules or excitation of electrons . In 1960, Martin Pope and some of his co-workers at New York University in

3914-683: The exciton energy level. Also in 1965, Wolfgang Helfrich and W. G. Schneider of the National Research Council in Canada produced double injection recombination electroluminescence for the first time in an anthracene single crystal using hole and electron injecting electrodes, the forerunner of modern double-injection devices. In the same year, Dow Chemical researchers patented a method of preparing electroluminescent cells using high-voltage (500–1500 V) AC-driven (100–3000   Hz) electrically insulated one millimetre thin layers of

4017-411: The kinetics and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes. As current through 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 be obtained by replacing ITO with a lower work function metal which increases

4120-524: The valence and conduction bands of inorganic semiconductors. Originally, the most basic polymer OLEDs consisted of a single organic layer. One example was the first light-emitting device synthesised by J. H. Burroughes et al. , which involved a single layer of poly(p-phenylene vinylene) . However multilayer OLEDs can be fabricated with two or more layers in order to improve device efficiency. As well as conductive properties, different materials may be chosen to aid charge injection at electrodes by providing

4223-553: The OLED material adversely affecting lifetime. Mechanisms to decrease anode roughness for ITO/glass substrates include the use of thin films and self-assembled monolayers. Also, alternative substrates and anode materials are being considered to increase OLED performance and lifetime. Possible examples include single crystal sapphire substrates treated with gold (Au) film anodes yielding lower work functions, operating voltages, electrical resistance values, and increasing lifetime of OLEDs. Single carrier devices are typically used to study

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4326-462: The PMOLED scheme, each row and line in the display is controlled sequentially, one by one, whereas AMOLED control uses a thin-film transistor (TFT) backplane to directly access and switch each individual pixel on or off, allowing for higher resolution and larger display sizes. OLEDs are fundamentally different from LEDs , which are based on a p-n diode crystalline solid structure. In LEDs, doping

4429-790: The United States and as the GX7 Mark II in Japan) was announced on April 4, 2016. The camera features many of the same features of the Panasonic GX8 camera but utilises a 16 megapixel sensor instead of the 20 megapixel sensor of the GX8. The Panasonic GX80/GX85 became the first Panasonic Micro Four Thirds camera to do without a low-pass filter . According to the claim made by Panasonic, the Panasonic GX80/GX85 will have 10% more fine detail resolving power than cameras with

4532-493: The United States developed ohmic dark-injecting electrode contacts to organic crystals. They further described the necessary energetic requirements ( work functions ) for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern OLED devices. Pope's group also first observed direct current (DC) electroluminescence under vacuum on a single pure crystal of anthracene and on anthracene crystals doped with tetracene in 1963 using

4635-433: The action of flowing liquids, such as pipelines and watercraft. Sacrificial anodes are also generally used in tank-type water heaters. In 1824 to reduce the impact of this destructive electrolytic action on ships hulls, their fastenings and underwater equipment, the scientist-engineer Humphry Davy developed the first and still most widely used marine electrolysis protection system. Davy installed sacrificial anodes made from

4738-429: The advantages of a wide variety, easy to purify, and strong chemical modifications. In order to make the luminescent materials to emit light as required, some chromophores or unsaturated groups such as alkene bonds and benzene rings will usually be introduced in the molecular structure design to change the size of the conjugation range of the material, so that the photophysical properties of the material changes. In general,

4841-444: The anode (even though it is negative and therefore would be expected to attract them, this is due to electrode potential relative to the electrolyte solution being different for the anode and cathode metal/electrolyte systems); but, external to the cell in the circuit, electrons are being pushed out through the negative contact and thus through the circuit by the voltage potential as would be expected. Battery manufacturers may regard

4944-422: The anode and the other the cathode according to the roles the electrodes play when the battery is discharged. This is despite the fact that the roles are reversed when the battery is charged. When this is done, "anode" simply designates the negative terminal of the battery and "cathode" designates the positive terminal. In a diode , the anode is the terminal represented by the tail of the arrow symbol (flat side of

5047-474: The anode combine with electrons supplied from the N-doped region, creating a depleted zone. As the P-doped layer supplies holes to the depleted region, negative dopant ions are left behind in the P-doped layer ('P' for positive charge-carrier ions). This creates a base negative charge on the anode. When a positive voltage is applied to anode of the diode from the circuit, more holes are able to be transferred to

5150-409: The anode is the positive terminal imposed by an external source of potential difference. The current through a recharging battery is opposite to the direction of current during discharge; in other words, the electrode which was the cathode during battery discharge becomes the anode while the battery is recharging. In battery engineering, it is common to designate one electrode of a rechargeable battery

5253-400: The anode of a galvanic cell , into an outside or external circuit connected to the cell. For example, the end of a household battery marked with a "+" is the cathode (while discharging). In both a galvanic cell and an electrolytic cell , the anode is the electrode at which the oxidation reaction occurs. In a galvanic cell the anode is the wire or plate having excess negative charge as

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5356-523: The anode, anions (negative ions) are forced by the electrical potential to react chemically and give off electrons (oxidation) which then flow up and into the driving circuit. Mnemonics : LEO Red Cat (Loss of Electrons is Oxidation, Reduction occurs at the Cathode), or AnOx Red Cat (Anode Oxidation, Reduction Cathode), or OIL RIG (Oxidation is Loss, Reduction is Gain of electrons), or Roman Catholic and Orthodox (Reduction – Cathode, anode – Oxidation), or LEO

5459-499: The back reflection of emitted light out to the transparent ITO layer. Experimental research has proven that the properties of the anode, specifically the anode/hole transport layer (HTL) interface topography plays a major role in the efficiency, performance, and lifetime of organic light-emitting diodes. Imperfections in the surface of the anode decrease anode-organic film interface adhesion, increase electrical resistance, and allow for more frequent formation of non-emissive dark spots in

5562-431: The cathodic protection. Impressed current anodes are used in larger structures like pipelines, boats, city water tower, water heaters and more. The opposite of an anode is a cathode . When the current through the device is reversed, the electrodes switch functions, so the anode becomes the cathode and the cathode becomes anode, as long as the reversed current is applied. The exception is diodes where electrode naming

5665-422: The cavity in a TEOLED could be especially designed to enhance the light output intensity and color purity with a narrow band of wavelengths, without consuming more power. In TEOLEDs, the microcavity effect commonly occurs, and when and how to restrain or make use of this effect is indispensable for device design. To match the conditions of constructive interference, different layer thicknesses are applied according to

5768-426: The depleted region, and this causes the diode to become conductive, allowing current to flow through the circuit. The terms anode and cathode should not be applied to a Zener diode , since it allows flow in either direction, depending on the polarity of the applied potential (i.e. voltage). In cathodic protection , a metal anode that is more reactive to the corrosive environment than the metal system to be protected

5871-474: The device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron holes into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton , a bound state of the electron and hole. This happens closer to

5974-459: The devices. Therefore, the development of devices based on small-molecule electroluminescent materials is limited by high manufacturing costs, poor stability, short life, and other shortcomings. Coherent emission from a laser dye-doped tandem SM-OLED device, excited in the pulsed regime, has been demonstrated. The emission is nearly diffraction limited with a spectral width similar to that of broadband dye lasers. Researchers report luminescence from

6077-410: The difference in energy between the HOMO and LUMO. As electrons and holes are fermions with half integer spin , an exciton may either be in a singlet state or a triplet state depending 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 triplet states ( phosphorescence ) is spin forbidden, increasing

6180-541: The electroluminescent material, which is in powder form. The mask is aligned with the mother substrate before every use, and it is placed just below the substrate. The substrate and mask assembly are placed at the top of the deposition chamber. Afterwards, the electrode layer is deposited, by subjecting silver and aluminum powder to 1000 °C, using an electron beam. Shadow masks allow for high pixel densities of up to 2,250 DPI (890 dot/cm). High pixel densities are necessary for virtual reality headsets . Although

6283-408: The electron-transport layer part of the emissive layer, because in organic semiconductors holes are generally more mobile than electrons. The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation whose frequency is in the visible region . The frequency of this radiation depends on the band gap of the material, in this case

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6386-423: The emissive layer that actually generates the light, are then sandwiched between the ITO anode and the reflective metal cathode. The downside of bottom emission structure is that the light has to travel through the pixel drive circuits such as the thin film transistor (TFT) substrate, and the area from which light can be extracted is limited and the light emission efficiency is reduced. An alternative configuration

6489-523: The emissive layer with a dopant emitter. The graded heterojunction architecture combines the benefits of both conventional architectures by improving charge injection while simultaneously balancing charge transport within the emissive region. During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. Anodes are picked based upon the quality of their optical transparency, electrical conductivity, and chemical stability. A current of electrons flows through

6592-435: The energy barrier of hole injection. Similarly, hole only devices can be made by using a cathode made solely of aluminium, resulting in an energy barrier too large for efficient electron injection. Balanced charge injection and transfer are required to get high internal efficiency, pure emission of luminance layer without contaminated emission from charge transporting layers, and high stability. A common way to balance charge

6695-410: The energy barriers for hole injection. Metals such as barium and calcium are often used for the cathode as they have low work functions which promote injection of electrons into the LUMO of the organic layer. Such metals are reactive, so they require a capping layer of aluminium to avoid degradation. Two secondary benefits of the aluminum capping layer include robustness to electrical contacts and

6798-434: The evacuated tube due to being heated by a filament, so electrons can only enter the device from the external circuit through the heated electrode. Therefore, this electrode is permanently named the cathode, and the electrode through which the electrons exit the tube is named the anode. The polarity of voltage on an anode with respect to an associated cathode varies depending on the device type and on its operating mode. In

6901-409: The event of a later convention change it would have become West to East, so that the East electrode would not have been the 'way in' any more. Therefore, "eisode" would have become inappropriate, whereas "anode" meaning 'East electrode' would have remained correct with respect to the unchanged direction of the actual phenomenon underlying the current, then unknown but, he thought, unambiguously defined by

7004-431: The filters absorb most of the emitted light, requiring the background white light to be relatively strong to compensate for the drop in brightness, and thus the power consumption for such displays can be higher. Color filters can also be implemented into bottom- and top-emission OLEDs. By adding the corresponding RGB color filters after the semi-transparent cathode, even purer wavelengths of light can be obtained. The use of

7107-496: The first two layers, after which ITO or metal may be applied again as a cathode . Later, the entire stack of materials is encapsulated. The TFT layer, addressable grid, or ITO segments serve as or are connected to the anode , which may be made of ITO or metal. OLEDs can be made flexible and transparent, with transparent displays being used in smartphones with optical fingerprint scanners and flexible displays being used in foldable smartphones . André Bernanose and co-workers at

7210-408: The following examples, the anode is negative in a device that provides power, and positive in a device that consumes power: In a discharging battery or galvanic cell (diagram on left), the anode is the negative terminal: it is where conventional current flows into the cell. This inward current is carried externally by electrons moving outwards. In a recharging battery, or an electrolytic cell ,

7313-469: The future. Since the later discovery of the electron , an easier to remember and more durably correct technically although historically false, etymology has been suggested: anode, from the Greek anodos , 'way up', 'the way (up) out of the cell (or other device) for electrons'. In electrochemistry , the anode is where oxidation occurs and is the positive polarity contact in an electrolytic cell . At

7416-401: The government's Department for Industry tried and failed to find industrial collaborators to fund further development. Chemists Ching Wan Tang and Steven Van Slyke at Eastman Kodak built the first practical OLED device in 1987. This device used a two-layer structure with separate hole transporting and electron transporting layers such that recombination and light emission occurred in

7519-563: The heated evaporation source and substrate, so that the organic or inorganic material from the evaporation source is masked off, or blocked by the sheet from reaching the substrate in most locations, so the materials are deposited only on the desired locations on the substrate, and the rest is deposited and remains on the sheet. Almost all small OLED displays for smartphones have been manufactured using this method. Fine metal masks (FMMs) made by photochemical machining , reminiscent of old CRT shadow masks , are used in this process. The dot density of

7622-571: The internal quantum efficiency of the device compared to a standard OLED where only the singlet states will contribute to emission of light. Applications of OLEDs in solid state lighting require the achievement of high brightness with good CIE coordinates (for white emission). The use of macromolecular species like polyhedral oligomeric silsesquioxanes (POSS) in conjunction with the use of phosphorescent species such as Ir for printed OLEDs have exhibited brightnesses as high as 10,000   cd/m . The bottom-emission organic light-emitting diode (BE-OLED)

7725-698: The larger the range of π-electron conjugation system, the longer the wavelength of light emitted by the material. For instance, with the increase of the number of benzene rings, the fluorescence emission peak of benzene , naphthalene , anthracene , and tetracene gradually red-shifted from 283 nm to 480 nm. Common organic small molecule electroluminescent materials include aluminum complexes, anthracenes , biphenyl acetylene aryl derivatives, coumarin derivatives, and various fluorochromes. Efficient OLEDs using small molecules were first developed by Ching W. Tang et al. at Eastman Kodak . The term OLED traditionally refers specifically to this type of device, though

7828-433: The least reactive materials for anodes. Platinum erodes very slowly compared to other materials, and graphite crumbles and can produce carbon dioxide in aqueous solutions but otherwise does not participate in the reaction. In a battery or galvanic cell , the anode is the negative electrode from which electrons flow out towards the external part of the circuit. Internally the positively charged cations are flowing away from

7931-451: The light absorption by the color filter, state-of-the-art OLED televisions can reproduce color very well, such as 100% NTSC , and consume little power at the same time. This is done by using an emission spectrum with high human-eye sensitivity, special color filters with a low spectrum overlap, and performance tuning with color statistics into consideration. This approach is also called the "Color-by-white" method. Anode An anode

8034-713: The light intensity is not affected, and essentially all ambient reflected light can be cut, allowing a better contrast on the display panel. This potentially reduced the need for brighter pixels and can lower the power consumption. Transparent OLEDs use transparent or semi-transparent contacts on both sides of the device 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 view displays in bright sunlight. This technology can be used in Head-up displays , smart windows or augmented reality applications. Graded heterojunction OLEDs gradually decrease

8137-650: The lion says GER (Losing electrons is Oxidation, Gaining electrons is Reduction). This process is widely used in metals refining. For example, in copper refining, copper anodes, an intermediate product from the furnaces, are electrolysed in an appropriate solution (such as sulfuric acid ) to yield high purity (99.99%) cathodes. Copper cathodes produced using this method are also described as electrolytic copper . Historically, when non-reactive anodes were desired for electrolysis, graphite (called plumbago in Faraday's time) or platinum were chosen. They were found to be some of

8240-456: The magnetic reference. In retrospect the name change was unfortunate, not only because the Greek roots alone do not reveal the anode's function any more, but more importantly because as we now know, the Earth's magnetic field direction on which the "anode" term is based is subject to reversals whereas the current direction convention on which the "eisode" term was based has no reason to change in

8343-445: The mask will determine the pixel density of the finished display. Fine Hybrid Masks (FHMs) are lighter than FFMs, reducing bending caused by the mask's own weight, and are made using an electroforming process. This method requires heating the electroluminescent materials at 300 °C using a thermal method in a high vacuum of 10   Pa. An oxygen meter ensures that no oxygen enters the chamber as it could damage (through oxidation)

8446-525: The middle of the organic layer; this resulted in a reduction in operating voltage and improvements in efficiency. Research into polymer electroluminescence culminated in 1990, with J. H. Burroughesat the Cavendish Laboratory at Cambridge University , UK, reporting a high-efficiency green light-emitting polymer-based device using 100   nm thick films of poly(p-phenylene vinylene) . Moving from molecular to macromolecular materials solved

8549-451: The more straightforward term "eisode" (the doorway where the current enters). His motivation for changing it to something meaning 'the East electrode' (other candidates had been "eastode", "oriode" and "anatolode") was to make it immune to a possible later change in the direction convention for current , whose exact nature was not known at the time. The reference he used to this effect was the Earth's magnetic field direction, which at that time

8652-402: The negative electrode as the anode, particularly in their technical literature. Though from an electrochemical viewpoint incorrect, it does resolve the problem of which electrode is the anode in a secondary (or rechargeable) cell. Using the traditional definition, the anode switches ends between charge and discharge cycles. In electronic vacuum devices such as a cathode-ray tube , the anode

8755-445: The other direction. Therefore, the electrodes are named based on the direction of this "forward" current. In a diode the anode is the terminal through which current enters and the cathode is the terminal through which current leaves, when the diode is forward biased . The names of the electrodes do not change in cases where reverse current flows through the device. Similarly, in a vacuum tube only one electrode can emit electrons into

8858-401: The principle of electrophosphorescence to convert electrical energy in an OLED into light in a highly efficient manner, with the internal quantum efficiencies of such devices approaching 100%. PHOLEDs can be deposited using vacuum deposition through a shadow mask. Typically, a polymer such as poly( N-vinylcarbazole ) is used as a host material to which an organometallic complex is added as

8961-484: The problems previously encountered with the long-term stability of the organic films and enabled high-quality films to be easily made. Subsequent research developed multilayer polymers and the new field of plastic electronics and OLED research and device production grew rapidly. White OLEDs, pioneered by J. Kido et al. at Yamagata University , Japan in 1995, achieved the commercialization of OLED-backlit displays and lighting. In 1999, Kodak and Sanyo had entered into

9064-539: The ratio of electron holes to electron transporting chemicals. This results in almost double the quantum efficiency of existing OLEDs. Stacked OLEDs use a pixel architecture that stacks the red, green, and blue subpixels on top of one another instead of next to one another, leading to substantial increase in gamut and color depth, and greatly reducing pixel gap. Other display technologies with RGB (and RGBW) pixels mapped next to each other, tend to decrease potential resolution. Tandem OLEDs are similar but have 2 layers of

9167-518: The resonance wavelength of that specific color. The thickness conditions are carefully designed and engineered according to the peak resonance emitting wavelengths of the blue light (460 nm), green light (530 nm), and red light (610 nm) color LEDs. This technology greatly improves the light-emission efficiency of OLEDs, and are able to achieve a wider color gamut due to high color purity. In " white + color filter method ", also known as WOLED, red, green, and blue emissions are obtained from

9270-430: The same color stacked together. This improves the brightness of OLED displays. In contrast to a conventional OLED, in which the anode is placed on the substrate, an inverted OLED uses a bottom cathode that can be connected to the drain end of an n-channel TFT, especially for the low-cost amorphous silicon TFT backplane useful in the manufacturing of AMOLED displays. All OLED displays (passive and active matrix) use

9373-485: The same white-light LEDs using different color filters. With this method, the OLED materials produce white light, which is then filtered to obtain the desired RGB colors. This method eliminated the need to deposit three different organic emissive materials, so only one kind of OLED material is used to produce white light. It also eliminated the uneven degradation rate of blue pixels vs. red and green pixels. Disadvantages of this method are low color purity and contrast. Also,

9476-605: The shadow-mask patterning method is a mature technology used from the first OLED manufacturing, it causes many issues like dark spot formation due to mask-substrate contact or misalignment of the pattern due to the deformation of shadow mask. Such defect formation can be regarded as trivial when the display size is small, however it causes serious issues when a large display is manufactured, which brings significant production yield loss. To circumvent such issues, white emission devices with 4-sub-pixel color filters (white, red, green and blue) have been used for large televisions. In spite of

9579-561: The stability and solubility of the polymer for performance and ease of processing. While unsubstituted poly(p-phenylene vinylene) (PPV) is typically insoluble, a number of PPVs and related poly(naphthalene vinylene)s (PNVs) that are soluble in organic solvents or water have been prepared via ring opening metathesis polymerization . These water-soluble polymers or conjugated poly electrolytes (CPEs) also can be used as hole injection layers alone or in combination with nanoparticles like graphene. Phosphorescent organic light-emitting diodes use

9682-688: The term SM-OLED is also in use. Molecules commonly used in OLEDs include organometallic chelates (for example Alq 3 , used in the organic light-emitting device reported by Tang et al. ), fluorescent and phosphorescent dyes and conjugated dendrimers . A number of materials are used for their charge transport properties, for example triphenylamine and derivatives are commonly used as materials for hole transport layers. Fluorescent dyes can be chosen to obtain light emission at different wavelengths, and compounds such as perylene , rubrene and quinacridone derivatives are often used. Alq 3 has been used as

9785-431: The timescale of the transition and limiting the internal efficiency of fluorescent OLED emissive layers and devices. Phosphorescent organic light-emitting diodes (PHOLEDs) or emissive layers make use of spin–orbit interactions to facilitate intersystem crossing between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency. Indium tin oxide (ITO)

9888-418: The triangle), where conventional current flows into the device. Note the electrode naming for diodes is always based on the direction of the forward current (that of the arrow, in which the current flows "most easily"), even for types such as Zener diodes or solar cells where the current of interest is the reverse current. In vacuum tubes or gas-filled tubes , the anode is the terminal where current enters

9991-455: The tube. The word was coined in 1834 from the Greek ἄνοδος ( anodos ), 'ascent', by William Whewell , who had been consulted by Michael Faraday over some new names needed to complete a paper on the recently discovered process of electrolysis . In that paper Faraday explained that when an electrolytic cell is oriented so that electric current traverses the "decomposing body" (electrolyte) in

10094-403: The voltage polarity of electrodes but the direction of current through the electrode. An anode is an electrode of a device through which conventional current (positive charge) flows into the device from an external circuit, while a cathode is an electrode through which conventional current flows out of the device. If the current through the electrodes reverses direction, as occurs for example in

10197-639: The world's first commercial shipment of inkjet-printed OLED panels. A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode , all deposited on a substrate . The organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over part or all of the molecule. These materials have conductivity levels ranging from insulators to conductors, and are therefore considered organic semiconductors . The highest occupied and lowest unoccupied molecular orbitals ( HOMO and LUMO ) of organic semiconductors are analogous to

10300-455: The world's largest OLED display manufacturers - Samsung Display, in 2002. The Sony XEL-1 , released in 2007, was the first OLED television. Universal Display Corporation , one of the OLED materials companies, holds a number of patents concerning the commercialization of OLEDs that are used by major OLED manufacturers around the world. On 5 December 2017, JOLED , the successor of Sony and Panasonic 's printable OLED business units, began

10403-443: The zinc coating becomes breached, either by cracking or physical damage. Once this occurs, corrosive elements act as an electrolyte and the zinc/iron combination as electrodes. The resultant current ensures that the zinc coating is sacrificed but that the base iron does not corrode. Such a coating can protect an iron structure for a few decades, but once the protecting coating is consumed, the iron rapidly corrodes. If, conversely, tin

10506-412: Was believed to be invariant. He fundamentally defined his arbitrary orientation for the cell as being that in which the internal current would run parallel to and in the same direction as a hypothetical magnetizing current loop around the local line of latitude which would induce a magnetic dipole field oriented like the Earth's. This made the internal current East to West as previously mentioned, but in

10609-429: Was readily visible in normal lighting conditions though the polymer used had 2 limitations; low conductivity and the difficulty of injecting electrons. Later development of conjugated polymers would allow others to largely eliminate these problems. His contribution has often been overlooked due to the secrecy NPL imposed on the project. When it was patented in 1974 it was given a deliberately obscure "catch all" name while

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