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99-777: AMOLED ( active-matrix organic light-emitting diode ; / ˈ æ m oʊ ˌ l ɛ d / ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescent material, and active matrix refers to the technology behind the addressing of pixels . Since 2007, AMOLED technology has been used in mobile phones, media players, TVs and digital cameras, and it has continued to make progress toward low-power, low-cost, high resolution and large size (for example, 88-inch and 8K resolution) applications. An AMOLED display consists of an active matrix of OLED pixels generating light (luminescence) upon electrical activation that have been deposited or integrated onto

198-476: 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

297-404: A thin-film transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel . Typically, this continuous current flow is controlled by at least two TFTs at each pixel (to trigger the luminescence), with one TFT to start and stop the charging of a storage capacitor and the second to provide a voltage source at the level needed to create

396-635: A Super AMOLED. Super AMOLED displays, such as the one on the Samsung Galaxy S21+ / S21 Ultra and Samsung Galaxy Note 20 Ultra have often been compared to IPS LCDs , found in phones such as the Xiaomi Mi 10T , Huawei Nova 5T , and Samsung Galaxy A20e . For example, according to ABI Research , the AMOLED display found in the Motorola Moto X draws just 92 mA during bright conditions and 68 mA while dim. On

495-404: A constant current to the pixel, thereby eliminating the need for the very high currents required for passive-matrix OLED operation. TFT backplane technology is crucial in the fabrication of AMOLED displays. In AMOLEDs, the two primary TFT backplane technologies, polycrystalline silicon (poly-Si) and amorphous silicon (a-Si), are currently used offering the potential for directly fabricating

594-406: 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

693-782: 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

792-471: 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

891-417: 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

990-431: 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

1089-617: 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

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1188-402: 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,

1287-456: A millisecond, and they consume significantly less power . This advantage makes active-matrix OLEDs well-suited for portable electronics, where power consumption is critical to battery life. The amount of power the display consumes varies significantly depending on the color and brightness shown. As an example, one old QVGA OLED display consumes 0.3 watts while showing white text on a black background, but more than 0.7 watts showing black text on

1386-470: 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

1485-472: 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

1584-538: A new company, Nouvoyance, Inc. to continue development of the PenTile technology. PenTile RGBG layout used in AMOLED and plasma displays uses green pixels interleaved with alternating red and blue pixels. The human eye is most sensitive to green, especially for high resolution luminance information. The green subpixels are mapped to input pixels on a one-to-one basis. The red and blue subpixels are subsampled, reconstructing

1683-539: A new solution-coated AMOLED display technology that is competitive in cost and performance with existing chemical vapor deposition (CVD) technology. Using custom modeling and analytic approaches, Samsung has developed short and long-range film-thickness control and uniformity that is commercially viable at large glass sizes. Compared to other display technologies , AMOLED screens have several advantages and disadvantages. AMOLED displays can provide higher refresh rates than passive-matrix, often have response times less than

1782-607: 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

1881-597: 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

1980-404: 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

2079-484: A white background, while an LCD may consume only a constant 0.35 watts regardless of what is being shown on screen. A new FHD+ or WQHD+ display will consume much more. Because the black pixels turn completely off, AMOLED also has contrast ratios that are significantly higher than LCDs. AMOLED displays may be difficult to view in direct sunlight compared with LCDs because of their reduced maximum brightness. Samsung's Super AMOLED technology addresses this issue by reducing

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2178-407: 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

2277-496: Is a type of light-emitting diode (LED) in which the emissive electroluminescent layer 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

2376-458: 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

2475-459: 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

2574-522: Is composed of one red, one green, and one blue subpixel (RGB), all of uniform size ". In traditional flat-panel screens, the resolution is defined by the number of red, green, and blue subpixels, in groups of three, in an array in each axis. As a result, each pixel or group of subpixels can render any colour on the screen, regardless of neighbouring pixels. This is not the case with PenTile screens. The Video Electronics Standards Association ( VESA ) method of measuring and defining resolution in color displays

2673-464: 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

2772-531: Is lower power consumption: the HTC One S 's use of a PenTile display makes it more energy efficient and thinner than equivalent LCD screens, giving it better battery life than the HTC One X 's IPS LCD. A PenTile AMOLED screen is also cheaper than an RGB stripe AMOLED. According to Samsung, PenTile AMOLED displays have a longer life span due to having fewer blue subpixels. Most PenTile displays use rectangular grids of alternating green and blue/red pixels. However

2871-590: Is mapped to either a red-centered logical pixel, or a green-centered logical pixel. PenTile was invented by Candice H. Brown Elliott, for which she was awarded the Society for Information Display 's Otto Schade Prize in 2014. The technology was licensed by the company Clairvoyante from 2000 until 2008, during which time several prototype PenTile displays were developed by a number of Asian liquid crystal display (LCD) manufacturers. In March 2008, Samsung Electronics acquired Clairvoyante's PenTile IP assets. Samsung then funded

2970-596: 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

3069-581: 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

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3168-465: 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

3267-476: 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

3366-442: 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

3465-479: Is to measure the contrast of line pairs, requiring a minimum of 50% Michelson contrast for displays intended for rendering text. The developers of PenTile displays use this VESA criterion for contrast of line pairs to calculate the resolutions specified. In the RGBG layout the alternate red and blue subpixels are 'shared' or sub-sampled with neighboring pixels. Due to the one third lower subpixel density on PenTile displays

3564-465: 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

3663-616: Is understood to be caused by the restriction of the number of subpixels that may participate in the image reconstruction when colors are highly saturated to primaries. In the RGBW case, this is caused as the W subpixel will not be available in order to maintain the saturated color. In the RGBG case, this effect will occur when the color boundary is primarily red or blue, as the fully populated (one green per pixel) sub-pixel cannot contribute. For all other cases, text and especially full color images are effectively reconstructed. The PenTile layout reduces

3762-453: 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

3861-577: The Motorola Atrix 4G 's display had "inaccurate colours and poor viewing angles, not to mention practically unreadable text at its furthest zoom". Also in a comparison between the original Droid Razr and the cheaper RAZR V , the RAZR V's TN TFT LCD (a low-end LCD, compared to the higher-end IPS panel LCD) was found to be much crisper than the Droid Razr's Super AMOLED Advanced PenTile despite both screens using

3960-637: 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

4059-514: The Samsung Galaxy S4 uses a PenTile Diamond Pixel array, where the green pixels are oval and repeat in a single line, while red and blue pixels are larger and alternate between the lines of green, ensuring more uniform colours with fewer aberrations compared to the earlier generation PenTile display on the Galaxy S III. PenTile displays for smartphones have received a mixed reception. For instance

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4158-668: 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

4257-716: The iriver Clix 2 portable media player. In 2008 it appeared on the Nokia N85 followed by the Samsung i7110 - both Nokia and Samsung Electronics were early adopters of this technology on their smartphones. Manufacturers have developed in-cell touch panels, integrating the production of capacitive sensor arrays in the AMOLED module fabrication process. In-cell sensor AMOLED fabricators include AU Optronics and Samsung . Samsung has marketed its version of this technology as "Super AMOLED". Researchers at DuPont used computational fluid dynamics (CFD) software to optimize coating processes for

4356-411: 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

4455-524: 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

4554-553: 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

4653-458: 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

4752-549: 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

4851-484: The active-matrix backplanes at low temperatures (below 150 °C) onto flexible plastic substrates for producing flexible AMOLED displays. AMOLED was developed in 2006. Samsung SDI was one of the main investors in the technology, and many other display companies were also developing it. One of the earliest consumer electronics products with an AMOLED display was the BenQ-Siemens S88 mobile handset and, in 2007,

4950-429: 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,

5049-499: 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

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5148-410: The brightness of the desaturated color image areas, such as black&white text, for improved outdoor view-ability. An ongoing controversy regarding the definition or measurement of resolution of color subpixelated flat panel displays led many people to question the resolution claims of PenTile display products. Journalists have noted that in " just about every flat-panel TV in existence, each pixel

5247-422: 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

5346-458: The chroma signal at a lower resolution. The luminance signal is processed using adaptive subpixel rendering filters to optimize reconstruction of high spatial frequencies from the input image, wherein the green subpixels provide the majority of the reconstruction. The red and blue subpixels are capable of reconstructing the horizontal and vertical spatial frequencies, but not the highest of the diagonal. Diagonal high spatial frequency information in

5445-616: The conventional three, using subpixel rendering combined with metamer rendering. Metamer rendering optimizes the energy distribution between the white subpixel and the combined red, green, and blue subpixels: W <> RGB, to improve image sharpness. The display driver chip has an RGB to RGBW color vector space converter and gamut mapping algorithm, followed by metamer and subpixel rendering algorithms. In order to maintain saturated color quality, to avoid simultaneous contrast error between saturated colors and peak white brightness, while simultaneously reducing backlight power requirements,

5544-470: 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

5643-459: 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

5742-410: 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

5841-509: The display backlight brightness is under control of the PenTile driver engine. When the image is mostly desaturated colors, those near white or grey , the backlight brightness is significantly reduced, often to less than 50% peak, while the LCD levels are increased to compensate. When the image has very bright saturated colors, the backlight brightness is maintained at higher levels. The PenTile RGBW also has an optional high brightness mode that doubles

5940-495: The display driver, allowing plug and play compatibility with conventional RGB (Red-Green-Blue) stripe panels. "PenTile Matrix" (a neologism from penta- , meaning "five" in Greek and tile ) describes the geometric layout of the prototypical subpixel arrangement developed in the early 1990s. The layout consists of a quincunx comprising two red subpixels, two green subpixels, and one central blue subpixel in each unit cell. It

6039-541: 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

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6138-408: 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

6237-423: 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

6336-523: 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

6435-435: 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

6534-410: 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

6633-431: 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

6732-796: The first generation AMOLED. The generic term for this technology is One Glass Solution (OGS). Below is a mapping table of marketing terms versus resolutions and sub-pixel types. Note how the pixel density relates to choices of sub-pixel type. (bits) 3040x1440 2280x1080 3040x1440 3040x1440 6.1 6.3 6.4 6.8 550 401 522 498 Samsung Galaxy S10 Samsung Galaxy Note 10 Samsung Galaxy S10+ Samsung Galaxy Note 10+ Samsung Galaxy Fold Samsung Galaxy Z Flip 2400x1080 3200x1440 6.1 6.4 6.7 6.8 6.9 386 (External display resolution for Samsung Galaxy Z Fold 2) 563 525 511 421 394 515 411 OLED An organic light-emitting diode ( OLED ), also known as organic electroluminescent ( organic EL ) diode ,

6831-496: 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

6930-401: 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

7029-563: 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

7128-508: The human eyes' red-sensing and green-sensing cone cells , while using the combined effect of all the color subpixels to present lower-resolution chroma (color) information to all three cone cell types. Combined, this optimizes the match of display technology to the biological mechanisms of human vision. The layout uses one third fewer subpixels for the same resolution as the RGB stripe (RGB-RGB) layout, in spite of having four color primaries instead of

7227-571: 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)

7326-698: 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

7425-406: The layout may cause color leakage image distortion, which can be reduced by filters. In some cases the layout causes reduced moiré and blockiness compared to conventional RGB layouts. The PenTile layout is specifically designed to work with and be dependent upon subpixel rendering that uses only one and a quarter subpixel per pixel, on average, to render an image. That is, that any given input pixel

7524-569: 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. PenTile These subpixel layouts are specifically designed to operate with proprietary algorithms for subpixel rendering embedded in

7623-708: 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

7722-445: 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)

7821-516: 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

7920-423: The number of subpixels needed to create a specified resolution. Consequently it is possible to achieve an HD resolution on a PenTile AMOLED screen at lower cost than other technologies, and most reviewers note that "300 ppi" (as per VESA - not full pixels) resolution displays (such as Samsung Galaxy S III ) make the PenTile effect less obvious than lower resolution PenTile displays ( Droid Razr ). The second advantage

8019-532: The other hand, compared with the IPS, the yield rate of AMOLED is low; the cost is also higher. "Super AMOLED" is a marketing term created by Samsung for an AMOLED display with an integrated touch screen digitizer : the layer that detects touch is integrated into the display, rather than overlaid on top of it and cannot be separated from the display itself. The display technology itself is not improved. According to Samsung, Super AMOLED reflects one-fifth as much sunlight as

8118-485: The pixel structure may be more visible when compared to RGB stripe displays with the same pixel density. The loss of subpixels for a given resolution specification has led some journalists to describe the use of PenTile as "shady practice" and "sort of cheating". For a given size and resolution specification, the PenTile screen can appear grainy, pixelated, speckled, with blurred text on some saturated colors and backgrounds when compared to RGB stripe color. This effect

8217-401: 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

8316-484: 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

8415-539: 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

8514-629: The red and blue channels of the input image are transferred to the green subpixels for image reconstruction. Thus the RG-BG scheme creates a color display with one third fewer subpixels than a traditional RGB-RGB scheme but with the same measured luminance display resolution . This is similar to the Bayer filter commonly used in digital cameras . As of 2021, "almost all OLED screens in portable consumer devices use some form of Pentile subpixel layout." PenTile RGBW technology, used in LCD, adds an extra subpixel to

8613-518: 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

8712-430: 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

8811-485: 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,

8910-605: 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

9009-564: The size of gaps between layers of the screen. Additionally, PenTile technology is often used for a higher resolution display while requiring fewer subpixels than needed otherwise, sometimes resulting in a display less sharp and more grainy than a non-PenTile display with the same resolution. The organic materials used in AMOLED displays are very prone to degradation over a relatively short period of time, resulting in color shifts as one color fades faster than another, image persistence , or burn-in . Flagship smartphones sold in 2020 and 2021 used

9108-561: 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

9207-684: 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

9306-431: 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)

9405-485: The traditional red, green and blue subpixels that is a clear area without color filtering material and with the only purpose of letting backlight come through, hence W for white . This makes it possible to produce a brighter image compared to an RGB-matrix while using the same amount of power, or produce an equally bright image while using less power. The PenTile RGBW layout uses each red, green, blue and white subpixel to present high-resolution luminance information to

9504-639: 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

9603-455: 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

9702-418: Was inspired by biomimicry of the human retina , which has nearly equal numbers of L and M type cone cells , but significantly fewer S cones. As the S cones are primarily responsible for perceiving blue colors, which do not appreciably affect the perception of luminance , reducing the number of blue subpixels with respect to the red and green subpixels in a display does not reduce the image quality. However,

9801-429: 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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