Organic Light-Emitting Diode

• Organic Light-Emitting Diode

https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html

Computer monitor Organic light-emitting diode

1 Organic light-emitting diode (OLED) monitors provide higher contrast and better viewing angles than LCDs but

they require more power when displaying documents with white or bright backgrounds. In 2011, a 25 in (64 cm) OLED monitor cost $7500,

but the prices are expected to drop.


Flexible organic light-emitting diode - Technical Details and Applications

1 An OLED emits light due to the electroluminescence of thin films of

organic semiconductors approximately 100 nm thick. Regular

OLEDs are usually fabricated on a glass substrate, but by replacing

glass with a flexible plastic such as polyethylene terephthalate (PET)

among others, OLEDs can be made both bendable and lightweight.



1 Such materials may not be suitable for comparable devices based on

inorganic semiconductors due to the need for lattice matching and the

high temperature fabrication procedure involved.



1 In contrast, flexible OLED devices can be fabricated by deposition of

the organic layer onto the substrate using a method derived from inkjet printing, allowing the inexpensive

and roll-to-roll fabrication of printed electronics.



1 Flexible OLEDs may be used in the production of rollable displays, electronic paper, or bendable

displays which can be integrated into clothing, wallpaper or other curved surfaces. Prototype displays have

been exhibited by companies such as Sony, which are capable of being

rolled around the width of a pencil.


Flexible organic light-emitting diode - Disadvantages

1 Both flexible substrate itself as well as the process of bending the device

introduce stress into the materials. There may be residual stress from the

deposition of layers onto a flexible substrate, thermal stresses due to the

different coefficient of thermal expansion of materials in the device, in addition to the external stress from the bending of

the device.



1 Stress introduced into the organic layers may lower the efficiency or

brightness of the device as it is deformed, or cause complete

breakdown of the device altogether



1 Encapsulation is another challenge for flexible

OLED devices


Light-emitting diode - Organic light-emitting diodes (OLEDs)

1 In an organic light-emitting diode (OLED), the electroluminescent material comprising the emissive layer of the diode is an organic

compound. The organic material is electrically conductive due to the

delocalization of pi electrons caused by conjugation over all or part of the molecule, and the material therefore functions as an

organic semiconductor. The organic materials can be small organic molecules in

a crystalline phase, or polymers.


Light-emitting diode - Organic light-emitting diodes (OLEDs)

1 The potential advantages of OLEDs include thin, low-cost displays with a low driving

voltage, wide viewing angle, and high contrast and color gamut. Polymer LEDs have the added benefit of printable and

flexible displays. OLEDs have been used to make visual displays for portable electronic

devices such as cellphones, digital cameras, and MP3 players while possible

future uses include lighting and televisions.


Organic light-emitting diode

1 An 'OLED' ('organic light-emitting diode') is a light-emitting diode (LED)

in which the emission (electromagnetic radiation)|emissive

electroluminescence|electroluminescent layer is a film of organic compound which emits light

in response to an electric current



1 There are two main families of OLED: those based on small molecules and those

employing polymers



1 An OLED display works without a backlight. Thus, it can display deep black

levels and can be thinner and lighter than a liquid crystal display (LCD). In low ambient light conditions such as a dark

room an OLED screen can achieve a higher contrast ratio than an LCD,

whether the LCD uses cold cathode|cold cathode fluorescent lamps or LED-backlit

LCD television|LED backlight.


Organic light-emitting diode - History

1 The first observations of electroluminescence in organic

materials were in the early 1950s by André Bernanose and co-workers at

the Nancy-Université, France



1 In 1960, Martin Pope and co-workers at New York University developed

ohmic dark-injecting electrode contacts to organic crystals



1 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 the exciton

energy level



1 Electroluminescence from polymer films was first observed by Roger Partridge at the

National Physical Laboratory (United Kingdom)|National Physical Laboratory in the United Kingdom. The device consisted of a

film of poly(N-Vinylcarbazole|n-vinylcarbazole) up to 2.2 micrometres thick located between

two charge injecting electrodes. The results of the project were patented in 1975Partridge, Roger Hugh, Radiation sources , Issue date: November 30, 1976 and published in 1983.



1 The first diode device was reported at Eastman Kodak by Ching W. Tang and Steven Van Slyke in 1987. This

device used a novel two-layer structure with separate hole

transporting and electron transporting layers such that

recombination and light emission occurred in the middle of the organic layer. This resulted in a reduction in

operating voltage and improvements in efficiency and led to the current era of OLED research and device

production.



1 Research into polymer electroluminescence culminated in 1990 with J. H. Burroughes et al. at

the Cavendish Laboratory in Cambridge reporting a high

efficiency green light-emitting polymer based device using 100nm

thick films of poly(p-phenylene vinylene).


Organic light-emitting diode - Working principle

1 A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode

and cathode, all deposited on a substrate (materials science)|

substrate



1 Originally, the most basic polymer OLEDs consisted of a

single organic layer



1 During operation, a voltage is applied across the OLED such that the anode

is positive with respect to the cathode



1 Phosphorescent organic light-emitting diodes 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.



1 Indium tin oxide (ITO) is commonly used as the anode

material



1 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



1 Single carrier devices are typically used to study the chemical kinetics|

kinetics and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes


Organic light-emitting diode - Small molecules

1 Efficient OLEDs using small molecules were first developed by Dr.

Ching W. Tang et al. at Eastman Kodak. The term OLED traditionally

refers specifically to this type of device, though the term SM-OLED is

also in use.



1 Molecules commonly used in OLEDs include organometallic chelation|

chelates (for example Tris(8-hydroxyquinolinato)aluminium|Alq3,

used in the organic light-emitting device reported by Tang et al.),

fluorescent and phosphorescent dyes and conjugated dendrimers



1 The production of small molecule devices and displays usually involves

Evaporation (deposition)|thermal evaporation in a vacuum



1 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.


Organic light-emitting diode - Polymer light-emitting diodes

1 Polymer light-emitting diodes (PLED), also light-emitting polymers (LEP), involve an electroluminescence|electroluminescent conductive polymer that emits light when

connected to an external voltage. They are used as 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.



1 Vacuum deposition is not a suitable method for forming thin films of polymers



1 Typical polymers used in PLED displays include derivatives of

poly(p-phenylene vinylene)|poly(p-phenylene vinylene) and

polyfluorene



1 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.


Organic light-emitting diode - Phosphorescent materials

1 Phosphorescent organic light emitting diodes use 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%.



1 Typically, a polymer such as poly(N-Vinylcarbazole|n-vinylcarbazole) is used as a host material to which an

organometallic Coordination complex|complex is added as a

dopant. Organoiridium compound|Iridium complexes such as Ir(mppy)3 are currently the focus of research, although complexes based on other heavy metals such as platinum have

also been used.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html


1 The heavy metal atom at the centre of these complexes exhibits strong spin-orbit coupling,

facilitating intersystem crossing between Singlet state|singlet and Triplet state|triplet

states. By using these phosphorescent materials, both singlet and triplet excitons

will be able to decay radiatively, hence improving the internal quantum efficiency of

the device compared to a standard PLED where only the singlet states will contribute

to emission of light.



1 Applications of OLEDs in solid state lighting require the achievement of high brightness with good CIE 1931

color space|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 10,000cd/m2.


Organic light-emitting diode - Structure

1 ; Bottom or top emission: Bottom or top distinction refers not to

orientation of the OLED display, but to the direction that emitted light

exits the device



1 ; Transparent OLEDs: 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.



1 ; Graded Heterojunction: Graded heterojunction OLEDs gradually

decrease the ratio of electron holes to electron transporting chemicals.

This results in almost double the quantum efficiency of existing

OLEDs.



1 ; Stacked 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. Currently, other display technologies

have the RGB (and RGBW) pixels mapped next to each other

decreasing potential resolution.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html


1 ; Inverted OLED: 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.


Organic light-emitting diode - Patterning technologies

1 Patternable organic light-emitting devices use a light or heat activated electroactive layer. A latent material (PEDOT-TMA) is included in this layer

that, upon activation, becomes highly efficient as a hole injection

layer. Using this process, light-emitting devices with arbitrary

patterns can be prepared.



1 Colour patterning can be accomplished by means of laser,

such as radiation-induced sublimation transfer (RIST).



1 Organic vapour jet printing (OVJP) uses an inert carrier gas, such as

argon or nitrogen, to transport evaporated organic molecules (as in

Organic Vapor Phase Deposition). The gas is expelled through a micron

sized nozzle or nozzle array close to the substrate as it is being

translated. This allows printing arbitrary multilayer patterns without

the use of solvents.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html


1 Like ink jet material depositioning, inkjet etching (IJE) deposits precise amounts of solvent onto a substrate designed to selectively dissolve the

substrate material and induce a structure or pattern


Organic light-emitting diode - Backplane technologies

1 For a high resolution display like a TV, a Thin-film transistor|TFT

backplane is necessary to drive the pixels correctly. Currently, low

temperature polycrystalline silicon (LTPS) - thin-film transistor (TFT) is

used for commercial AMOLED displays. LTPS-TFT has variation of the performance in a display, so

various compensation circuits have been reported.


Organic light-emitting diode - Backplane technologies

1 Due to the size limitation of the excimer laser used for LTPS, the

AMOLED size was limited. To cope with the hurdle related to the panel

size, amorphous-silicon/microcrystalline-

silicon backplanes have been reported with large display prototype

demonstrations.


Organic light-emitting diode - Fabrication

1 Transfer-printing is an emerging technology with the capability to

assemble large numbers of parallel OLED and AMOLED devices under

efficient conditions


Organic light-emitting diode - Advantages

1 The different manufacturing process of OLEDs lends itself to several

advantages over flat panel displays made with LCD technology.



1 ; Lower cost in the future: OLEDs can be printed onto any suitable

substrate (printing)|substrate by an inkjet printer or even by screen

printing, theoretically making them cheaper to produce than LCD or

plasma displays



1 ; Lightweight and flexible plastic substrates: OLED displays can be

fabricated on flexible plastic substrates leading to the possible fabrication of flexible organic light-

emitting diodes for other new applications, such as rollable display|roll-up displays embedded in fabrics or clothing. As the substrate used can be flexible substrate|flexible

such as polyethylene terephthalate (PET), the displays may be produced

inexpensively.



1 ; Wider viewing angles and improved brightness: OLEDs can enable a

greater artificial contrast ratio (both dynamic range and static, measured

in purely dark conditions) and a wider viewing angle compared to

LCDs because OLED pixels emit light directly. OLED pixel colors appear correct and unshifted, even as the viewing angle approaches 90° from

Surface normal|normal.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html


1 ; Better power efficiency and thickness: LCDs filter the light

emitted from a backlight, allowing a small fraction of light through



1 ; Response time: OLEDs also can have a faster response time than

standard LCD screens. Whereas LCD displays are capable of between

Liquid crystal display#Specifications|1 and 16 ms response time offering a refresh rate of 60 to 480Hz, an OLED

theoretically can have a response time less than 0.01 ms, enabling a

refresh rate up to 100,000Hz .. OLEDs also can be run as a flicker

display, similar to a CRT, in order to eliminate the sample-and-hold effect that creates motion blur on OLEDs.


Organic light-emitting diode - Disadvantages

1 ; Current costs: OLED manufacture currently requires process steps that

make it extremely expensive. Specifically, it requires the use of

low-temperature polysilicon backplanes; LTPS backplanes, in turn,

require laser annealing from an amorphous silicon start, so this part

of the manufacturing process for AMOLEDs starts with the process

costs of standard LCD, and then adds an expensive, time-consuming

process that cannot currently be used on large-area glass substrates.



1 ; Lifespan: The biggest technical problem for OLEDs was the limited

lifetime of the organic materials



1 ; Color balance issues: Additionally, as the OLED material used to produce blue light degrades

significantly more rapidly than the materials that produce other colors,

blue light output will decrease relative to the other colors of light



1 ; Efficiency of blue OLEDs: Improvements to the efficiency and lifetime of blue OLEDs is vital to the success of OLEDs as replacements

for LCD technology



1 ; Water damage: Water can damage the organic materials of the displays.

Therefore, improved sealing processes are important for practical

manufacturing. Water damage especially may limit the longevity of

more flexible displays.



1 ; Outdoor performance: As an emissive display technology, OLEDs

rely completely upon converting electricity to light, unlike most LCDs which are to some extent reflective



1 ; Power consumption: While an OLED will consume around 40% of the

power of an LCD displaying an image that is primarily black, for the

majority of images it will consume 60%–80% of the power of an LCD


Organic light-emitting diode - Manufacturers and commercial uses

1 OLED technology is used in commercial applications such as displays for mobile phones and

portable digital media players, car radios and digital cameras among

others



1 OLEDs have been used in most Motorola and Samsung color cell

phones, as well as some HTC Corporation|HTC, LG and Sony

Ericsson models.Electronic News, [ http://www.edn.com/index.asp?

layout=articlearticleid=CA516009partner=enews OLEDs Replacing LCDs

in Mobile Phones], April 7, 2005, retrieved on July 28, 2007



1 The Google and HTC Nexus One smartphone includes an AMOLED screen, as does HTC's own HTC Desire|Desire and HTC Legend|

Legend phones. However due to supply shortages of the Samsung-

produced displays, certain HTC models will use Sony's S-LCD|SLCD

displays in the future, while the Google and Samsung Nexus S

smartphone will use Super Clear LCD instead in some countries.



1 OLED displays were used in watches made by Fossil (JR-9465) and Diesel (DZ-7086).



1 Other manufacturers of OLED panels include Anwell Technologies Limited (Hong Kong), AU Optronics (Taiwan), Chimei Innolux Corporation (Taiwan),

LG (Korea), and others.



1 In 2009, Shearwater Research introduced the Predator as the first

color OLED diving computer available with a user replaceable battery.



1 DuPont stated in a press release in May 2010 that they can produce a

50-inch OLED TV in two minutes with a new printing technology. If this can

be scaled up in terms of manufacturing, then the total cost of OLED TVs would be greatly reduced.

Dupont also states that OLED TVs made with this less expensive

technology can last up to 15 years if left on for a normal eight hour day.



1 The use of OLEDs may be subject to patents held by Eastman Kodak, DuPont, General Electric, Philips|

Royal Philips Electronics, numerous universities and others.OLED-Info.com, [ http://www.oled-

info.com/tags/companies/kodak Kodak Signs OLED Cross-License

Agreement], retrieved on March 14, 2008. There are by now thousands of patents associated with OLEDs, both from larger corporations and smaller

technology companies.



1 Research In Motion|RIM, the maker of BlackBerry smartphones, have

unofficially announced that their upcoming BlackBerry 10 devices will use OLED displays. This marks the upcoming BB10 smartphones as

some of the first to use OLED displays.



1 Foldable OLED smartphones could be as much as a decade away because of the cost

of producing them


Organic light-emitting diode - Fashion

1 Textiles incorporating OLEDs are an innovation in the fashion world and pose for a way to integrate lighting

to bring inert objects to a whole new level of fashion


Organic light-emitting diode - Samsung applications

1 By 2004 Samsung, South Korea's largest conglomerate (company)|

conglomerate, was the world's largest OLED manufacturer,

producing 40% of the OLED displays made in the world, and as of 2010

has a 98% share of the global AMOLED market



1 Samsung SDI announced in 2005 the world's largest OLED TV at the time, at . This OLED featured the highest

resolution at the time, of 6.22 million pixels. In addition, the company

adopted active matrix based technology for its low power

consumption and high-resolution qualities. This was exceeded in January 2008, when Samsung

showcased the world's largest and thinnest OLED TV at the time, at

31inches (78cm) and 4.3mm.



1 In May 2008, Samsung unveiled an ultra-thin 12.1inch (30cm) laptop

OLED display concept, with a 1,280×768 resolution with infinite

contrast ratio. According to Woo Jong Lee, Vice President of the Mobile

Display Marketing Team at Samsung SDI, the company expected OLED

displays to be used in notebook PCs as soon as 2010.



1 In October 2008, Samsung showcased the world's thinnest OLED display, also the first to be flappable

and bendable



1 In the same month, Samsung unveiled what was then the world's largest OLED Television

at 40-inch with a Full HD resolution of 1920×1080 pixel.40-inch OLED panel from Samsung. Hdtvinfo.eu (2008-10-30) In the FPD International, Samsung stated that its

40-inch OLED Panel is the largest size currently possible. The panel has a contrast

ratio of 1,000,000:1, a colour gamut of 107% NTSC, and a luminance of 200cd/m² (peak

luminance of 600cd/m²).



1 At the Consumer Electronics Show|Consumer Electronics Show (CES) in

January 2010, Samsung demonstrated a laptop computer with a large, transparent OLED

display featuring up to 40% transparency and an animated OLED

display in a photo ID card.



1 Samsung's latest AMOLED smartphones use their Super AMOLED trademark, with the

Samsung Wave S8500 and Samsung i9000 Galaxy S being launched in

June 2010. In January 2011 Samsung announced their Super AMOLED Plus

displays, which offer several advances over the older Super

AMOLED displays: real stripe matrix (50% more sub pixels), thinner form factor, brighter image and an 18% reduction in energy consumption.



1 At CES 2012, Samsung introduced the first 55 TV screen that uses

Super OLED technology.Clark, Shaylin (2012-01-12).

[http://www.webpronews.com/ces-2012-samsung-oled-awards-2012-01 CES 2012: Samsung’s OLED TV Rakes In Awards]. WebProNews. Retrieved

on 2012-12-03.



1 On January 8, 2013, at CES Samsung unveiled a unique curved 4K Ultra S9

OLED television, which they state provides an IMAX-like experience for viewers.Rougeau, Michael (2013-01-

08). [http://www.techradar.com/news/television/hdtv/samsungs-curved-oled-tv-

provides-an-imax-like-experience-1123683]. Techradar. Retrieved on

2013-01-08.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html


1 On August 13, 2013, Samsung announced availability of a 55-inch

curved OLED TV (model KN55S9C) in the US at a price point of

$8999.99.Boylan, Chris (2013-08-13). Big Picture Big Sound. Retrieved on

2013-08-13.



1 On September 6, 2013, Samsung launched its 55-inch curved OLED TV

(model KE55S9C) in the United Kingdom with John Lewis.



1 Samsung introduced the Galaxy Round smartphone in the Korean market in October 2013. The device features a 1080p screen,

measuring , that curves on the vertical axis in a rounded case. The corporation has promoted the following advantages: A new feature called Round Interaction that allows users to look at

information by tilting the handset on a flat surface with the screen off, and the feel of one continuous transition when the user switches

between home screens.


Organic light-emitting diode - Sony applications

1 The Sony CLIÉ PEG-VZ90 was released in 2004, being the first PDA

to feature an OLED screen. Other Sony products to feature OLED

screens include the MZ-RH1 portable minidisc recorder, released in 2006

and the Walkman X Series.



1 At the 2007 Las Vegas Valley|Las Vegas Consumer Electronics Show

(CES), Sony showcased 11-inch (28cm, resolution 960×540) and 27-inch (68.5cm), full HD resolution at 1920×1080) OLED TV models.Sony

announces a 27-inch OLED TV



1 In May 2007, Sony publicly unveiled a video of a 2.5-inch flexible OLED

screen which is only 0.3 millimeters thick



1 In July 2008, a Japanese government body said it would fund a joint project of leading firms, which is to develop a key technology to produce large,

energy-saving organic displays



1 In October 2008, Sony published results of research it carried out with

the Max Planck Institute over the possibility of mass-market bending displays, which could replace rigid

LCDs and plasma screens. Eventually, bendable, see-through

displays could be stacked to produce 3D images with much greater

contrast ratios and viewing angles than existing products.



1 Sony exhibited a 24.5 (62cm) prototype OLED 3D television during

the Consumer Electronics Show in January 2010.



1 In January 2011, Sony announced the PlayStation Vita handheld game

console (the successor to the PlayStation Portable|PSP) will feature

a 5-inch OLED screen.



1 On February 17, 2011, Sony announced its 25 (63.5cm) OLED

Professional Reference Monitor aimed at the Cinema and high end Drama

Post Production market.



1 On June 25, 2012, Sony and Panasonic announced a joint venture for creating low cost mass production

OLED televisions by 2013.


Organic light-emitting diode - LG applications

1 As of 2010, LG Electronics produced one model of OLED television, the

15inch 15EL9500[http://www.lg.com/uk/tv-audio-video/televisions/LG-oled-tv-15EL9500.jsp LG 15EL9500 OLED

Television]


Organic light-emitting diode - Mitsubishi applications

1 Lumiotec is the first company in the world developing and selling, since January 2011, mass-produced OLED lighting panels with such brightness and long lifetime. Lumiotec is a joint

venture of Mitsubishi Heavy Industries, ROHM, Toppan Printing,

and Mitsui Co.


Organic light-emitting diode - Mitsubishi applications

1 On June 1, 2011, Mitsubishi installed a 6-meter OLED 'sphere' in Tokyo's

Science Museum [ http://www.mitsubishielectric.com/ne

ws/2011/0601.html MITSUBISHI ELECTRIC News Releases Installs 6-

Meter OLED Globe at Science Museum]. Mitsubishielectric.com

(2011-06-01). Retrieved on 2012-11-12.


Organic light-emitting diode - Recom Group/video name tag applications

1 On January 6, 2011, Los Angeles based technology company Recom

Group introduced the first small screen consumer application of the OLED at the Consumer Electronics

Show in Las Vegas


LED - Organic light-emitting diodes (OLEDs)

1 In an organic light-emitting diode (organic light-emitting diode|OLED),

the electroluminescence|electroluminescent material

comprising the emissive layer of the diode is an organic compound. The

organic material is electrically conductive due to the Delocalized

electron|delocalization of pi electrons caused by conjugated system|

conjugation over all or part of the molecule, and the material therefore

functions as an organic semiconductor.


LED - Organic light-emitting diodes (OLEDs)

1 The potential advantages of OLEDs include thin, low-cost displays with a low driving

voltage, wide viewing angle, and high contrast and color gamut. Polymer LEDs have the added benefit of printable and

flexible organic light-emitting diode|flexible displays. OLEDs have been used to make

visual displays for portable electronic devices such as cellphones, digital cameras, and MP3 players while possible future uses

include lighting and televisions.


Organic light-emitting diode roll-up display

1 A 'flexible organic light emitting diode (FOLED)' is a type of organic light-emitting

diode (OLED) incorporating a flexible plastic Substrate (semiconductor)|substrate on

which the electroluminescence|electroluminescent organic semiconductor is deposited. This enables the device to be bent

or rolled while still operating. Currently the focus of research in industrial and academic groups, flexible OLEDs form one method of

fabricating a rollable display.


Organic light-emitting diode roll-up display - Technical details and applications

1 An OLED emits light due to the electroluminescence of thin films of

organic semiconductors approximately 100nm thick. Regular OLEDs are usually fabricated on a glass Substrate (semiconductor)|

substrate, but by replacing glass with a flexible plastic such as

polyethylene terephthalate (PET) among others, OLEDs can be made

both bendable and lightweight.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html

Organic light-emitting diode roll-up display - Technical details and applications

1 Such materials may not be suitable for comparable devices based on

inorganic semiconductors due to the need for lattice matching and the

high temperature fabrication procedure involved.


Organic light-emitting diode roll-up display - Disadvantages

1 Both flexible substrate itself as well as the process of bending the device introduce Stress (mechanics)|stress

into the materials. There may be residual stress from the deposition of

layers onto a flexible substrate, thermal stresses due to the different coefficient of thermal expansion of

materials in the device, in addition to the external stress from the bending

of the device.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html

Organic light-emitting diode roll-up display - Disadvantages

1 Encapsulation is another challenge for flexible

OLED devices


Display examples - Organic light-emitting diode

1 [http://www.rpi.edu/~simonk/pdf/natacadLighting.pdf rpi.edu –

Lighting industry, Structure and technology in the transition to solid

state]


Display examples - Organic light-emitting diode

1 2003 Active-matrix OLED (AMOLED):[http://de.wikipedia.org/w/index.php?title=Organische_Leuchtdiodeoldid=

88934244 WP-de Organische Leuchtdiode] 2011-05-17


Phosphorescent organic light-emitting diode

1 'Phosphorescent organic light-emitting diodes' ('PHOLED') are a

type of OLED|organic light-emitting diode (OLED) that use the principle of

phosphorescence to obtain higher internal efficiencies than fluorescent OLEDs. This technology is currently

under development by many industrial and academic research

groups.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html

Phosphorescent organic light-emitting diode - Method of operation

1 Like all types of OLED, phosphorescent OLEDs emit light due

to the electroluminescence of an organic semiconductor layer in an

electric current. Electrons and electron hole|holes are injected into the organic layer at the electrodes and form excitons, a bound state of

the electron and hole.



1 Electrons and holes are both fermions with half integer spin

(physics)|spin. An exciton formed by the recombination of two such

particles may either be in a singlet state or a triplet state, depending on how the spins have been combined.

Statistically, there is a 25% probability of forming a singlet state

and 75% probability of forming a triplet state. Decay of the excitons

results in the production of light through spontaneous emission.



1 In OLEDs using fluorescent organic molecules only, the decay of triplet excitons is quantum mechanically

forbidden by selection rules, meaning that the lifetime of triplet

excitons is long and phosphorescence is not readily

observed



1 However, phosphorescent OLEDs generate light from both triplet and

singlet excitons, allowing the internal quantum efficiency of such devices

to reach nearly 100%.



1 This is commonly achieved by doping a host molecule with an

organometallic Coordination complex|complex


Phosphorescent organic light-emitting diode - Applications

1 Due to their potentially high level of energy efficiency, even when

compared to other OLEDs, PHOLEDs are being studied for potential use in

large-screen displays such as computer monitors or television

screens, as well as general lighting needs


Phosphorescent organic light-emitting diode - Challenges

1 One problem that currently hampers the widespread adoption of this

highly energy efficient technology is that the average lifetimes of red and

green PHOLEDs are often tens of thousands of hours longer than those

of blue PHOLEDs. This may cause displays to become visually distorted

much sooner than would be acceptable for a commercially viable

device.https://store.theartofservice.com/the-organic-light-emitting-diode-toolkit.html

Polyfluorene - Organic light-emitting diodes (OLEDs)

1 In recent years many industrial efforts have focused on tuning the color of lights using polyfluorenes


Polyfluorene - Organic light-emitting diodes (OLEDs)

1 Substitution at the nine position with various moieties has also been examined as a means to control the color emitted by polyfluorene. In the past researchers have tried putting alkyl substituents on the ninth position, however it has been found that by putting bulkier groups,

such as alkoxyphenyl groups, the polymers had enhanced blue emission stability and

superior polymer light-emitting diode performance (compared to polymers which

have alkyl substituents at the ninth position).


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Organic Light-Emitting Diode