OLED

Some screens make their own light.

They use thin, special layers. These layers glow when power flows through them. This helps your phone and TV look bright.

The layers are made of special stuff. This stuff is between two metal parts. When electricity moves, the layers shine. This can make screens that bend. They can even make screens that you see through!

It is a cool way to see colors.

Some screens can make their own light. These are called OLEDs. The name stands for organic light-emitting diode.

An OLED uses a thin film of organic material. This film sits between two metal parts. These parts are called electrodes. One is the anode and one is the cathode.

When electricity flows, it moves through the organic layer. This causes the material to glow. This glow creates the light you see on a screen. Scientists use these to make TVs and smartphones. Some OLEDs can even be flexible. This means they can bend for foldable phones.

Some OLEDs are also transparent. This lets you see through the screen. In a display, tiny dots called pixels make the picture. An AMOLED screen uses a special part called a thin-film transistor. This part can turn each pixel on or off. This helps the screen show very clear images.

Researchers have worked on this for many years. They first saw organic materials glow in the 1950s. In 1987, chemists made the first practical OLED device.

An OLED is a special type of light. The name stands for organic light-emitting diode.

These devices are very important for our modern world. You can find them in many things you use every day. They are used in television screens and computer monitors. They also power portable tools like smartphones and handheld game consoles. Some OLEDs are even transparent or flexible. This allows for foldable smartphones or screens you can see through.

How does an OLED make light? It works by using a thin layer of organic material. This layer sits between two metal parts called electrodes. One electrode is the anode and the other is the cathode.

When electricity flows, it moves through the organic layer. Electrons move from the cathode toward the anode. At the same time, "holes" move from the anode toward the cathode. These electrons and holes meet and combine in the middle. This event creates a tiny burst of light. The color of the light depends on the energy of the material used.

People have been studying this for a long time. In the early 1950s, André Bernanose and his team saw organic materials glow. They used high voltages on materials like acridine orange dye. In 1960, Martin Pope at New York University studied how to make better contacts. His work helped create the way electricity enters modern OLEDs. Later, in 1965, researchers at Dow Chemical patented a way to use thin layers of phosphor. In 1974, Roger Partridge created a polymer version of this technology.

Making these screens became much easier with new discoveries. In 1987, chemists Ching Wan Tang and Steven Van Slyke built the first practical OLED. They used two layers to help the light work better. This made the device use less power. In 1990, J. H. Burroughes reported a high-efficiency green light device. In 1995, J. Kido helped make white OLEDs for lighting.

By 1999, Kodak and Sanyo made the first full-color OLED display. It was only 2.4 inches big. In 2007, Sony released the XEL-1, which was the first OLED television.

OLEDs are different from the regular LEDs used in many lights. Regular LEDs use a solid crystal structure. OLEDs use organic films instead. This difference allows OLEDs to be very thin and light. They can also be made into different shapes. Some screens use a system called AMOLED to control every tiny pixel. This uses a thin-film transistor to turn each pixel on or off. This makes the picture look very sharp and clear.

This technology is why your phone screen looks so bright and colorful.

An organic light-emitting diode, or OLED, is a specialized type of light-emitting diode (LED). Unlike standard LEDs, which use crystalline solid structures, OLEDs use an emissive layer made of organic compound films.

These organic materials emit light when they respond to an electric current. Because they use organic layers, these devices can be made very thin, flexible, or even transparent.

This unique property makes them essential for modern digital displays. You can find them in television screens, computer monitors, and portable devices like smartphones and handheld game consoles. They are also being researched for use in solid-state lighting.

The mechanism of an OLED relies on the movement of charges through organic semiconductors. These materials have conductivity levels ranging from insulators to conductors.

An OLED is built with an organic layer situated between two electrodes: the anode and the cathode. Typically, at least one electrode is transparent. To make light, a voltage is applied so the anode is positive compared to the cathode. Electrons flow from the cathode into the lowest unoccupied molecular orbital (LUMO) of the organic layer. Simultaneously, "holes" are injected from the anode into the highest occupied molecular orbital (HOMO).

Electrostatic forces pull these electrons and holes toward each other. When they meet, they recombine to form an exciton, which is a bound state of the electron and hole. As the exciton decays, the electron relaxes to a lower energy level and releases energy as visible light. The specific frequency, or color, of this light depends on the band gap, which is the energy difference between the HOMO and LUMO.

OLED technology can be organized into different families and control schemes. There are two main families: those based on small molecules and those using polymers.

Additionally, adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC), which operates slightly differently. To manage the pixels on a screen, manufacturers use two primary control schemes. A passive-matrix (PMOLED) scheme controls each row and line sequentially, one by one. In contrast, an active-matrix (AMOLED) scheme uses a thin-film transistor (TFT) backplane. This allows the device to directly access and switch each individual pixel on or off. AMOLED is preferred for higher resolution and larger display sizes.

The history of OLED is a long journey of scientific discovery. In the early 1950s, André Bernanose and his colleagues at Nancy-Université first observed electroluminescence in organic materials. They applied high alternating voltages to materials like acridine orange dye. In 1960, Martin Pope at New York University developed electrode contacts that are the basis for modern charge injection. By 1963, Pope's group observed direct current electroluminescence using a silver electrode at 400 volts. In 1965, Wolfgang Helfrich and W. G. Schneider produced the first double injection recombination electroluminescence. Later, in 1974, Roger Partridge created the first Polymer LED (PLED). His work used a film of polyvinylcarbazole up to 2.2 micrometers thick.

Practical, efficient OLEDs arrived through major breakthroughs in the late 20th century. In 1987, chemists Ching Wan Tang and Steven Van Slyke at Eastman Kodak built the first practical OLED device. They used a two-layer structure with separate hole and electron transporting layers. This design allowed recombination to happen in the middle of the organic layer, which improved efficiency and lowered operating voltage. In 1990, J. H. Burroughes reported a high-efficiency green light-emitting polymer device using 100nm thick films. By 1995, J. Kido and his team pioneered white OLEDs, which led to commercialized OLED-backlit displays and lighting.

Commercialization progressed rapidly through the late 1990s and early 2000s. In 1999, Kodak and Sanyo announced the world's first 2.4-inch active-matrix, full-color OLED display. By 2002, they presented a 15-inch HDTV prototype based on white OLEDs. Manufacturing of small molecule OLEDs began in 1997 with Pioneer Corporation, followed by TDK in 2001. Samsung Display became one of the largest manufacturers after its predecessor, Samsung-NEC, grew in 2002.

A major milestone for home entertainment occurred in 2007, when Sony released the XEL-1, the first OLED television. More recently, in 2017, JOLED began the first commercial shipment of inkjet-printed OLED panels.

OLED technology connects to many different fields of science and engineering. In materials science, researchers study how to use doping to increase radiative efficiency or change the wavelength of light emission. They also work on graded heterojunction architectures to improve quantum efficiency. For example, a 2011 development improved quantum efficiency up to 19% by varying material composition within the emissive layer. This technology also links to the field of plastic electronics. Because OLEDs can be made flexible, they are vital for the development of foldable smartphones.

They also enable advanced features like transparent displays used with optical fingerprint scanners.