How OLED screens are made

Every pixel is a thin organic film that glows by itself, so there is no backlight at all.

stations: 6
things upstream: 42
raw sources: 16
steps from the ground: 9

The short version

An OLED screen starts with a glass sheet carrying a transistor grid. Transparent indium tin oxide forms the anode, thin organic films are deposited above it, and a metal cathode goes on top. Small-molecule films are evaporated in a vacuum, while polymer films can be spin-coated or inkjet printed.

Build the transistor grid

A thin-film transistor backplane is etched onto glass so that each pixel can be switched on its own. This is the active-matrix form, called AMOLED.

Goes in
Glass
Lay a clear anode

Indium tin oxide is deposited as the anode because it is transparent and good at injecting positive charge into the organic layer.

Goes in
Indium tin oxide
Evaporate the organic films

Small-molecule materials are vapor-deposited in vacuum chambers, layer by layer, which keeps the film growth and the device build in one controlled environment. Polymer films, which would break apart in vacuum, are spin-coated or printed from solution instead.
Cap with a metal cathode

A low work function metal such as barium or calcium injects electrons. It is reactive, so it gets a capping layer of aluminum that also reflects light forward.

Goes in
Aluminum
Seal against air

The organic stack is sealed beneath a barrier layer or glass cover, because moisture and oxygen degrade the films.
Test every pixel

Panels are lit and inspected for dead pixels and uneven color before they are shipped.

End of the lineOLED screen Next it goes into smartphone, television, smartwatch.

Worth repeating

The first commercial shipment of inkjet-printed OLED panels began on 5 December 2017.
In 1990, researchers at Cambridge reported a green polymer OLED using films only 100 nm thick.
OLED pixels emit their own light, so black pixels simply switch off.