Making OLEDs

The biggest part of manufacturing OLEDs is applying the
organic layers to the substrate. This can be done in three
ways:

* Vacuum deposition or vacuum thermal evaporation (VTE) -
In a vacuum chamber, the organic molecules are gently heated
(evaporated) and allowed to condense as thin films onto
cooled substrates. This process is expensive and inefficient.
* Organic vapor phase deposition (OVPD)
In a low-pressure, hot-walled reactor chamber, a carrier gas
transports evaporated organic molecules onto cooled
substrates, where they condense into thin films. Using
a carrier gas increases the efficiency and reduces the cost
of making OLEDs.
* Inkjet printing - With inkjet technology, OLEDs are
sprayed onto substrates just like inks are sprayed onto paper
during printing. Inkjet technology greatly reduces the cost
of OLED manufacturing and allows OLEDs to be printed onto
very large films for large displays like 80-inch TV screens
or electronic billboards.

Small Molecule OLED vs. Polymer OLED

The types of molecules used by Kodak scientists in 1987 in
the first OLEDs were small organic molecules. Although small
molecules emitted bright light, scientists had to deposit
them onto the substrates in a vacuum.

Since 1990, researchers have been using large polymer
molecules to emit light. Polymers can be made less
expensively and in large sheets, so they are more suitable
for large-screen displays.