Organic Light Emitting Diode

OLED is an acronym which stands for Organic Light Emitting Diode. an OLED is an electronic device made by placing organic thin film material between two conductors. When an electric current is applied, a bright light is emitted.

According to researchers, this piece of technology is 200 times smaller than a strand of human hair. It is a new technology and an advancement upon the regularly used LED technology. This technology was first introduced in 2009, where LED television set was much brighter and slimmer in sizes than its predecessors which include, the outdated cathode ray tube (CRT), plasma, and liquid crystal displays (LCD). The OLED screen technology now provides flexibility to curve screens and roll up screens.

Brief History

OLED technology was invented by researchers in a company called Eastman Kodak in 1987. the company has released several of the first OLED equipped products e.g. EasyShare LS633, which was the first Kodak camera with the OLED technology.

What is OLED structure

The OLED structure is made up of several microscopic layers.

1. Cathode: the cathode injects electrons into the emissive layer.
2. Emissive layer: this layer is made of polyfluorene and transports electrons from the cathode to the anode. This is where light is made.
3. Conducting layer: this layer is made of polyaniline and transports "holes" from the anode to the cathode.
4. Anode: this is kept transparent, is usually made of Indium tin oxide (ITO) and removes electrons.
5. Substrate: the substrate supports the OLED.

OLED structure
OLED structure


How OLED emits light 

OLED emits light when a battery or any power supply is connected to the cathode and the anode (forward biased). It uses almost the same principle as a regular diode (see the working principle of a diode). At the boundary between the emissive and the conductive layers, electrons find electron holes then the OLED emits light.

The different types of OLED include

The passive-matrix

the passive-matrix





The active-matrix









transparent structure
Transparent structure






flexible structure
Flexible structure












  • It is thinner, lighter and more flexible
  • It is very bright
  • It consumes much less power
  • It has a large field of view



  • A lifetime of about 22000hrs
  • Difficult to manufacture
  • Not suitable for water