OLED tutorial-OLED basics,OLED types,OLED structure,Working
This OLED tutorial covers OLED basics, OLED types, OLED structure and OLED working operation. The OLED tutorial also provides links on advantages and disadvantages of OLED and difference between OLED, LED and LCD.
What is OLED?
OLED stands for Organic Light Emitting Diode. Solid state OLEDs are easier to fabricate and hence are replacing CRTs or LED displays due to flexibility. It is an electronic device made by placing series of organic thin films between the two conductors. A bright light is emitted when electrical current is being applied.
They are thin-film organic semiconductor light emitting devices. OLED works on the same principle of electro-luminescence. Anode is transparent and made of indium tin oxide. Cathode is reflective and made of metal. When an external potential is applied across the electrodes, positive and negative charges are injected. These electrons and holes shift inside the material and re-combine to form excitons and consecutively emits photons.
As shown in the figure-1, OLED structure consists of
Cathode, Emissive Layer, Conductive Layer, Anode and substrate.
It uses thin film of organic material sandwiched between
two electrodes viz. anode and cathode. Let us understand constructions and functions of each
of these layers of OLED structure.
Substrate: It is made of thin translucent glass or foil material. It functions as base of the OLED structure.
Anode: Its main function is to emit electrons when voltage is applied across its terminals. Hence it is called as emitter.
Organic layer:It contains conductive polymer made of hydrogen or carbon molecules. It is situated above anode layer.
Conductive layer: It is made of organic plastic molecules. It helps to move holes from the anode.
Emissive layer: It is made of organic materials which are different than used in conductive layer. It helps to transport electrons from the cathode.
Cathode: It is top part of the OLED. It injects electrons when potential difference is applied across its terminals.
OLED Working Operation
Let us understand how OLED works.
• Due to battery or power supply, voltage is being applied to the OLED.
• As a result current flows from cathode to the anode through the organic layers.
• This process gives electrons to the emissive layer and removes electrons from conductive layer.
• Removal of electrons from conductive layer leave out holes which need to be filled with electrons in emissive layer.
• The holes jump to emissive layer and will recombine with electrons. As electrons drop into holes, they release their extra energy as light. This way light emission takes place in the OLED device.
Based on number of layers OLEDs can be classified into two layer OLED and three layer OLED.
➨In the two layer OLEDs, electrons are injected from cathode into lowest unoccupied molecular orbital. Simulataneously holes are injected from anode into highest occupied molecular orbital.
➨In the three layer OLEDs, the conductive layer is replaced with electron transport layer and hole transport layer.
➨Based on working, features and applications OLEDs are further divided into following.
• PMOLED (Passive Matrix OLED)
• AMOLED (Active Matrix OLED)
• TOLED (Transparent OLED)
• FOLED (Foldable OLED)
• White OLED
• Top Emitting OLED
Advantages and Disadvantages of OLED
Refer benefits or advantages and drawbacks or disadvantages of OLED >>.
Difference between OLED, LED and LCD
Refer OLED vs LED vs LCD >> which mentions difference between OLED with LED and LCD types.
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