OLED Technology

What is an OLED?

OLED stands for Organic Light Emitting Diode and is made up of individual image elements called pixels comprised of organic chemical compounds which emit light when an electric current is applied between a anode and cathode of each pixel. This process is similar in operation to a standard LED operation where light emission is through the recombination of electrons and holes from the cathode and anode.

OLED vs. LCD

OLEDs and LCDs are used in display devices but are very different in how they present their display information. An OLED is an emissive type of display meaning it’s self-illuminating. An LCD, however, presents information via transmissive or transflective methods, which means that image illumination is supplied with methods such as a backlight and room light or the sun.

PMOLED vs. AMOLED

PMOLED stands for Passive Matrix OLED and is fabricated of emitting OLED pixel arrays configured in columns and rows with each pixel intersecting at a column row. These OLED pixels are arranged where their anodes are current driven by an electronic controller chip which also controls the cathode turn on to produce the desired display image.

The controller electronic continually scans the entire OLED column and row array at a set frame rate to produce an image. Because of this, the most power efficient display designs are best in smaller display sizes of 3” or less.

AMOLED stands for Active Matrix OLED and is fabricated similarly to a TFT display with each individual pixel element being addressable unlike the row and column design of a PMOLED. PMOLED displays are good for displaying text but fall short when displaying moving images due to the time needed to scan the rows and columns which can cause a perceived ghosting.

On the contrary, with an AMOLED, each individual OLED pixel can be turned on individually without the need to scan an entire array making them far superior for moving images. This allows the AMOLED to produce an image without any ghosting. This individually pixel design also allows for better illumination control for a brighter, higher contrast, more power efficient display. AMOLED displays are much faster the LCDs which makes them more attractive for video displays.

Advantages and disadvantages of OLEDS

OLED displays have an advantage over other displays such as TFT LCD displays since they are a self emitting light source and do not need a separate external light source in order to display an image. Therefore, they are more efficient. This self-illumination allows OLED displays to be much thinner than other technologies and can even be used in flexible displays as well. Some other advantages are:

• Superior viewing angle
• High brightness and contrast
• Fast response time
• Small size form factors
• Well suited for battery driven applications

Besides the noted advantages of OLED display, some of the disadvantages include:

• Shorter lifetime then some other display technologies. This shorter lifetime is mainly due to the blue organic material but lifetime gets better all the time but is also due to moisture migration.
• Poor sunlight readability.
• The current production processes make it difficult and costly to produce large displays so most are limited to handheld devices, but like the lifetime issue this eventually will be improved.

Uses for OLEDS

OLED displays have found their way into many handheld products since their onset and continue to be popular in the mobile market. OLED displays can also be found in gaming applications and audiovisual applications such as programmable push button switches. OLED displays can also be found in cameras, PDA’s, and a few small TV’s.