Organic LED, OLED Basics Tutorial

- details and overview about OLED, organic LED displays, what they are, their limitations, advantages and applications.

Organic LEDs or OLEDs are now an established area of the overall LED market.

OLEDS are being used in many applications from television set screens, and computer monitors, along with other small, portable system screens such as mobile smartphones to watches, advertising, information, and indication. OLEDs are also used in large-area light-emitting elements for general illumination.

Currently OLEDs emit less light than their in-organic counterparts, but their flexibility means that they can be used in a much greater number of applications.


Organic LED overview

the organic LED, OLED has many of the properties of a traditional organic LED. It is a PN junction cross which light flows.

However, rather than using the traditional in-organic materials, OLEDs utilise organic compounds for the PN junction. These materials include a variety of substances, but materials such as Aluminium 8-hydroxyquinoline and diamene are often used.


OLED advantages & disadvantages

OLED technology is finding its niche in a variety of applications because it is able to provide a number of advantages:

  • Flexible:   It is possible to make OLED displays flexible by using the right materials and processes.
  • Very thin:   OLED displays can be made very thin, making them very attractive for televisions and computer monitor applications.
  • Colour capability:   It is possible to fabricate OLED displays that can generate all colours.
  • Power consumption:   The power consumed by an OLED display is generally less than that of an LCD when including the backlight required. This is only true for backgrounds that are dark, or partially dark.
  • Bright images:   OLED displays can provide a higher contrast ratio than that obtainable with an LCD.
  • Wide viewing angle:   With many displays, the colour becomes disported and the image less saturated as the viewing angle increases. Colours displayed by OLEDs appear correct, even up to viewing angles approaching 90°.
  • Fast response time:   As LCDs depend upon charges being held in the individual pixels, they can have a slow response time. OLEDs are very much faster. A typical OLED can have a response time of less than 0.01ms.
  • Low cost in the future:   OLED fabrication are likely to be able to utilise techniques that will enable very low cost displays to be made, although these techniques are still in development. Current costs are high.

OLED displays do have their disadvantages:

  • Moisture sensitive:   Some types of OLED can be sensitive to moisture.
  • Limited life:   The lifetime of some displays can be short as a result of the high sensitivity to moisture. This has been a limiting factor in the past.
  • Power consumption:   Power consumption can be higher than an equivalent LCD when white backgrounds are being viewed as the OLED needs to generate the light for this which will consume more power. For images with a darker background power consumption is generally less.
  • Lifespan:   The lifespan of the OLED displays is a major problem. Currently they are around half that of an LCD, being around 15 000 hours.
  • UV sensitivity:   OLED displays can be damaged by prolonged exposure to UV light. To avoid this a UV blocking filter is often installed over the main display, but this increases the cost.

Types of OLEDs

Organic LED, OLED technology can be divided into two types of organic LED technologies:

  • Small Molecule OLED, SM-OLED:   The small molecule type of organic LED was originally championed by Kodak, and is often the type referred to be the name OLED.
  • Polymer LED, PLED:   Polymer LEDs, PLEDs, may also be known as Light Emitting Polymers, LEPs.

OLEDs are being seen used increasingly in view of the advantages which they possess. While they still have some disadvantages, significant development effort is being focussed on this technology around the globe because of its potential which is starting to be taped.

By Ian Poole


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