Organic LED

Latest in LED Technology - Organic LEDs

Conventional LED

LEDs are known as Light Emitting Diodes. Light-emitting diodes are made up of using semiconductors such as Gallium Arsenide, Gallium Phosphide, and Gallium Nitride, have been around since the late ’50s. The main applications of LEDs are indicator lamps, calculators, large advertising signs with high brightness. Limitation of LEDs Though such crystalline LEDs are not inexpensive, but it has its own limitation like integrating them into small high-resolution displays. LED.’s work well in giant screens and advertising displays like those in Times Square, they cannot easily be used to create small, high-resolution screens for portable computers.

Organic LEDs – A breakthrough in LED technology

To overcome the difficulties faced by the conventional LEDs, the Organic LEDs has entered into the field. Organic light-emitting devices (OLEDs) operate on the principle of converting electrical energy into light, a phenomenon known as electroluminescence. They exploit the properties of certain organic materials which emit light when an electric current passes through them. In its simplest form, an OLED consists of a layer of this luminescent material sandwiched between two electrodes. When an electric current is passed between the electrodes, through the organic layer, light is emitted with a color that depends on the particular material used. In order to observe the light emitted by an OLED, at least one of the electrodes must be transparent. Advantages of OLEDs When OLEDs are used as pixels in flat panel displays; they give greater viewing angle, lighter weight, and quicker response. Since only the part of the display that is actually lit up consumes power, the most efficient OLEDs available today use less power. Because OLEDs are self-luminous, backlights are not required as in liquid-crystal displays (LCDs). OLEDs have very low power requirements and are thin, bright and efficient.

Advantages

The different manufacturing process of OLEDs lends itself to several advantages over flat-panel displays made with LCD technology.

Lower cost in the future

OLEDs can be printed onto any suitable substrate by an inkjet printer or even by screen printing theoretically making them cheaper to produce than LCD or plasma displays. However, fabrication of the OLED substrate is more costly than that of a TFT LCD, until mass production methods lower cost through scalability.

Light weight & flexible plastic substrates 

 OLED displays can be fabricated on flexible plastic substrates leading to the possibility of Organic light-emitting diode roll-up display being fabricated or other new applications such as roll-up displays embedded in fabrics or clothing.  As the substrate used can be flexible such as PET.  The displays may be produced inexpensively.

Wider viewing angles & improved brightness: OLEDs can enable a greater artificial contrast ratio (both dynamic range and static, measured in purely dark conditions) and viewing angle compared to LCDs because OLED pixels directly emit light. OLED pixel colors appear correct and unshifted, even as the viewing angle approaches 90 degrees from normal.

Better power efficiency: LCDs filter the light emitted from a backlight, allowing a small fraction of light through so they cannot show true black, while an inactive OLED element does not produce light or consume power.

Response time

 OLEDs can also have a faster response time than standard LCD screens. Whereas LCD displays are capable of a 1 ms response time or less offering a frame rate of 1,000 Hz or higher, an OLED can theoretically have less than 0.01 ms response time enabling 100,000 Hz refresh rates.

Disadvantages

            There are some disadvantages in OLED and they are all listed below

Water damage

Water can damage the organic materials of the displays. Therefore, improved sealing processes are important for practical manufacturing. Water damage may especially limit the longevity of more flexible displays.

Outdoor performance

 As an emissive display technology, OLEDs rely completely upon converting electricity to light, unlike most LCDs which are to some extent reflective; e-ink leads the way in efficiency with ~ 33% ambient light reflectivity, enabling the display to be used without any internal light source. The metallic cathode in OLED acts as a mirror, with reflectance approaching 80%, leading to poor readability in bright ambient light such as outdoors. However, with the proper application of a circular polarizer and anti-reflective coatings, the diffuse reflectance can be reduced to less than 0.1%. With 10,000 incident illumination (typical test condition for simulating outdoor illumination), that yields an approximate contrast of 5:1.

Power consumption

 While an OLED will consume around 40% of the power of an LCD displaying an image which is primarily black, for the majority of images it will consume 60–80% of the power of an LCD - however it can use over three times as much power to display an image with a white background such as a document or website. This can lead to disappointing real-world battery life in mobile devices.

Screen burn-in

                Unlike displays with a common light source, the brightness of each OLED pixel fades depending on the content displayed. The varied lifespan of the organic dyes can cause a discrepancy between red, green, and blue intensity. This leads to image persistence, also known as burn-in.

Applications of OLEDs

OLEDs have been proposed for a wide range of display applications including magnified micro displays, wearable, head-mounted computers, digital cameras, personal digital assistants, smart pagers, virtual reality games, and mobile phones as well as medical, automotive, and other industrial applications. These OLEDs with its full color displays will replace today’s liquid crystal displays (LCDs) used in laptop computers and may even one day replace our ordinary CRT-screens.

Future scope of OLEDs

 In OLEDs as crystalline order are not required, organic materials, both molecular and polymeric, can be deposited far more cheaply than the inorganic semiconductors of conventional LED’s Patterning is also easier, and may even be accomplished by techniques borrowed from the printing industry. Displays can be prepared on flexible, transparent substrates such as plastic. These characteristics form the basis for a display technology that can eventually replace even paper, providing the same resolution and reading comfort in a long-lived, fully reusable (and eventually recyclable) digital medium.