OLED displays have long been touted as the successor to current dominant technologies like LCD (liquid crystal displays). Whilst they have been adopted by a number of smartphone manufacturers, and have advantages over LCD in terms of colour depth and power consumption, OLEDs have yet to make an impact on the market for larger display screens, like computer monitors and TVs.
Several electronics manufacturers have been promising ultra-high quality OLED TVs and flexible or semi-transparent OLED-powered gadgets for quite some time, but problems with commercialization of the technology have pushed release dates back.
What are OLEDs?
An organic light-emitting diode, or OLED, uses an organic film in its emissive electroluminescent layer. It is manufactured by placing organic thin films in series between two conductors. When an electrical current is applied, it emits a bright light.
OLEDs are widely used in digital displays in handheld devices such as phones, PDAs, games consoles, etc and also in TV screens and PC monitors. OLED displays can use two schemes: passive-matrix (PMOLED) or active-matrix (AMOLED). AMOLEDs enable larger sizes in displays and need a thin-film transistor backplane.
Figure 1. Samsung show off their forthcoming range of OLED TVs at CES (Consumer Electronics Show) 2012. Image Credits: Samsung News Center.
Benefits of OLED Displays
The key benefits of OLED displays compared to LCD displays are listed below:
- Higher durability and wider operating temperature range
- Higher contrast ratio
- Brighter screens
- Full viewing angle
- Faster response time
- High power efficiency
- Lighter and flexible screens
- New flexible, ultra-thin, or transparent displays
Novel Display Applications of OLEDs
By virtue of their unique properties, OLEDs allow for some great new possibilities in displays. Several recent developments in innovative display technology would not be possible without OLEDs.
Samsung Display Co., the display unit of South Korean electronics major Samsung, is all set to begin large-scale production of flexible displays for smartphones using bendable plastic based on a novel, low-cost flexible OLED technology. This is a bold move that can render your smart phones lighter and more durable.
These flexible displays will use OLEDs which are very thin and can be used on flexible materials such as metal foils or plastics. Although flexible OLEDs have been in the market for years and other key players such as Sony have been experimenting with this technology for many years now, commercialization of these devices has not been attempted so far because of technological challenges in large-scale production.
In 2009, researchers from Toshiba, Japan, developed a wallpaper that can turn into a TV screen with the help of OLED technology. Thanks to nanotechnology, this flexible paper can turn an entire wall into a display screen as well as show customized images to fit your mood. Improvements to the OLED technology have enabled this breakthrough in wallpapers by making the paper emit light.
To increase the efficiency of OLEDs, the wallpaper uses light coming from an ultra-fine grating, which is made of self-assembled nanoparticles. Another interesting possibility, according to the researchers, is that these wall papers can eliminate the need for traditional lighting systems as they themselves can emit light. This novel technology is still in the research phase and commercial production may take years.
Figure 2. Demonstration of LG's 55 inch OLED TV at CES 2012.
Current Status of OLED Market
According to the latest report by NPD DisplaySearch, shipping of OLED TVs is all set to start by the end of 2012 - some models, including 55 inch TVs from Samsung and LG, will be available by Christmas.
OLED TVs will remain a high-end, premium product, however. The report reveals that about 500 OLED TVs will be shipped this year. It has also forecasted that shipments will hit 1 million in the year 2014.
The delay in commercialization of OLED TVs is said to be due to challenges in mass production and high retail prices. Taiwan, China and Japan are also expected to join the race by starting production of AMOLED TV panels in 2014.The report also forecast that OLED will penetrate over 3% of the TV market by the year 2016.
According to this report, the main market and technical challenges faced by OLED TVs are:
- Technical difficulties in making large panels
- High costs and low manufacturing yields
- High retail price
- High competition
- Market entry timing
Future Potential of OLED Technology
In an interesting development in 2011, which has paved the way for easier commercialization of OLED displays, researchers from the University of Florida developed a novel light emitting transistor design which suggested ways around some stumbling blocks on the way to manufacturing large OLED screens.
Despite their advantages over LCDs, OLEDs have so far been largely restricted to small, hand-held displays because of barriers in producing transistors that drive these diodes. The new transistor design overcomes this by using organic semiconductors which drive high currents for OLEDs in a much more efficient manner with the help of carbon nanotubes at lower voltages. The research team combined the OLEDs and the transistor to produce a light emitting transistor, which contains carbon nanotubes and is called vertical organic light-emitting transistor (CN-VOLET). It is said to have an efficiency that is eight times more than that of similar devices.
Lower costs and decrease in manufacturing complexity are some of the advantages of this integrated design. Another advantage is, the light emitter is capable of occupying a larger pixel area and provides the same light output at a lower current density, which is claimed to increase the life span of these devices. The researchers feel that apart from its application in consumer electronics, this breakthrough design can help in developing in more affordable RFID tags, which retailers use for inventory tracking, in the distant future.
The OLED technology has opened up an exciting new world of opportunities with their unique properties and benefits. However, OLED displays have some disadvantages such as poor outdoor performance, shorter lifespan, susceptibility to water damage, and colour balance issues as the screens age, which limits their application. Further development of the technology will be needed to ensure these problems are overcome.
Currently, there is a lot of research and development going on in the field of OLEDs and experts feel that these might lead to novel applications such as automotive dashboards, heads-up displays, home and office lighting and billboard-type displays in the future. OLED devices can keep refreshing information at real time and videos can look more realistic in them. So we can also fancy thin and foldable OLED newspapers in the future, which keep refreshing news even as you read them!
Sources and Further Reading