Opsys' Dendrimer Materials Make World's Most Efficient Solution Processed OLEDs
Added: (Thu May 16 2002)
Pressbox (Press Release) -
Scientists sponsored by display technology developer Opsys Limited have developed high efficiency bi-layered green organic light emitting diode (OLED) devices. A maximum efficiency of 40 lm/W at 400 cd/m2 was recorded for the OLEDs, which contain a solution processed light emitting dendrimer layer. These results are the most efficient ever reported for such devices.
The work is a collaboration by Opsys sponsored teams led by Dr Paul Burn and Dr Oleg Salata at the University of Oxford, and by Professor Ifor Samuel, Royal Society Research Fellow at the University of St Andrews. This latest result builds upon Opsys’ recent groundbreaking announcement of 6.9 lm/W at 1500 cd/m2 for a single-layered dendrimer device and brings dendrimer technology closer to commercial viability for efficient, low cost manufacturing of flat panel displays.
Currently, displays based on small molecule fluorescent materials are regarded as the most mature in the field of OLEDs. However, small molecule materials can only be deposited by evaporation techniques and it is believed that in the future solution processing will provide a lower cost approach to large area full colour displays.
Michael Holmes Opsys CEO commented, “The production of high efficiency bi-layered OLEDs builds on Opsys’ recent dendrimer developments and consolidates our position as a leading display technology developer.
“Dendrimers have the potential to make long-term improvements in colour quality, power efficiency, lifetime and processing costs of displays. These are vital for OLEDs to fulfil their potential for growth within the displays sector and to meet their transformational expectations in lighting, décor and signage applications.”
Opsys is the exclusive licensee of patent applications involved in this work and the publication of these results further strengthens the company’s position as the key intellectual property holder of light emitting dendrimer technology for OLEDs.
The results will be announced by Professor Ifor Samuel at the forthcoming ‘Society for Information Display 2002’ conference in Boston, MA, in the latest news session, paper L8, Room 304, Hynes Convention Center, on Wednesday 22 May. They will also be published in a paper entitled “A Green Phosphorescent Dendrimer for Light-emitting Diodes” in Advanced Materials, on 4 July 2002.
Notes to Editors
Light emitting dendrimers show a number of benefits that make them particularly attractive for the development of low cost, high efficiency OLED displays:
ˇ Dendrimers can incorporate the best features of small molecule materials, such as highly efficient phosphorescent emitting cores, whilst also being solution processable.
ˇ The processing and electronic properties of dendrimers can be optimised independently. The core, for example, can be chosen to determine the key electronic properties such as light emission whilst the surface groups can be selected to give the desired solubility.
ˇ Control over intermolecular interactions can be achieved within dendrimers by modifying the number of generations of the branched dendrons. This control is vital to minimise the quenching of luminescence in OLEDs, thus maximising efficiency.
ˇ Phosphorescent dendrimers employ emission from both singlet and triplet excited states, making it theoretically possible to produce OLEDs with a 100% internal quantum efficiency.
Devices made using an iridium-dendrimer solution processed layer and an electron-transporting layer were found to have a maximum efficiency of 40 lm/W (55 cd/A) at 4.5 V and 400 cd/m2. Turn-on voltages were normally 3.0 V and a maximum brightness of 12000 cd/m2 at 7.0 V has been observed.
Light emitting dendrimers constitute a new but rapidly maturing materials technology in the field of OLEDs. They comprise an organic or organometallic light emitting core, which is connected to surface groups by branched organic dendrons.
The dendritic structure controls core-core interactions and hence the photoluminescence and device properties of the materials. A key advantage of dendrimers is that the luminescent cores are kept well apart by the bulky dendrons, which minimises luminescence quenching.
Opsys, headquartered in Oxford, UK, was founded in 1997 to advance cutting edge light emitting technology for flat displays. Opsys’ researchers work closely with academics from both Oxford and St Andrews Universities in order to put innovative technologies on to an industrial development footing. Opsys intends to license its dendrimer materials for use in OLED displays.
In 2001, Opsys established a 42,000 sq. ft. research and prototyping facility based in Fremont, California, for the development of small to medium sized custom displays for the portable electronics industry. For further information about Opsys, visit www.opsysdisplays.com.
About the OLED displays markets
Market research company Display Search expects that by 2005, OLED technology will have carved a 14% market share, at the expense of LCDs, in the mobile telephone and PDA market. Display Search also predicts that OLED revenues are expected to rise at a compound annual growth rate of 110% to reach as high as $2.2 billion in 2006. Similarly, Stanford Resources forecasts that the worldwide OLED market will be valued at $2.3 billion in 2008.
The industry is targeting a wide range of electronics products for OLEDs, including mobile phones, PDAs, digital cameras, camcorders, microdisplays, and eventually personal computer and consumer products.