How do PLEDs displays work?
What are polymers?
What are dendrimers and what makes them different from polymers?
What makes PLEDs unique?
How are PLED displays made?
How big can PLED displays be manufactured?
Approximately how much will it cost?
What are PLED displays used for?
Can I buy a PLED display from you?
When will products incorporating PLEDs be available in consumer products?
Who invented PLEDs?
Can I buy shares in CDT?
Who are CDTs strategic partners?
Who are CDT's licensees?
Where can I find out more?

How do PLEDs displays work?
PLED displays are made by applying a thin film of light-emitting polymer onto a glass or plastic substrate coated with a transparent electrode.  A metal electrode is sputtered or evaporated on top of the polymer.  Application of an electric field between these two electrodes results in emission of light from the polymer.  When a current is applied, electrons from the cathode migrate through the cell and meet positive 'holes' migrating from the anode.  When they meet, they form so-called excitons, and as the electrons drop into the holes, energy is released as light. See also How PLEDs work. 

What are polymers?
Polymers are long chains of organic molecules. PLEDS are special classes of polymer which have been found to emit light when stimulated electrically. PLEDs can be formulated to generate specific colours of light and have properties that are compatible with both the intended application as well as the process for deposition. There are currently two major families of PLED organic polymers: poly p-phenylenevinylene (PPV) and polyfluorene (PF).

What are dendrimers and what makes them different from polymers?
Typically polymers have only two end groups, one at each end of the polymer chain. Branching can be introduced into the polymer along the polymer backbone, thereby increasing the number of end groups present. Branching can be important in terms of cross-linking and in the formation of three- dimensional networks or films. At high levels of branching, hyper branched or star-like polymers can be made. Dendrimers are similar to hyper-branched polymers. They possess repeating units in their structure that radiate from a central core. The synthetic scheme used in preparing dendrimer materials is extremely precise and well-controlled, with each successive layer being added to the molecule one step at a time. Dendrimers are usually of a precise molecular weight, i.e. they are monodispersed. The chains radiating from the central core are usually referred to as dendrons. Looking from the exterior of the molecule, a dendrimer appears spherical with the end groups of each dendron lying on the surface of the sphere. These groups can be used in further reactions, such as cross linking, or may be used to modify the surface properties of the material, e.g. to make it more or less hydrophilic. Dendimers have an extremely high concentration of functional groups or functionality for their molecular weight or volume.

What makes PLEDs unique?
PLEDs are one of the major Organic Light Emitting Diode (OLED) technology platforms being forecasted by industry analysts as the next major breakthrough in electronic displays. PLEDs provide the basis for developing new products such as wristwatch televisions, flexible or formable displays, and will ultimately provide an alternative to the traditional "big-and-bulky" cathode ray tube (CRT) now used in conventional televisions and computer monitors.
Because PLEDs emit their own light, they are brighter, clearer, and have a virtually unlimited viewing angle. Their high contrast and wide dynamic brightness capabilities make them a better solution for night and daylight use. PLEDs also have a fast image refresh rate that is maintained at low temperature, which makes them ideal for full colour video in TV, internet devices, PDAs and next generation mobile phones. Because PLEDs do not require a power hungry backlight, they are energy efficient and are thinner and lighter weight.

How are PLED displays made?
One of CDT's innovations is the creation of displays by ink-jet printing light emitting polymers onto a sheet of glass or plastic, which offers a low cost route to colour displays.  As devices can be manufactured on flexible plastic substrates, it is even possible to make displays that have a non-planar shapes.

Much of the clean room equipment required to manufactured PLEDs already exists in an LCD plant. In fact the manufacturing process for PLEDs is much simpler than for LCD: they do not have backlights, polarizers or colour filters and need fewer process steps. The key difference is that a PLED display can be ink jet printed using conventional ink jet printing technology.

In January 2002, CDT announced completion of its new 1,750 square meter US$25 million Technology Development Centre in Godmanchester, UK.  It includes a 600 square metre state-of-the-art clean room comprising class 1000 and class 100 areas, and fabrication of pilot quanities of PLED displays on the 350 x 350 mm line has begun. The Centre has broadened the scale and scope of PLED-based intellectual property, technology and manufacturing know-how as well as manufacturing tools and materials available to its licensees and strategic partners.

How big can PLED displays be manufactured?
Like all flat panel display technologies, initial products will be relatively small in size, typically less than 2 in. diagonal. Displays up to 17 in. have been demonstrated and ultimately, because of the scalability of ink jet printing, displays of 30-40 in. diagonal are expected. Because of their relative simplicity and flexibility in manufacturing, different technology sets could enable modular display devices that can be tiled to produce very large displays.

Approximately how much will it cost?
Costs to manufacture, when compared with LCDs of comparable volume and maturity of production tools and processes, are expected to be 20-40% lower.

What are PLED displays used for?
PLED has four key applications:

• Large single pixel displays can be used in lighting applications, replacing incandescent and fluorescent bulbs.
• Low information content displays where inorganic LEDs are currently used: video, hi-fi, shaver, watch etc
• Displacement of cathode ray tube (CRT) or LCD (traditional television and computer display applications): mobile phones, digital assistants, computers and televisions.
• New display applications for which PLED characteristics make it uniquely suited. E.g., replacement for traditional automotive instrument panel, dynamic advertising applications, graphical signs for point of sale or purchase, electromechanical signage, bio-medical testing.

Can I buy a PLED display from you?
Not directly. CDT has a broad, global plan for developing polymer technology to a stable and mature commercial level and speeding its transfer into manufacturing for a wide range of market applications. The scope of the plan includes basic research in polymer materials and synthesis, and development of material systems, device architectures, manufacturing tools, equipment and processes, and alternative synergistic technologies for plastic substrates, active and smart circuits and web processing. Collaboration, joint venture, and licensing are the business tools CDT is employing with strategic companies around the world to ensure successful PLED commercialisation.

When will products incorporating PLEDs be available in consumer products?
They already are! The first PLED products were launched in 2002 by CDT licensees. Philips introduced an electric shaver with an orange battery gauge display and Delta Optoelectronics used a green 16x64 display in an MP3 player. In 2003, Dupont launched a PLED display for the APED range of MP3 players marketed by Evolution Technologies. The display is marketed with the brand name Olight and it is 2.1 inches diagonally with a 128x64 resolution.

Osram Opto Semiconductors currently offers evaluation kits of the technology, branded as Pictiva. While the first PLED products are small (< 2”), low information content, single colour, passive matrix displays, Philips, Toshiba-Matsushita Display, DuPont, Microemissive Display Ltd., Samsung SDI and Seiko-Epson have demonstrated full colour active and passive matrix displays. Toshiba-Matsushita Display exhibited an ink jet printed, full colour, video capable, 17-inch 1280 x 768 PLED prototype display at the SID trade show in 2002.

Dai Nippon Printing (DNP), another CDT licensee, has showcased PLED displays incorporated into advertising with a resolution of 94x54, 96x64 or 128x64 on book covers and posters.

Who invented PLEDs?
In 1989, researchers at the Cambridge University Cavendish Laboratory found that passing an electric current through certain polymers made them emit light. How PLEDs work.
Cambridge Display Technology (CDT) was formed in 1992 to commercialise the technology that evolved from this discovery.  CDT owns the fundamental intellectual property and expertise in light-emitting polymers (PLEDs).  A team of over eighty scientists is now responsible for the development of this technology.

Can I buy shares in CDT?
CDT is a privately held company and is not listed on a stock market. Since July 1999, the ultimate holding company has been CDT Acquisition Corporation, a USA corporation.

Who are CDT's licensees?
CDT’s PLED technology has already been licensed to world class OEMs, including Philips, Seiko Epson, Osram, Dupont and Delta Optoelectronics, as a route to making lighter, brighter, less power-consuming and more responsive displays for next generation products such as mobile phones, PDAs and eventually computer monitors and televisions.  CDT licensees are now working on scale-up and commercialisation into consumer electronics in the months to come.

Who are CDTs strategic partners?
In addition, CDT has strategic partners in a wide range of technologies and related industries, including Bayer AG, Covion, Dow Chemical, Eastgate Technologies, Sumitomo Chemical, ST Microelectronics and Tokki Corporation with numerous others being developed.

Where can I find out more?
A good start would be to follow our Useful Links to some of our partners and technology collaborators, and to the related trade press. You can also follow up on our Technical References to published works. If you'd like to contact us for more information, we'd be delighted to hear from you.