fantastic plastic

The Georgia Tech Center for Organic Photonics and Electronics (COPE) and Solvay announced a $3 million deal for OLED research today.

COPE has already developed a unique material platform for OLEDs that may be deposited over large areas by ink-jet printing and patterned using standard photolithography. Tech researchers have found that exposing the material to ultraviolet light leads to hardened materials that are insoluble and maintain stability under high temperatures. This allows researchers to build a multi-layered solid-state device from liquid materials. […]

COPE, through the research group of Jean-Luc Bredas, already conducts research activities with the University of Mons-Hainaut in Belgium. Georgia Tech has two international campuses, Georgia Tech Lorraine in Metz, France, and Georgia Tech Singapore. […]

In addition to Marder and Bredas, two other principals at COPE are Bernard Kippelen, associate director of COPE and professor in Tech’s School of Electrical and Computer Engineering and Marcus Weck, associate professor in the School of Chemistry and Biochemistry.

DuPont has announced solution-processable small molecule OLED materials, enabling low-cost deposition techniques previously only possible with polymeric OLED materials.

DuPont’s latest technological achievement enables — for the first time — the combination of high performance and long lifetime of small molecule OLED materials with a printing process that is substantially lower cost and more scalable to larger display sizes than the industry incumbent processes, such as vapor deposition. Through a combination of innovative processing device architecture and new materials, DuPont has demonstrated printing of small molecule OLED materials from solution.

DuPont has achieved lifetimes of the three primary colors each exceeding 10,000 hours of white lifetime (or 40,000 hours for a typical video) at the brightnesses required for a 200 nit display. With this development, DuPont has demonstrated that OLEDs can be manufactured at high yields and low total cost.

A while ago a group at Philips research presented (’Video-speed electronic paper based on electrowetting‘, Nature Vol. 425, pp. 383-385, 25 September 2003; link to pdf reprint) a novel display type based on the principle of electrowetting.
Liquavista, a spin-out with New Venture Partners as main investor and Philips remaining a shareholder, is now commercialising this technology (press release).

Some of the benefits compared to other display technologies are:

• video speed
• low power consumption
  (less need for supplimentary illumination)
• indoor & outdoor usability
• no inherent limit on viewing angle

Regarding the manufacturing process, Liquavista is building on existing LCD technoloy:

To contemplate the development and promotion of a new technology, without considering accessibility of large scale manufacturing resource would challenge the benefits of even the most exciting of technologies. That is why, from the outset, Liquavista has developed electrowetting display technology to be almost entirely compatible with existing display manufacturing techniques and processes. […]
A proprietary low cost, scalable fill process, performed at the bipane level, and patented by Liquavista, improves further on the standard LCD manufacturing cycle.

More background information here.

Quantum Paper Inc. (nothing on their website yet) appears to be a relatively new player in the electronic paper business.

According to PrintWeek, the company claims it has created the “first production quantities”:

The US firm said its paper features an electronic display that can be printed on ordinary paper, board or plastic. […]
President Michael Feldman said: […] “The technology is prototype, but we hope to roll out licences for printers to make electronic paper-based displays later this year. “It is made on paper by standard printing presses, with no need for specialised gear.”
Chief technology officer Dr William Ray said: “It is one of the most important developments in printing in more than 10 years. “The paper is a unique marriage between the relative simplicity and low cost of printing and the high technology of pixel-based electronic displays.” He claimed it had the potential to replace mobile phone and computer screens, interactive billboards and high-definition TVs at a “fraction of today’s cost”.

Unfortunately no technical information yet, but some more PR at package printing:

“This technology has the potential to transform printing as we know it,” says Dr. William J. Ray, the principal inventor and Quantum Paper’s chief technology officer. “It is no exaggeration to call Quantum Paper’s electronic paper as one of the most important developments in the printing industry in more than 100 years.”
The technology can also be used to create the equivalent of television on paper. Quantum Paper has fully addressable, high-quality dynamic color displays under development with the potential of replacing conventional cell phone and PDA screens, computer monitors, interactive billboards, electronic wallpaper, and high-definition televisions at a fraction of today’s cost.
“Quantum Paper’s electronic paper is a unique marriage between the relative simplicity and low cost of conventional printing and the high technology of pixel-based electronic displays,” said Ray. “The performance of our displays meets or exceeds that of competing technologies but our electronic paper can be manufactured at such a low cost as to be considered disposable.”

[via MobileRead]

A research team including Stephen Forrest and Mark Thompson have published their work on
“Management of singlet and triplet excitons for efficient white organic light-emitting devices”
in Nature (440, 908-912; 13 Apr 2006)

From the Scientific American:

“A 100-watt bulb is about 15 lumens per watt and we’re at about 25 lumens per watt just on the lab bench,” Forrest says.
The diode also requires a lower voltage than purely phosphorescent devices do thanks to its fluorescent component […]
Challenges remain before light-emitting ceilings can become common. Among other things, scientists will need to find a material to encase the sensitive diodes. “This doesn’t need a vacuum but it does need a moisture barrier and that can be expensive,” Forrest explains. “The biggest barrier to large scale production is simply cost. It costs very little to make a light bulb today.”

In the abstract of the of the artice the increased energy efficiency of white OLEDs compared to incandescent lighting and the compatibility with low-cost manufacturing methods are mentioned, as well as a few details of the new approach:

The most impressive characteristics of such devices reported to date have been achieved in all-phosphor-doped devices, which have the potential for 100 per cent internal quantum efficiency: the phosphorescent molecules harness the triplet excitons that constitute three-quarters of the bound electron-hole pairs that form during charge injection, and which (unlike the remaining singlet excitons) would otherwise recombine non-radiatively.
Here we introduce a different device concept that exploits a blue fluorescent molecule in exchange for a phosphorescent dopant, in combination with green and red phosphor dopants, to yield high power efficiency and stable colour balance, while maintaining the potential for unity internal quantum efficiency.
Two distinct modes of energy transfer within this device serve to channel nearly all of the triplet energy to the phosphorescent dopants, retaining the singlet energy exclusively on the blue fluorescent dopant. Additionally, eliminating the exchange energy loss to the blue fluorophore allows for roughly 20 per cent increased power efficiency compared to a fully phosphorescent device.
Our device challenges incandescent sources by exhibiting total external quantum and power efficiencies that peak at 18.7 +/- 0.5 per cent and 37.6 +/- 0.6 lm W(-1), respectively, decreasing to 18.4 +/- 0.5 per cent and 23.8 +/- 0.5 lm W(-1) at a high luminance of 500 cd m(-2).

Previous white OLEDs (WOLEDs) suffered from poor colour stability due to the limited lifetime of the blue electrophosphorescent component. A note on the increased lifetime compared of these new WOLEDs, from the BBC:

Previous attempts to make OLEDs like this have largely failed to make an impact because traditional phosphorescent blue dyes are very short lived.
The new polymer uses a fluorescent blue material instead which lasts much longer and uses less energy.

Thin Film Electronics and Xaar have presented the first printed polymer memory device at the IPEX ‘06. From the presentation (available online; 12 MB PDF file):

A 100 bit non-volatile re-writable cross-point array memory device was presented, in which all layers were printed.
- top & bottom electrodes: conducting polymer Baytron P Jet HC (220um linewidth)
- dielectric layer: ferroelectric polymer
- substrate: PET foil
- contact pads: silver nano-particle ink

[previous post on Thin Film Electronics]

EETimes is reporting on a new printhead using an OLED light source.

Epson Corp. said it has developed a print head using an organic light-emitting diode (OLED) light source, which is touted as achieving printing performance comparable to that of laser printer heads.
Sumitomo Chemical Co. Ltd. collaborated with Epson on the prototype printer head from the material side, supplying red polymer OLED material. […]
Epson intends to merge its low-temperature polysilicon TFT technology with the OLED technology to build a one-body printer head module with OLED and IC integrated on it.

Printers using an array of inorganic LEDs instead of a laser as light source have been around for a while. From an article from 2002:

LED (light-emitting diode) page printing - invented by Casio, championed by Oki and also used by Lexmark - was touted as the next big thing in laser printing in the mid-1990s.

Unlike laser printers, LED printers do not require any moving parts (mirrors) to selectively illuminate the photo-receptive drum, but are limited in resolution by the size of the LEDs.

Acreo, in collaboration with Linköping University, are developing low-cost electronics printed on paper. Their focus is on electrochemical devices, such as electrochromic displays. The change between bright and dark state is based on the difference in absorbtion of a polymer, e.g. PEDOT:PSS, in the oxidised versus the reduced state. Switching occurs at low voltages (0.6 to 0.9V), but is inherently slow (~1s).
The difference in conductivity of polymers, such as PEDOT:PSS, PANI, Polypyrrole and Polyhexylthiophene, between different redox states can be used to fabricate electrochemical transistors.

Other applications exploiting a change in material properties upon oxidation/reduction are a wettability switch and and a switchable polariser.

Acreo is using different printing techniques (e.g. screen- and offset-printing) to deposit layers such as the conducting polymer and polymer electrolyte layers.

Thin Film Electronics (TFE) are developing low-cost non-volatile memory, consisting of a bistable polymer layer between two arrays of orthogonal addressing lines. This technology provides several advantages compared to conventional, silicon-based memory. As the memory function is a property of the acticve layer, no circuitry is required in the actial memory element. Further, the simple architecture allows stacking of multiple layers for greater capacity per unit area. Using printing methods to deposit the solution-based promises low manufacturing costs.

From recent coverage of Printed Electronics USA 05 by IDtechEx (Feb 13, 2006):

Thin Film Electronics of Sweden described how it can print memory on plastic film. It has now demonstrated kilobit level memory but seeks to license not produce and the gigabyte on a postage stamp, with its immense commercial potential, is still elusive.

TFE’s website does not provide a lot of information on the material used for the active layer, but according to some of their patents (US 6,982,895, US 6,937,500, US 6,841,818) a polymeric ferroelectric or electret material, such as PVDF, can be used. A more recently filed patent (US200524343) concerns interlayers (e.g. metal oxides or ternary ceramics) between the electrode(s) and the active polymer layer.

This article at IDTechEx talks about the decline of the traditional printing industry, and new markets in the field of printed electronics.

Are the ink makers, machinery suppliers and others variously specialising in flexo, litho, ink jet, screen, gravure and other technologies looking like the steam engine experts of one hundred years ago? The answer is probably not. Certainly there is a fascinating escape route opening up for some. It is the printing of electronics.

Apart from cost savings, printing electronics enables the fabrication of new (flexible) devices and easier integration of components (e.g. displays, batteries, antennas, resistors, …).

Printed electronics will kick the silicon chip out of the talking gift card as well as the discrete components and wires to which it is attached. But that is the least of what it will do. The film Minority Report showed it giving us the moving colour display and voice over on the cornflake packet. Interactive games on disposable paper packaging have already been demonstrated in real life but more serious uses will also drive printed electronics forward.

The following table lists some of the companies involved in the printing of functional devices (Source IDTechEx)

BusinessWeek has a story on electronic ink applications, such as Hitachi’s electronic paper advertisement displays, updated via wireless connection.
They remind us of the fact that modern information technoloy has not led to the once envisioned paper-free office.

But the fact is, paper hasn’t gone away. The spread of the Internet and the rise of the PC have made information ever more accessible, leading not to the death of paper but to its proliferation. In 2004, worldwide paper production was roughly 400 million tons, compared with about 300 million in 1995, according to Japan Pulp & Paper statistics.

It remains to be seen whether or how soon e-paper will replace real paper. Applications such as rewritable shop price tags and billboards, where e-paper can provide added functionality, compared with traditional paper,

could help the market for e-paper surge to nearly $900 million by 2011, from $2 million last year, according to Tokyo-based market watcher Techno System Research.

The article goes on to mention colour electronic paper and printable OLEDs.
It’s cleary a business article, so we can forgive them for confusing some of the technical details:

Despite their differences, LCDs and OLEDs share two important traits: They can quickly change what they display and don’t need a backlight, so the only time they use power is when text or images change.

Of course LCDs and OLEDs are fast compared to most e-paper types, but, unlike bistable e-paper, constantly require power. Also, most LCDs do need a backlight (or frontlight), at least for low-light situations.

As reported here, the UK start-up Novalia

expects to launch its patented electronic card game by the end of 2006.
Printed electronics company Novalia is in advanced discussions with a printing company to produce the electronics on the cards. […]
Stone [Nick Stone, founder of Novalia] says that it is likely Novalia will be working with packaging companies and other end users within the next year and use the same technology on promotional packaging.
Stone is looking at various printing methods for the cards and says they could be printed using litho printing, screen printing or flexography. […]
Novalia had considered licensing out the technology but has instead decided to provide the printing company with the electronic technology. This decision will enable Novalia to work with other packaging and toy companies and provide them with the technology first hand.
Possible packaging applications could include a cereal box that could be cut up to form part of an electronic card game. […]
Stone says that the next stage of advancement will be to print the batteries, display and transistors as part of the process, although this will be some time in the future.

By using existing printing technology and focusing on simple applications, Novalia aims to keep costs low and allow the technology to progress more quickly.

In Optomec’s M³D (Maskless Mesoscale Materials Deposition) system particles are generated from a liquid (typically a suspension) raw material using an ultrasonic or pneumatic atomiser. The resulting aerosol is deposited via a nozzle and focused with flow guidance using an additional gas. A deposited precursor material is then converted using conventional heating or, in the case of heat-sensitive substrates, laser sintering.
This technique allows the additive deposition of lines with of 10 micron width. More details can be found in this article (pdf file, Sept. 2001) or on their website.
According to their website, the main applications are:

Printed Circuit Boards
M³D can fabricate high-density circuitry in materials such as copper, silver and gold with line widths down to 10 microns and smaller. In addition to “direct write” of conductive traces, the M³D system can be used to deposit a full range of electronics materials, including insulators, adhesives, and even intermediary materials such as photo-resist or seed layers for copper plating.

Embedded Passives and Components
M³D […] can directly manufacture high tolerance passives with a wide range of resistance values in a single layer. The solution can also be used to “embed” other components, such as capacitors, filters, antennae, etc., and can further be used for producing the trace interconnects within a layer.

Flex Circuits
M³D is ideal for the production of circuits on flexible substrates since the process operates at extremely low temperatures. In such applications, M³D has demonstrated excellent adhesion to the substrate, sufficient to withstand the stresses of dynamic flexing.

Hybrid Manufacturing for Electronic Devices
[…] M³D demonstrations in this area include sub-micron layers of platinum for fuel cells, high-density back planes (organic and metal) for flat panel displays, and deposition of photo-resist for MEMS production. Additionally, M³D systems are being used to repair production defects on flat panel displays.

Semiconductor Packaging

The technology has also been applied to the patterning of various bio materials including viable enzymes and living cells.

The Holst centre, an independent research center set up by IMEC and TNO,

will develop future generations of wireless autonomous transducer solutions and systems-in-foil. […] Philips, a leading player in the field of polymer electronics and microsystems, has committed to become the first industrial partner.

The centre, to be located at the High Tech Campus in Eindhoven (NL),

will start with two strategic program initiatives. IMEC will lead the wireless autonomous transducer solutions initiative. The system-in-foil research and development initiative will be managed by TNO. The synergy between both initiatives will be fully utilized by the creation of joint strategic R&D activities. […]
Within the Holst Centre, IMEC will expand its current research for wireless autonomous microsystems with focus on ultra-low-power radio; ultra-low-power signal processing; micro-power generation, storage and management; sensor and actuator technology. […]
TNO […] has built expertise around the industrialization of microsystems and polymer electronics, which it will contribute to the Holst Centre. In the Holst Centre, capabilities in the fields of printing of polymers, large-area deposition and structuring of thin layers and design of device architectures will be further developed. The Centre will use these capabilities to create and demonstrate ‘sensing and acting surfaces’, large-area, thin-layered products such as organic lighting and signage, sensor tags and organic electronics.

Researchers at the HP Labs in Bristol (UK) have developed a prototype bistable passive matrix LCD display (3cm x 4cm, 128 x 96 x RGB).

The development is targeted at applications such as electronic books and magazines and digital posters and photographs, rather than video displays such as TVs and computer monitors. […]

The bistability of the display is achieved using a special surface structure embossed in the plastic substrate.

In the HP Labs prototype, the ability of the pixel to remember its state is produced by tiny posts less than a thousandth of a millimeter wide, which are imprinted on to the plastic. These posts hold the liquid crystal in one of two orientations, corresponding to ‘on’ and ‘off’.

The display also has electrodes that are integrated with the printed color filters, further simplifying the device. The electrodes and color filters are made by imprinting shapes on to the plastic, and then using the shapes as templates for the color filter and electrode materials. This gives very precise control of features – such as metal lines five microns wide.

“All of the patterning in the prototype has been carried out by printing-like processes,” said Geisow. “The details of the processes are still being developed, and we expect it will take a few more years of further applied research to properly develop and assess their commercial potential.”

Coverage at The Register.