Here Comes Second Generation Printed Electronics

By Dr Peter Harrop
IDTechEx

Second generation printed electronics has arrived and its impact on society will be immense. A major new industry is born. Transparent solar cells will be on watches by year end and vast areas of printed flexible photovoltaics will be available within the next few years. Heliovolt promises a high efficiency silicon-free photovoltaic film in 2007. Polymer alternatives will have lower efficiency but often be lower in cost. Announcements have yet to be made but IDTechEx has identified several companies that will be commercialising polymer solar film in 2007.

Light emitting moving colour displays, vehicle and room lighting on flexible substrates, the electronic book and many forms of disposable electronics are near to mass rollout. An example of a Sony e-book developed with e-ink electrophoretics is shown below. Some new versions are flexible and use printed polymer Thin Film Transistor Circuits TFTCs from Plastic Logic as back plane drivers. Working samples of these have been widely available in 2006.

This year saw smart drug packs with printed sensors and sometimes printed batteries. These have unique electronic identification and they record which pill was removed when, because 50% of patients take their medication incorrectly. Initially they are being used to improve drug trials such as the National Institute of Health trial of Azithromycin and a Novartis trial this year. We already have flexible, electroluminescent colour displays from billboards to animated watch backgrounds.

Photovoltaics
Potential markets for low cost printed and thin film photovoltaics vary from feeding national power grids to use on smart packaging and toys. We need photovoltaics that is one tenth of the manufacturing cost and installation cost of today’s silicon solutions and with none of their supply shortages. Within reason, it will not matter if the replacement has a larger footprint, particularly if it is flexible and/ or transparent. If its efficiency is 5-10% vs double or treble that for silicon, it will not matter in most applications because the other benefits will prevail. For example it can go over a window or conform to the shape of a vehicle. However, it is a challenge to achieve the 10,000 hours life necessary for an entry level printed product and 50,000 hours for mainstream use. The same can be said of OLED displays, signage and lighting on flexible film but progress is being made and products are starting to sell.

Conductor challenges
Although printed conductive polymers still exhibit one hundred to one million ohms per square – more like a resistor than a conductor – they are beginning to be used. However, for now it is more significant that high speed printing of self-sintering silver inks is now available with RFID antennas being printed directly onto label feedstock.

Of the many printed or ultimately printable electronic devices being launched, most will not use conductors that possess the triple virtues of printability, low cost and, where needed, good transparency in the right combination. For example, indium tin oxide is often still used for almost all semi-transparent conductors and the cost of indium recently jumped from $60 to $1000 per kilogram. That must be solved.

Nevertheless, transparent Die Sensitised Solar Cells DSSC will be available as tiles 10 centimeters square from two companies and Heliovolt will commercialize a different solar cell that does not have the disadvantages of silicon yet has high efficiency. DSSC cells are particularly efficient in diffuse daylight but some polymer cells are particularly efficient in garnering energy from infrared not just the visible frequencies. In principle, they could work in the dark and be more flexible and lower in cost.

Hybrid constructions usually win
The terms polymer and organic electronics are losing their meaning because the more sophisticated second generation printed and thin film electronics are usually optimal if both inorganic and organic elements are exploited. For example many forms of so called organic photovoltaics incorporate carbon buckyballs or nanotubes. The focus is turning from the semantics of the science to the practicalities of the application. Currently this includes new printed batteries, photoelectrics, high information flexible military displays and printed microwave rectifiers.

Unprecendented virtues

Disposable right through to top specification – it is all there in the new programs. After all, these printed and potentially printed technologies avoid the poisons involved in making and assembling most silicon devices and printed circuit boards. They can be more damage tolerant, even rollable. They eliminate the interconnects and therefore failure modes suffered when silicon chips are connected to other components. Installation may be as simple as applying sticky tape. Alternatively, they can be printed onto transparent sheet that doubles as a quality loudspeaker thanks to NXT technology. All this creates applications where cost is not always the prime consideration. However, the resulting ubiquitous disposable electronics will be a huge business.

The major international conference on the subject “Printed Electronics USA” takes place in Phoenix Arizona, December 5-6 with presentations from most of the organisations mentioned above, from three US military organisations and from Japan, Taiwan, Germany, France, the UK, Israel and elsewhere – all best in class speakers from the leading developers and users including Nokia, Honeywell, Motorola and Xerox. There is even a tour of the legendary display laboratory of Arizona State University. There are Masterclasses and a profusion of backup material. The conference looks at the big picture with the emphasis on commercialisation. See www.printelec.com and read “Printed Electronics 2006-2016” www.idtechex.com