Nowadays, the term printed electronics is taken to include printed electrics and even thin film devices that are likely to be printed in due course. Anything less risks missing the big picture, the subject is moving on so rapidly.
Of the different components that are becoming printable, Organic Light Emitting Diodes (OLEDs) are very important. This is because they are set to replace many of today's electronic displays with something more economical and with better performance. They will do the same with much of today's lighting as well. In both cases, the change will be accelerated by the advent of cost-effective flexible displays because they will have lower purchase and installation costs and they will open up a vast number of new applications where light emitting surfaces have been impractical in the past. However, cost-effective, flexible OLEDs with suitably long life may not be in mass production for a decade despite hundreds of organisations developing them.
About 70% of the patents on printed electronics, in the broad definition, relate to OLEDs and that is out of proportion to their potential. For example, light emitting displays will probably always suffer from being more expensive, poorer in definition and more wasteful of power than the best non-emitting displays. By contrast, electrophoretic signage and e-books only need power when their images are changed.
Electrochromic and thermochromic displays are inherently cheaper and they, and ac electroluminescent displays, are available in flexible form today. Printed flexible AC electroluminescent displays are even available in areas of hundreds of square meters. All displays can be improved and all have considerable unrealised market potential. There is therefore scope for many more companies to work on the other displays, because fewer than twenty companies are involved seriously today. For example, more effort in improving their colours and lifetime would be well justified.
Many other areas of printed and potentially printed electronics are being relatively neglected. Take batteries. Most potential applications of printed electronics call for batteries, preferably of low cost and flexible. The technical requirements vary greatly between the different applications, yet we are stuck with a handful of suppliers who either offer carbon zinc with its limited life, power storage and rate of delivery or lithium technologies with their problems of cost and environmental credentials. (Some would add that lithium is also a fire hazard given what has happened with large lithium batteries in electric vehicles and laptops but the tiny amount of material in a printed lithium battery means that fire or explosion is the least of its problems.) The important question is, "Who is working on the intermediate printed battery technology demanded by the market place?" With large battery technology we have nickel metal hydride for example. For printed electronics we have nothing.
A similar question can be asked about large printed memory - from kilobytes to gigabytes. So few companies are working on this that AMD has about 80% of the patents for potentially printable, thin film versions, yet large memory will be needed for a high proportion of applications involving printed transistors.
Printing of transistors and of photovoltaics seem to have their fair share of the cake, with about 100 organisations now working on each. Several companies promise initial commercialisation one or other of these this year and many are to be on flexible substrates. In particular, the Japanese have moved into overdrive in registering patents relevant to printed transistors in the last year.
One can not be as sanguine about printed sensors, fuel cells or even development of alternatives to printing silver for conductors, fuses, antennas and so on. Too few organisations are working on these aspects.
A major impediment to the commercialisation of printed electronics is the large footprint. For transistors, this is caused by the large feature size, for conductors by the poor conductance of the inks and for photovoltaics by the poor efficiency. It therefore comes as a surprise that few are working on the printing of one component on top of another because this would reduce overall footprint and improve reliability by eliminating conventional interconnects. There are therefore many sectors of printed electronics with little competition and great needs and most players would be wise to be profitably serving these as they watch the impending shakeout of OLED developers from a safe distance.
For the latest on all these opportunities attend Printed Electronics Europe 2007; held in Cambridge on 17-18 April. See www.IDTechEx.com/peEUROPE for more details.