Packaging and Converting Essentials

By Dr Peter Harrop

Here come organics

Silicon has had a good run in the electronics industry but the lowest cost chips have not changed much in price for decades and wide area silicon, as with solar cells, is heavy, expensive and in need of huge government subsidies to be sold in any volume. Truly flexible – as opposed to bendable-silicon is non-existent in practicable form. Enter organic electronics that can be printed, unlike silicon, and is potentially of low cost and very versatile, being useful for sensors, power, memory, logic, lighting and much else besides. Here we are not just talking of organic semiconductors but of dielectrics, conductors and light emitters for example. Many conferences and companies use the terms organic or plastic electronics and there is even a trade association. The progress of this new industry is phenomenal. So that is the end of the story?

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Not that simple

Nothing could be further from the truth. Organic electronics certainly holds the high ground in many aspects of potentially low cost and wide area electronics and electrics. Nanoident of Austria recently built the world’s first fab for printed organic semiconductors, focussing on photodetector arrays initially. However, these devices employ nanoparticle metals for their ink jet printed conductors, including electrodes.

Inorganic and hybrid constructions are often best

Most companies developing Organic Light Emitting Diodes OLEDs employ indium tin oxide ITO semi transparent electrodes and most other “organic” devices, including transistors employ metal conductors. Indeed, given the mobility and therefore the operating frequency of organic transistor semiconductors, companies such as Motorola and Hewlett Packard in the USA are additionally researching inorganic semiconductors. Even Merck of Germany, a leader in organic semiconducting inks, has done the same, partnering with the Technical University of Darmstadt in Germany. It invested $1.4 million in the joint venture's first year of operation.

In other words, it is complementary to learn how to print a transparent inorganic semiconductor, with up to 400 times the mobility, alongside trying to invent stable, low cost organic semiconductors with device mobility exceeding 10 cm2/Vs, when even improving on one tenth of that is proving tough. Further, anyone waiting for a cost-effective, completely organic laminar battery to drive these circuits may have to wait a long time, though it would be nice to co-deposit one.

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