The Market for Organic and Printed Electronics
Then there is recent success with transistors using silicon nanoparticles in organic inks. It used to be believed that both inorganic and organic semiconductors had to be as crystalline as possible to give high charge carrier mobility and therefore high frequency of operation in transistors. However, the InGaZnO transistors being printed by Tokyo Institute of Technology and Toppan Printing Japan are amorphous. An organic carrier is used in the ink. The resulting transistor arrays form backplanes for flexible electrophoretic displays.
Breakdown of the old certainties
Enthusiasts for organic electronics have begun to think that almost anything will eventually be possible with their technology. A very important milestone in this has been Merck announcing a 3.5cm2/vs stable, printable polymer. This is the final nail in the coffin of thin film amorphous silicon in transistors. aSi is not suitable for low cost flexible substrates and now it no longer has an advantage over printed organic semiconductors in mobility and therefore frequency of operation.
On the other hand, we have identified no significant progress towards economic, printable, organic dielectrics of high permittivity. These are needed for transistor gates, capacitors and so on and there may be fundamental limits to the permittivity of organic compounds. It was perceived that the traditional ceramic high permittivity dielectrics would never be printed ie we would never learn how to “print pottery”. Fortunately, the laboratories of Motorola and Hewlett Packard have proved that wrong, even with the archetypal barium titanate.
The US company Evident is supplying inorganic compound quantum dots a few nanometers across in organic carriers. Universities are printing these to make improved transistors, solar cells and so on. Rare materials are not needed but the quantum effects involved are magic indeed. Bear in mind that the Nobel Prize winning physicist Richard Feynman said, “Nobody understands quantum theory.”