Organic printed electronics has attracted hundreds of participants over the years. However, the topic is as much about inorganic electronics as it is organics - organic electronics is not the end game for all printed electronics.
The truth is that organic, inorganic and composite materials will always be needed. Every year, many putative suppliers of organic printed products and materials leave the business because they cannot find markets for the currently chemically fragile and/or electronically poor materials and devices that often result.
Electronic parameters are typically ten to one hundred times inferior with organics. Others are improving their organics to find a foothold and many organic device developers now use more and more inorganic materials and constructions in and on their organic devices to make them work more satisfactorily, metal oxide barrier layers - against gas and water ingress - on organic light emitting diodes (OLEDs) and organic photovoltaics being examples, as are metal and metal oxide conductors on most so-called organic devices. Transistion metals are used in the preparation of carbon nanotubes for printed electronics and so on.
Indeed, there are huge markets for organic devices that have inferior electronic performance but other valued, unique benefits, an excellent example being the organic photovoltaics prioritised by consumer goods companies because they are potentially very low cost and safe with children.
IDTechEx believes that outdoor photovoltaics on buildings etc needs to last at least 20 years and tolerate extremes of radiation, thermal and mechanical attack. It is therefore best left to those supplying silicon, CdTe and copper indium gallium diselenide solutions but that ultimate potential of say two billion square meters a year is matched by a similar potential on consumer goods using organics lasting only two or three years in disposable applications. These may eventually be sold in trillions but they will have a tiny area on each package or product. QuantaSol's SB-QWSC GaAs photovoltaic cell is believed to be the highest performing single-junction concentrator cell in the world with the potential to enhance multi-junction cells to record efficiencies.The company claims that the use of inorganic quantum dots can turn the old concept of a luminescent solar collector into a practical concentrator and "The quantum efficiency, tunability of absorption threshold, and size of the redshift make quantum dots an ideal replacement for the organic dyes whose performance limited this inexpensive technology".
In 2007 and 2008 at least ten companies exited from OLEDs. In 2008, Nanoident, in printed reverse OLEDs - photodetectors - was one of several organic electronics businesses going under though many more entered the business.
Merck Chemicals, a successful supplier of organic chemicals for printed electronics, sponsored major work on inorganic metal oxide semiconductors at Darmstadt University to widen its portfolio. It mimics its work on printing oligomer precursors because oligomers themselves cannot usually be printed. It is developing printable inorganic semiconductor precursors based on zinc oxide to overcome the problem of high annealing temperatures with current inorganic compound semiconductors. Several companies are now commercialising nanosilicon printed transistors, with Kovio in the lead. Organic electronics printer ACREO has spun off WebShape doing dry phase patterning of metals such as aluminum antennas. Nevertheless OLED lighting has huge potential as do OLED displays, both with organic semiconductors. There is a place for everyone.
In 2009, ORFID and Motorola gave up on organic printed transistors and another operation is for sale. However, although organic transistors are about to succeed at the bottom of the market, there is a surge in work on zinc oxide based semiconductors for mainstream transistors and other applications. For example, Kodak has recently developed a fast, printing-like process to fabricate high-performance zinc oxide (ZnO) transistors in open atmospheric conditions.
IDTechEx find that of all of printed, organic and flexible electronics in 2009, the majority are based on inorganic materials, as shown below.
2009 market size comparing predominately organic and inorganic electronics, $ billions
Source: IDTechEx report "Inorganic and Composite Printed Electronics 2009-2019"
The only successful very wide area printed light emitting displays remain entirely inorganic, using doped zinc sulphide, indium tin oxide transparent electrodes, metal back electrodes and inorganic protection layers. The only commercially successful alternative to silicon photovoltaics is thin film cadmium telluride. The only printed piezoelectrics are made of lead zirconate titanate. The only fully printed batteries are manganese dioxide zinc but lithium ion and lithium polymer alternatives are beginning to be partly printed.
Thermoelectrics can be more efficient when thin, so several organisations, including CEA Liten a subsidiary of the French Atomic Energy Commission are developing thin film, including printed, thermoelectrics.
Bismuth telluride is the compound typically used. In a new twist, in mid 2009, researchers at the University of Chicago and Lawrence Berkeley National Laboratory have developed an "electronic glue" that could accelerate advances in semiconductor-based technologies, including solar cells and thermoelectric devices that convert sun light and waste heat, respectively, into useful electrical energy. Nanocrystals of silicon etc are sometimes unable to efficiently transfer their electric charges to one another due to surface ligands-bulky, insulating organic molecules that cap them. The inorganic "electronic glue" developed in Dmitri Talapin's laboratory at the University of Chicago now solves the ligand problem.
Inorganic and composite constructions will be at least half the market for printed electronics in the years to come. The unique IDTechEx report "Inorganic and Composite Printed Electronics 2009-2019" details these advances and forecasts future demand.
Only IDTechEx conferences showcase inorganic elements, compounds and composites to the extent of their importance in the marketplace, as well as the important advances in organic materials.