Organic and printed electronics

Organic and printed circuits are revolutionising microelectronics

Plastics with modifiable material properties, dimensionally stable as thermoplastics, thermosets or elastomers, films or coatings, granular or expanded, are an indispensable part of our everyday lives – in anything from simple items of daily life to intricately designed structural elements in vehicles and buildings.

Plastics’ structural diversity is now being augmented by a further dimension: with suitable molecular configuration, they can also be used as electrical conductors and semiconductors (albeit with still limited mobility of the charge carriers). They thus serve as system components of “organic” and “printed” electronics. “Organic” because their transistors, sensors and LEDS are not based on silicon or gallium arsenide, but on carbon derivatives. And “printed” because two-dimensional circuit patterns can be printed “from the reel” with structural fineness of just a few tens of micrometres onto flexible and also transparent substrates by using conventional mass printing processes (flexo, screen-printing, inkjet).

Integration in objects
This yields electronically or photonically functionalised surfaces, three-dimensionally on all conceivable objects and even textiles. They form capacitive touch sensors, large-area luminous fields with OLEDs (organic light-emitting diodes), sensors and detectors for environmentally or medically important data such as temperature and humidity. They operate as organic solar cells. Or as flat, printed batteries for miniaturised devices. This facilitates new, exotic applications in “smart” objects and their networking in the “Internet of Things”.

The latest (fifth) edition of the Roadmap of the OE-A (Organic and Printed Electronics Association), a work group of VDMA (German Engineering Federation) with over 220 members worldwide, illustrates the state of progress and trends in organic electronics for a ten-year period.

OLED screens and displays, the first mass market
The small OLED displays in mobile phones and smartphones have already developed into a mass market. As a result, sales with organic electronics came to roughly USD 9 billion last year. This has been forecast to develop into a global annual market of USD 200 billion by 2025. Colour-intensive and high-contrast OLED screens for 55″ televisions are already available (e.g. from Samsung and LG), although they currently cost USD 10,000.

Flexible displays for e-readers
The e-readers from Amazon and Sony with “electronic paper” from E-Ink enjoy widespread popularity because of the energy-efficient, bistable principle of their electrophoretic displays. They are essentially ideal for presenting static content such as book pages.

The next development step will bring forth lighter, flexible and maybe even roll-up e-readers and tablets without the heavy cover glass. The most progress here has been made by Plastic Logic that produces backplanes of organic thin film transistors (OTFTs), i.e. the active matrix for individual pixel control.

What is still hampering the development of organic photovoltaics and display technology is their hermetic encapsulation to provide protection from atmospheric water vapour that corrodes their electrodes and shortens their service life. The solution is laminated barrier films, for which transparent layers of amorphous silicon dioxide appear to be very well suited.

Application driving forces
The driving forces in the development of applications can be found in the automotive, pharmaceutical, consumer electronics and “smart” packages for foods, medicines and other consumer items. With inexpensive printed, radio-frequency identification (RFID) tags, smart packages are capable of making merchandise management more efficient and, with dynamically updated display fields, of informing the consumer of the best-before date, drawing attention to gaps in the cooling chain for sensitive goods and guaranteeing the authenticity of high-grade articles by establishing links to traceable supply chains.

Next in line are organic displays and touch sensors in premium class cars as replacements for mechanical indicators and switches. Then there are reversing lights with OLEDs, among other things at Audi, so that today’s LED lights can be replaced to save energy.

OLED lighting
OLED light sources are competing with established LEDs and halogen lamps. They promise dynamically colour-controllable light emitted uniformly over a large area and can be attached in architecturally attractive ways to the surfaces even of familiar objects in the home.

Organic photovoltaics and batteries
Organic photovoltaics (OPV) is already commercially available as local supply sources for mobile data and consumer devices. The long-term prospects include applications in the envelopes of vehicles and buildings (BIPV, building-integrated photovoltaics).

Available as system components are printed data memories – in the form of the ferroelectric, non-volatile memory films of the Norwegian manufacturer Thinfilm. These can be combined with a transistor logic produced at contract researcher PARC in California to yield software-addressable memory modules. With a printed thermistor as a temperature sensor and a display field together with a printed battery, they can be extended into a complete measuring system.

Printed batteries are also a focus of system integration. They can be integrated with display and luminous fields, touch sensors and solar cells in packages, textiles and other consumer items, elevating them to new levels of value and functionality.

Innovations in the organic and printed electronics sector will also be on show at the Printed Electronics Products and Solutions Pavilion at K 2013, the world’s No. 1 trade fair for the plastics and rubber industry, in Düsseldorf from 16 to 23 October. This is where not only printing technologies but also functionalised surfaces such as RFID solutions, flexible displays and OLEDs will be given a platform for presentation to trade visitors from processing and user industries.