Organic Chemists Developing Plastic Electronics

Electronic media are becoming an increasingly important part of our everyday lives. One of the most exciting developments in the display industry has been the emergence of ‘plastic electronics’, or Polymer Organic Light Emitting Diodes (P-OLEDs).

Plastic electronics contain an organic polymer sandwiched between two electrodes. When a charge is injected, the polymer emits light. The colour of the light emitted can be changed by altering the properties of the polymer. P-OLED displays have a significant advantage over LCD screens because they do not require an external light source. This means they are much more energy efficient, as well as being brighter, clearer and more long-lasting than existing screens.

Organic LEDs are already used in products such as mobile phones, electric shavers and medical devices. Soon, P-OLEDs will be used in a huge range of applications, from televisions to lighting. It is also predicted that plastic electronics will give rise to a whole new range of products, including rollable electronic displays, ultra-efficient lighting and low-cost, long-life solar cells.

Discovering the potential of PPV

It was researchers at the University of Cambridge who uncovered the potential of polymers to act as LEDs back in 1989. They found that poly(p-phenylene vinylene) (PPV) (Fig. 1) emits a green-yellow light. The first P-OLEDs were very inefficient, but developments in the field quickly followed. Improvements in P-OLEDs have come from multidisciplinary research involving synthetic chemists, physicists and engineers.

The structure of PPV

Organic chemists have designed a range of reactions to alter the structure of PPV and other polymers. This means that luminescence, efficiency and stability have all been improved over the past two decades.

Another advantage P-OLEDs have over traditional display screens is that they can be made using normal printing methods. This is because the polymers used are soluble in various organic solvents, and so can be deposited using an ordinary inkjet printer! This means there is no need for complicated vacuum deposition methods, and means that plastic electronics could be printed over very large areas.

Today, many start-up companies such as Cambridge Display Technology, MicroEmmisive Displays and Lumicure are working to commercialise the technology. The market value of plastic electronics in 2009 was $2 billion, but is predicted to rise to $120 billion by 2020.

References

1 J H Burroughes, D D C Bradley, A R Brown, R N Marks, K Mackay, R H Friend, P L Burn, A B Holmes, Nature, 1990, 347, 539
2 A C Grimsdale, K L Chan, R E Martin, P G Jokisz, A B Holmes, Chem. Rev., 2009, 109, 897
3 U Mitschke, P Bäuerle, J. Mater. Chem., 2000, 10, 1471