Breakthrough achieved in flexible electronics

Scientists in Singapore have developed conducting polymer films that can give a superior performance in plastic electronics.

Plastic, or organic, electronics are made from carbon-based semiconductors that could provide flexible, lightweight large area and additively-manufactured devices. Examples of these include organic light-emitting diodes, solar cells and transistors. These newly designed films by the researchers provide unrivalled ohmic contacts – low resistance junctions providing current conduction from metal to semiconductor and vice versa.

Team leader Dr Png Rui-Qi, from the National University of Singapore (NUS), said: “The lack of a general approach to make ohmic contacts has been a key bottleneck in flexible electronics. Our work overcomes this challenge to open a path to better performance in a wide range of organic semiconductor devices.”

The researchers discovered how to design polymer films with the desired extreme work functions needed to make ohmic contacts. The work function is the minimum amount of energy needed to liberate an electron from a film surface into a vacuum. The research showed work functions as high as 5.8 and as low as 3.0 electron-volts can be processed at low cost.

Dr Rui-Qi’s research team developed a concept of doped conducting polymers with bonded ionic groups. In this, doped mobile charges cannot dissipate away as their counter-balancing ions are chemically bonded. Dr Rui-Qi said: “As a result, these conducting polymers can remain stable despite their extreme work functions and provide the desired ohmic contacts.”

This was a collaboration by the materials chemistry and physics team at the NUS, and scientists from Cambridge Display Technology Ltd, a subsidiary of Sumitomo Chemical Co. Ltd.

The research was published in Nature.