Polymer matches silicon in semi-conductor stakes

Materials scientists have developed a semi-conducting polymer that, for the first time, conducts electricity at levels similar to conventional silicon-based semi-conductors. 

These polymers could lead to ’a new generation of low cost, flexible, lightweight and, ultimately, large area electronic applications,’ predicted lead researcher Iain McCulloch from Merck Chemicals, Southampton, UK.

Polymer semi-conductors offer several advantages over silicon-based varieties, including low cost, mechanical flexibility and ease of fabrication. They could form the basis for new types of display material, including the much heralded electronic paper. Unfortunately, semi-conducting polymers have so fair failed to match the electronic performance of silicon semi-conductors, and have also proved prone to extensive oxidation when exposed to air.

McCulloch, and colleagues in the US, created the semi-conducting polymer by attaching the linear conjugated co-monomer thieno[3,2-b]thiophene to an alkyl thiophene polymer backbone. Following controlled heating and cooling (annealing), this polymer crystallised to form large, ordered domains through which electric current could pass. 

’This exceptional crystallinity gives rise to the dramatic improvement in performance,’ explained McCulloch. In addition, the polymer structure, specifically the presence of the thienothiophene, helps to protect it against oxidation. ’Devices show good stability in low-humidity air, giving encouragement that routine encapsulation technology will be adequate to preserve performance,’ McCulloch told Chemistry World.

’This is very exciting work,’ agreed John de Mello, lecturer in nanomaterials at Imperial College, London, who conducts research into organic semi-conductors. ’[It] represents an important step towards establishing semi-conducting polymers as practical backplane materials.’ [A backplane is a circuit board that connects several electrical connectors in parallel]

Jon Evans