Low cost polymers could enable new flexible electronics applications

The work is the latest effort in a long search for semiconducting polymers that can be solution processed and printed, but which retain well defined electronic properties. However, a problem with these materials is their internal structure can trap electrons and slow their transport. Polymer molecules, says the research team, consist of at least one long backbone chain, with shorter chains at the sides. While these side chains which make conjugated polymers easy to process, they also increase the amount of disorder, leading to more trapped electrons and poorer performance. However, the Cambridge team has discovered a class of conjugated polymers that is extremely tolerant to any disorder introduced by the side chains. "What is most surprising about these materials is that they appear amorphous at the microstructural level, while at the electronic level they allow electrons to move nearly as freely as in crystalline inorganic semiconductors," said Mark Nikolka, a PhD student at the University's Cavendish Laboratory. The team, led by Professor Henning Sirringhaus, found the materials are approaching disorder free limits and that every molecular unit along the polymer chain can participate in the transport of charges. "These materials resemble tiny ribbons of graphene in which the electrons can zoom fast along the length of the polymer chain, although not yet as fast as in graphene," said Dr Deepak Venkateshvaran. "What makes them better than graphene, however, is they are much easier to process and therefore much cheaper."