The team says that, while conjugated semiconducting (or plastic) polymers have optical and electronic properties which make them attractive in the production of OPVs, OLEDs and lasers, their vertical charge carrier mobility – the ability of charge to move inside the material – has been too low. However, the team, led by Professor David Barbero, has found that, by aligning polymer chains vertically, high charge transport and high mobility can be obtained without chemical doping.
“The transport of electric charge is greatly enhanced solely by controlled chain and crystallite orientation inside the film,” he said. “The mobility measured was approximately 1000 times higher than previously reported in the same organic semiconductor.”
According to Prof Barbero, the work will be of importance in polymer solar cells and organic photodiodes, where charge is transported vertically. “Typically, plastic semiconductors – which are semi-crystalline –
have hole mobilities about 10,000 times lower than doped silicon, which is used in many electronic devices. Now, we show it is possible to obtain much higher mobility – much closer to that of silicon – by controlled vertical chain alignment and without doping.”
