Trap-Free Space-Charge-Limited Hole Transport in a Fullerene Derivative

Fullerenes and their derivatives are well-known electron-transport materials for organic (opto)electronic devices, but the extent to which they can transport holes is strongly disputed. To resolve the matter, this study quantifies bulk hole transport in a fullerene derivative. Remarkably, hole transport here is trap-free, with a high mobility equal to that for electrons. This demonstration that fullerenes can exhibit balanced, bipolar charge transport, which is unusual for organic semiconductors, is interesting for application in organic photovoltaics and ambipolar transistors.