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

Fullerenes and their derivatives are well-known electron-transporting materials used in organic solar cells and transistors. However, the extent to which fullerenes are able to transport holes is heavily disputed. Using selective Ohmic contacts, we study the bulk hole and electron transport in a bisadduct fullerene derivative. Trap-free space-charge-limited hole and electron currents are measured, with a hole mobility equivalent to the electron mobility. Our results identify the bisadduct fullerene as an organic semiconductor with balanced bipolar bulk transport with excellent electron and hole mobilities.