Passivation of trap states in unpurified and purified C60 and the influence on organic field-effect transistor performance

We investigate trap-state passivation by addition of ultra-low amounts of n-dopants in organic field-effect transistors (OFET) made of as-received and purified fullerene C-60. We find a strong dependence of the OFET threshold voltage (V-T) on the density of traps present in the layer. In the case of the unpurified material, V-T is reduced from 17.9 V to 4.7 V upon trap passivation by a dopant:C-60 ratio of similar to 10(-3), while the I-on/off current ratio remains high. This suggests that ultra-low doping can be used to effectively compensate impurity and defect-related traps. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772551]