Enhanced environmental stability of n-type polymer transistors with nickel contacts

N-type organic field-effect transistors have suffered from poor environmental instability. Here, we report that, by using nickel (Ni) instead of the commonly used gold (Au) as contact electrodes, n-type polymer transistors showed much improved stability upon annealing in nitrogen and exposure to air. In particular, Au-contacted devices exhibited pronounced ambipolar conduction whereas Ni-contacted devices retained fairly good unipolar properties. The results are important to build stable n-type polymer transistors at low cost.