Emergence of n-type characteristic of conjugated polymer field-effect transistors with calcium source-drain electrodes

We fabricated field-effect transistors (FETs) using a highly soluble fluorene-based polymer as an active layer utilizing a low-work-function metal, calcium as a source-drain electrode material. The n-type characteristic of polymer FETs was successfully realized by lowering the electron injection barrier, although polymer FETs with gold source-drain electrodes did not exhibit n-type or p-type characteristic. The well-defined n-type FET provides a useful means of measuring the electron transport property of new organic semiconductors.