Ambipolar Carrier Injections Governed by Electrochemical Potentials of Ionic Liquids in Electric-Double-Layer Thin-Film Transistors of Lead- and Titanyl-Phthalocyanine

Electric-double-layer thin-film transistors of lead- and titanyl-phthalocyanine with ionic-liquid gate dielectrics exhibit ambipolar behavior with low threshold voltages less than ±2 V. Their threshold gate voltages are found to depend significantly on the ionic liquids, being proportional to the electrochemical potential of the ionic liquids. This dependence can be understood by an energy diagram of the frontier orbitals of PbPc and TiOPc, and the electrochemical potentials of the ionic liquids.