Enhanced Performance of Thiophene-Rich Heteroacene, Dibenzothiopheno [6,5-b:6',5'-f] Thieno[3,2-b]Thiophene Thin-Film Transistor with MoO_x Hole Injection Layers

In this letter, we demonstrated a high performance organic thin-film transistor using thermally evaporated amorphous phase MoO_x as a hole injection layer between metal electrodes and organic semiconductor. The fabricated organic thin-film transistors showed the field-effect mobility of 7 cm²/Vs in linear and saturation regimes and an ON/OFF current ratio of 10⁷. The MoO_x hole injection layers significantly reduced the injection barrier from metal electrode, resulting in the improvement of ohmic contact properties of a synthesized thiophene-rich heteroacene, dibenzothiopheno [6,5-b:6',5'-f] thieno [3,2-b] thiophene p-type organic semiconductor, as compared with those with single metals. Furthermore, high performance organic thin-film transistors can be successfully realized with Al electrode, which is not suitable for p-type organic semiconductors due to its low work function by introducing a 75-nm-thick MoO_x hole injection layer.