Transistor Properties of 2,7-Dialkyl-Substituted Phenanthro[2,1-b:7,8-b']dithiophene.

A new phenacene-type molecule with five fused aromatic rings was synthesized: 2,7-didodecylphenanthro[2,1-b:7,8-b']dithiophene ((C12 H25 )2 -i-PDT), with two terminal thiophene rings. Field-effect transistors (FETs) using thin films of this molecule were fabricated using various gate dielectrics, showing p-channel normally-off FET properties with field-effect mobilities (μ) greater than 1 cm2  V-1 s-1 . The highest μ value in the thin-film FETs fabricated in this study was 5.4 cm2  V-1 s-1 , when a 150 nm-thick ZrO2 gate dielectric was used. This implies that (C12 H25 )2 -i-PDT is very suitable for use in a transistor. Its good FET performance is fully discussed, based on electronic/topological properties and theoretical calculations.