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 ((CH)-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 cm V s. The highest μ value in the thin-film FETs fabricated in this study was 5.4 cm V s, when a 150 nm-thick ZrO gate dielectric was used. This implies that (CH)-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.