Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophenes

Abstract

Field-effect transistors (FETs) have been fabricated with thin films of a series of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene derivatives (C_n-PDTs). The FET characteristics of C_n-PDT thin-film FETs with an SiO₂ gate dielectric as well as high-k gate dielectrics were recorded, and the dependence of the field-effect mobility, μ, on the number (n) of carbon atoms in the alkyl chains was investigated, showing that the 2,9-didodecylphenanthro[1,2-b:8,7-b′]dithiophene (C₁₂-PDT) thin-film FET displays superior properties, with μs as high as 1.8 cm² V⁻¹ s⁻¹ for the SiO₂ gate dielectric and 2.2 cm² V⁻¹ s⁻¹ for the HfO₂ gate dielectric. The average μ values, 〈μ〉, reach 1.1(5) and 1.8(6) cm² V⁻¹ s⁻¹, respectively, for the SiO₂ and ZrO₂ gate dielectrics. Low-voltage operation, showing an absolute average threshold voltage 〈|V_th|〉 of ∼11 V, was implemented, together with the above high 〈μ〉 of ∼2 cm² V⁻¹ s⁻¹. Also, a flexible FET was fabricated with a parylene gate dielectric. The results of this study show the potential of the C₁₂-PDT molecule for application in a high-performance transistor.