Organic Field-Effect Transistors Based on Benzodithiophene-Dimer Films

We fabricated organic field-effect transistors (OFETs) based on benzodithiophene (BDT)-dimer films by vacuum evaporation. The surface of the BDT-dimer films deposited on a SiO2 gate insulator was so rough that excellent FET characteristics were not obtained. However, the surface morphology of the films deposited on poly(methyl methacrylate) buffer layers was significantly improved, and dense grains of submicron size were formed. Grain size increased from the submicron scale to the micron scale by reducing growth rate from 0.035 to 0.02 nm/s. The fabricated OFETs have shown p-type FET characteristics with a carrier mobility of 0.016 cm2 V-1 s-1. More importantly, it has been demonstrated that the performance of the BDT-dimer OFET is much more stable in air than that of the pentacene OFET.