Comparison of p-channel transistors based on α,ω-hexyl-distyryl-bithiophene prepared using various film deposition methods

Abstract

We present a series of organic thin film transistor (OTFT) devices realized by vacuum evaporation, spin-coating, drop casting and inkjet printing and a comparative analysis of their electrical response/behavior obtained under identical measurement conditions. A small molecule, α,ω-hexyl-distyryl-bithiophene DH- DS2T, was used as a hole transporting active layer. Structure and morphology of thin films have been studied by atomic force microscopy, X-ray diffraction and optical microscopy. Different parameters linked directly to the processes (solvent, concentration, deposition method, surface, post-treatment…) are identified as key factors controlling film quality/crystallinity and device performances. This systematic study reveals the factors that limit efficient charge transport at the macroscopic scale of the channel length in OTFT devices.