A Solution Processable Dithioalkyl Dithienothiophene (DSDTT) Based Small Molecule and Its Blends for High Performance Organic Field Effect Transistors.

Abstract

The 3,5-dithiooctyl dithienothiophene based small molecular semiconductor <b>DDTT-DSDTT</b> (<b>1</b>), end functionalized with fused dithienothiophene (<b>DTT</b>) units, was synthesized and characterized for organic field effect transistors (OFET). The thermal, optical, electrochemical, and computed electronic structural properties of <b>1</b> were investigated and contrasted. The single crystal structure of <b>1</b> reveals the presence of intramolecular locks between S(alkyl)···S(thiophene), with a very short S-S distance of 3.10 Å, and a planar core. When measured in an OFET device compound <b>1</b> exhibits a hole mobility of 3.19 cm² V^-1 s^-1, when the semiconductor layer is processed by a solution-shearing deposition method and using environmentally acceptable anisole as the solvent. This is the highest value reported to date for an all-thiophene based molecular semiconductor. In addition, solution-processed small molecule/insulating polymer (<b>1</b>/PαMS) blend films and devices were investigated. Morphological analysis reveals a nanoscopic vertical phase separation with the PαMS layer preferentially contacting the dielectric and <b>1</b> located on top of the stack. The OFET based on the blend comprising 50% weight of <b>1</b> exhibits a hole mobility of 2.44 cm² V^-1 s^-1 and a very smaller threshold voltage shift under gate bias stress.