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

The 3,5-dithiooctyl dithienothiophene based small molecular semiconductor DDTT-DSDTT (1), end functionalized with fused dithienothiophene (DTT) units, was synthesized and characterized for organic field effect transistors (OFET). The thermal, optical, electrochemical, and computed electronic structural properties of 1 were investigated and contrasted. The single crystal structure of 1 reveals the presence of intramolecular locks between S(alkyl)center dot center dot center dot S(thiophene), with a very short S-S distance of 3.10 angstrom, and a planar core. When measured in an OFET device compound 1 exhibits a hole mobility of 3.19 cm(2) 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 (1/P alpha MS) blend films and devices were investigated. Morphological analysis reveals a nanoscopic vertical phase separation with the P alpha MS layer preferentially contacting the dielectric and 1 located on top of the stack. The OFET based on the blend comprising 50% weight of 1 exhibits a hole mobility of 2.44 cm(2) V-1 s(-1) and a very smaller threshold voltage shift under gate bias stress.

Automated summary

A small molecular semiconductor based on 3,5-dithiooctyl dithienothiophene was synthesized and characterized for organic field effect transistors, showing a high hole mobility. Adding 1 into the blend can improve device performance, forming a nanoscopic vertical phase separation morphology.