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)···S­(thiophene), with a very short S–S
distance of 3.10 Å, and a planar core. When measured in an OFET
device compound 1 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
(1/PαMS) blend films and devices were investigated.
Morphological analysis reveals a nanoscopic vertical phase separation
with the PαMS 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 cm2 V–1 s–1 and a very smaller threshold voltage shift under gate bias stress.