Influence of contact resistances on high-mobility top-gate organic transistors based on didodecylbenzothienobenzothiophene

Reducing the channel length of organic field-effect transistors (OFETs) is highly desirable to develop flexible and printable electronic devices with high operational frequency and output current, and the use of a top-gate/bottom-contact (TG/BC) configuration could be advantageous for fabricating OFETs with short channel length using solution-processable organic materials. In this study, we fabricate high-mobility TG/BC OFET devices based on didodecylbenzothieonobenzothiophene (C
12
-BTBT) by the spin-coating method and investigate the influence of contact resistances on the field-effect mobility in the short-channel devices. Solution-processed TG/BC C
12
-BTBT FETs with channel length of
$10\ \mu \mathrm{m}$
exhibit a high mobility of approximately 3 cm
²
S
⁻¹
in the linear regime, while the mobility in the saturation regime decreases as the gate voltage is increased. The decrease in the saturation mobility can be attributed to a large reduction of the effective gate voltage caused by the voltage drop at the source contact resistance.