Threshold voltage control of copper phthalocyanine based organic field-effect transistors with a poly (N-vinylcarbazole) buffer layer

Copper phthalocyanine (CuPc) based organic field-effect transistors (OFETs) with controllable threshold voltages (V
_T
s) were demonstrated by inserting a poly(N-vinylcarbazole) (PVK) buffer layer between CuPc and SiO
₂
. The PVK buffer layer enhances the crystallinity and improves the morphology of CuPc film, resulting in higher mobility up to 8.6 × 10
^-3
cm
²
V
^-1
s
^-1
. The V
_T
s of the device can be changed systematically from 63 to -10 V with the shift of starting V
_GS
from 100 to 0 V in a single device. The controllable V
_T
and much wider extend of V
_T
can be attributed to the Fowler-Nordheim tunneling of electrons into PVK buffer layer.