Influence of ambient atmosphere on the electrical properties of organic thin film transistors

We have fabricated organic thin film transistors (OTFT) using nickel phthalocyanine (NiPc) as an active layer. The organic thin films were deposited via sublimation under a secondary vacuum. The dependence of electrical characteristics on an ambient atmosphere is studied. Transient behaviour of the OTFT is also investigated showing the presence of a time delay in drain current when gate bias is applied. It is found that this time delay depends closely on the ambient atmosphere in addition with electrical field. Tests of ozone detection using NiPc based on OTFTs were carried out exhibiting a high sensitivity to ozone. We have demonstrated that electrical properties of the OTFTs are highly affected by ozone but not by oxygen. Our results show that NiPc-based OTFTs can represent a new class of ozone sensors.