Abstract
Organic field-effect transistors (OFETs) were found to be highly sensitive to the environment air composition due to the direct interaction between the thin semi-conducting layer of the OFET and the analyte. Despite a large number of works in this area, there is still a lack of understanding of the fundamental operation of such sensor devices. , The researches came to the agreement only in two fundamental relations – the thinner the semiconductor layer the higher the device sensitivity and sensory response mechanism of NO2 sensing should be related to the OFET doping. In common researches describe sensing mechanism of OFET through analyte sorbtion on the semiconductor surface leading to the change of electrical characteristics of the OFET by interaction between semiconductor and analyte. However, there is currently no complete understanding of how exactly these interactions occur and what properties of the analyte or semiconducting molecules affect them. In this talk, the sensory properties of OFETs based on various benzothienobenzothiophene derivatives will be presented and discussed. The findings demonstrated that the sensitivity s mainly determined by the difference in the energy levels of the semiconductor and analyte, and the closer the levels, the higher the sensitivity. At the same time, it is noted that the morphology and semiconducting molecules packing can also significantly affect the sensitivity of the OFET (in the case of sensitivity presence according to the proximity of energy levels). In addition, it was shown that in some cases (sensing NO2 for instance) sensitivity of the devices depends on the density of free charge traps, and the higher the density of free traps, the higher the sensitivity. Also the further verification the suggested factors affecting on sensory mechanism will be presented using OFETs based on thiophene-phenylene and aryl-diazafluoren derivatives.