Most organic thin-film transistors have been fabricated on SiO2/Si substrates to test their carrier mobility. High substrate temperature is usually required to achieve high mobility. Alternatively, high annealing temperature is needed. High mobility at low substrate temperature is desirable for low-cost device fabrication, and is important for flexible electronics using plastic films. The glass temperatures of common clear plastic substrates such as poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) are 75-80 and 120 °C, respectively
In Prof. Katz’s group, new N,N’-disubstituted-1,4,5,8-naphthalene tetracarboxylic acid diimides with fluorinated phenylethyl groups were synthesized. In particular, N,N’-bis(pentafluorophenylethyl)-1,4,5,8-naphthalene tetracarboxylic acid diimide (5FPE-NTCDI) showed high electron mobility, over 0.1 cm2/Vs in air, even though the film was deposited at room temperature. Also, Prof. Katz’s group demonstrated flexible and transparent OTFTs with mobility of up to 0.23 cm2/Vs on clear, plastic PET film, with low hysteresis. Their results suggest that n-channel organic semiconducting materials can be used for easily processed flexible OTFT circuits in air.
