Modeling the behavior of charge carrier mobility with temperature in thin-film polymeric transistors

In this paper we study the dependence of charge carrier mobility with temperature in polymeric TFTs, PTFTs, using an expression previously derived by us, which has the advantage with respect to previous expressions, that most model parameters represent physical device parameters. Upper gate PTFTs fabricated with polymethyl methacrylate, PMMA, on poly(3-hexyl thiophene), P3HT, and with PMMA on poly(9,9-dioctylfluorene-co-bithiophene), F8T2, working in the temperature range between 300 K and 370 K were used in this study. Each model parameter was extracted at each temperature to determine its variation with T, observing that the bias enhancement parameter for mobility varies much slower than expected, if the characteristic temperature of the distribution of states DOS is considered constant. In this work, this behavior, which has been noticed but not explained before, is analyzed and interpreted, concluding that it has to be considered to represent correctly the behavior of mobility in the normal temperature operating range of PTFTs. Comparison of experimental and calculated data demonstrates the good agreement obtained, showing an Arrhenius-type dependence of the charge carrier mobility with an activation energy in the order of 70 meV and 120 meV for P3HT and F8T2 PTFTs, respectively.