n-Channel Organic Thin-Film Transistors based on Naphthalene-Bis(dicarboximide) Polymer for Organic Transistor Memory Using Hole-Acceptor Layer

An investigation of threshold voltage shifts in organic thin-film transistors (OTFTs) based on poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis( dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} [P(NDI2OD-T2)] with additional poly(3-hexylthiophene) (P3HT) films on a poly(methyl methacrylate) (PMMA) organic dielectric layer is reported. With a top source-drain contact structure, the device exhibited a unipolar property with n-channel characteristics similar to those of the P(NDI2OD-T2)-only device. Furthermore, the existence of P3HT films as hole acceptor-like storage layers resulted in reversible V(th) shift upon the application of external gate bias (V(bias)) for a certain bias time (T(bias)). Hence, the P(NDI2OD-T2)/ P3HT-OTFTs exhibited a large memory window (Delta V(th) = 10.7V) for write and erase electrically without major degradation in saturation mobility [mu(sat) = 1,8-2.8) x 10(-4) cm(2) V(-1) s(-1)]. These results clearly indicate the utility of the naphthalene-bis(dicarboximide) (NDI)-based polymer-hole acceptor layer in the development of n-channel organic transistor memories. (C) 2011 The Japan Society of Applied Physics