Fabrication and electrical characteristics of organic thin film transistor using π-conjugated dendrimer

We fabricated organic thin film transistors (OTFTs) by using soluble pi-conjugated dendrimers of 4(HPBT)-benzene, 4(HPTT)-benzene, and 4(HPDTT)-benzene. Electrical characteristics such as current-voltage characteristic curves and their temperature dependence were measured for the dendrimer-based OTFT devices. The active layer using planar pi-conjugated dendrimers was spin-coated, and thermally grown silicon dioxide layer was used as a dielectric layer. Through the measurements of source-drain currents with varying gate voltages, we obtained charge carrier mobility (mu), on/off current ratio (I-on/off), and threshold voltage (V-th). The 4(HPBT)-benzene and 4(HPTT)-benzene-based OTFT devices showed that the mu's were similar to 6.2 x 10(-3) cm(2)/Vs and similar to 1.9 x 10(-1) cm(2)/Vs, respectively. We measured temperature-dependent mobility and activation energy (E-a) of the dendrimer-based OTFTs by using Arrhenius fitting. The E-a's of 4(HPTT)-benzene and 4(HPDTT)-benzene-based OTFTs were estimated to be similar to 0.39 eV and similar to 0.13 eV, respectively. In case of 4(HPBT)-benzene-based OTFT, two trap levels were measured and the E-a's were estimated to be similar to 0.027 eV and similar to 0.22 eV. (C) 2007 Elsevier B.V. All rights reserved.