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

We fabricated organic thin film transistors (OTFTs) by using soluble π-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 π-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 (μ), on/off current ratio (Ion/off), and threshold voltage (Vth). The 4(HPBT)-benzene and 4(HPTT)-benzene-based OTFT devices showed that the μʹs were ∼6.2 × 10−3 cm2/V s and ∼1.9 × 10−3 cm2/V s, respectively. We measured temperature-dependent mobility and activation energy (Ea) of the dendrimer-based OTFTs by using Arrhenius fitting. The Eaʹs of 4(HPTT)-benzene and 4(HPDTT)-benzene-based OTFTs were estimated to be ∼0.39 eV and ∼0.13 eV, respectively. In case of 4(HPBT)-benzene-based OTFT, two trap levels were measured and the Eaʹs were estimated to be ∼0.027 eV and ∼0.22 eV.