Optimization of Temperature-Mediated Organic Semiconducting Crystals on Soft Polymer-Treated Gate Dielectrics

Abstract

The temperature-mediated crystal structures of N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) on organo-compatible polymer/ SiO2 bilayer dielectrics, including either physisorbed or grafted polystyrenes (PSs), were examined and correlated with their electrical characteristics in organic field-effect transistors (OFETs). The crystallinity of the PTCDI-C13 films on these dielectrics increased with increasing annealing temperature (T-A), but the semiconductor-dielectric interfaces were also changed depending on the surface properties of the polymeric dielectrics. When T-A was increased above the glass transition temperature of PSs, the 20-30 nm thick physisorbed PS layers became softened and further dewetted from the oxide surfaces, resulting in the subsidence and disconnection of PTCDI-C13 crystal grains into the undulated PS layers. In contrast, the PS monolayer grafted to the SiO2 surface could maintain a wetting layer even at T-A = 200 degrees C, resulting in a hydroxyl free dielectric surface and highly pi-conjugated structures of T-A-mediated PTCDI-C13 crystals to achieve high-performance OFETs (field-effect mobility up to 0.2 cm(2) V-1 s(-1), threshold voltage similar to 1.0 V, on-off current ratio >10(6), and no gate sweep hysteresis).