Soft Rubbery Small Molecule for Gate-Dielectric Surface Engineering of Organic Thin-Film Transistors

Modifying the dielectric surface properties plays a crucial role in the growth of vacuum-deposited small-molecule semiconductors in bottom-gate organic thin-film transistors (OTFTs). In this study, m-bis-(triphenylsilyl)-benzene (TSB3), a small molecule with a low glass transition temperature, was blended with a poly-(methyl methacrylate) (PMMA) polymer dielectric to control the gate dielectric surface properties. The weight ratio of TSB3 affects the surface roughness and surface energy of the dielectric layers; therefore, the growth mode of the small pentacene molecules is tuned. It was found that at an optimum weight ratio, rubbery TSB3 molecules promoted the lateral diffusion of pentacene molecules during deposition and enhanced the connectivity among the crystals. OTFTs prepared from these pentacene crystals exhibited superior field-effect mobilities and gate bias stabilities compared to those with crystals grown on a pristine PMMA surface. The versatility of TSB3 molecules was also confirmed by applying this strategy to a variety of vinyl polymers including polystyrene and poly-(alpha-methylstyrene). Therefore, it is expected that blending rubbery TSB3 molecules into polymer dielectrics can be effective for the realization of high-performance OTFTs.