Facile dielectric surface-modification methodology for high-performance polymer transistors via thermal evaporation of polydimethylsiloxane

Abstract

Here we demonstrate a novel surface-modification methodology for dielectric layers to be used for high-performance organic field-effect transistors (OFETs). Instead of conventional solution-processed polymeric thin films or self-assembled monolayers such as octadecyltrichlorosilane, we introduce thermally evaporated thin films of polydimethylsiloxane (PDMS) processed at atmospheric conditions. The thermally evaporated PDMS (TEP) thin film possesses various merits compared to other surface-treated films in terms of surface hydrophobicity, smoothness, reproducibility, and large-area deposition. From surface energy analyses, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, grazing incident X-ray diffraction, and atomic force microscopy analyses, we prove the overall superiority of TEP over other surface-treated films for OFETs. Using a conventional semiconducting polymer of poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), OFETs with TEP dielectric layers are demonstrated to have higher charge carrier mobility, better on/off ratio, and superior reproducibility compared to OFETs with other buffer layers. The relationships between dielectric surface properties and OFET performance are fully discussed in conjunction with the above-mentioned analyses. In addition, the reproducibility of the TEP-based OFET is demonstrated by long-term fabrication and measurement analyses.