Crystalline nanostructure and morphology of TriF-IF-dione for high-performance stable n-type field-effect transistors

Abstract

The device performance and stability of n-type organic field-effect transistors (OFETs) based on 1,2,3,7,8,9-hexafluoro-indeno[1,2-b]fluorene-6,12-dione (TriF-IF-dione) were investigated. The electrical characteristics of TriF-IF-dione FETs were optimized by systematically controlling the dielectric surface properties via insertion of organic interlayers, such as self-assembled monolayers (NH₂–, CH₃–, and CF₃–) or polymeric layers (polystyrene, PS) at the semiconductor–SiO₂ dielectric interfaces. In particular, a thin PS buffer layer on the SiO₂ surface provided a device that performed well, with a field-effect mobility of 0.18 cm² V⁻¹ s⁻¹ and an on–off current ratio of 4.4 × 10⁶. The improvements in the performance of TriF-IF-dione OFET conveyed by the PS interlayers were examined in terms of the crystalline nanostructure and the charge modulation effects in the channel. These properties were strongly correlated with, respectively, the hydrophobicity and the electron-donating characteristics of the dielectric surface. The TriF-IF-dione FETs with a PS interlayer showed excellent electrical stability attributed to high activation energies for charge trap creation. A complementary inverter comprising both p-type pentacene and n-type TriF-IF-dione was also successfully demonstrated.