Interface engineering and solid-state organization for triindole-based p-type organic thin-film transistors

Abstract

Inspired by the excellent device performance of triindole-based semiconductors in electronic and optoelectronic devices, the relationship between the solid-state organization and the charge-transporting properties of an easily accessible series of triindole derivatives is reported herein. The vacuum-evaporated organic thin-film transistors (OTFTs) exhibited a non ideal behaviour with a double slope in the saturation curves. Moreover, the treatment of the gate insulator of the OTFT device with either a self-assembled monolayer (SAM) or a polymer controls the molecular growth and the film morphology of the semiconducting layer, as shown by X-ray diffraction (XRD) analyses, atomic force microscopy (AFM) and theoretical calculations. N-Trihexyltriindole exhibited the best device performance with hole mobilities up to 0.1 cm² V⁻¹ s⁻¹ at the low V_G range and up to 0.01 cm² V⁻¹ s⁻¹ at high V_G, as well as enhanced I_on/I_off ratios of around 10⁶. The results suggest that the non-ideal behaviour of the here studied OTFT devices could be related to the higher interfacial disorder in comparison to that in the bulk.