Acetylene bridged alkoxyphenanthrene and triarylamine-based triads for low threshold voltage with high mobility OFETs

Abstract

A series of new triarylamine appended alkoxyphenanthrenes connected through acetylene bridges were synthesized for high-performance p-channel OFETs. These semiconductors exhibited high-lying HOMO energy levels up to −5.16 eV, enabling hole-transport properties and reducing the energy barrier for charge injection. Phenanthrene-based organic field-effect transistors were fabricated in the bottom-gated top-contact architecture, and the device performances were dramatically improved with electron-rich substituents. The OFET devices exhibited a maximum charge carrier mobility of up to 3.5 cm² V⁻¹ s⁻¹ with a high ON/OFF current ratio of 10⁸ and the lowest threshold voltage of −3 V. Altering the donor arms in D′–π–D–π–D′ based phenanthrenes highly influences the molecular packing, thin film morphology, and charge transport of the active layer, which results in high OFET performance. The efficient π–π interactions and the crystalline nature of the films are well proved by GIXRD and SEM analyses.