Usefulness of Polar and Bulky Phosphonate Chain-End Solubilizing Groups in Polymeric Semiconductors

A series of highly soluble copolymers (EH4P-Th, EH4P-Se, EH4P-TT, and EH4P-BT) based on phosphonate chain-end functionalized diketopyrrolopyrrole monomer and four different counterpart comonomers with varied electron-donating strength and conjugation length have been synthesized, characterized, and used in p-channel organic field-effect transistors (OFETs). It was found that introducing different counterpart comonomers into the main backbone alters the copolymers’ intrinsic properties, including absorption, frontier energy levels, molecular microstructure, and charge transport in OFETs. In OFETs fabricated on n -octadecyltrimethoxysilane (OTS)-treated silicon (Si)/silicon dioxide (SiO 2 ) surfaces, the copolymers exhibit good hole transport with maximum hole mobility (μ h ) of 1.46 × 10 –1 cm 2 V –1 s –1 in EH4P-TT, which is attributed to edge-on packing, fibrillar intercalating networks…