Investigation and Modulation of Charge Transport Properties with Thin Films of an Isoindigo-Based Donor-Acceptor Molecular Semiconductor

Charge mobility plays a crucial role in determining the performance of organic semiconducting devices. Organic semiconductors (OSCs) based on donor–acceptor (D-A) small molecules generally have planar backbones that facilitate charge transport. However, their hole transport property in thin film transistors (TFTs) still required to be further improved, and simultaneously achieving electron transport alongside hole transport remains a great challenge due to the presence of electron traps on the substrate surface. In this study, an isoindigo-based oligothiophene that is a D-A small molecule, was synthesized and employed as an active layer in TFTs. The impact of thermal annealing on the structure, morphology and charge transport properties of its thin films was investigated. By implementing a facile surface engineering, electron traps on the SiO2 dielectric surface were effectively eliminated. As a result, the charge transport behavior in the TFTs was successfully transformed from solely p-type to ambipolar characteristics. This accomplishment holds great significance for the advancement of optoelectronic devices in which both p-type and n-type conduction are harnessed.