Thionation Enhances the Electron Mobility of Perylene Diimide for High Performance n-Channel Organic Field Effect Transistors

Perylene diimides (PDIs) are one of the most widely studied n-type materials, showing great promise as electron acceptors in organic photovoltaic devices and as electron transport materials in n-channel organic field effect transistors. Amongst the well-established chemical modification strategies for increasing the electron mobility of PDI, substitution of the imide oxygen atoms with sulfur, known as thionation, has remained largely unexplored. In this work, it is demonstrated that thionation is a highly effective means of enhancing the electron mobility of a bis-N-alkylated PDI derivative. Successive oxygen-sulfur substitution increases the electron mobility such that the fully thionated derivative (S4) has an average mobility of 0.16 cm(2) V-1 s(-1). This is two orders of magnitude larger than the nonthionated parent compound (P), and is achieved by solution deposition and without thermal or solvent vapor annealing. A combination of atomic force microscopy and 2D wide angle X-ray scattering experiments, together with theoretical modeling of charge transport efficiency, is used to explain the strong positive correlation observed between electron mobility and degree of thionation. This work establishes thionation as a highly effective means of enhancing the electron mobility of PDI, and provides motivation for the development of thionated PDI derivatives for organic electronics applications.