Anisotropic valence band dispersion of 2D molecular crystals of C6-DPA and its charge transport dependence

Abstract

The unique properties and potential optoelectronic applications of two-dimensional molecular crystals (2DMCs) of organic semiconductors make them fascinating research subjects. With advancements in crystal engineering, it is becoming reality to produce 2DMCs with molecular-level thickness and large areas up to the centimeter scale, enabling us to directly explore the electronic structure of 2DMCs and to correlate them with their electrical properties. Here, we investigated the electronic structure of 2DMCs of C6-DPA using photoemission spectroscopy and electrical properties based on organic field-effect transistors. Our findings indicate that anisotropic band dispersion is present in the ab plane of the 2DMCs of C6-DPA which is in good agreement with the in-plane anisotropic mobility, i.e., the direction of the strongest molecular overlap coincides with the direction of the highest mobility.