Theoretical insight on the charge transport properties: The formation of “head-to-tail” and “head-to-head” stacking of asymmetric aryl anthracene derivatives

Organic semiconductors (OSCs) are widely used in flexible display, renewable energy, and biosensors, owing to their unique solid-state physical and optoelectronic properties. Among the abundant crystal library of OSCs, asymmetric aryl anthracene derivatives have irreplaceable advantages due to the interplay between their distinct π-conjugated geometry and molecular stacking as well as efficient light emission and charge transport properties that can be simultaneously utilized. However, the poor crystal stacking patterns of most asymmetric molecules limit their utility as excellent OSCs. Thus, it is crucial to clarify the structural features that enable the extremely ordered stacking and favorable electronic structure of asymmetric anthracene derivatives to become high-performance OSCs. This contribution investigates the charge transport properties of a series of asymmetric aryl anthracene derivatives to reveal the modulation factors of the molecular stacking modes and to explore the structural factors, which are beneficial to charge transport. The analysis demonstrated that the vinyl-linker facilitated the injection of hole carriers, and the alkynyl-linker effectively reduces the reorganization energy. Importantly, the linear polarizability and permanent dipole moment of a single molecule play a vital regulation to molecular stacking modes and the transfer integral of the dimer. The "head-to-head stacking" motif shows a compact stacking pattern and the maximum 2D anisotropic mobility more than 10 cm2 V-1 s-1. These findings sharpen our understanding of the charge transport properties in asymmetric organic semiconductors and are essential for developing a diverse range of high-performance OSC materials.