Theoretical investigations on the charge transport properties of anthracene derivatives with aryl substituents at the 2,6-position—thermally stable “herringbone” stacking motifs

Abstract

High-performance organic semiconductor materials based on the small aromatic anthracene-core and its derivatives develop comparatively slowly due to the lack of a profound understanding of the influence of chemical modifications on their charge-transfer properties. Herein, the electronic properties and the charge transport characteristics of several typical anthracene-based derivatives with aryl groups substituted at the 2,6-site are systematically investigated by multi-scale simulation methods including Molecular Dynamics (MD) simulation and the full quantum nuclear tunneling model in the framework of density functional theory (DFT). To elucidate the origin of different charge transport properties of these anthracene-based materials, analysis of the molecular stacking and noncovalent intermolecular interaction caused by different substituents was carried out. The results indicate that the electron and hole injection capabilities and the air oxidation stability of the anthracene derivatives are greatly improved when the size of the aryl substituent increases. In addition, the incorporation of 2,6-site aryl substituents can inhibit the stretching vibration of the anthracene-core during charge transport, and allow molecular packing along the long axis (a-axis of DPA and BDBFAnt, and c-axis of dNaAnt) with almost no slippage, and the main transport channels remain unchanged, exhibiting more isotropic 2D transport properties. It should be emphasized that the edge-to-face dimers with smallest dihedral angles are closest to the thermally stable dimer model, with relatively larger π-orbital distributions in transmission channels (dimer 1, 2) and the largest spatial overlap, resulting in the largest hole transfer integral in DPA (V_h1/h2 = 57 meV). Although the analysis of the thermal disorder effect shows a phonon scattering effect, the maximum hole mobility of the DPA molecule is still as high as 1.5 cm² V⁻¹ s⁻¹.