Effect of dihydropyrazine on structures and charge transport properties of N-heteropentacenes matters: A theoretical investigation

A family of N-heteropentacenes acted as promising candidates for organic semiconductor materials is of immense interest. It should be attributed to the following reasons that (1) the positions, numbers and valence-states of N atom in N-heteropentacenes can effectively tune their electronic structure, stability, solubility, and molecular stacking; (2) diverse intermolecular interaction and π-stacking motifs appear in their crystals. The effect of the position and number of the 6-π-pyrazine on their structures and charge-transport properties has been systematically investigated in our previous work (J. Phys. Chem. C 115 (2011) 21416). Therefore, in this work, the study on the role of 8-π-dihydropyrazine with another valence-state N atoms is our focus. Density functional theory, Marcus electron transfer theory and Brownian diffusion assumption coupled with kinetic Monte-Carlo simulation are applied into this investigation. Our theoretical results indicate that in contrast with pyrazine, dihydropyrazine introduced is more helpful for promoting p-type organic semiconductor materials. For molecule 4, hole mobility of its single crystal theoretically reach 0.71 cm² V^-1 s^-1, and coupled with its fine hole-injection ability, it should be a promising candidate for p-type organic semiconductor materials. Although the lowest triplet-state energies of the molecules studied are very small, introduction of dihydropyrazine is very helpful for increasing the energies.