Theoretical investigations on charge-transfer properties of pentacenequinone derivatives as n-type organic semiconductors.

Electron mobilities of two pentacenquinone derivatives as n-type organic semiconductors, 5,7,12,14-tetraaza-6,13-pentacenquinone (TAPQ5) and 1,4,8,11-tetraaza-6,13-pentacenquinone (TAPQ7), have been investigated at the molecular and crystal levels by means of the density functional theory (DFT) calculations and the incoherent charge-hopping model. It was found that these materials have lower LUMO energy levels, which can easily function as n-type organic semiconductors. The reorganization energy and transfer integral are the two important factors for tuning the electron transfer. The small reorganization energy and the large transfer integral for electron transport suggested that they have relatively high electron mobilities. The transfer integral among the dominant hopping pathways showed that the electron transport processes occur in parallel dimers between two neighboring molecules with π-stacking interactions. On the basis of the angular resolution anisotropic mobility investigation, TAPQ5 and TAPQ7 exhibit remarkable angular dependence of mobilities and anisotropic behaviors. The results are helpful for experimentalists to choose the candidate materials and to design novel organic semiconductors.