Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We gratefully acknowledge the financial support for this work at the Georgia Institute of Technology by the Deanship of Scientific Research of King Abdulaziz University under an International Collaboration Grant (Award No. D-001-433), the National Science Foundation through its MRSEC program (Award No. DMR-0819885), and by King Abdullah University of Science and Technology (V.C.). We also acknowledge the support of the Office of Naval Research (GlobalAward No. N62909-15-1-2003) and KAUST competitive research funding for the work at the King Abdullah University of Science and Technology. We thank Dr. Sean M. Ryno for many useful discussions.